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The rockfish (Sebastes schlegeli) and striped beakperch (Oplegnathus fasciatus) were released in marine ranching areas in Korea, Japan, and China to maintain fishery resources in coastal areas. To estimate the density and biomass of fishery resources, the target strength (TS) of target marine organisms is needed to scale integrated volume backscattering coefficients. In this study, the target strength–length (TS–L) relationship for live rockfish and striped beakperch was derived using ex situ methods at a frequency of 200 kHz. The TS-L function for rockfish and striped beakperch can be expressed as TSAvg. = 20logTL − 69.25 (R2 = 0.35) and TSAvg. = 20logFL − 67.01 (R2 = 0.31), respectively. These results can be used to assess the growth, density, and abundance of the two species using acoustics. [ABSTRACT FROM AUTHOR]

Objective: The Striped Bass Morone saxatilis is one of the most sought‐after recreational fish species along the US Atlantic coast. Regulations and a strong conservation ethic among anglers make Striped Bass among the most frequently released coastal marine fishes. A recent rule requires anglers to use circle hooks when targeting Striped Bass with natural baits, yet the conservation benefit of this action remains unclear. Methods: We used acoustic telemetry to monitor the fate of Striped Bass that were recreationally caught with baited hooks (n = 349) and to estimate the influence of various biological (fish size), fishery (fight time, handling time, hook location, bait type, and hook type), and environmental (water temperature and air temperature) variables on postrelease survival. Result: A semi‐quantitative score of fish release condition was the single best predictor of mortality. A broader dataset that included untagged fish (n = 716) was used to identify the best predictors of fish release condition, which included hook location and handling time. Conclusion: Contrary to expectations, the circle hooks used in this study did not result in lower release mortality than conventional J‐hooks. Impact statementStriped Bass are a popular recreational sport fish in the United States, with most fish being caught and released. To increase the survival of released fish, anglers are now required to use circle hooks when fishing with bait. This study found that using circle hooks does not increase the survival of released Striped Bass. [ABSTRACT FROM AUTHOR]

The impact of recreational fisheries on marine ecosystems is often overshadowed by commercial fisheries, although recreational fishing harvest can be substantial, especially for species that are either overfished or experiencing overfishing. Delaware is a small coastal state with ~1,000,000 residents and nearly 272,000 resident and non‐resident anglers. We used publicly available data for Delaware's recreational fisheries during 1981–2021 to determine the nine most caught fish species and to evaluate trends in total numbers caught, harvested, released, and catch per unit effort (CPUE). The top nine most frequently captured fish by recreational anglers were Summer Flounder (Paralichthys dentatus), Atlantic Croaker (Micropogonias undulatus), Bluefish (Pomatomus saltatrix), Black Sea Bass (Centropristis striata), Weakfish (Cynoscion regalis), White Perch (Morone americana), Tautog (Tautoga onitis), Striped Bass (Morone saxatilis), and Spot (Leiostomus xanthurus). The proportion of fish released increased through time for all nine species, suggesting that the recreational fishery in Delaware is transitioning from a harvest‐oriented to a catch‐and‐release‐oriented fishery. Observations of higher release rates in recreational fisheries of Delaware are consistent with the findings elsewhere in the world for freshwater and marine systems. [ABSTRACT FROM AUTHOR]

Species delimitation can be based on the consideration of several different criteria, including the differentiation of ecological or functional traits. Two species of Pacific rockfish, the dark rockfish (Sebastes ciliatus) and the dusky rockfish (Sebastes variabilis), appear to represent recently divergent evolutionary lineages. We evaluate evidence for the differentiation of these two species in somatic shape using geometric morphometrics at two locations in the northeast Pacific where they occur in sympatry. The somatic shape was significantly different between species, but the species' shape did not vary between the two locations. Sebastes ciliatus had an upturned and relatively smaller head, eye, and jaw, and an elongated midbody, whereas S. variabilis had a downturned and larger head, eye, and jaw, and a shorter midbody. These results suggest that S. ciliatus and S. variabilis are morphometrically differentiated in a similar way in both locations. The somatic shape differentiation between these two sympatric species is similar to genus-wide patterns of somatic shape differentiation. [ABSTRACT FROM AUTHOR]

Striped Bass (Morone saxatilis) monitoring and research in California's Central Valley primarily occurs in the Sacramento River basin and the Sacramento-San Joaquin Delta. A relatively under-studied contingent of the Striped Bass population is present in the San Joaquin River and its tributaries. One such tributary, the Stanislaus River, is an important source of natural production of native anadromous fishes, including fall-run Chinook Salmon (Oncorhynchus tshawytscha), Steelhead (O. mykiss), and Pacific Lamprey (Entosphenus tridentatus). Because Striped Bass are a non-native piscivore, characterizing when and where their distribution overlaps with native fishes is a first step to assessing the potential for negative inter-specific interactions. We compiled incidental observations of Striped Bass made during long-term (1996 to 2021) salmonid monitoring programs performed at different times of the year, and found that Striped Bass were present at monitoring locations throughout most of the year, although not detected in every year. We also used data on Striped Bass captured during boat electrofishing surveys conducted during the 2019, 2020, and 2021 juvenile salmonid emigration season (February to June), for a more detailed evaluation of Striped Bass occupancy within the lower 65 kilometers of the Stanislaus River. Median fork length (FL) of Striped Bass captured from February to April was significantly larger than those captured in May and June (p < 0.001). Using dynamic occupancy models, we showed that Striped Bass larger than 300 mm FL were present, and their occupancy increases earlier in the year than individuals under 300 mm FL. In all 3 years, occupancy estimates were greater than 80% of the lower Stanislaus River by May. Our results suggest a high degree of spatial and temporal overlap with native migratory fishes, which may have important implications for understanding and managing how predation affects juvenile salmon and other native species. [ABSTRACT FROM AUTHOR]

A 12-week feeding trial assessed the impact of protein-to-lipid ratios (P:L) on the growth, feed and protein utilization, digestive enzyme activity, and fillet composition of juvenile striped bass (Morone saxatilis) raised at summer local seawater temperature conditions (21 °C). A 3 × 2 factorial design, using three protein levels (40, 44, and 48%) and two lipid levels (12 and 16%) resulting in six diets (40:12, 44:12, 48:12, 40:16, 44:16, and 48:16) was used. Hatchery-reared fish with an initial weight of 11.4 ± 0.2 g were used. Laboratory-formulated experimental diets were randomly assigned to triplicate groups of 22 fish in 500-L tanks connected to a recirculating seawater (35.4 ± 3 ppt) system, and fish were fed manually to apparent satiation four times a day. Survival rates were higher than 96% across all treatments, remaining unaffected by dietary treatments. Fish fed the 44:12 and 48:12 diets resulted in significantly higher weight gain (WG) (274.1 ± 18.4 and 306.8 ± 19.8, respectively), final body weight (FBW) (42.4 ± 1.2 g and 47.1 ± 2.4 g, respectively), and specific growth rate (SGR) (1.6 ± 0.06 and 1.7 ± 0.06, respectively). Diets with 12% lipid resulted in feed conversion rate (FCR) values closer to 1, and the 48:16 (1 ± 0.03) treatment resulted in no significant differences compared to the 12% lipid dietary treatments. Similar trends were observed for protein efficiency ratio (PER), with comparable values for the 40:12 (2.0 ± 0.1), 44:12 (2.2 ± 0.1), 48:12 (2.0 ± 0.1), and 48:16 (2.1 ± 0.1) treatments. A strong relationship between dietary P:E ratios and SGR, PER, and FCR was observed among treatments, which helped explain the interactions between protein and lipid obtained. An estimated dietary P:E ratio between 11 and 12 is suggested for efficient protein and feed utilization for this species under our culture conditions. The apparent digestibility coefficient (ADC %) was significantly higher in the 12% lipid diets (65.01 ± 3.06%), influenced solely by lipid content. Enzyme activity for trypsin and chymotrypsin in the pyloric caeca (PC) and intestines (I) were higher in the 48:12 treatment (893.5 ± 18.1, 1087.3 ± 55.5, 12.2 ± 0.3, and 8.3 ± 0.2 Units/g organ, respectively). L-aminopeptidase activity (PC) was higher in the 48:12 treatment (1007.7 ± 101.8 Units/g organ), while L-aminopeptidase (I) had higher values in the 48:16 treatment (2217.2 ± 161.3 Units/g organ). In the case of lipase (PC), activity was higher in the 12% lipid treatments, while in the intestine, the highest activity was recorded in the 44:12 treatment (1084.4 ± 87.0). The activity of proteases, except for L-aminopeptidase (PC), directly correlated with improvements in SGR, PER, feed intake (FI), and FCR which helps explain the observed results. The Hepatosomatic index (HSI) was significantly higher in the 40:12 treatment while the liposomatic index (LSI) and viscerosomatic index (VSI) indices showed no significant differences between the 40:12, 44:12, 48:12, and 48:16 treatments, respectively. Importantly, the lipid content in the fillet did not significantly decrease with reduced lipid content in the diet, an important issue for market acceptance. Results from the present study suggest an optimal P:L ratio of 48:12 for juvenile striped bass raised in seawater under local summer conditions (21 °C). [ABSTRACT FROM AUTHOR]

