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CC chemokine ligand 17 (CCL17) is a CC chemokine present in various species, including fish and mammals. CCL17 plays an important role in various organs, including innate immune defense in mammals, but its role and histological expression in fish have not been elucidated yet. Black rockfish (Sebastes schlegelii) is an economically important aquatic organism in East Asia that has recently been damaged by diverse biological and environmental factors, resulting in enormous financial losses. Although the functions of various immunomodulatory genes in black rockfish have been studied, the histological expression and function of CCL17 from S. schlegelii (SsCCL17) have not been investigated. We conducted homology analysis of the SsCCL17 amino acid sequence in black rockfish by comparing it with those of mammalian, avian, and fish species. Additionally, we proved that SsCCL17 was considerably activated in the ovary and brain of black rockfish using histological analyses via staining with hematoxylin and eosin and in situ hybridization. Moreover, in primary cells collected from the ovarian tissues of black rockfish, cell cycle progression and the expressions of ovarian development-related genes in response to female reproductive hormones were confirmed by quantitative PCR. Finally, the modulatory role of SsCCL17 in ovarian development was assessed using siRNA transfection in primary cells isolated from ovarian tissues of black rockfish, Collectively, we determined the tissue-specific localization of SsCCL17 and its function in the ovary of S. schlegelii , for the first time. • CCL17 in Sebastes schlegelii is orthologous to mammals and fish species. • CCL17 is specifically expressed in the brain and ovary of Sebastes schlegelii. • CCL17 modulates ovarian development genes in Sebastes schlegelii. • CCL17 regulates cell cycle induced by female reproductive hormone in black rockfish. [ABSTRACT FROM AUTHOR]

Viviparous rockfishes (Sebastes spp.) are ecologically and economically important fisheries and aquaculture species. Because the males lack obvious morphological characteristics related to reproductive status, it is challenging to select semen donors for artificial insemination. We previously identified lipocalin-type prostaglandin D 2 synthase homolog protein (LPGDShp) in the urine of male black rockfish (Sebastes schlegelii). Subsequently, LPGDShp-like protein (hereafter, lipocalin-like protein) was immunologically detected in the serum of two Sebastes species, black rockfish and white-edged rockfish (S. taczanowskii). In the present study, an enzyme-linked immunosorbent assay (ELISA) was developed to explore the potential of serum lipocalin-like protein as a biomarker for selecting mature males. The ELISA measured lipocalin-like protein in the sera of black rockfish and white-edged rockfish over an assay range between 0.391 and 12.5 ng/mL. In male black rockfish, serum levels of lipocalin-like protein were higher during the copulation season, and they were higher than levels in females during both the copulation and non-copulation seasons. In male white-edged rockfish sampled nearly monthly for a year, serum lipocalin-like protein levels showed synchronous dynamics with gonadosomatic index (GSI). Histological examination of testis revealed that the serum levels were elevated in the late/functional maturation stages, as compared to early/mid-maturation and resting stages. In both rockfish species, while serum levels of lipocalin-like protein were positively correlated with GSI in males, no such trend was observed in females. These results indicate, for the first time, that serum lipocalin-like protein can be employed as a hematological biomarker to detect the reproductive status of male rockfishes. • An enzyme-linked immunosorbent assay was developed for a lipocalin-like protein. • Serum levels of the protein were quantified in two rockfish species. • Levels of the protein were elevated in males during the copulation season. • Lipocalin-like protein positively correlated with male gonadosomatic index. • Lipocalin-like protein is a candidate biomarker of reproductive male Sebastes. [ABSTRACT FROM AUTHOR]

Growth arrest and DNA damage-inducible 45 alpha, b gene (gadd45ab) is a key homologue of gadd45a subfamily, which participates in several biological processes, such as inflammation and apoptosis. Black rockfish (Sebastes schlegelii) is an important commercial fish species in China. In current study, black rockfish gadd45ab (Ss _ gadd45ab) was characterized as a target gene of miR-20b-5p. The results indicated that high evolutionary conservations were found in the sequence and structure of Ss_gadd45ab , which was also detected to locate on the cytomembrane in the black rockfish intestine. The expressions of Ss_gadd45ab and diverse cytokines related to immune response were significantly induced with different patterns by the infection of E. tarda. Moreover, all tested immune genes were dramatically up-regulated when Ss _ gadd45ab was overexpressed in the intestine cells, and significant up-regulations and down-regulations of almost these immune genes were observed in the overexpressed cells during the LPS stimulation at 12 h and 24 h, respectively, which implied the potential regulations of Ss _ gadd45ab in the immune system. Meanwhile, the overexpression of Ss _ gadd45ab was found to prevent the invasion of E. tarda and promote the cell apoptosis in the intestine cells of black rockfish. Therefore, a profile of a novel regulatory mechanism of Ss _ gadd45ab targeted by miR-20b-5p in the inflammatory and apoptotic responses of black rockfish during pathogenic infections was hypothesized. Even though the potential functions of Ss _ gadd45ab on the inflammation and apoptosis in the black rockfish intestine during pathogenic infections have been described preliminarily in this study, more efforts are still urgent to be done for the further verification of this regulatory mechanism in black rockfish. • Ss _ gadd45ab and cytokines in MAPK and NF-κB pathways dramatically expressed in black rockfish intestine infected by bacteria. • Overexpressed Ss _ gadd45ab prevented E. tarda invasion and promoted the apoptosis of intestine cells in black rockfish. • The predicted target relationship between Ss _ gadd45ab and miR-20b-5p was confirmed by the dual-luciferase reporter assay. [ABSTRACT FROM AUTHOR]

This study assessed the impact of replacing fish meal (FM) with a blend of corn gluten meal and meat meal (BCM) at a ratio of 1:2 on the growth performance, digestive enzyme activity, and nonspecific immune response of juvenile black rockfish (Sebastes schlegelii). Seven experimental diets were formulated. The control (BCM0) diet contained 65% FM. Subsequently, 10, 20, 30, 40, 50, and 60% FM in BCM0 diet were replaced with BCM, referred to as the BCM10, BCM20, BCM30, BCM40, BCM50 and BCM60, respectively. Each diet was randomly assigned to triplicate groups of 30 rockfish (initial body weight: 3.6 ± 0.01 g) for 8 weeks. The BCM0–BCM50 diets resulted in no significant differences in final body weight (FBW), weight gain (WG), and specific growth rate (SGR), whereas the BCM60 diet led to the lowest FBW, WG, and SGR. The feed consumption and feed efficiency of rockfish fed BCM10–BCM50 diets did not differ significantly from those of rockfish fed the BCM0 diet. Intestinal trypsin and lipase activities showed a linear decrease with increasing substitution levels of BCM in the experimental diets. Moisture levels increased with elevated BCM replacement in diets, whereas crude protein and lipid levels decreased with increased BCM replacement. Whole-body amino acid profiles of rockfish, except for glycine and proline content, were not significantly affected by diet. However, lysozyme and catalase activities exhibited quadratic responses to increasing dietary BCM levels, and superoxide dismutase activity and glutathione content showed a negative linear response. Overall, these results show that a blend of corn gluten meal and meat meal can replace up to 50% of dietary FM without adversely affecting the growth performance of juvenile rockfish. • A blend of corn gluten meal and meat meal (BCM) in a 1:2 ratio is a good protein source of protein for black rockfish. • Substituting up to 50% FM with BCM did not have adverse effects on growth and feed utilization. • Intestinal trypsin and lipase activities showed a linear decrease with increasing substitution levels of BCM. • With increased dietary BCM, plasma superoxide dismutase activity and glutathione concentration decreased linearly. [ABSTRACT FROM AUTHOR]

Aquaculture faces increasing challenges from parasitic infections, notably impacting the marine cage farming of Korean rockfish (Sebastes schlegelii). A primary contributor to these challenges is the monogenean parasite Microcotyle sebastis , which incurs significant economic losses. To formulate effective management strategies, it is essential to understand how environmental variables influence the reproductive behavior and survival of M. sebastis. In this study, we conducted controlled in vitro experiments to assess the fecundity, hatching success, and viability of M. sebastis across a temperature range from 25 °C to 4 °C, as well as under varying light/dark conditions. We found that the parasite's fecundity was optimal at 15 °C and minimal at 4 °C. Survival rates exhibited an inverse correlation with increasing temperatures. The hatching process was most rapid at 25 °C, with no hatching observed at 4 °C. Upon hatching, the maturation and lifespan of oncomiracidia varied depending on temperature: cilia degenerated within 36 h at temperatures ranging from 25 °C to 15 °C, whereas at 10 °C, cilia began to degenerate on the fourth day post-hatching, surviving for up to nine days. Interestingly, conditions of perpetual darkness led to increased egg production and survival rates compared to light exposure. Our findings provide critical insights into the adaptive responses of parasites to environmental changes and suggest that current deworming strategies may not adequately address the rapid hatching and increased egg production of M. sebastis. We emphasize the need for ongoing research to adapt aquaculture management strategies to the evolving challenges posed by parasites and recommend that future research focus on field studies examining the impact of environmental variables and multiple parasite species. • Microcotyle sebastis impacts marine farming of Korean rockfish. • Survival curve vary with temperature: 4 °C shows no mortality; 35 °C is fatal. • Fecundity is optimal at 15 °C and temperature-dependent. • Light exposure accelerates M. sebastis mortality compared to darkness. • Current deworming methods may be insufficient due to M. sebastis 's adaptability. [ABSTRACT FROM AUTHOR]

We determined if ideal protein (IP) fishmeal-free (FMF) or all-plant protein (PP) diets of available ingredients satisfied production needs of hybrid striped bass (HSB; Morone chrysops x M. saxatilis) grown to market size in ponds managed according to industry practices, and if phytase (Phy) superdosing (20,000 FTUs) could alleviate inorganic phosphorus supplementation. An off-the-shelf commercial feed (COM), an IP control diet containing 16% fishmeal (FM), and four IP test diets with or without phytase superdosing (FMF, FMF + Phy, PP, PP + Phy) were evaluated. Inorganic phosphorus was excluded from phytase treated diets. Hybrid striped bass (averaging 344 g/fish) were stocked (5187 fish/ha) in 4 ponds/diet (0.1 ha) and grown for 5.5 months. Most responses of the five ideal protein diets did not differ significantly (P > 0.1) from the COM. Only net fish yield, weight gain, and FCR of the PP diet were less than those of the COM diet. Fish fed FMF and FMF + Phy diets had higher fish yields, mean weights, and gains than PP and PP + Phy diets. FMF ponds had fewer than expected large (907–1134 g) and more jumbo (>1135 g) fish and FMF + Phy ponds had fewer medium (680–906 g) and more large fish. PP ponds had fewer than expected jumbo fish. The COM diet resulted in larger livers (HSI), lower muscle ratio, but less feed phosphorus added to ponds compared to the FM diet. Absence of differences for other responses confirms the FM diet is a valid proxy for the COM diet. Phytase increased energy and protein retention of the PP diet but not the FMF diet. FM can be replaced with animal and/or plant proteins exclusively without major reductions in hybrid striped bass performance. The PP diet likely requires optimization of Met and branched chain amino acid levels to improve performance. Inorganic phosphorus can be replaced by diet phytase top-coating and judicious inclusion of phytate‑phosphorus without negative impact on HSB production. Phytase superdosing of the FMF and PP diets did not improve production variables but did improve mineral retentions, more so for the PP diet. Phytase superdosing reduced feed phosphorus fed by 60% and pond phosphorus loading by 40% but requires optimization of inclusion levels and economic evaluation before recommendation. • Hybrid striped bass can be grown to market size on an all-plant protein diet. • Dietary fishmeal was replaced totally by plant proteins or animal plus plant proteins. • Dietary inorganic P was replaced totally by phytase top-coating. • Dietary phytase reduced feed P fed by 60% and pond P loading by 40%. [ABSTRACT FROM AUTHOR]