Estuarine environments are recognized as critical nursery habitats that are necessary to sustain overall fish production. Striped bass Morone saxatilis support recreational and commercial fisheries along the Atlantic coast of the United States, and annual surveys to assess juvenile (age-0) abundance in Chesapeake Bay, the major producing area for the population, have long been used in management. Factors that contribute to high juvenile abundance are not fully understood. We used catch data from fishery-independent surveys coupled with hindcasts from a pair of numerical models to quantify the extent of summer habitats used by age-0 striped bass throughout Chesapeake Bay for 1996–2017. Specific conditions that defined habitat suitability for age-0 striped bass varied throughout the summer and among years, reflecting changes in water quality and habitat use. Shallow, nearshore areas throughout the Bay consistently supported suitable conditions for age-0 striped bass, but the estimated extent of suitable habitat varied annually at both regional and local, tributary-specific, scales. Although the areal extent of suitable habitat Bay-wide in early summer declined since 1996, fish production was not limited. Nonetheless, a pattern of increasing relative abundance of age-0 striped bass with greater extent of suitable habitats in Chesapeake Bay was observed, suggesting that the availability of suitable habitats at the scale of individual tributaries and Bay-wide may play an important role in production of this estuarine-dependent species. [ABSTRACT FROM AUTHOR]

Abstract Background Understanding growth regulatory pathways is important in aquaculture, fisheries, and vertebrate physiology generally. Machine learning pattern recognition and sensitivity analysis were employed to examine metabolomic small molecule profiles and transcriptomic gene expression data generated from liver and white skeletal muscle of hybrid striped bass (white bass Morone chrysops x striped bass M. saxatilis) representative of the top and bottom 10 % by body size of a production cohort. Results Larger fish (good-growth) had significantly greater weight, total length, hepatosomatic index, and specific growth rate compared to smaller fish (poor-growth) and also had significantly more muscle fibers of smaller diameter (≤ 20 µm diameter), indicating active hyperplasia. Differences in metabolomic pathways included enhanced energetics (glycolysis, citric acid cycle) and amino acid metabolism in good-growth fish, and enhanced stress, muscle inflammation (cortisol, eicosanoids) and dysfunctional liver cholesterol metabolism in poor-growth fish. The majority of gene transcripts identified as differentially expressed between groups were down-regulated in good-growth fish. Several molecules associated with important growth-regulatory pathways were up-regulated in muscle of fish that grew poorly: growth factors including agt and agtr2 (angiotensins), nicotinic acid (which stimulates growth hormone production), gadd45b, rgl1, zfp36, cebpb, and hmgb1; insulin-like growth factor signaling (igfbp1 and igf1); cytokine signaling (socs3, cxcr4); cell signaling (rgs13, rundc3a), and differentiation (rhou, mmp17, cd22, msi1); mitochondrial uncoupling proteins (ucp3, ucp2); and regulators of lipid metabolism (apoa1, ldlr). Growth factors pttg1, egfr, myc, notch1, and sirt1 were notably up-regulated in muscle of good-growing fish. Conclusion A combinatorial pathway analysis using metabolomic and transcriptomic data collectively suggested promotion of cell signaling, proliferation, and differentiation in muscle of good-growth fish, whereas muscle inflammation and apoptosis was observed in poor-growth fish, along with elevated cortisol (an anti-inflammatory hormone), perhaps related to muscle wasting, hypertrophy, and inferior growth. These findings provide important biomarkers and mechanisms by which growth is regulated in fishes and other vertebrates as well.

Sablefish (Anoplopoma fimbria, Anoplopomatidae) and shortraker rockfish (Sebastes borealis, Sebastidae) co-occur in deepwater marine habitats in the northeast Pacific. Both species are economically valuable, but their ecologies are not well known. We used stable isotope analysis of carbon and nitrogen to explore isotopic niches of A. fimbria and S. borealis in two distinct locations—a deep strait in the inside passage area and an open coastal area of the continental shelf, both in southeast Alaska, USA. Anoplopoma fimbria and S. borealis exhibited similar positions of isotopic niches based on nitrogen and carbon isotopic ratios, suggesting potential interspecific competition, especially in the inside location. In addition, S. borealis had a smaller niche breadth compared to A. fimbria in the coastal location. Both species had enriched nitrogen and carbon isotopic ratios in the inside location compared to the coastal location. Differences in isotopic niches between these two locations suggest the possibility of location-specific variation in isotopic niches of these two species of widespread, abundant deepwater fishes. [ABSTRACT FROM AUTHOR]

Objective: Coldwater releases from reservoirs support economically valuable sport fisheries for salmonids in the southern United States. The tailwater of Lewis Smith Dam in northwestern Alabama supports the only coldwater fishery in the state, with monthly stockings of about 1500 catchable‐size (200–406 mm total length) Rainbow Trout Oncorhynchus mykiss. Historically, the return to angler creel has been low in this fishery, and few large Rainbow Trout are caught. Numerous potential predators of stocked trout exist in this tailwater, including Gulf‐strain Striped Bass Morone saxatilis, which are stocked annually in a downstream reservoir. Thus, the objective of this study was to quantify the amount of predation, which occurs on Rainbow Trout in the Smith Lake tailwater. Methods: Potential predators of Rainbow Trout were collected six times over a 3‐week period after stocking in March, May, June, and October 2018. Result: Rainbow Trout were found in the stomachs of Striped Bass, hybrid striped bass (White Bass Morone chrysops × Striped Bass), Largemouth Bass Micropterus nigricans, and Chain Pickerel Esox niger. Only Striped Bass exhibited substantial predation on stocked Rainbow Trout, with 75% of these fish having at least one trout in their stomach. Of all identifiable prey items, Rainbow Trout composed 82% of the Striped Bass diet by number across all four sample months and constituted more than 65% of the Striped Bass diet by number in each sample month. Bioenergetics models predicted that a population of 500 Striped Bass living continuously in the tailwater from March through October could consume all Rainbow Trout stocked during each month. If Striped Bass vacated the area or switched from trout to other diet items for one‐third of each month, they could still consume almost 60% of stocked trout. Conclusion: Results of this study demonstrate that Striped Bass are significant predators of Rainbow Trout in the Smith Lake tailwater and are likely one of the main factors mediating Rainbow Trout survival and persistence in this fishery. Impact statementLow return rates to anglers of stocked Rainbow Trout in an Alabama tailwater fishery are likely due to high rates of predation by native Gulf‐strain Striped Bass. This research demonstrates that Striped Bass in the tailwater could consume 60% or more of the stocked trout during each month. [ABSTRACT FROM AUTHOR]

Increased interest in marine fish farming in the United States has led to a need for fundamental economic information on production of candidate species for commercialization in various production systems. Funding for the project targeted those species with potential for production in southern tier states in the United States. Sufficient technical data were found to develop comprehensive budget analyses to estimate growout production costs for four scales of production for each of 10 species with potential for production in ponds, 13 in recirculating aquaculture systems (RAS), and five in net pens. The choice of species/production system scenarios was based on evidence of successful production on farms or in research. Estimation of production costs with enterprise budgets can provide useful guidance to identify the types of improved efficiencies that have the greatest effect on economic viability even when commercial farm data are not available. Commercial farm data were used where available, but for most species, data were available only from studies conducted under research conditions. Per‐kg costs of production were lowest for net pen production, followed by ponds, with production costs in RAS two to five times greater than in ponds or net pens. Ponds and net pens generally exhibited greater efficiency of use of capital assets across species than did RAS that resulted in lower percentages of fixed costs and lower annual costs per kg of fish produced. All five species evaluated for net pen production were estimated to be profitable, including redfish, Sciaenops ocellatus (also known as red drum), striped bass, Morone saxatilis, cobia, Rachycentron canadum, red snapper, Lutjanus campechanus, and seriolids (generic budget for almaco jack, Seriola rivoliana, California yellowtail, Seriola lalandi, and greater amberjack, Seriola dumerili), four in ponds (redfish, hybrid drum, ♀Pogonias cromis × ♂Sciaenops ocellatus, black sea bass, Centropristis striata, and cobia), but none of the RAS scenarios showed profitability at average yields (kg/cubic meter) reported in the literature. Comprehensive data on growout production of marine finfish species in the United States is generally lacking, and there is a strong need for production trials conducted under near‐commercial conditions with an endpoint of market‐sized fish. Production trials should be conducted in ponds (≥0.1 ha), net pens, and RAS tanks of a size that simulate commercial production conditions. Adequate production trial databases would provide opportunities to develop economic optimization models that would provide useful guidance for prospective producers. Average yields (kg/cubic meter) in RAS will need to be much greater than currently reported in the research literature for RAS production to be economically sustainable. Net pen production appears to be profitable in the United States, but effective permitting procedures are not in place. Providing research support for the US redfish sector that has developed effective production and marketing models could serve as a foundation for developing additional species and offer opportunities for diversification on marine finfish farms. [ABSTRACT FROM AUTHOR]

In reports on stock assessments for rockfish species on the West Coast of the United States, the need for additional biological data to provide more accurate estimates of population abundance is commonly cited. Improvement of population estimates is important because those data are used to set catch quotas along this coast of the nation. The recreational charter boat fleet in the state of California has historically landed large amounts of rockfish species; however, vessels in this fleet discard carcasses once fillets have been removed from fish. These carcasses could be a valuable source of age, length, and sex data, with a standardized measurement method used to relate the post-fillet length of carcasses to the pre-fillet length. To determine the feasibility of a program to collect rockfish carcasses for biological data, specimens of 4 rockfish species were captured off the central coast of California and measured before and after filleting. Pre-fillet lengths were accurately predicted on the basis of post-fillet elongate length for blue (Sebastes mystinus), gopher (S. carnatus), copper (S. caurinus), and vermilion (S. miniatus) rockfish. A high percentage (87.5%) of the carcasses had identifiable gonads, a fortunate result because the availability of sex data on measured specimens is an important consideration for species with dimorphic growth. This new data source based on information from carcasses can be used to enhance the length-at-age and life history data available for stock assessments or other biological studies of rockfish populations. [ABSTRACT FROM AUTHOR]

Hybridization can provide evolutionary benefits (e.g., population resilience to climate change) through the introduction of adaptive alleles and increase of genetic diversity. Nevertheless, management strategies may be designed based only on the parental species within a hybrid zone, without considering the hybrids. This can lead to ineffective spatial management of species, which can directly harm population diversity and negatively impact food webs. Three species of rockfish (Brown Rockfish (Sebastes caurinus), Copper Rockfish (S. auriculatus), and Quillback Rockfish (S. maliger)) are known to hybridize within Puget Sound, Washington, but genetic data from these species are used to infer population structure in the entire genus, including in species that do not hybridize. The goal of this project was to estimate the hybridization rates within the region and determine the effect of hybridization on geographic patterns of genetic structure. We sequenced 290 Brown, Copper, and Quillback rockfish using restriction‐site associated DNA sequencing (RADseq) from four regions within and outside Puget Sound, Washington. We show that (i) hybridization within Puget Sound was asymmetrical, not recent, widespread among individuals, and relatively low level within the genome, (ii) hybridization affected population structure in Copper and Brown rockfish, but not in Quillback Rockfish and (iii) after taking hybridization into account we found limited directional dispersal in Brown and Copper rockfish, and evidence for two isolated populations in Quillback Rockfish. Our results suggest that rockfish population structure is species‐specific, dependent on the extent of hybridization, and cannot be inferred from one species to another despite similar life history. [ABSTRACT FROM AUTHOR]

DNA methylation plays an important role in various biological processes, including cell differentiation, ageing, and cancer development. The most important methylation in mammals is 5-methylcytosine mostly occurring in the context of CpG dinucleotides. Sequencing methods such as whole-genome bisulfite sequencing successfully detect 5-methylcytosine DNA modifications. However, they suffer from the serious drawbacks of short read lengths and might introduce an amplification bias. Here we present Rockfish, a deep learning algorithm that significantly improves read-level 5-methylcytosine detection by using Nanopore sequencing. Rockfish is compared with other methods based on Nanopore sequencing on R9.4.1 and R10.4.1 datasets. There is an increase in the single-base accuracy and the F1 measure of up to 5 percentage points on R.9.4.1 datasets, and up to 0.82 percentage points on R10.4.1 datasets. Moreover, Rockfish shows a high correlation with whole-genome bisulfite sequencing, requires lower read depth, and achieves higher confidence in biologically important regions such as CpG-rich promoters while being computationally efficient. Its superior performance in human and mouse samples highlights its versatility for studying 5-methylcytosine methylation across varied organisms and diseases. Finally, its adaptable architecture ensures compatibility with new versions of pores and chemistry as well as modification types. DNA methylation is vital for various biological processes. Here, the authors present Rockfish, a deep learning algorithm that enhances 5-methylcytosine detection using Nanopore sequencing. Rockfish offers higher accuracy, lower read depth requirements, and greater confidence in crucial genomic regions. [ABSTRACT FROM AUTHOR]

Objective: The antiparasitic effect of peracetic acid (PAA) was evaluated against an infestation of the protozoan Trichodina spp. in naturally infected juvenile domestic seventh‐generation (F7) Striped Bass Morone saxatilis. Methods: Replicated treatments (n = 3) consisted of 1 and 2 mg/L PAA and a control; treatments were applied every other day for three treatments (30‐min static exposure). Infestation intensity was enumerated 20–24 h after each treatment by counting the number of Trichodina present in a wet mount of excised gill tissue. Result: Neither treatment rate was able to completely eradicate the parasite; however, 2 mg/L PAA resulted in a statistically significant reduction, which equated to 75% reduction of observed parasites. Conclusion: The 2‐mg/L PAA treatment regimen in the present study is proposed as a safe, environmentally friendly, and effective method for reducing the intensity of Trichodina infestations in Striped Bass. Impact statementDefining new treatment regimens for common aquaculture parasites is beneficial to the industry. Emphasis on environmentally friendly chemicals is also good for the industry. Improving animal welfare can be achieved by reducing parasites in fish. [ABSTRACT FROM AUTHOR]