Pyroptosis, a kind of pro-inflammatory programmed necrosis, can be caused by pathogens. Edwardsiella piscicida is a common pathogenic bacterium, which can infect several teleosts including black rockfish (Sebastes schlegelii), leading to serious disease. However, the interaction mechanism between E. piscicida and immune cells in S. schlegelii is not clear. Herein, we showed that upon the stimulation with E. piscicida , head kidney macrophages (HKMs) exhibited remarkable pyroptosis phenomena, including evident cell swelling, membrane rupture, DNA damage, and cleavage of SscGSDMEb. Furthermore, the transcriptome profiles of HKMs infected with E. piscicida were examined. A total of 198 differentially expressed genes (DEGs) were identified and significantly enriched in the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways related to immunity. The expression of several pyroptosis-associated genes changed significantly after E. piscicida infection. Moreover, we found reactive oxygen species (ROS) was essential in pyroptosis and inflammatory response induced by E. piscicida. Together, we revealed that E. piscicida invasion caused pyroptosis in HKMs of S. schlegelii , key genes and pathways in pyroptosis were obtained. This study could prove novel insights into the immune mechanism underlying the resistance of teleosts to pathogen invasion. • The effect of Edwardsiella piscicida on macrophages of black rockfish (Sebastes schlegelii) is described. • A type of cell death, pyroptosis caused by E. piscicida , in black rockfish is described and verified. • The key genes and pathways during the pyroptosis caused by E. piscicida infection were revealed by RNA-seq. [ABSTRACT FROM AUTHOR]

A 6-week growth trial was conducted to assess the replacement of fishmeal (FM), soy protein concentrate (SPC) and fish oil (FO) by Arthrospira sp. and Schizochytrium limacinum meals in diets for hybrid striped bass (Morone chrysops × M. saxatilis) juveniles of 10.6 ± 0.2 g initial individual weight (±standard deviation). A control diet was formulated with equivalent contributions of FM and SPC to provide 40% crude protein. Menhaden FO was the main lipid source, providing 10% crude fat. Five experimental diets replaced 10, 20, 30, 40 and 50% of FM, SPC, and FO from the control diet by combining two algal meals derived from the freshwater autotroph Arthrospira sp. and the marine heterotroph S. limacinum. Each diet was randomly assigned to three replicate aquaria, and twelve group-weighed fish were stocked per aquarium. Fish were group-weighed weekly to adjust the feeding ration, which started at 6% and gradually decreased to 3%, confirmed by visual feeding cues to avoid overfeeding. At the end of the trial, no statistical differences for responses such as condition factor (P = 0.6778), hepatosomatic index (P = 0.4542), intraperitoneal fat ratio (P = 0.0997), or feed efficiency (P = 0.2210) were detected. However, statistically significant differences were observed for percent weight gain (WG; P = 0.0323) and thermal growth coefficient (TGC; P = 0.0164). Weight gain (209.5%) and TGC (0.088) of fish fed the control diet was significantly lower than in fish fed the 30 and 50% replacement diets (WG: 232.8–235.3%), but no differences were detected among fish fed any other replacement level (WG: 217.1–227.9%). Whole-body proximate composition showed no statistical differences among fish for crude protein, moisture, or ash, except for crude fat content (P < 0.0001); the highest percentage of fat (9.3%) was observed in fish fed the 30% replacement level. The dietary fatty acid profile influenced the fatty acid profile of fish, eliciting an increment in the content of specific fatty acids, such as 16:0, 18:2n-6 and 22:6n-3. Although higher docosahexaenoic acid (DHA) content was observed in whole-body of hybrid striped bass fed the experimental diets, this fatty acid did not contribute to a higher body lipid content. The findings indicate that the combination of Arthrospira sp. and S. limacinum meals can replace a significant proportion of fish-derived feedstuffs in hybrid striped bass feeds, promoting suitable growth performances with up to 50% replacement under these conditions, and promoting the accumulation of DHA in fish tissues, which would ultimately benefit consumers. • Arthrospira sp. and S. limacinum meals favored the replacement of fish derived feedstuffs in hybrid striped bass diets. • Microalgae meals improved growth performance of hybrid striped bass with up to 50% replacement of fishmeal and fish oil. • Docosahexaenoic acid accumulation in fish due to the dietary inclusion of S. limacinum would ultimately benefit consumers. [ABSTRACT FROM AUTHOR]

Processed microalgae concentrates recently have been considered potentially viable alternatives to partially replace fishmeal (FM) and fish oil in aquafeeds. Two feeding trials were conducted to evaluate incremental replacement of FM and soy protein concentrate (SPC) with different types of microalgae in the diet of hybrid striped bass. Microalgae evaluated in feeding trial 1 included dried products from monocultures of Phaeodactylum tricornutum and Nanochloropsis salina , as well as mixed cultures of those two species. Several preparations of Chlorella sp. lipid extracted by various means as well as bluegreen algae biomass (BGAB) also were evaluated. In feeding trial 2, the microalgae products supporting most efficient fish performance in feeding trial 1 were reassessed along with mixed cultures of Phaeodactylum tricornutum and Nanochloropsis salina as well as BGAB. Two additional mixed cultures of Nanochloropsis salina with Amphora sp. or Cylindrotheca sp. also were evaluated. Algae products were substituted to replace either 10, 15 or 20% of protein provided equally from menhaden FM and SPC in the Reference diet. All diets were isonitrogenous (40% crude protein) and isocaloric (3.3 kcal digestible energy g −1 ), and each were fed to triplicate groups of juvenile fish with average initial weights (+SEM) of 15.1 ± 0.6 g and 21.4 ± 1.3 g/fish in feeding trials 1 and 2, respectively for 7 weeks. Weight gain and feed efficiency ratio (FER) of hybrid striped bass were high (>330% of initial weight and 0.79) but significantly (P < 0.05) affected by diet in trial 1 with no mortality. Fish fed the Reference diet and the one containing BGAB had the greatest but similar weight gain. Substitution of the other algae meals significantly reduced weight gain by 8.2 to 14.7% compared to the Reference diet. Most diets containing algae meal yielded similar FER as the Reference diet except for those containing solvent-extracted Chlorella sp . (both 10% and 20% substitution), Phaeodactylum tricornutum (10%), and Phaeodactylum tricornutum  ×  Nanochloropsis salina (10% and 20%), in which FER was significantly reduced by 5.8 to 8.1%. Whole-body proximate composition and protein retention efficiency values revealed no significant differences among diets. In feeding trial 2, the various diets with algae products substituted at 10 or 15% of dietary protein did not significantly affect growth performance or whole-body composition of hybrid striped bass compared to the Reference diet. In conclusion, replacement of up to 15% crude protein in the Reference diet with BGAB, the Phaeodactylum tricornutum and Nanochloropsis salina mixture, as well as mixtures of Nanochloropsis salina with Amphora sp. or Cylindrothecatheca sp. was possible without affecting growth performance or body composition of hybrid striped bass. [ABSTRACT FROM AUTHOR]

Striped bass ( Morone saxatilis ) and their hybrids have been well studied and are widely cultured in freshwater ponds as food and gamefish. Recent industry expansion has generated an interest in strain-specific broodstock development for marine netpen and pond culture. In this effort, Atlantic and Gulf coast striped bass strains were cultured in recirculating aquaculture systems (RAS) at different salinities for up to two years and production and morphometric parameters (specific growth, feed conversion, fillet yield, condition factor and stripe patterns) were compared. Striped bass juveniles produced from wild-caught broodstock from rivers in Nova Scotia, Delaware, Virginia, North and South Carolina, Florida, Texas and a selected, domesticated strain were reared in triplicate fresh (0 ppt), brackish (5 ppt) and saltwater recirculating (30 ppt) systems. After one year of age, a subset of fish were implanted with passive integrated transponder (PIT) tags, combined into a larger, “common-garden”, saltwater, recirculating system and monitored over an additional year. Parental broodstock and cultured offspring were fin-clipped and genotyped to identify juvenile family origin. Final weights of fish after one and two years averaged approximately 0.5 and 2.5 kg, respectively and did not differ by water salinity. Growth rates and condition factors differed by strain, but condition factor was not correlated with fillet yield. Consistent with other studies, juvenile fish from South Carolina and Nova Scotia were found to be slow growing compared to migratory Atlantic and Gulf strains. Mixed model analyses showed that family, and family by strain interactions were significant, but accounted for less growth variance than strain alone. These results indicate that family-based selection by strain may be useful in striped bass broodstock development programs. [ABSTRACT FROM AUTHOR]

In previous work, we demonstrated that diets containing 40% digestible protein (DP) (45% crude protein) and 18% lipid supplemented with Met and Lys resulted in superior performance and nutrient retentions in hybrid striped bass (HSB) compared to less energy-dense diets when rearing HSB at temperatures similar to the summer growing period of the Southern U.S. The current work was aimed at vetting previous results in pond production of market-size HSB at commercial stocking densities to assess impacts on fish production indices and water quality parameters. Diets were formulated to contain digestible protein levels ranging from 41% to 35% DP and 15% crude lipid. The trial was conducted during the hottest portion of the growing season when impacts of feeding have the greatest influence on pond water quality. The 6-month pond (0.1 ha; 0.25 ac) study began with advanced juveniles (121.4 ± 3.21 g/fish; mean ± SD) in May 2013 and concluded with market sized fish in October 2013. Final fish size ranged from 448 ± 24 g to 1122 ± 46 g with food conversions ranging from 1.34–1.37. Results suggest that DP can be lowered from 41% DP to 35% DP by careful diet formulation while supplementing the first three limiting amino acids (Met, Lys Thr) without detrimental changes to body composition or nutrient retentions. Market size distributions, nutrient retention, and pond water quality dynamics in relation to test diets are also discussed. [ABSTRACT FROM AUTHOR]

The trial investigated the effects of dietary supplementation with the commercial prebiotic galactooligosaccharide (1% GOS; GOS diet), the commercial probiotic Pediococcus acidilactici MA18/5 M (6.3 log CFU g − 1 PA; PA diet) and their combination as synbiotic (1% GOS and 6.3 log CFU g − 1 PA; SYN diet) on the growth, innate immunity and disease resistance of juvenile rockfish ( Sebastes schlegeli ). Triplicate groups of fish (18.2 ± 0.3 g) were fed one of the four diets for 8 weeks and then subjected to a standard challenge with Edwardsiella tarda by intraperitoneal injection. The results showed significant ( P < 0.05) improvement in growth performance in the SYN compared to the control group with intermediary benefits for PA and GOS. White blood cells count was significantly enhanced in the PA and GOS groups with a further significant increase for the SYN diet. In accordance and compared to the control; serum lysozyme and bacteriostatic activities against Vibrio anguillarum and Escherichia coli were increased in all supplemented groups while serum alternative complement activity was elevated in the SYN group. In addition, the skin mucus bacteriostatic activities were significantly influenced by dietary treatments. The beneficial effects observed on circulating innate immune parameters were validated by a higher survival pattern following intraperitoneal challenge with E. tarda in the PA and SYN groups. This study contributes to the knowledge on the mode of action of GOS and PA and demonstrates their potential as natural health and growth promoters in the rockfish on-growing aquaculture industry. [ABSTRACT FROM AUTHOR]