Background: Understanding growth regulatory pathways is important in aquaculture, fisheries, and vertebrate physiology generally. Machine learning pattern recognition and sensitivity analysis were employed to examine metabolomic small molecule profiles and transcriptomic gene expression data generated from liver and white skeletal muscle of hybrid striped bass (white bass Morone chrysops x striped bass M. saxatilis) representative of the top and bottom 10 % by body size of a production cohort. Results: Larger fish (good-growth) had significantly greater weight, total length, hepatosomatic index, and specific growth rate compared to smaller fish (poor-growth) and also had significantly more muscle fibers of smaller diameter (≤ 20 µm diameter), indicating active hyperplasia. Differences in metabolomic pathways included enhanced energetics (glycolysis, citric acid cycle) and amino acid metabolism in good-growth fish, and enhanced stress, muscle inflammation (cortisol, eicosanoids) and dysfunctional liver cholesterol metabolism in poor-growth fish. The majority of gene transcripts identified as differentially expressed between groups were down-regulated in good-growth fish. Several molecules associated with important growth-regulatory pathways were up-regulated in muscle of fish that grew poorly: growth factors including agt and agtr2 (angiotensins), nicotinic acid (which stimulates growth hormone production), gadd45b, rgl1, zfp36, cebpb, and hmgb1; insulin-like growth factor signaling (igfbp1 and igf1); cytokine signaling (socs3, cxcr4); cell signaling (rgs13, rundc3a), and differentiation (rhou, mmp17, cd22, msi1); mitochondrial uncoupling proteins (ucp3, ucp2); and regulators of lipid metabolism (apoa1, ldlr). Growth factors pttg1, egfr, myc, notch1, and sirt1 were notably up-regulated in muscle of good-growing fish. Conclusion: A combinatorial pathway analysis using metabolomic and transcriptomic data collectively suggested promotion of cell signaling, proliferation, and differentiation in muscle of good-growth fish, whereas muscle inflammation and apoptosis was observed in poor-growth fish, along with elevated cortisol (an anti-inflammatory hormone), perhaps related to muscle wasting, hypertrophy, and inferior growth. These findings provide important biomarkers and mechanisms by which growth is regulated in fishes and other vertebrates as well. [ABSTRACT FROM AUTHOR]

The study aimed to uncover the molecular response of juvenile Sebastes schlegelii to air exposure stress by identifying differentially expressed genes (DEGs) that may underlie their anti-stress mechanisms. Juvenile Sebastes schlegelii were subjected to varying durations of air exposure stress. The total RNA was extracted from whole tissues and sequenced using the Illumina NovaSeq 6000 platform. The transcriptome data were analyzed to identify DEGs through pairwise comparisons across a control group and two experimental groups exposed to air for 40 s and 2 min 30 s, respectively. The comparative DEG analysis revealed a significant number of transcripts responding to air exposure stress. Specifically, 5173 DEGs were identified in the 40 s exposure group (BS) compared to the control (BC), 6742 DEGs in the 2 min 30 s exposure group (BD) compared to the control (BC), and 2653 DEGs when comparing the BD to the BS group. Notably, Gene Ontology (GO) analysis showed an enrichment of DEGs associated with peptidase activity and extracellular regions, suggesting a role in the organism's stress response. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis pointed to the involvement of metabolic pathways, which are crucial for energy management under stress. The upregulation of protein digestion and absorption pathways may indicate a physiological adaptation to nutrient scarcity during stress. Additionally, the identification of antibiotic biosynthesis pathways implies a potential role in combating stress-induced infections or damage. The identified DEGs and enriched pathways provide insights into the complex anti-stress response mechanisms in juvenile Sebastes schlegelii. The enrichment of peptidase activity and extracellular region-related genes may reflect the initiation of tissue repair and immune response following air exposure. The connection between protein digestion and absorption pathways and anti-stress capabilities could be interpreted as a metabolic readjustment to prioritize energy-efficient processes and nutrient assimilation during stress. The role of antibiotic biosynthesis pathways suggests a defensive mechanism against oxidative stress or microbial invasion that might occur with air exposure. [ABSTRACT FROM AUTHOR]

Simple Summary: Our findings highlight significant distinctions in body coloration between wild and hatchery-reared individuals, and a ten-day rearing period under colored ambient light can notably change the coloration of hatchery-reared marbled rockfish. Additionally, our research reveals a preference among juvenile marbled rockfish for a red-light environment, alongside a consistent negative phototactic response to yellow and blue light colors. These results emphasize the substantial influence of hatchery rearing conditions on fish body color and morphological color-changing abilities, and elucidate ambient light color preferences. Our study emphasizes the importance of considering modifications to the hatchery environment, particularly in regulating ambient light color, within stock enhancement programs. Hatchery rearing significantly influences the phenotypic development of fish, with potential adverse effects for the post-release performance of hatchery-reared individuals in natural environments, especially when targeted for stock enhancement. To assess the suitability of releasing hatchery-reared fish, a comprehensive understanding of the phenotypic effects of captive rearing, through comparisons with their wild conspecifics, is essential. In this study, we investigated the divergence in body coloration between wild and hatchery-reared marbled rockfish Sebastiscus marmoratus. We examined the selection preferences for different light colors and assessed the impact of different ambient light colors on the morphological color-changing ability of juvenile marbled rockfish. Our findings revealed significant differences in body color between wild and hatchery-reared marbled rockfish. The hue and saturation values of wild marbled rockfish were significantly higher than those of their hatchery-reared counterparts, indicative of deeper and more vibrant body coloration in the wild population. Following a ten-day rearing period under various light color environments, the color of wild marbled rockfish remained relatively unchanged. In contrast, hatchery-reared marbled rockfish tended to change their color, albeit not reaching wild-like coloration. Light color preference tests demonstrated that wild juvenile marbled rockfish exhibited a preference for a red-light environment, while hatchery-reared individuals showed a similar but weaker response. Both wild and hatchery-reared marbled rockfish displayed notable negative phototaxis in the presence of yellow and blue ambient light. These results highlight the impact of hatchery rearing conditions on the body color and morphological color-changing ability, and provide insight into light color selection preferences of marbled rockfish. To mitigate the divergence in phenotypic development and produce more wild-like fish for stocking purposes, modifications to the hatchery environment, such as the regulation of ambient light color, should be considered. [ABSTRACT FROM AUTHOR]

Successful reproduction is critical to the growth and persistence of marine fish populations, yet how changes in the environment influence reproduction remains largely unknown. We explored how shifting ocean conditions influenced larval production in four species of long-lived, live-bearing rockfish (Sebastes spp.) in the California Current. Brood fecundity, body size, and environmental information were analyzed from the mid-1980s through 2020. Interannual variation in brood fecundity was greater than 50% in the single-brooding yellowtail rockfish (S. flavidus) and widow rockfish (S. entomelas). Brood fecundity varied less in chilipepper (S. goodei) and bocaccio (S. paucispinis), two species capable of multiple broods per year. In these two species, interannual fecundity variability is more likely to depend on the number of broods produced than on brood size alone. In all four species, brood fecundity was positively correlated with maternal length and body condition. Variable ocean conditions influenced the strength of maternal size effects by year. These results provide evidence for reproductive plasticity and environmental effects on fecundity, with implications for changes in population reproductive potential with climate change. [ABSTRACT FROM AUTHOR]

The price of fishmeal (FM) has been increasing continuously due to the expansion of the gap between its stable production and rising demand. Therefore, plant protein sources are widely applied in the aquaculture industry to accomplish the protein requirement of farmed fish species. However, the massive number of results produced under various experimental conditions appended challenges for comprehensive summarization and comparison of the effects of plant protein sources on carnivorous fish species. Thus, a systemic review and meta‐analysis were conducted to compare the impacts of various plant protein sources on growth, feed utilization efficiencies, blood lipid, and liver health of representative carnivorous species. Supported by the data from 256 articles, our results indicated that Atlantic salmon, African catfish, Black seabass, and Hybrid striped bass were better at utilizing plant protein sources than Grouper and Japanese seabass. Cottonseed and lupin proteins were promising protein alternatives, while rapeseed showed significant growth suppression effects for these carnivorous fish species. Besides, deep processing methods such as fermentation and enzymolysis alleviated undesirable consequences effectively when less than half of FM was replaced by plant protein sources. Moreover, the optimal plant protein sources are discussed for each fish species. Overall, this article depicts the impact patterns of major plant protein sources on carnivorous farmed fish species and lays a solid foundation for further investigation on mechanisms for improving plant protein utilization. [ABSTRACT FROM AUTHOR]