Fish meal (FM) is widely used as a main protein source in formulated feed for marine fish culture. However, the production of FM has shrunk or plateaued due to the overfishing and climate change in the wild. Meat meal (MM) is known as a good replacer for FM in fish feeds. Dietary replacement effect of MM for FM on the growth, feed consumption, feed utilization, body composition, hematology, and innate immune responses of rockfish was determined. A total of 630 fish (initial weight of 2.3 g) was randomly distributed into 21, 50 L flow-through tanks (30 fish/tank). Seven experimental diets were formulated. The control (MM0) diet contained 55% FM. Then, 10, 20, 40, 60, 80, and 100% FM in the MM0 diet were replaced with MM, referred to as the MM10, MM20, MM40, MM60, MM80, and MM100 diets, respectively. All experimental diets were allocated to triplicate groups of fish. Fish were hand-fed to visual satiation twice a day for 8 weeks. Increased substitution of FM with MM in diets resulted in decreased essential amino acids (EAA), such as lysine and threonine and the sum n-3 highly unsaturated fatty acids, but increased EAA, such as arginine and methionine, and the sums of saturated and monoene FA. Weight gain (9.8 g/fish) of fish fed the MM10 diet was significantly (P <.003) greater than that (8.8, 8.9, 8.2, and 7.9 g/fish, respectively) of fish fed the MM0, MM60, MM80, and MM100 diets. Specific growth rate (SGR) (2.93%/day) of fish fed the MM10 diet was significantly (P <.004) higher than that (2.79, 2.69, and 2.64%/day, respectively) of fish fed the MM0, MM80, and MM100 diets. Weight gain and SGR of fish fed the MM100 diet were (P <.05) significantly lower than those of fish fed the MM0 diet. Feed consumption (9.34 g/fish) of fish fed the MM10 diet was significantly (P <.002) higher than that (8.72, 8.59, 8.32, and 8.10 g/fish, respectively) of fish fed the MM0, MM60, MM80, and MM100 diets. Feed efficiency (1.04%) of fish fed the MM10, MM40, and MM60 diets was significantly (P <.009) higher than that (0.99, and 0.98%, respectively) of fish fed the MM80, and MM100 diets. Condition factor, protein efficiency ratio, protein retention, hematological parameters, and innate immune responses (lysozyme and superoxide dismutase activities) of fish was not significantly (P >.05) different among the experimental diets. The chemical composition, and AA and FA profiles of the whole-body fish were not influenced by the experimental diets. In conclusion, dietary substitution FM up to 80% with MM can be made without deteriorating growth performance of rockfish. However, the optimum substitution level of FM with MM in diets were estimated to be 18.5, and 18.2% based on regression analysis of weight gain and SGR of rockfish, respectively. • Substitution effect of fish meal with meat meal in diets on performance of rockfish was determined. • Weight gain and SGR of fish fed the MM100 diet were significantly lower than those of fish fed the MM0 diet. • Dietary substitution FM up to 80% with MM can be made without deteriorating growth performance of rockfish. [ABSTRACT FROM AUTHOR]

Disease outbreaks in intensive aquaculture, particularly from bacterial pathogens, represent major constraints to efficient fish production. Therefore, development of novel disease treatment and prevention strategies have been receiving considerable attention in recent years. This study analyzed the efficacy of the organic acid poly-β-hydroxybutyrate (PHB) as an immunomodulator in hybrid striped bass (Morone chrysops × M. saxatilis) (HSB) and red drum (Sciaenops ocellatus) based on both in vitro and in vivo approaches. In vitro immunological assays, namely intra- and extra-cellular superoxide anion production and bactericidal capacity of HSB head kidney-derived leukocytes were determined to be significantly (P < 0.05) reduced when graded doses of sodium 3-hydroxybutyrate (3HB; 0.0, 0.5, 1.0, 2.0, 4.0 and 8.0 mM), a precursor to PHB, was supplemented in the cell culture media. For the HSB in vivo feeding trial, PHB-synthesizing bacteria, Zobellella denitrificans (ZD1), were supplemented to basal diets to produce five isonitrogenous and isolipidic experimental diets (40% crude protein and 10% crude lipid) containing PHB in stepwise increments (0.0, 0.125, 0.25, 0.5, 1.0, and 2.0% of dry-diet weight). In addition, a control diet was supplemented with 0.5% of a commercial purified PHB product. In a separate feeding trial, a commercial PHB product was supplemented to a practical basal diet in stepwise increments (0.0,0.125, 0.25, 0.5, and 1.0%) to isonitrogenous and isolipidic experimental diets (40% crude protein and 10% crude lipid). Juvenile HSB, and red drum (∼5.5, and 4.4 g/fish initial weight, respectively) in separate feeding trials were stocked in 38-L aquaria operated as a recirculating aquaculture systemHSB experimental diets were randomly assigned to quadruplicate aquaria of fish while the red drum experimental tdiets were randomly assigned to quintuplicate aquaria and fed for an 8-week period. HSB and red drum exhibited limited responses to graded levels of PHB, including percentage weight gain, feed efficiency, protein conversion efficiency and hepatosomatic index. Only juvenile red drum showed significantly (P < 0.05) increased muscle yield values with increasing dietary PHB while whole-body proximate composition analyses revealed no significant (P > 0.05) differences, except for HSB whole-body crude lipid. Thus, PHB (ZD1-derived and commercial) had limited effects on growth parameters, body condition factors, and immunological responses of both HSB and red drum juveniles. • 3-hydroxybutyrate (3HB) decreased measured innate immune responses of hybrid striped bass head kidney-derived leukocytes in vitro. • PHB supplementation had limited responses on growth performance and whole-body composition of juvenile hybrid striped bass and red drum. • Red drum exposed to a Photobacterium infection had higher survival when supplemented with the PHB ingredient than fish fed the basal treatment. [ABSTRACT FROM AUTHOR]

Selection for resistant lines is an important part in black rockfish (Sebastes schlegelii) breeding program. The identification of markers closely linked to disease-resistance is an essential step for the improvement of the resistance in S. schlegelii through marker-assisted selection (MAS). However, lack of parental genomic information increased the difficulty for MAS. In the present study, by using whole genome re-sequencing strategy and bulked segregant analysis (BSA), 704,630 SNPs and 253,436 in/del within the two extreme phenotypes were identified in S. schlegelii. Furthermore, using combination of SNP frequency difference and Eucildean distance, we conducted linkage analysis of SNPs located in immune-related genes, and identified markers associated with Vibrio anguillarum resistance. A total of 64 SNPs was identified as candidate SNPs between susceptible and resistant groups, 48 SNPs located in 43 genes were selected for further genotyping analysis in verification population and 7 of them showed significant association with V. anguillarum -resistance (P < 0.05). Generalized multifactor dimensionality reduction (GMDR) was performed to analyze the SNP-SNP interaction. The best three-factor model consisted of loci from Casp8 , Pglyrp2 and Gnb1 was considered to be associated with V. anguillarum resistance in S. schlegelii. Combining the actual phenotype with predicted phenotype, the best three-factor model was proved to have 69.1% identification accuracy. Our study demonstrated that the genetic analysis with the application of BSA-seq has propelling effect in disease resistance and will assist the selective breeding of S. schlegelii with V. anguillarum resistance. • BSA-seq was firstly used to detect SNPs associated with V. anguillarum resistance in black rockfish. • Expression of 4 candidate genes showed significant difference in genotypes. • The GMDR analysis was performed to detect the combined effects of all 7 potential loci. • Three-factor model could be used as a high-efficiency marker for MAS in black rockfish. [ABSTRACT FROM AUTHOR]

Extrusion technology is known to enhance feed quality by controlling feed processing conditions. Although extrusion technology has been extensively used to improve livestock feed quality, research on its effects on quality in fish is lacking. Furthermore, studies on feed processing, the physical properties of feed produced using extruders, and the effects of extrusion on formulated feed quality remain scarce. Therefore, in this study, we investigated the effects of extrusion pressure and raw material particle size on the growth performance and digestive physiology of rockfish (Sebastes schlegeli). Experimental diets were prepared under different extrusion pressures by manipulating the screw speed [low pressure (LP), 1080 rpm/min; high pressure (HP), 620 rpm/min] and mean raw material particle sizes [small size (SS), 199.1 μm3; large size (LS), 1026.8 μm3] in a two-level factorial design. Four experimental diets (SS/LP, SS/HP, LS/LP, and LS/HP) were randomly assigned to 12 tanks (3 replicates), which were each stocked with 30 fish (initial mean body weight, 82.7 ± 0.2 g). After a 16-week feeding trial, observations showed that SS and LP enhanced fish weight gain and plasma growth-related hormone activity. In addition, SS and LP increased intestinal digestive activity in fish, positively affecting growth. These results indicate that manipulating physical pellet qualities by adjusting the feed ingredient extrusion pressure and raw material particle size can improve the growth performance and digestive physiology of rockfish, which should be considered in feed manufacturing. • Extrusion pressure and particle size improved rockfish growth rate and growth hormone activity. • Higher water absorption ability of feed was associated with better fish growth. • SS and LP enhanced fish weight gain and plasma growth-related hormone activity. • SS and LP increased the digestive activity of the intestines. [ABSTRACT FROM AUTHOR]

The study analyzed demand for fish in the United States by the number of species purchased from a basket of species, rather than the usual approach focusing on one single species. The basket includes largemouth bass, hybrid striped bass, bluegill, walleye, yellow perch, rainbow trout, Great Lakes whitefish, lake trout, barramundi, and tilapia. These results largely confirm that consumers purchase different fish species or a combination of them from time to time and that consumers pay little attention to green factors such as sustainability, 3rd party certification and hormone-free when purchasing seafood. It appears that the effects of green credence attributes may not apply generically to a collection of fish or that the utility of green characteristics to seafood demand may be declining. As for production systems, although a higher percentage of consumers indicated preference for wild-caught fish, the importance of farmed fish to them was found to increase fish purchased. • Modeling seafood demand from a basket of species. • Consumers do demand a collection of seafood species. • The importance of green factors may not apply generically to a basket of fish. • A higher percentage of consumers indicate preference for wild fish ex ante , but they purchase farmed fish more. [ABSTRACT FROM AUTHOR]

Collectins, which belong to C-type lectins, are pattern recognition molecules of the innate immune system exhibiting binding ability to carbohydrate structures on microorganisms. CL-L1, a member of the collectin family, participates in host defense via recognizing pathogen structures and modulating complement activation, and also plays roles in developmental processes. Although research progress obtained in mammals, comparative studies of CL-L1s outside mammals are still very limited so far. In this research, CL-L1s from a range of vertebrates were analyzed in gene synteny, phylogenetic relationship and protein features. It's revealed that CL-L1 is widely distributed and generally conserved in vertebrates. The gene locus of CL-L1 exists stably and protein modules, i.e. the N-terminal region, collagen-like region, neck region and CRD, are conserved in a series of vertebrates. But it's worth noting that some characteristic motifs, i.e. EPN and WND, which are important in binding carbohydrates, are partly or completely lost in the CRDs of CL-L1s in teleost species. The CL-L1 in a marine teleost, the black rockfish, designated as SsCL-L1, is analyzed next. SsCL-L1 has incomplete motifs in its CRD, but shows different binding affinities to a series of monosaccharide. SsCL-L1 can bind different bacteria with different intensities, and agglutinate bacteria in the presence of Ca2+. Sugar binding mechanism of SsCL-L1 needs further studies and results in this work will promote the understanding of CL-L1 evolution in vertebrates and facilitate knowledge of immunological roles of fish collectins. • CL-L1s are conserved in vertebrates. • CL-L1s of teleost fish have undergone special evolution in their CRDs. • SsCL-L1 has binding abilities to different monosaccharide and bacteria. [ABSTRACT FROM AUTHOR]

Two experiments were conducted to investigate the effects of replacing fish meal (FM) with fermented soybean meal (FSM) on growth performance, body composition, antioxidant enzyme activity and disease resistance of rockfish, Sebastes schlegeli , at the juvenile and grower stages. Five isonitrogenous (51%) and isocaloric (21.0 MJ kg − 1 ) diets were formulated to contain 0, 8, 16, 24 and 32% FSM, replacing approximately 0, 10, 20, 30 and 40% of the FM protein (designated as FSM0, FSM8, FSM16, FSM24 and FSM32, respectively). Each experimental diet was fed to triplicate groups of juvenile (1.2 ± 0.04 g; EXP I) and grower (148.2 ± 2.9 g; EXP II) rockfish to apparent satiation twice daily for 8 weeks. Juvenile rockfish fed the FSM32 diet showed significantly lower weight gain (WG) than those fed the FSM0, FSM8 and FSM16 diets. Feed efficiency (FE) and protein efficiency ratio (PER) of fish fed the FSM16, FSM24 and FSM32 diets were significantly lower than those of fish fed the FSM0 and FSM8 diets. Fish fed the FSM24 diet exhibited significantly lower daily feed intake (DFI) than fish fed the FSM0 and FSM8 diets. However, growth performance and feed utilization efficiency of grower rockfish did not show any definite pattern of change due to feed composition. The viscerosomatic index (VSI) of juvenile fish fed the FSM32 diet was significantly lower than those of all the other experimental groups. Replacement of FM with FSM, up to 40%, had no significant effect on whole body and muscle proximate and amino acid compositions of juvenile and grower rockfish, respectively. The plasma antioxidant enzyme activity of grower fish was significantly enhanced by the dietary inclusion of the FSM compared with the control group. Survival of juvenile fish after intraperitoneal injection of Edwardsiella tarda was not affected by dietary treatment. These results indicate that FSM can be used successfully as a replacement for FM at levels up to 10% in diets for juvenile rockfish while at least 40% of dietary FM protein can be replaced by FSM without causing any adverse effect on grower rockfish performance. Statement of relevance 1. There have been a few studies examining the efficiency of fermented soybean meal (FSM) as a possible fish meal substitute in fish feed. However, to the best of our knowledge no studies have been reported on the use of FSM as a substitute for fish meal in diet for rockfish. 2. The results of this study indicate that FSM can be used successfully as a replacement for FM at levels up to 20% in diets for juvenile rockfish while at least 40% of dietary FM protein can be replaced by FSM without causing any adverse effect on grower rockfish performance. 3. As feed cost accounts for almost half of the fish production costs, the results of our experiments can be useful for formulation of more cost-effective practical diets for juvenile and grower rockfish. [ABSTRACT FROM AUTHOR]

An 8-week feeding trial was conducted to characterize the pantothenic acid deficiency signs and quantify the dietary requirement of juvenile hybrid striped bass, Morone chrysops × Morone saxatilis . A basal diet composed of fish muscle and crystalline amino acids was analyzed to contain 5 mg of pantothenate/kg and supplemented with calcium d -pantothenate resulting in five diets with graded pantothenate levels of 5, 10, 20, 30 and 40 mg/kg diet. Each diet was fed to triplicate groups of hybrid striped bass juveniles (initial average weight 1.6 g) in a recirculating system at 26.0 ± 1 °C. Fish fed the unsupplemented basal diet performed poorly in terms of growth parameters and exhibited typical signs of pantothenic acid deficiency such as hemorrhages, sluggishness, high mortality, anemia and severe hyperplasia of the epithelial cells of gill lamellae. Fish fed the diet containing 10 mg of pantothenate/kg diet performed significantly better than fish fed the basal diet but poorly when compared with the responses of fish fed diets containing 20, 30 and 40 mg of calcium d -pantothenate/kg diet. Also, pantothenic acid-deficiency signs were apparent in fish fed the diet containing 10 mg/kg diet; whereas, no deficiency signs were observed in fish fed diets supplemented with the higher levels. Based on these data, the dietary pantothenic acid requirement of hybrid striped bass was quantified at 18.8 mg/kg diet based on broken-line regression analysis of weight gain data. Statement of relevance Pantothenic acid deficiency in hybrid striped bass was characterized and the minimum dietary pantothenic acid requirement was determined to be 18.8 mg/kg based on weight gain. This information will assist in refining diet formulations for hybrid striped bass. [ABSTRACT FROM AUTHOR]

To investigate the effects of stocking density on Korean rockfish culture, two rearing experiments, each including three densities and lasting 1 year, were performed. In the first experiment, the low, medium, and high stocking densities were 2.7, 3.9, and 5.6 kg/m 3 , respectively; in the second experiment, the densities were 3.9, 6.4, and 8.7 kg/m 3 , respectively. The temperature and salinity measured 6.9 °C–25.1 °C and 30.7–34.8 psu, respectively. The results showed that the average total lengths of the fish at low, medium, and high densities were 25.0 ± 0.1, 24.1 ± 0.2, and 23.6 ± 0.2 cm, respectively, with the fish in the low-density group growing significantly faster than those in the higher-density groups ( P < 0.05). The daily feeding rate did not vary significantly ( P > 0.05). The total outputs per unit area (kg/m 3 ) at low, medium, and high densities were 9.0, 14.2, and 18.7 kg/m 3 , respectively. These two results suggest that high-density cage culture of Korean rockfish could improve economic efficiency. To ensure the stable production of Korean rockfish by cage culture, comprehensive studies on other aspects of the process such as skeletal abnormality, disease, and health are necessary. [ABSTRACT FROM AUTHOR]

Teleosts and other aquatic ectotherms have the ability to withstand prolonged periods of low water temperatures (cold-acclimation) and fasting, and can often respond with phases of accelerated (compensatory) growth when favorable conditions are restored. We assessed whether complete feed restriction prior to (24°C, days 0–23) and/or during (14°C, days 24–114) a simulated period of cold-acclimation could elicit episodes of compensatory growth (CG) and catch-up growth upon warm-up to 24°C and satiation feeding (days 115–148). Control hybrid striped bass (HSB: Morone chrysops × Morone saxatilis) were fed to satiation throughout the entire experiment under these temperature fluctuations. Compensatory growth and ultimately catch-up growth were achieved in groups of HSB that were deprived of feed during either the initial period at 24°C (days 0–23), during the cold-acclimation period (14°C, days 24–114), or during both of these periods (days 0–114). Further, it appears that HSB are better able to compensate for weight loss when skeletal length is not significantly compromised during the treatment period, which occurred in HSB feed restricted during cold-acclimation only. The most dramatic CG responses were defined by specific growth rates (SGRs) up to 4.2 times that of controls and were accompanied by hyperphagia and improvements in temporal and overall feed conversion. Levels of plasma insulin-like growth factor (IGF)-1 and muscle IGF-1 mRNA were significantly correlated to growth rate for all groups throughout the experiment (R2 =0.40, 0.23, respectively), with an overcompensation of both observed in HSB with the most elevated SGRs during the CG response. Interestingly, opposing trends were observed between muscle mRNA expression of growth hormone receptor (GHR)-1 and -2, with fasting at 24°C and 14°C resulting in depressed levels of GHR-1 and elevated levels of GHR-2 relative to controls. Levels of muscle myostatin (MSTN)-1 mRNA were significantly depressed in HSB fasted at 24°C and/or 14°C while MSTN-2 mRNA was lower following initial feed restriction at 24°C. Likewise, levels of unprocessed pro-MSTN (precursor) and mature MSTN protein were both depressed in fasted fish at 24°C. This study demonstrates that a previous period of feed restriction and cold-acclimation followed by realimentation at more favorable water temperatures produces a strong CG response and catch-up growth in fish. These studies also suggest that an overcompensation of circulating and local IGF-1 along with changes in MSTN mRNA and protein expression may contribute to accelerated growth rates characteristic of CG. Furthermore, our studies indicate that overall feed conversion can improve by as much as 30% with CG induced through temperature and feeding manipulations with no adverse effects on growth of HSB. This raises the possibility that CG protocols can improve production efficiency of HSB and other temperate teleosts in pond or tank culture. [ABSTRACT FROM AUTHOR]

Marbled rockfish (Sebastiscus marmoratus) is a common coastal fish in China with considerable market value. The artificial culture of this species has not been widely popularized, and there have been few research on its vaccine or immune adjuvant. In this study, we performed transcriptome analysis of marbled rockfish spleen and liver tissue samples at 12 and 48 h after the polyinosinic-polycytidylic acid (poly(I:C)) challenge. Compared with the control group, 1067 and 598 differentially expressed genes (DEGs) were identified in the spleen and liver, respectively. GO, and KEGG enrichment analyses of DEGs revealed that some immune-related biological processes and pathways were significantly changed after poly(I:C) treatment, including primary immunodeficiency, the NF-kappa B signaling pathway, the Jak-STAT signaling pathway, and the PPAR signaling pathway. In conclusion, the findings of this research provide new insights into the immune response of marbled rockfish against poly(I:C) at the transcriptome level, and enrich the theoretical basis for the development of its immune adjuvant. • Transcriptome changes of the spleen and liver of marbled rockfish stimulated by poly(I:C) were detected using RNA-seq. • Differentially expressed genes were identified based on bioinformatics methods. • Gene annotation and functional analysis of DEGs revealed immune-related signaling pathways with significant enrichment. • This study would promote the understanding of the antiviral immune response mechanism of marbled rockfish. [ABSTRACT FROM AUTHOR]