The fish communities of the Sacramento–San Joaquin Delta and its tributaries in California’s Central Valley have been irreparably altered through introductions of numerous fish species, including Striped Bass (Morone saxatilis), black bass (Micropterus spp.), and catfishes (Ameiurus spp. and Ictalurus spp.). Research into how predation by non-native piscivores affects native anadromous species has focused on the Sacramento and San Joaquin river mainstems and Delta habitats, through which all anadromous species must pass. Yet, the ranges of non-native fishes extend into upstream tributaries. We collected diets from native and non-native piscivores in the Stanislaus River, a tributary to the San Joaquin River and a remaining stronghold for native fishes. Piscivorous fishes primarily consumed invertebrates and the native species fall-run Chinook Salmon (Oncorhynchus tshawytscha) and Pacific Lamprey (Entosphenus tridentatus). Juvenile Chinook Salmon and Pacific Lamprey were consumed at higher frequencies than any other potential fish prey species, particularly by Striped Bass and black bass. The frequency of native fishes in predator diets was similar across years, despite contrasting hydrologic conditions; 2019 (wet year), 2020 (dry year), and 2021 (critically dry year). Our results show that Pacific Lamprey were frequently consumed by native and non-native piscivores, and that juvenile Chinook Salmon experience substantial predation early in their migration, regardless of hydrologic conditions.

Background: We recently reported that supplementing glycine to soybean meal-based diets is necessary for the optimum growth of 5- to 40-g (Phase-I) and 110- to 240-g (Phase-II) hybrid striped bass (HSB), as well as their intestinal health. Although glycine serves as an essential substrate for syntheses of creatine and glutathione (GSH) in mammals (e.g., pigs), little is known about these metabolic pathways or their nutritional regulation in fish. This study tested the hypothesis that glycine supplementation enhances the activities of creatine- and GSH-forming enzymes as well as creatine and GSH availabilities in tissues of hybrid striped bass (HSB; Morone saxatilis♀ × Morone chrysops♂). Methods: Phase-I and Phase-II HSB were fed a soybean meal-based diet supplemented with 0%, 1%, or 2% glycine for 8 weeks. At the end of the 56-d feeding, tissues (liver, intestine, skeletal muscle, kidneys, and pancreas) were collected for biochemical analyses. Results: In contrast to terrestrial mammals and birds, creatine synthesis occurred primarily in skeletal muscle from all HSB. The liver was most active in GSH synthesis among the HSB tissues studied. In Phase-I HSB, supplementation with 1% or 2% glycine increased (P < 0.05) concentrations of intramuscular creatine (15%–19%) and hepatic GSH (8%–11%), while reducing (P < 0.05) hepatic GSH sulfide (GSSG)/GSH ratios by 14%–15%, compared with the 0-glycine group; there were no differences (P > 0.05) in these variables between the 1% and 2% glycine groups. In Phase-II HSB, supplementation with 1% and 2% glycine increased (P < 0.05) concentrations of creatine and GSH in the muscle (15%–27%) and liver (11%–20%) in a dose-dependent manner, with reduced ratios of hepatic GSSG/GSH in the 1% or 2% glycine group. In all HSB, supplementation with 1% and 2% glycine dose-dependently increased (P < 0.05) activities of intramuscular arginine:glycine amidinotransferase (22%–41%) and hepatic γ-glutamylcysteine synthetase (17%–37%), with elevated activities of intramuscular guanidinoacetate methyltransferase and hepatic GSH synthetase and GSH reductase in the 1% or 2% glycine group. Glycine supplementation also increased (P < 0.05) concentrations of creatine and activities of its synthetic enzymes in tail kidneys and pancreas, and concentrations of GSH and activities of its synthetic enzymes in the proximal intestine. Conclusions: Skeletal muscle and liver are the major organs for creatine and GSH syntheses in HSB, respectively. Dietary glycine intake regulates creatine and GSH syntheses by both Phase-I and Phase-II HSB in a tissue-specific manner. Based on the metabolic data, glycine is a conditionally essential amino acid for the growing fish. [ABSTRACT FROM AUTHOR]

Artificial enhancement and release activity is an important method in the restoration of fishery resources. In order to understand the possible genetic effect of hatchery-released populations on wild populations during the artificial enhancement and release activities of Sebastiscus marmoratus in Zhoushan waters, we utilized mitochondrial DNA control region sequences to examine the genetic diversity in four S. marmoratus populations, including one farmed population, one released population and two wild populations. A total of 68 haplotypes from 123 individuals were detected, including 3 shared haplotypes. Haplotype diversity ranged from 0.944 to 0.980, with a mean of 0.966. The nucleotide diversity ranged from 0.020 to 0.025, with a mean of 0.022. Analysis of Molecular Variance (AMOVA) indicated that the primary genetic variation occurs within populations and the index of genetic differentiation between populations (FST) among the four populations showed no differentiation. The results indicate that the current artificial enhancement and release has not impacted the S. marmoratus population in Zhoushan waters. Continued long-term monitoring is essential to protect the high-quality germplasm resources of S. marmoratus. [ABSTRACT FROM AUTHOR]

The present study was conducted to evaluate the availability of citrus byproduct (CBP) as a vitamin C additive compared with the L-ascorbyl-polyphosphate (LAPP) for juvenile Korean rockfish Sebastes schlegelii. Four experimental diets, based on the basal diet (Con; semi-purified, crude protein 48%), were prepared by supplementing LAPP or CBP to achieve a dietary vitamin C concentration of 90 or 360 mg/kg (designated as LAPP90, LAPP360, CBP90, and CBP360, respectively). Three replicate groups of S. schlegelii (mean body weight ± standard deviation = 4.5 ± 0.0 g) were fed the experimental diets for 13 weeks. After the feeding trial, growth performance, feed utilization efficiency, and survival were significantly lower in the Con group. Liver vitamin C concentration was significantly increased (36.7–117 mg/kg) with increasing dietary LAPP levels; however, there was no significant difference in the CBP groups (14.2–14.3 mg/kg) compared with the Con group. Bone collagen concentration was significantly affected by LAPP and CBP supplementation. The LAPP and CBP groups showed significantly higher lysozyme activity and total immunoglobulin levels than the Con group. Disease resistance against Streptococcus iniaewas significantly improved in the LAPP and CBP groups (60–92% survival) than in the Con group (39% survival). These results indicate that dietary vitamin C is essential for S. schlegelii and CBP could be a LAPP substitute as a vitamin C additive. [ABSTRACT FROM AUTHOR]

It is widely known that all-female fish production holds economic value for aquaculture. Sebastes schlegelii, a preeminent economic species, exhibits a sex dimorphism, with females surpassing males in growth. In this regard, achieving all-female black rockfish production could significantly enhance breeding profitability. In this study, we utilized the widely used male sex-regulating hormone, 17α-methyltestosterone (MT) at three different concentrations (20, 40, and 60 ppm), to produce pseudomales of S. schlegelii for subsequent all-female offspring breeding. Long-term MT administration severely inhibits the growth of S. schlegelii, while short term had no significant impact. Histological analysis confirmed sex reversal at all MT concentrations; however, both medium and higher MT concentrations impaired testis development. MT also influenced sex steroid hormone levels in pseudomales, suppressing E2 while increasing T and 11-KT levels. In addition, a transcriptome analysis revealed that MT down-regulated ovarian-related genes (cyp19a1a and foxl2) while up-regulating male-related genes (amh) in pseudomales. Furthermore, MT modulated the TGF-β signaling and steroid hormone biosynthesis pathways, indicating its crucial role in S. schlegelii sex differentiation. Therefore, the current study provides a method for achieving sexual reversal using MT in S. schlegelii and offers an initial insight into the underlying mechanism of sexual reversal in this species. [ABSTRACT FROM AUTHOR]