Two trials on striped bass larvae, both 2 × 2 factorial design and 16 days duration starting at 12 days post-hatch (dph; 3 mg body weight, BW), compared the effect of stocking density (both trials 3 vs. 15 larvae/L; rearing volume 15 L) and daily fixed ration of stage II enriched Artemia (Trial 1: 1000 vs. 250; Trial 2: 250 vs. 50 Artemia per larva per day; Art/l/d) based on initial stocking density. Losses of larvae were categorized as either retrieved mortalities or 'missing' due to cannibalism. In Trial 1, ration (1000 vs. 250 Art/l/d) had a highly significant (p < 0.001) effect on both overall losses (4 vs. 22%) and final mean wet BW (55 vs. 18 mg), whereas stocking density had a minor influence on losses (p = 0.038), and no effect on final BW (p = 0.700). Losses due to cannibalism in Trial 1 were very low (< 3%). In Trial 2, by contrast, cannibal losses were up to 52%, and overall losses up to 80% primarily due to the low ration of 50 Art/l/d. Overall losses in Trial 2 were strongly dependent on ration (p = 0.028), but independent of stocking density (p = 0.426). Some cannibals grew very fast, their final BW > 10-fold greater than conspecifics. In a small production trial, larvae stocked at 15/L were offered a daily ration that increased progressively from 250 Art/l/d at 14 dph to 1200 Art/l/d at 29 dph. Survival was 95% due to negligible cannibalism. Overall, the study presents a protocol for the indoor intensive production of striped bass through the larval stage with minimal losses to cannibalism. • Cannibalism among striped bass larvae can be eliminated when sufficient food is provided. • Survival and growth of striped bass larvae were proportional to Artemia ration. • Survival and growth of striped bass larvae were independent of stocking density. • Losses due to cannibalism ranged from 0 to 52% dependent on Artemia ration. [ABSTRACT FROM AUTHOR]

Abstract: Many Korean rockfish farms (Sebastes schlegeli) have suffered from a disease causing high mortalities, since outbreaks of furunculosis first occurred in 2008. The aims of this study were to investigate the causal agent of the disease as well as the epidemiological aspects of its occurrence. Rockfish and low-value fish which are used as feed in rockfish farms were sampled and examined for isolation of the causal agent of the disease. All isolates derived from the rockfish were non pigmented, relatively slow-growing bacteria, which were characterized as atypical Aeromonas salmonicida. In particular, vapA gene sequences of the isolated bacteria were most closely related to A. salmonicida. Some of the sampled low-value fish, including big head croaker, Japanese anchovy, and Konoshiro gizzard shad, were infected with atypical A. salmonicida as well. In this study, a total of 22 isolates of A. salmonicida were each determined to be partially resistant to amoxicillin and to oxytetracycline and trimethoprim/sulfamethoxazole. The mean value generated by normalized resistance interpretive (NRI) analysis for florfenicol was 36.6mm, with a standard deviation (SD) of 2.2mm. Using a 2.0 SD limit, the wild type cut off value was ≥32mm, indicating that our isolates were all classified as wild type strains for florfenicol. This study indicates that low-value fish used as feed in the sea-cage rockfish farms are a key source of furunculosis, which may cause continuous disease incidence since the first outbreaks. [Copyright &y& Elsevier]

Abstract: Substitution of fishmeal with alternate proteins in aquafeeds often results in dietary imbalances of first-limiting essential amino acids (EAA) and poorer fish performance. This growth trial was undertaken to test the hypothesis that ideal protein theory accurately predicts first-limiting amino acids and optimum lysine level for a fishmeal-free, commercial-grade diet formulated for hybrid striped bass (HSB). The ideal model for formulation was the amino acid pattern of hybrid striped bass muscle. A negative control diet based on soybean (45%), corn gluten (10%), and poultry by-product (13%) meals was formulated on an ideal basis to contain 18% lipid, 40% crude protein (CP), 36% digestible protein (DP) and 1.8% Lys from intact sources. Met and Thr were then added at levels equivalent to 40% protein from HSB muscle to form a basal diet that was fortified with seven levels of Lys (2.2 to 6.4g/g diet) that bracketed the predicted ideal Lys requirement (3.5g/g diet) for this formulation. Diets were extruded to achieve similar characteristics as a commercial-grade feed and fed to juvenile fish (118g BW) for 84 d. Response data were subjected to polynomial and exponential regression and the best model per response selected based on the lowest error (MSE) and p-values and the highest adjusted R2. Selected models were used to derive dietary Lys levels required to reach 95% (R95) or 99% (R99) of the minimum or maximum response. Final fish weights (328–369g) increased linearly with increasing dietary Lys. Weight gain, average daily feed intake (1.42–1.7%), and feed efficiencies at 4-, 8-, and 12-week intervals were modeled by cubic functions that yielded consistent R95 and R99 levels of about 2.4 and 4.3g Lys/g diet, respectively. These values evenly bracketed the predicted ideal Lys requirement. Slightly higher Lys requirement was found for optimum FE at 4weeks and smaller fish, as opposed to 8 or 12weeks and larger fish. Whole body composition was unresponsive to diet Lys level; however, higher dietary Lys was required to minimize liver size (4.8 to 5.2g Lys/g diet) than to minimize body fat (2.5 to 3.1g Lys/g diet) or maximize muscle ratio (1.8 to 3.9g Lys/g diet). Whole body protein, lipid, energy, and EAA retentions were also consistent with cubic functions that generally confirmed the predicted ideal Lys requirement with notable exceptions. Retention of Lys decreased exponentially with increasing dietary Lys, whereas, Met retention decreased in a linear fashion, corroborating that Met was first-limiting in this diet formula, as predicted. Retention of Thr and branched-chain amino acids were optimized at higher Lys levels (3.9–4.5g/g diet) than those required to maximize growth parameters. Protein accretion (g/fish/d) responded quadratically to Lys intake predicting maximum deposition at 0.10 to 0.16g Lys/fish/d. Histological assessment of intestines in fish fed these high-soybean meal test diets did not reveal any lesions associated with enteritis for any diet and overall normal intestinal morphology was observed in all fish sampled. [Copyright &y& Elsevier]

Abstract: Various studies with fish species indicate that dietary arginine (Arg) and glutamine (Gln) supplementation may support an enhanced performance beyond simply improving weight gain. Therefore, a feeding trial was conducted to determine the effects of dietary Arg or Gln on growth performance, immune responses and intestinal morphology of juvenile hybrid striped bass, Morone chrysops × Morone saxatilis (4.1±0.02g, initial average weight). The basal diet was formulated from menhaden fishmeal and solvent-extracted soybean meal to contain 45% crude protein and 10% lipid. Arginine and Gln were singularly added to the basal diet at either 1% or 2% or both amino acids were added in combination at 1% to formulate experimental diets with adjustments in glycine to maintain all diets iso-nitrogenous. Fish were fed the experimental diets for a period of 8weeks, at the end of which final weight, specific growth rate and feed efficiency were significantly (P <0.05) higher in fish fed diets supplemented with Arg at either 1 or 2%, Gln at 1%, Arg and Gln both at 1%, but not in those fed the diet supplemented with Gln at 2%. Arginine and/or Gln supplementation tended to improve neutrophil oxidative radical production, but not significantly (P >0.05). However, significantly higher serum lysozyme activity was observed in fish fed the diet supplemented with Arg at either 1 or 2% and Gln at 1%. Intracellular superoxide anion production by hybrid striped bass macrophages also tended to increase, while extracellular superoxide anion production was significantly improved by supplementation of Arg at 1% and Gln at either 1 or 2% of diet. Morphometric analyses demonstrated positive effects of both dietary Arg and Gln on histo-morphological measurements in different portions of the gastrointestinal tract of hybrid striped bass. The 1% Arg diet resulted in the greatest increases in size of the chosen enteric structures, but the other four experimental diets also significantly improved the scores for various intestinal portions compared to fish fed the basal diet. Results from the present experiment demonstrate the importance of dietary supplementation of both Arg and Gln in improving growth performance, eliciting positive changes to several components of the innate immune system, and also benefiting the intestinal functionality of hybrid striped bass. [Copyright &y& Elsevier]

Abstract: Hybrid striped bass (Morone chrysops × M. saxatilis) aquaculture is a major commercial enterprise in the United States and internationally. Efforts to decrease diet costs and limit dependence on fishmeal have led to the development of plant-based diets as alternative aquafeeds. Due to limiting concentrations of some amino acids such as methionine and cystine, in plant meals such as soybean meal, supplementation of plant-based diets with methionine or other sulfur amino acid compounds may be required. High levels of soybean meal also may reduce the bioavailability of minerals such as zinc due to the inhibitory effects of phytate. Therefore, the current study was conducted to evaluate different sulfur amino acid and zinc supplements in soybean-meal-based diets with hybrid striped bass for possible refinement of diets and reduction of production costs. In the first feeding trial, a basal soybean-meal-based diet (56% soybean meal and 15% fishmeal) marginally deficient in total sulfur amino acids (TSAA) (1.10% methionine and cystine) was supplemented with either l-methionine, methionine hydroxyl analog (MHA) calcium salt or Mintrex® (liquid MHA with chelated zinc) and fed to triplicate groups of juvenile hybrid striped bass for 10weeks. The different methionine supplements provided similar weight gain, feed efficiency ratio (FER) and protein efficiency ratio (PER) values that tended to be greater than observed in fish fed the basal diet. Mintrex® supplementation provided much higher plasma zinc concentrations compared to fish fed the other methionine supplements. In additional feeding trials, a soybean-meal-based control diet containing l-methionine to satisfy the requirement for TSAA was supplemented with varying concentrations of zinc sulfate or Mintrex®, each to provide 5, 10, and 20μg Zn/kg diet, and fed to juvenile hybrid striped bass. The different zinc concentrations did not affect zinc integration into the scale or bone of hybrid striped bass after 8weeks of feeding. Zinc from zinc sulfate in comparison to Mintrex® was absorbed slightly but significantly better based on postprandial serum zinc concentrations of fish fed the two products at the same dietary zinc concentration; however, these absorption differences did not affect long-term zinc deposition in the scale and bone. [Copyright &y& Elsevier]

Aquaculture of hybrid Morone species is preferred over that of purebred strains due to their higher growth rates and resilience to a wide range of rearing conditions. One of the most popular hybrids is the sunshine bass, which is a cross between white bass (M. chrysops) females and striped bass (M. saxatilis) males. Yet, despite their growing economic importance, a detailed description of sunshine bass larval development under captive conditions is missing. Here, we provide a detailed staging system of hatchery-reared sunshine bass larvae. Based on externally visible features, we define 15 distinct stages from hatching to juvenile stage (2–43 days post-fertilization). We identified a biphasic pattern of larval growth, with a 2-fold increase in growth rates (from 0.2 to 0.4 mm/day) around the onset of metamorphosis and larger variations in length and weight after the completion of metamorphosis. Both age (R2 = 0.93) and standard length (R2 = 0.89) were good predictors of larval stage. Overall, this work provides a reference for studies of factors that affect sunshine bass larval development and, thus, is an important step towards resolving bottlenecks in larval rearing operations in this species. [Display omitted] • A developmental atlas for the commercially important sunshine bass was missing. • We provide a detailed staging system for larval development of this fish. • Both age and standard length are good predictors of the larval stage. • The staging system can be used to precisely map and diagnose developmental delays. • The staging system can be used as a tool to optimize indoor larval rearing operations. [ABSTRACT FROM AUTHOR]

Chemokines are a superfamily of structurally related cytokines, which could interact with chemokine receptors, a superfamily of seven-transmembrane domain G-coupled receptors, to play crucial roles in guiding cell mobilization in development, homeostasis, and immunity. Among them, the CC subfamily is the largest subfamily with several members. In the present study, 24 CC chemokine ligands and 12 CC chemokine receptors were systematically identified from Black rockfish (Sebastes schlegelii). Sequence analyses indicated that most CC chemokine ligands, located in extracellular region, possess SCY domain, and CC chemokine receptors, located in plasma membrane, harbored the seven-transmembrane-region domain. Subsequently, the phylogeny, synteny, genome organization, and evolutionary analyses were performed to annotate these genes, and revealed that the tandem duplications (CCL19, CCL20a, CCL32, CCL33, CCL36, CCL38, CCR2, and CCR8), the whole genome duplications (CCL20, CCL25, CCR6, CCR9, and CCR12), and the teleost-specific members (CCL32–36, CCL38, CCL39, CCL44, and CCR12) led to the expansion of CCLs and CCRs in S. schlegelii. In addition, CCLs and CCRs were ubiquitously expressed in nine examined healthy tissues, with high expression levels in gill, head kidney, and spleen. Moreover, most CCLs and CCRs were significantly differentially expressed in head kidney, liver, and gill after A. salmonicida infection, and their expression patterns exhibited tissue-specific and time-dependent manner. Finally, the protein-protein interaction network (PPI) analysis indicated that CCLs and CCRs interacted with a few immune-related genes such as interleukins, CD genes, and TLR genes, etc. These results should be valuable for comparative immunological studies and provide insights for further functional characterization of chemokines and receptors in teleost. • 24 CC chemokines and 12 CC receptors were identified in Sebastes schelgelii. • Tandem duplications and teleost-specific members led to the expansion of CC chemokines in Sebastes schelgelii. • CCLs and CCRs were expressed at high levels in gill, head kidney, and spleen. • Most genes were significantly differentially expressed in head kidney, liver, and gill after Aeromonas salmonicida infection. • CCLs and CCRs interacted with interleukins, CD genes, and TLRs, etc. [ABSTRACT FROM AUTHOR]

Abstract: The present study evaluates the extent to which the viviparous reproductive strategy that characterizes the genus Sebastes (rockfish) can be expressed in culture. In addition, the growth patterns of rockfish were examined during the early phases of growth pertinent to the culture of the species. Using grass rockfish (Sebastes rastrelliger) as our model, it was demonstrated that all phases of ovarian seasonal cyclicity could proceed under controlled environmental conditions. Rockfish successfully spawned in our facility and subsequently passed through successive phases of oocyte development during the normal reproductive season before follicular atresia was observed in the absence of fertilization. Fish introduced into culture in an advanced stage of vitellogenesis became pregnant in the absence of males 14–55 days later. This observation is consistent with the view that delayed fertilization occurs in rockfish and establishes that wild caught specimens for spawning purposes are not confined to pregnant females. By monitoring growth parameters in two groups of brown rockfish (S. auriculatus) introduced into culture during their first and second year of development a comprehensive picture of early growth was established. Overall changes in both weight and length followed a sigmoid curve comprising an early phase of exponential growth transitioning to a phase of exponential decay. The constituent phases of this curve, as expressed in the two age groups, and the combined growth data over a period of 1083 culture-days were precisely described by the Gompertz equation. This equation also described the growth of young-of-the-year copper rockfish (S. caurinus) with similar accuracy. Validation of the applicability of our Gompertz equation was achieved by reference to growth parameters of brown rockfish of known age raised from birth at UCSB. Our mathematical model precisely depicted growth with age from birth to the period of sexual maturity. These data on growth in relation to age may find broad application in fisheries management plans allowing for evaluation of population changes over time and be useful in determining and improving the culture potential of nearshore rockfish species. [Copyright &y& Elsevier]

Abstract: Total plasma protein (TPP) is a broad clinical indicator of health, stress, and well being. A simple and rapid technique for determining TPP is refractometry, which measures the refractive index of all dissolved materials in solution. It was hypothesized that plasma dissolved solids in fish held at increasing salinity levels would result in plasma samples with a higher refractive index and affect true TPP readings. Efficacy of refractometry over a range of salinities was evaluated by comparing TPP values obtained by refractometry with those obtained by a dye-binding assay (Biuret method) specific to proteins. Blood analytes were evaluated in hybrid striped bass Morone chrysops × M. saxatilis (HSB) acclimated to nominal salinities of 0, 10, 20, and 30 g L−1. Hybrid striped bass acclimated to hypertonic environments exhibited higher (P <0.05) electrolytes, TPP, and osmolality than those acclimated to low salinity, but were still within the normal reference interval for HSB. Although salinity affected TPP determined by both methods, the observed increase in TPP values over the range of salinities was significantly greater in samples analyzed by refractometry. Total plasma protein concentrations measured by refractometry were always higher and the difference in absolute values determined by the two methods appears to be caused by a factor not measured in this investigation. It is concluded that refractometry is not well suited for analyzing accurate TPP in HSB or determining relative changes in TPP across a range of salinities. [Copyright &y& Elsevier]

Abstract: Commercially farmed, hybrid striped bass – female white bass (Morone chrysops) crossed with male striped bass (Morone saxatilis) – represent a rapidly growing industry in the United States. Expanded production of hybrid striped bass, however, is limited because of uncontrolled variation in performance of fish derived from undomesticated broodstock. A 10×10 factorial mating design was employed to examine genetic effects and heritability of growth-related traits based on dam half-sib and sire half-sib families. A total of 881 offspring were raised in a common environment and body weight and length were recorded at three different times post-fertilization; parentage of each fish was inferred from genotypes at 10 nuclear-encoded microsatellites. Dam and sire effects on juvenile growth (weight and length) and growth rate were significant, whereas dam by sire interaction effect was not. The dam and sire components of variance for weight and length (at age) and growth rate were estimated using a Restricted Maximum Likelihood algorithm. Estimates of broad-sense heritability of weight, using a family-mean basis, ranged from 0.67±0.17 to 0.85±0.07 for dams; estimates for sires ranged from 0.43±0.20 to 0.77±0.10. Estimates of broad-sense heritability of growth rate (based on weight), using a family-mean basis, ranged from 0.69±0.12 to 0.82±0.09 for dams and from 0.69±0.13 to 0.81±0.08 for sires. Similar results were obtained with length data. Both genetic and phenotypic correlations between weight and length were close to unity. High genetic (0.98–0.99) and phenotypic (0.79) correlations between growth rates measured at two time intervals suggested that selection for growth rate at an early life stage could affect growth rate at a later life stage. Estimates of general combining ability (GCA) for growth rates differed significantly among dams and among sires, whereas estimates of specific combining ability (SCA) for each dam×sire combination did not differ significantly from zero. These results suggest that additive-effect genes contributed to the differences in juvenile growth. [Copyright &y& Elsevier]

Abstract: Three separate experiments were conducted with juvenile hybrid striped bass to determine the effects of levamisole as a feed supplement on growth performance, innate immunity and specific antibody responses, as well as resistance to Streptococcus iniae and Aeromonas hydrophila infection. A basal diet was formulated to contain 40% protein, 10% lipid and an estimated digestible energy level of 3.5 kcal/g. Four levels (100, 250, 500 and 1000 mg/kg) of levamisole were added to the basal diet in place of cellulose. After the 3-week feeding period in feeding trial 1, enhanced weight gain was generally observed in fish fed the diets supplemented with a low level (<500 mg/kg) of levamisole. Dietary supplementation of levamisole at 100 mg/kg significantly (P <0.05) enhanced growth and feed efficiency, compared to fish fed the basal diet. Fish fed diet supplemented with 1000 mg levamisole/kg diet showed chronic toxicity signs of inferior growth, reduced feed intake and feed efficiency. Although the extracellular superoxide anion production of head kidney cells, hematocrit, serum lysozyme and peroxidase were not significantly affected by dietary treatments, intracellular superoxide anion production of head kidney macrophages of fish fed 250 mg levamisole/kg diet was significantly (P <0.05) higher than that of fish fed the other four diets. The hypothesized benefits of dietary supplementation of levamisole in reducing mortality from infection of pathogenic bacteria including S. iniae and A. hydrophila were not proven after two separate 3-week feeding trials and disease challenges in the present study. Agglutinating antibody titers of individual fish were highly varied and not significantly influenced by dietary levamisole at the tested levels. [Copyright &y& Elsevier]

Abstract: Adult striped bass (Morone saxatilis) were exposed to various combinations of constant or anually-cycling daylength and water temperature. Constant conditions (15 h days, 18 °C) were those normally experienced at spawning and cycling conditions simulated natural changes at Chesapeake Bay latitude. Females exposed to constant long (15 h) days and cycling water temperature (TEMPERATURE group) had blood plasma levels of sex steroids (testosterone [T] and estradiol-17β [E2]) and vitellogenin (Vg), and profiles of oocyte growth, that were nearly identical to those of females held under a natural photothermal cycle (CONTROL group). Several fish from these two groups were induced to spawn fertile eggs. Females constantly exposed to warm water (18 °C), with or without a natural photoperiod cycle (PHOTOPERIOD and STATIC groups, respectively), had diminished circulating levels of gonadal steroid hormones and Vg, impaired deposition of yolk granules in their ooplasm, and decreased oocyte growth, and they underwent premature ovarian atresia. Males exposed to cycling water temperature (CONTROL and TEMPERATURE groups) spermiated synchronously during the natural breeding season, at which time they also had had high plasma androgen (T and 11-ketotestosterone [11-KT]) levels. The timing of spermiation was highly asynchronous among males in groups of fish held constantly at 18 °C (STATIC and PHOTOPERIOD groups) and this asynchrony was associated with diminished plasma androgen levels. Termination of spermiation by males exposed to cycling water temperature coincided with a sharp decline in levels of plasma androgens about a month after water temperature rose above 18 °C. In contrast, most males held constantly at 18 °C sustained intermediate levels of plasma androgens and spermiated until the end of the study in late July. The annual cycle of water temperature clearly plays a prominent role in the initiation, maintenance, and termination of the striped bass reproductive cycle. In females, a decrease in water temperature below values experienced at spawning appears to be required for vitellogenesis and oocyte growth to proceed normally. Constant exposure of males to spawning temperature disrupts synchronous spermiation but also delays testicular regression, which may be useful for spawning fish after the natural reproductive season. [Copyright &y& Elsevier]

Abstract: Domesticated male striped bass were selected as high cortisol stress responders (HCR) or low cortisol stress responders (LCR) by ranking mean 1-h post-stress plasma cortisol levels following a 2-min standardized net challenge once per month for four consecutive months. During the selection period, HCR and LCR fish maintained a significant divergence in post-stress cortisol levels, but these differences were abolished coincident with the onset of sexual maturation. LCR fish stressed monthly during gonadal maturation and weekly during the spawning season had plasma testosterone (T) and 11-ketotestosterone (11-KT) levels 3–5 times lower than stressed HCR fish. During the simulated spawning season, plasma cortisol and glucose levels were moderately elevated but similar in HCR and LCR fish. There were no differences in sperm quality between HCR and LCR males; however, more HCR fish began spermiating earlier and maintained a spermiation response longer than LCR fish. There were no significant differences in weight, length or coefficient of condition, but HCR fish had a significantly greater specific growth rate on two sample intervals when compared to LCR fish. These results show that male striped bass selected for low cortisol stress responsiveness and exposed to repeated stress have diminished circulating levels of T and 11-KT associated with a shorter duration spermiation response when compared to males selected for high cortisol stress responsiveness. The data suggest that LCR male striped bass subjected to significant stress during maturation and spawning may have impaired reproductive performance. [Copyright &y& Elsevier]