Simple Summary: Fish meal is commonly used as the main protein source in fish feeds, but its high price has restricted the use of fish meal. Thus, looking for a substitute with an inexpensive and sustainable source for fish meal in fish feeds is highly needed. Nevertheless, replacement of fish meal with an alternative source in fish feeds commonly reduces the palatability of diets, leads to reduced feed intake, and lowers growth performance. Our previous study reported that up to 20% of fish meal could be substitutable with chicken by-product meal in the feed of rockfish without deteriorating their growth and feed intake. This study evaluates the impact on growth and feed availability from including jack mackerel meal in rockfish diets which otherwise replace 20% fish meal with chicken by-product meal. With fish fed a 55% fish-meal-based diet, the inclusion of 60 and 80% jack mackerel meal in low-fish-meal diets achieved superior weight gain, specific growth rate, and feed consumption. Furthermore, compared to an 80% inclusion level, the slightly but not significantly higher economic profit index was obtained in rockfish fed the low-fish-meal diet with 60% jack mackerel meal in diets. Therefore, the manipulation of jack mackerel meal as feed enhancer in the low-fish-meal diet, which otherwise replaces 20% fish meal with chicken by-product meal, could improve the growth performance and feed consumption of rockfish. This study was conducted to elucidate the impact on the growth and feed availability of rockfish (Sebastes schlegeli) from including jack mackerel meal (JMM) in feeds which otherwise substitute 20% fish meal (FM) with chicken by-product meal (CBM). Six formulated feeds were designed to be isonitrogenous and isolipidic. Specifically, 55% FM was included in the control (Con) diet. In the Con diet, 20% FM was substituted by CBM, and then the graded levels (0, 20, 40, 60, and 80%) of JMM were included instead of FM, named as the C20J0, C20J20, C20J40, C20J60, and C20J80 diets, respectively. Five hundred and forty juvenile rockfish (initial weight of 11.2 g) were assigned to 18 tanks. All experimental feeds were fed to triplicate groups of rockfish twice daily for 8 weeks. Superior weight gain, specific growth rate (SGR), and feed intake of rockfish fed the C20J60 and C20J80 diets compared to rockfish fed the Con and C20J0 diets were observed. However, the feed utilization, biological indices, proximate composition, amino acid profiles, and blood chemistry of the rockfish were not affected by the dietary treatments. The slightly but not significantly higher economic profit index and growth performance were obtained in the C20J60 diet compared to the C20J80 diet. In conclusion, the C20J60 diet was the most recommendable treatment based on the improvement in growth performance (weight gain and SGR) and feed intake of rockfish, and the highest economic return to farmers. [ABSTRACT FROM AUTHOR]

The inner ear of teleost fish regulates the ionic and acid-base chemistry and secretes protein matrix into the endolymph to facilitate otolith biomineralization, which is used to maintain vestibular and auditory functions. The otolith is biomineralized in a concentric ring pattern corresponding to seasonal growth, and this calcium carbonate (CaCO3) polycrystal has become a vital aging and life-history tool for fishery managers, ecologists, and conservation biologists. Moreover, biomineralization patterns are sensitive to environmental variability including climate change, thereby threatening the accuracy and relevance of otolith-reliant toolkits. However, the cellular biology of the inner ear is poorly characterized, which is a hurdle for a mechanistic understanding of the underlying processes. This study provides a systematic characterization of the cell types in the inner ear of splitnose rockfish (Sebastes diploproa). Scanning electron microscopy revealed the apical morphologies of six inner ear cell types. In addition, immunostaining and confocal microscopy characterized the expression and subcellular localization of the proteins Na+-K+-ATPase, carbonic anhydrase, V-type H+-ATPase, Na+-K+-2Cl−-cotransporter, otolith matrix protein 1, and otolin-1 in six inner ear cell types bordering the endolymph. This fundamental cytological characterization of the rockfish inner ear epithelium illustrates the intricate physiological processes involved in otolith biomineralization and highlights how greater mechanistic understanding is necessary to predict their multistressor responses to future climate change. [ABSTRACT FROM AUTHOR]

Objective: The sunshine bass (female White Bass Morone chrysops × male Striped Bass M. saxatilis) is an important food fish raised in U.S. aquaculture. Spawning is performed by manually stripping and fertilizing White Bass eggs with Striped Bass sperm. Embryos hatch in approximately 48 h. Mature sunshine bass females can become fertile and produce viable eggs, which is problematic in commercial food‐fish production; therefore, triploid fish are desired. Methods: The present nonreplicated study incorporated three warm and three cold temperature shocks, along with three postfertilization initiation times and three exposure times for each temperature, during initial stages of incubation to induce triploidy. After exposure to temperature shocks, fertilized eggs were incubated in experimental hatching systems. The best performing cold and warm temperatures and times (and an ambient diploid control) were then used to incubate fertilized eggs in a commercial‐scale trial using standard industry practices with a single batch of eggs. Larvae were stocked at about 185,000 larvae/ha (75,000 larvae/acre) in newly filled and fertilized ponds. Fry were sampled weekly and harvested at 30 days. Result: There were 15 survivors from the pond containing fish derived from cold‐shocked fertilized eggs; these individuals were tested via Coulter Counter, and no triploids were detected. Testing of 50 survivors from the pond containing fish derived from warm‐shocked fertilized eggs indicated that 14% were triploid. Conclusion: Therefore, initial trials indicate that warm temperature shock is preferable to cold shock for inducing a greater percentage of triploid sunshine bass. Impact statementSuccessful use of temperature shock during the initial stages of fertilized egg incubation to produce triploid sunshine bass leads to a new method to improve sustainability and profitability for farmers. [ABSTRACT FROM AUTHOR]

The first record of abnormal body coloration in Sebastes koreanus Kim and Lee, 1994, from the Yellow Sea of China, was documented based on morphological characteristics and DNA barcoding. The two rockfish specimens were collected from the coastal waters of Qingdao, China, and the whole body and all fins of them were red. Of the two red-colored rockfish, there were tiny deep red spots on each fin, 2 red radial stripes behind and below the eyes and 1 large deep red blotch on the opercula, while the similar stripe and spot patterns are also present in the S. koreanus specimens with normal body coloration. The countable characteristics of the two specimens are in the range of the morphometry of S. koreanus. To further clarify the species identity and taxonomic status of the two specimens, DNA barcode analysis was carried out. The genetic distance between the red-colored rockfish and S. koreanus was 0, and the minimum net genetic distances between the red-colored rockfish and other Sebastes species except for S. koreanus were 3.0%, which exceeds the threshold of species delimitation. The phylogenetic analysis showed that the DNA barcoding sequences of the two red-colored rockfish clustered with the S. koreanus sequences. The above results of DNA barcode analysis also support that the two red-colored rockfish could be identified as the species of S. koreanus. The mechanism of color variation in S. koreanus is desirable for further research and the species could be an ideal model to study the color-driven speciation of the rockfishes. [ABSTRACT FROM AUTHOR]

Flavobacterium plurextorum is a potential fish pathogen of interest, previously isolated from diseased rainbow trout (Oncorhynchus mykiss) and oomycete‐infected chum salmon (Oncorhynchus keta) eggs. We report here the first complete genome sequence of F. plurextorum RSG‐18 isolated from the gut of Schlegel's black rockfish (Sebastes schlegelii). The genome of RSG‐18 consists of a circular chromosome of 5,610,911 bp with a 33.57% GC content, containing 4858 protein‐coding genes, 18 rRNAs, 63 tRNAs and 1 tmRNA. A comparative analysis was conducted on 11 Flavobacterium species previously reported as pathogens or isolated from diseased fish to confirm the potential pathogenicity of RSG‐18. In the SEED classification, RSG‐18 was found to have 36 genes categorized in 'Virulence, Disease and Defense'. Across all Flavobacterium species, a total of 16 antibiotic resistance genes and 61 putative virulence factors were identified. All species had at least one phage region and type I, III and IX secretion systems. In pan‐genomic analysis, core genes consist of genes linked to phages, integrases and matrix‐tolerated elements associated with pathology. The complete genome sequence of F. plurextorum RSG‐18 will serve as a foundation for future research, enhancing our understanding of Flavobacterium pathogenicity in fish and contributing to the development of effective prevention strategies. [ABSTRACT FROM AUTHOR]

Objective: Female age at maturity and fecundity for the Atlantic stock of Striped Bass Morone saxatilis were estimated using histological methods and image analysis. Methods: Ovaries were obtained from surveys encompassing the spring spawning season (March–July; n = 343), primarily from the Chesapeake Bay, and in the fall months (September–December; n = 85), primarily from the Atlantic coast. Histological examination of oocytes revealed some Striped Bass in intermediate stages of maturation during the spawning season. These individuals were identified as undergoing pubertal development, defined as the transition from the juvenile stage to first sexual maturity. Pubertal development was characterized by ovaries containing a population of enlarged, lipid‐filled oocytes but noticeably lacking vitellogenin‐derived yolk globules during the spawning season, and those ovaries were classified as immature. Toward the end of the spawning season, increasing proportions of Striped Bass with unspawned ovaries and oocytes undergoing total atresia were observed. Result: The female age and length at 50% maturity in Atlantic Striped Bass based on spring samples were 5.5 years and 609 mm total length, respectively. Fecundity was determined gravimetrically via image analysis of ovarian tissue samples from spawning capable individuals (n = 67). Potential annual fecundity was found to exhibit hyperallometric scaling with respect to body size. Specifically, the scaling exponent for the length–fecundity relationship was 3.24, which was greater than the scaling exponent of 3.05 for the length–body mass relationship. This indicates that large females possess a disproportionately greater reproductive capacity with respect to body mass than the equivalent biomass of smaller females. Conclusion: Compared with previous studies spanning over a half‐century, age at 50% maturity and fecundity were found to be relatively invariant, although variation found between contemporary studies may represent methodological and interpretive differences. Reproductive‐related life history traits of female Atlantic Striped Bass are apparently robust to long‐term decadal changes in fishing intensity, stock size, habitat alterations, and environmental conditions. Impact statementAtlantic Striped Bass are an iconic U.S. East Coast sport fish and a commercially important species. We determined that half of females reach sexual maturity between ages 5 and 6. Additionally, we found that larger (older) females produce more eggs per kilogram body mass than smaller (younger) females. These findings should be considered in future stock management. [ABSTRACT FROM AUTHOR]

White bass (Morone chrysops) are a popular sportfish throughout the southern United States, and one parent of the commercially-successful hybrid striped bass (M. chrysops ♂ x M. saxatilis ♀. Currently, white bass are cultured using diets formulated for other carnivorous fish, such as largemouth bass (Micropterus salmoides) or hybrid striped bass and contain a significant percentage of marine fish meal. Since there are no studies regarding the utilization of alternative proteins in this species, we evaluated the global gene expression of white bass fed diets in which fish meal was partially or totally replaced by various combinations of soybean meal, poultry by-product meal, canola meal, soy protein concentrate, wheat gluten, or a commercial protein blend (Pro-Cision™). Six isonitrogenous (40% protein), isolipidic (11%), and isocaloric (17.1 kJ/g) diets were formulated to meet the known nutrient and energy requirements of largemouth bass and hybrid striped bass using nutrient availability data for most of the dietary ingredients. One of the test diets consisted exclusively of plant protein sources. Juvenile white bass (40.2 g initial weight) were stocked into a flow-through aquaculture system (three tanks/diet; 10 fish/tank) and fed the test diets twice daily to satiation for 60 days. RNA sequencing and bioinformatic analyses revealed significant differentially expressed genes between all test diets when compared to fish meal control. A total of 1,260 differentially expressed genes were identified, with major ontology relating to cell cycle and metabolic processes as well as immune gene functions. This data will be useful as a resource for future refinements to moronid diet formulation, as marine fish meal becomes limiting and plant ingredients are increasingly added as a reliable protein source. [ABSTRACT FROM AUTHOR]

Background: Salinomycin, an antibiotic, have potential as a veterinary drug for fish due to its anti-parasitic activity against several fish parasites. Thus the residual levels of salinomycin in muscles of two significant aquaculture species in Korea, olive flounder and black rockfish, were analyzed using HPLC-MS-MS. Results: The proper method to analyze the residual salinomycin in fish muscles using LC-MS-MS was settled and the method was validated according to CODEX guidelines. The residues in three distinct groups for two fish species were analyzed using the matrix match calibration curves at points of five different times following oral administration. After oral administration, salinomycin rapidly breaks down in both olive flounder and black rockfish. After 7th days, the average residue in all groups of two fish spp. decreased below limit of quantitation (LOQ). Conclusion: Due to low residue levels in fish muscles, salinomycin may therefore be a treatment that is safe for both fish and humans. This result could contribute to establishment of MRL (minimal residual limit) for approval of salinomycin for use in aquaculture. [ABSTRACT FROM AUTHOR]

Variation in the recruitment of salmon is often found to be correlated with marine climate indices, but mechanisms behind environment–recruitment relationships remain unclear and correlations often break down over time. We used an ecosystem modeling approach to explore bottom‐up and top‐down mechanisms linking a variable environment to salmon recruitment variations. Our ecosystem model incorporates a regional ocean circulation submodel for hydrodynamics, a nutrient‐phytoplankton‐zooplankton submodel for producing planktonic prey fields, and an individual‐based model (IBM) representing juvenile Chinook salmon (Oncorhynchus tshawytscha), combined with observations of foraging distributions and diet of a seabird predator. The salmon IBM consists of modules, including a juvenile salmon growth module based on temperature and salmon–prey availability, a behavior‐based movement module, and a juvenile salmon predation mortality module based on juvenile salmon size distribution and predator–prey interaction probability. Seabird–salmon interactions depend on spatial overlap and juvenile salmon size, whereby salmon that grow past the size range of the prey distribution of the predator will escape predation. We used a 21‐year historical simulation to explore interannual variability in juvenile Chinook salmon growth and predation‐mediated survival under a range of ocean conditions for sized‐based mortality scenarios. We based a series of increasingly complex predation scenarios on seabird observational data to explore variability in predation mortality on juvenile Chinook salmon. We initially included information about the predator spatial distribution, then added population size, and finally the predator's diet percentage made up of juvenile salmon. Model agreement improves with added predator complexity, especially during periods when predator abundance is high. Overall, our model found that when the fraction of juvenile salmon in seabird diet increased relative to alternate prey (e.g., Northern anchovy Engraulis mordax, and juvenile rockfish Sebastes spp.), there was a concomitant decrease in salmon cohort survival during their first year at sea. [ABSTRACT FROM AUTHOR]