Abstract: In previous studies, we found that rapidly confined hybrid striped bass (Morone saxatilis male×Morone chrysops female) developed a syndrome characterized by the immediate and dramatic loss of their skin. We have named this phenomenon the Acute Ulceration Response (AUR). AUR is characterized by the rapid onset of severe epidermal degeneration, erosion, and ulceration on the body skin and fins, as well as corneal ulceration, in stressed hybrid striped bass. In the present study, we have shown that acute confinement stress can also cause AUR in a taxonomically wide array of fish species, including guppy (Poecilia reticulata), freshwater angelfish (Pterophyllum scalare) and channel catfish (Ictalurus punctatus) after a 2-h stress. However, we could not induce AUR in rainbow trout (Oncorhynchus mykiss). The AUR lesions were similar to those seen previously in hybrid striped bass. As AUR might be expected to predispose fish to secondary microbial infections, we examined the skin of hybrid striped bass for bacterial infection after experimental induction of AUR. These experiments showed that even fish with severe skin damage could rapidly heal their wounds without obvious consequences within several days. Bacterial numbers in AUR lesions remained low, ∼104 cfu/g of fin tissue, throughout the recovery period. However, if hybrid striped bass with AUR were exposed to even low doses (1 zoospore/ml) of the water mold Saprolegnia, a relatively weak, opportunistic pathogen, the fish developed severe saprolegniosis as soon as 48 h after challenge, with 87.5% infected and 87.5% dead within 4 days post-challenge. In contrast, none of the control fish (no AUR, but exposed to Saprolegnia) developed saprolegniosis. These data provide strong evidence that AUR might play a critical role in skin ulcer epidemics of many fish species that are preceded by an acute stress. Furthermore, our data suggest that environmental pathogen load plays a critical role in determining if AUR lesions will heal spontaneously or instead will lead to devastating disease losses. [Copyright &y& Elsevier]

Abstract: This study was conducted to evaluate the effects of dietary microbial phytase supplementation on nutrient digestibility, growth performance and body composition in juvenile Korean rockfish fed soybean meal-based diets. Nine experimental diets were formulated to be isonitrogenous and isocaloric to contain 48.6% crude protein (CP) and 15.9 kJ of available energy/g with or without dietary phytase (Natuphos-5000™, BASF, NJ, USA) supplementation. White fish meal (FM) provided 89.1% of the total protein in the basal diet (S0), in the other eight diets, 30 or 40% FM protein was replaced by soybean meal: 70% FM+30% soybean meal (S30); 70% FM+30% 1000 U phytase pretreated SM (S30PP1000); 70% FM+30% SM+1000 U phytase/kg diet (S30P1000); 70% FM+30% SM+2000 U phytase/kg diet (S30P2000); 60% FM+40% SM (S40); 60% FM+40% 1000 U Ptre SM (S40PP1000); 60% FM+40% SM+1000 U phytase/kg diet (S40P1000); and 60% FM+40% SM+2000 U phytase/kg diet (S40P2000). After 2 weeks of the adaptation, triplicate groups of 20 fish initially averaging 7.25±0.04 g (mean±S.D.) were randomly distributed into the aquarium and were fed one of the experimental diets for 8 weeks. By the end of the 8-week feeding trial, supplementation of phytase significantly improved the apparent digestibility coefficient (ADC) of phosphorus in rockfish diets (P<0.05) containing 30% and 40% soybean meal regardless of the level and method of phytase supplementation. Supplementation of phytase significantly increased the ADC of dry matter in diets containing 30% soybean meal (P<0.05). However, phytase had no influence on growth performance and whole body composition of fish. The pretreatment of soybean meal with 1000 U phytase improved weight gain (WG) when 30% fish meal protein was replaced by soybean meal. Based on the experimental results, we conclude that supplementation of phytase can improve the apparent digestibility coefficient of phosphorus in Korean rockfish. [Copyright &y& Elsevier]

Two species of freshwater stenohaline fish (channel catfish, Ictalurus punctatus; and goldfish, Carassius auratus) and four species of euryhaline fish (rainbow trout, Oncorhynchus mykiss; brown trout, Salmo trutta; striped bass, Morone saxatilis; and Gulf sturgeon, Acipenser oxyrinchus desotoi) were raised in salinities from 0‰ to 9‰, and then their resting ammonia and urea excretion were compared. The ammonia excretion of channel catfish, goldfish, rainbow trout, and brown trout was higher in 9.0‰ salinity than in the other tested salinities, but ammonia excretion by Gulf sturgeon and striped bass was lowest in 9.0‰ salinity. The urea excretion of goldfish and channel catfish increased with increasing salinity, while that of Gulf sturgeon did not change and that of all other species decreased. In the higher salinities, excretion of urea-N as a percentage of the total nitrogen excretion (ammonia-N plus urea-N) increased for channel catfish, goldfish, and Gulf sturgeon but decreased for the other species. Overall, the effects of salinity were similar for two stenohaline species, while the euryhaline species were more variable. [Copyright &y& Elsevier]

In the present study, motility, ultrastructure and fertilization capacity of fresh and cryopreserved striped bass spermatozoa were investigated in order to evaluate semen dilution ratio, freezing rate and cryomedia. Four dilution ratios (semen/cryomedia), and four freezing rates were evaluated on the basis of post-thaw sperm motility. The dilution ratio of 1:3 yielded the highest (P<0.05) post-thaw motility. Sperm cryopreserved with a freezing rate of -40°C min-1 resulted in a higher percentage of motile sperm (P<0.05) than other lower freezing rates we examined. Six cryomedia with various dimethyl sulfoxide (DMSO) and glycine concentrations were tested for their influences on ultrastructure, post-thaw motility and fertilizing capacity of cryopreserved sperm. The ultrastructural results revealed that the plasma membranes of spermatozoa were better protected with the higher DMSO concentrations we examined. Two cryomedia containing 5% or 7.5% DMSO, both with glycine added, resulted in the highest (P<0.05) post-thaw motility compared with other cryomedia without glycine. The percentage of eggs fertilized with sperm cryopreserved in six cryomedia ranged from 26±2.1% (2.5% DMSO without glycine) to 54±5.6% (7.5% DMSO with glycine), which were equivalent to 44% and 90% of fresh semen controls. No differences (P>0.05) were detected in the percentage of eggs fertilized among DMSO concentrations that did not contain glycine, although post-thaw motility did vary significantly (P<0.05) in these treatments. These results suggest that adding glycine to our basic cryomedia containing DMSO increases the fertilization capacity of these cryopreserved spermatozoa. [Copyright &y& Elsevier]

Viviparous black rockfish, Sebastes schlegeli, mate in November, fertilization occurs in the following April and birth of larvae in May at the Miyako Station of the Japan Sea-Farming Association (JASFA). Developmental stages of intra-ovarian embryos in individual female black rockfish reared in an indoor tank were examined using a cannulation method on almost the same day (April 24 or 25) for three successive years. The estimated delivery occurred near the predicted date regardless of the year. This indicates that black rockfish have individually specific annual cycle of fertilization and embryonic development. Understanding individual annual cycles of parturition is very useful for efficient broodstock management and juvenile production for aquaculture and stock enhancement. [Copyright &y& Elsevier]

Future expansion of the hybrid striped bass (Morone saxatilis) industry is limited in part by continued reliance upon wild sources for seedstock and the absence of domesticated broodstocks. Inherent in the development of a domesticated stock is the ability to identify and select individuals with superior performance attributes. Since the response to stress is a characteristic that may be of value in a culture environment, we evaluated a population of male striped bass for relative stress responsiveness. Male broodstock comprised of three families (MD, MD36 and NC) were exposed to a 1-min net challenge monthly for six consecutive months and then bled 1-h following the stressor. Mean plasma cortisol was highest (295±20.4 ng/ml) in July and reached its lowest level (88±10.9 ng/ml) in December at the end of the study suggesting that the fish adapted to the stressor. When fish were ranked for stress responsiveness based on their mean cortisol levels, high responders (HR; n=6) could be distinguished from low responders (LR; n=6) on the first three sample dates. When the fish were segregated by family, NC fish had significantly lower post-stress plasma cortisol and glucose levels when compared to MD and MD36 fish suggesting that the stress response is a genetically linked trait in striped bass as shown for other species. Selected HR fish were significantly longer than LR fish throughout the study but their weights were not significantly different. However, LR individuals had significantly better condition than HR fish throughout the study suggesting that there may be differences in energy partitioning between the two groups. Selected HR fish injected with bovine corticotropin releasing hormone (bovine corticotropin releasing hormone (bCRH); 50 μg/kg BW) had significantly greater plasma cortisol levels than injected LR fish 1 and 3 h following injection. Cortisol in bCRH-injected LR individuals did not change from pre-injection values. Plasma glucose in bCRH-injected animals followed a profile commonly observed following a stressful event, but there was no difference between HR and LR individuals. These results indicate that post-stress plasma cortisol levels are useful for identifying divergent stress responsiveness in male striped bass. [Copyright &y& Elsevier]

This study was designed to test the possibility that Streptococcus iniae enters through the gills and causes infection in hybrid striped bass. To determine the dose response, four groups of fish were inoculated with S. iniae via the gills with a dose of 5.0×105, 2.6×106, 5.0×106, or 1.0×108 CFU/fish. One group of fish was inoculated with tryptic soy broth (TSB) via the gills to serve as controls. The cumulative percent mortality was 13%, 27%, 100% and 100% for 5.0×105, 2.6×106, 5.0×106 and 1.0×108 CFU/fish, respectively. We also examined the tissue dissemination of S. iniae at 0.5, 4, 8, 12, 24, 48 and 72 h after experimental gill inoculation. Fish were inoculated with 2.6×106 or 5.0×106 CFU/fish, which caused low and high mortality, respectively. Within 48 h, fish inoculated with the 2.6×106 dose were culture positive on the gill surface, blood of the first and second gill arches, blood of the third and fourth gill arches and the nares. However, for the dose of 5.0×106 CFU/fish, S. iniae was also isolated from the olfactory, optic and cerebellum regions of the brain, eye, head kidney, trunk kidney, spleen and liver at 48 h. For the 2.6×106 dose, S. iniae was not isolated until 48 h post-inoculation, but was isolated at 12 h for the 5.0×106 dose. The results of this study indicate that S. iniae can enter hybrid striped bass through the gills. However, mortality at similar S. iniae doses was lower than we previously observed by inoculation of the nares. [Copyright &y& Elsevier]

Two separate feeding trials were conducted to evaluate graded levels of dried brewers yeast in the diet of hybrid striped bass. A basal diet was formulated to contain 40% protein, 10% lipid and an estimated digestible energy level of 3.5 kcal/g. In Trial 1, three incremental levels of dried brewers yeast (1%, 2% and 4% of diet) were added to the basal diet in place of cellulose. In Trial 2, the same levels of brewers yeast were added to the basal diet, but menhaden fish meal and menhaden oil were adjusted to provide isonitrogenous and isolipidic diets. Each diet was fed to three (Trial 1) or four (Trial 2) replicate groups of juvenile hybrid striped bass twice daily at rates approximating apparent satiation for 6 or 8 weeks. After the second feeding trial, a Streptococcus iniae bath challenge was executed to test the effects of diet on disease resistance.Enhanced weight gain and feed efficiency were generally observed in fish fed the diets supplemented with yeast compared to the basal diet in both trials. In the second trial, body composition of whole fish, hemocrit and serum lysozyme levels were observed to be within normal ranges and not influenced by the various dietary treatments. After 9 weeks of feeding in the second trial, exposure to S. iniae resulted in no mortality and reduced signs of disease in fish fed diets supplemented with 2% and 4% brewers yeast, while 20% mortality was observed in fish fed the control diet (P=0.1).In the second trial, blood neutrophil oxidative radical production, extracellular and intracellular superoxide anion production of head kidney macrophages and serum lysozyme were measured after 16 weeks of feeding each diet. Fish fed the diet with 2% brewers yeast were found to have significantly (P<0.01) higher blood neutrophil oxidative radical and extracellular superoxide anion production of head kidney macrophages than control fish. However, no significant differences in intracellular superoxide anion and serum lysozyme were observed among the treatments.Based on the result of this study, it is concluded that brewers yeast positively influenced growth performance and feed efficiency of hybrid striped bass as well as resistance to S. iniae infection. In addition, results of immune response assays demonstrate that brewers yeast can be administered for relatively long periods without causing immunosuppression. [Copyright &y& Elsevier]

A feeding trial of three dietary digestible protein (DP) levels (37%, 42% and 47%) and two dietary digestible lipid (DL) levels (7% and 14%) factorial design with three replications was conducted to investigate the proper dietary protein and lipid (energy) levels for the growth of juvenile rockfish. Fish, average initial weight 21.9 g, were fed the experimental diets for 20 weeks. Weight gain improved with increasing dietary DP and DL levels. Weight gain of fish fed the diet containing 47% DP was significantly higher (P<0.05) than that of fish fed the diet containing 37% DP, and was not different from that of fish fed the diet containing 42% DP at the 14% DL level. However, weight gain was not significantly affected by dietary DP level at the 7% DL level. Feed efficiency ratio of fish was improved as dietary DP and DL levels increased, whereas there was no significant difference between those of fish fed the diets containing 42% or 47% DP at the same dietary DL level. Feed efficiency ratio of fish fed the 14% DL diets was significantly higher (P<0.05) than that of fish fed the 7% DL diets at the same DP level. Hepatosomatic index (HSI), visceralsomatic index (VSI), protein efficiency ratio, and protein retention were significantly influenced by dietary DL level, but not by dietary DP level. Daily feed intake tended to decrease with increasing DP and DL levels. Lipid contents of whole body, liver and viscera increased with increasing DP and DL levels, whereas dorsal muscle lipid was not affected by dietary DP and DL levels. The apparent digestibility coefficients (ADC) of protein and nitrogen-free extract (NFE) were not significantly affected by dietary DP and DL, while ADC of dry matter, lipid and energy increased with dietary DP and DL. The results of this study indicate that an increase of dietary lipid level has protein-sparing effect, and the diet containing 42% DP and 14% DL (4.2 kcal DE/g diet) is optimal for growth and effective protein utilization of juvenile rockfish. [Copyright &y& Elsevier]

Diploid and triploid sunshine bass (white bass ♀×striped bass ♂) were produced in 1990 at Florida''s Richloam Fish Hatchery. Triploidy was induced with hydrostatic pressure. Fry were cultured to phase I in earthen ponds in Webster and Gainesville, FL, and transported to Leetown, WV, where they were held in circular flow-through fiberglass tanks. Ploidy of treated fish was determined with a Coulter counter and triploids were segregated from diploids. In April 1991, control diploid and triploid populations were graded to remove the largest and smallest individuals, and four 0.2-ha hypalon-lined ponds were stocked with 600 fish each; two ponds contained triploids and two contained diploids. Triploids and diploids were not significantly different in average fork length (FL) or weight at stocking. Triploids averaged 231 mm and 181.2 g, compared to diploid averages of 233 mm and 188.9 g. Monthly samples indicated that diploids grew faster than triploids; mean weights and lengths were both significantly different after 3 months. When harvested in October, triploids averaged 358 mm and 867.9 g, whereas diploids averaged 381 mm and 1153.5 g. Survival of triploids and diploids was 97.0% and 95.9%, respectively. Mean standing crop was 2496.3 kg/ha for triploids and 3280.6 kg/ha for diploids. Male diploids and most female diploids were sexually mature at 2 years of age. Sterility of triploids was confirmed as gonads remained reduced and dysfunctional at 5 years of age. [Copyright &y& Elsevier]

Apparent digestibility coefficients of dry matter, crude protein, energy, and amino acids in white fish meal, anchovy meal, meat meal, feather meal, blood meal, soybean meal, corn gluten meal, cottonseed meal, wheat flour, and brewer''s yeast were determined for juvenile and grower rockfish. Apparent digestibility coefficients were determined using a reference diet with chromic oxide indicator and test diets that contained 70% reference diet, by weight, and 30% of the feed ingredient being evaluated. The juvenile and grower fish averaging 30 and 300 g were held in 200 l tanks at a density of 50 and 8 fish per tank, respectively. Feces were collected from three replicate groups of fish using a fecal collection column attached to fish rearing tank. Apparent dry matter digestibility of ingredients decreased as nitrogen-free extract or fiber contents of ingredients increased, ranging from 73–95% for animal products and corn gluten meal to 32–54% for soybean meal, cottonseed meal, wheat flour and brewer''s yeast. Apparent energy digestibility of ingredients followed similar trends to differences in dry matter digestibility. Apparent protein digestibilities of animal and plant products ranged 63–95% and 73–92%, respectively. White fish meal, anchovy meal, meat meal, and corn gluten meal showed the higher protein digestibility among ingredients tested (P<0.01), regardless of fish size. Apparent digestibilities of protein and energy were not affected by fish size (P>0.05), except for feather meal. These data provide more precise information concerning nutrient and energy utilization of rockfish and will allow ingredient substitutions in practical feed based on levels of available nutrients. [Copyright &y& Elsevier]

NLR (NOD-like receptor) is a large class of cytoplasmic family protein that belonging to the pattern recognition receptors (PRRs), which exerts autoimmune activities by detecting pathogen-associated molecular patterns (PAMPs) and regulating immune related pathways. Black rockfish (Sebastes schelgelii) is an important economic fish widely located in coastal areas of East Asia. With the enlargement of its cultivation scale, various pathogens threaten its production, which resulted in dramatic economic losses. However, little information is available about the NLR genes in S. schlegelii. In this study, 23 NLR genes were identified and classified in S. schlegelii based on the whole genome database. Phylogenetic analysis showed that these NLR genes was clearly divided into five subfamilies. Comparison of copy numbers in vertebrates showed NLRC3 or NLRC3-like genes expanded in teleost fish about ~5–50 million years ago. The Ka/Ks ratios of most NLR genes were less than one, indicating they underwent purifying selection except for APAF1. Protein-protein interaction analysis showed that NLR proteins interacted with immune molecules such as caspase, ripk2 and TRAF. Besides, the expression patterns of NLR genes in mucosal tissues after Edwardsiella tarda infection were investigated by qRT-PCR. These results provided valuable evidence for understanding of the immune regulation mechanism and function of NLR genes in S. schlegelii. • Totally, 23 NLR genes were identified in S. schelgelii. • The characteristics and expression patters to E. tarda of NLRs were analyzed. • The expansion time of fish-specific NLRC3 or NLRC3-like family were estimated. [ABSTRACT FROM AUTHOR]

Artificial diets affect the growth and gut morphology of carnivorous fishes. In this study, we compared a laboratory raised rockfish, Sebastes schlegelii (a carnivore), fed an artificial diet (Lab fish), and the wild-captured rockfish (Wild fish) to confirm the effect of an artificial diet on pyloric caecal morphology and motility. We also established an in vitro method to quantify pyloric caecal sac motility and compared it between Lab and Wild fish. The pyloric caecal length per unit body length, the pyloric caecal weight per unit body weight, and the pyloric caecal weight per length were significantly greater in the Wild fish than in the Lab fish. Additionally, both of the circular and longitudinal muscularis layers were significantly thicker in the Wild fish than in the Lab fish. The pyloric caecal motor frequency of the Wild fish was higher than that in the Lab fish, but the contractile pressure of the pyloric caeca did not change under conventional conditions. These results suggest that the thickness of the tunica muscularis of the pyloric caeca may be involved in its motility, and the pyloric caeca of the Lab fish may not be able to provide functionality in this respect. In conclusion, under artificial rearing conditions, the artificial diet reduced the thickness of the tunica muscularis and reduced the motor frequency of the pyloric caeca in rockfish. • An in vitro assay method for fish pyloric caecal motility was established. • Pyloric caeca (PC) of Kurosoi rockfish were compared between lab-reared fish (Lab fish) and wild fish. • PC motor frequency was lower in Lab fish. • PC tunica muscularis in Lab fish was atrophied. • Artificial diets likely lead to muscle atrophy, affecting motor frequency. [ABSTRACT FROM AUTHOR]

A dietary requirement for the sulfonic acid taurine has been documented in many marine species. However, it has not been well studied in hybrid fish with freshwater and marine genes, such as the hybrid striped bass (Morone chrysops x M. saxatilis). Therefore, an 8-week feeding trial was conducted to evaluate the effects of various levels of dietary taurine on growth performance, health, and body composition of juvenile hybrid striped bass. Four diets were formulated from practical ingredients and supplemented with DL-methionine at 0.54% of dry weight to meet the hybrid striped bass' established total sulfur amino acid requirement of 1.0% of dry diet, and taurine was supplemented incrementally at 0, 0.5, 1, and 2% of dry weight. Two additional diets were prepared without DL-methionine supplementation to be marginally deficient in methionine (0.49% by weight) and either supplemented with or without taurine at 1% dry weight to evaluate the potential interactions between methionine and taurine. Diets containing increment levels of taurine were determined to show no significant (P >.05) differences in terms of weight gain, feed efficiency (FE), whole-body composition, hepatosomatic index (HSI), intraperitoneal fat ratio (IPF ratio), or muscle yield. However, hybrid striped bass fed the methionine-deficient diets had significantly (P <.05) reduced percentage weight gain and FE as well as reduced muscle yield and HSI compared to fish fed the methionine-supplemented diets. Interestingly, taurine inclusion at 1% in the diet containing 0.49% methionine increased weight gain and feed efficiency of fish compared to those fed the diet without supplemental taurine or methionine. These results indicated that growth performance and body composition of hybrid striped bass did not respond to taurine supplementation when dietary methionine was adequate but did respond when dietary methionine was limiting. • Taurine supplementation up to 2% of dry diet increased plasma taurine concentrations in hybrid striped bass. • Taurine supplementation up to 2% of dry weight in a methionine-sufficient diet did not significantly enhance growth performance. • Taurine supplementation in a methionine-deficient diet increased growth performance similar to a methionine-sufficient diet indicating sparing of the sulfur amino acid requirement. [ABSTRACT FROM AUTHOR]