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Objective: Two separate trials were conducted to evaluate the digestibility of a novel alternative ingredient, enhanced torula yeast (TY) Cyberlindnera jadinii, in diets for hybrid Striped Bass (HSB; White Bass Morone chrysops × Striped Bass M. saxatilis) and to evaluate graded inclusion levels of this product when replacing soybean products. Methods: In trial 1, the digestibility of TY was determined by testing a reference diet and a TY diet (reference and TY ingredient at an 80:20 ratio). A total of 90 fish were fed the experimental digestibility diets for 21 days, and fecal samples were collected using the stripping technique. In trial 2, a comparative feeding trial evaluated the replacement of soybean meal by TY on a crude protein basis at 50, 100, 200, and 300 g of TY/kg of experimental diet. A total of 150 HSB (18.6 ± 0.21 g/fish [mean + SE]) were distributed among fifteen 110‐L glass aquaria. Each diet was fed to triplicate groups of fish for 9 weeks. Result: In trial 1, apparent digestibility coefficients for protein, lipid, organic matter, and energy of TY were 0.97, 0.98, 0.75, and 0.75, respectively. The availability of essential amino acids also was generally high, ranging from 0.74 to 0.99. For trial 2, a second‐order polynomial regression indicated that the optimal inclusion levels of TY in diets were 102, 112, and 109 g/kg for weight gain, feed efficiency, and protein conversion efficiency, respectively. However, the muscle yield linearly decreased with the graded inclusion levels of TY. Linear increases in intraperitoneal fat, hepatosomatic index, and whole‐body lipid were observed as the inclusion of TY increased in the diet. Conclusion: In conclusion, nutrients from TY were well utilized by HSB, and it can replace soybean products without affecting growth performance, with the optimal TY inclusion level being 102–112 g/kg of diet. Impact statementThere is an increasing demand for environmentally friendly and cost‐effective alternative feed ingredients because of many fish species produced in intensive aquaculture requiring high‐quality protein ingredients. This study evaluated a torula yeast product that can be grown on complex carbohydrates derived from the wood industry, thereby converting low‐value substrates to a high‐quality protein ingredient. Based on results from separate digestibility and comparative feeding trials, nutrients from TY were well utilized by hybrid Striped Bass and the torula yeast product could replace soybean products without affecting growth performance, with the optimal inclusion level of 102–112 g per kg of diet. [ABSTRACT FROM AUTHOR]

Assessing the potential impacts of wind farm noise on fish is a crucial aspect of Environmental Impact Assessment (EIA) studies. There is increasing evidence of disturbances and effects on hearing and behavior in animals. The black rockfish (Sebastes schlegelii) is a commercially valuable rocky reef fish native to East Asia. However, empirical studies that measure the actual consequences are lacking. In this study, we used auditory evoked potentials (AEP) to assess the effects of dominant frequency noise emitted by offshore wind farms on the auditory sensitivity, hearing threshold, swimming, and feeding behavior of juvenile black rockfish. The experimental findings revealed that the most sensitive sound frequency was 200 Hz, with the lowest hearing threshold recorded at 86.4 ± 3.4 dB re 1 mPa. Following 3 and 7 days of exposure to 200 Hz noise at 110 dB, threshold shifts in black rockfish reached 19.0 dB and 13.3 dB, respectively. During the subsequent recovery phase, these shifts decreased to approximately 9.8 dB after 3 days, respectively. The noise-exposed group exhibited higher swimming duration, moving distance, and caudal fin swing frequency compared to the control group without noise exposure. Furthermore, noise prolonged the feeding rate of black rockfish. Our findings provide the first evidence of noiseinduced temporary threshold shift and behavioral disturbances in juvenile black rockfish, implying potential fitness consequences associated with noise pollutant. [ABSTRACT FROM AUTHOR]

Introduction: Preserving the marine ecological environment and safeguarding marine species is a global priority. However, human overfishing has led to a drastic decline in fish species with longer growth cycles, disrupting the equilibrium of the marine ecosystem. To address this issue, researchers are turning to deep learning techniques and state-of-the-art underwater devices, such as underwater robots, to explore the aquatic environment andmonitor the activities of endangered populations. This approach has emerged as a focal point of recent research in protecting the marine ecological environment. This study employs a deep learningbased object detection algorithm to identify fish species in complex underwater environments. Methods: The algorithm is built upon the You Only Look Once version 7(YOLOv7) algorithm, with the addition of the attention mechanism Convolutional Block Attention Module (CBAM) in the network's backbone. CBAM enhances the feature maps through the fusion of spatial attention and channel attention, ultimately improving the robustness and accuracy of the model's inference by replacing the original loss function CIoU with SCYLLAIntersection over Union(SIoU). In this paper, the rockfish pictures in the dataset Label Fishes in the Wild published by the National Marine Fisheries Service are selected, and the underwater image enhancement model (UWCNN) is introduced to process the pictures. Result: The experimental results show that the mean average precision (mAP) value of the improvedmodel on the test set is 94.4%, which is 3.5% higher than the original YOLOv7 model, and the precision and recall rate are 99.1% and 99%, respectively. The detection performance of the algorithm in the field of complex underwater environment is improved. Discussion: The underwater fish detection scheme proposed in this study holds significant practical value and significance in promoting the conservation of marine ecosystems and the protection of fish species. [ABSTRACT FROM AUTHOR]

Migratory behaviors of coastal Striped Bass Morone saxatilis are diverse and vary by latitude along the U.S. Atlantic Coast. Northern populations (e.g., north of Cape Hatteras, North Carolina) are anadromous, with spawning occurring in tidal freshwater/brackish rivers and adults leaving spawning locations during the winter to conduct north–south coastal migrations. The central Atlantic comprises a mixture of potamodromous and anadromous types, completing the natural continuum of behavioral modes along latitudinal ecotones. Southern populations (e.g., south of Cape Hatteras, North Carolina) are typically resident and potamodromous, completing full life cycles within river systems, and do not migrate along the Atlantic Coast. There are limited studies that have investigated daily movement of Striped Bass in the Southeast and no studies have documented movement of Striped Bass in the Great Pee Dee River, particularly with reference to spawning migrations. The objective of this study was to describe daily movement patterns and centers of attraction (e.g., spawning and resting stages) of Striped Bass in the Great Pee Dee River, South Carolina. We implanted 10 fish with hydroacoustic transmitters between 2013 and 2016. We describe daily movement and behavior using the state-space model with a two-dimensional spatial coordinate system. We recorded a total of 94,857 data points across all individuals and receivers. We observed two movement patterns. One group completed a seasonal migration (i.e., were recorded swimming upstream or downstream) that coincides with spring spawning season. A second group was present in the lower river section and Winyah Bay during the winter for 3 consecutive years but were never observed migrating up the Great Pee Dee River during the spring. One individual was documented swimming 80 river km north in the Atlantic Intracoastal Waterway, suggesting there are important overwintering locations outside their natal river. Additionally, there were significant gaps in observations for all individuals, particularly in the summer. It is possible that fish are leaving the main stem in search of thermal refuge within small tributaries. Identifying these overwintering areas and tributaries that serve as summer refuge is needed to determine stressors and fishing pressure of this important species. [ABSTRACT FROM AUTHOR]

Objective: Chesapeake Bay water temperatures have increased through time, and under various climate change scenarios they are projected to increase by an additional 2–6°C by the end of the 21st century. Previous work has shown that water temperatures are the primary trigger for Striped Bass Morone saxatilis spawning. Methods: Using spawning stock survey data (1985–2020) from the Potomac River and upper Chesapeake Bay and temperature data from an ichthyoplankton survey (sampled non‐continuously between 1954 and 2021) in the Nanticoke and Choptank rivers, this study examined how water temperature milestones that are important for Striped Bass spawning have changed over time as well as how selectivity‐corrected total female catch per unit effort has shifted with changes in water temperature and the age structure of the stock. Result: Water temperatures observed in the spawning stock survey were lower in the 1980s and 1990s and have been higher since the 2000s. A significant change in timing of the start of spawning was not detected in the spawning stock survey data, but a significant change was found in the timing of the end of spawning, suggesting that the spawning season has shortened. In addition, the date on which the last prespawn female was observed on the spawning grounds has also occurred earlier in the year since the 2000s. Results from the long‐term temperature data collected in the Choptank and Nanticoke rivers only showed a significant change through time for the start of spawning in the Nanticoke River. Conclusion: While these changes could affect egg and larval Striped Bass survival either through either direct mortality due to water temperature or changes in the timing of zooplankton blooms, the effects of climate change could be mitigated by having a broad range of spawning ages to maximize the chances that larval Striped Bass matching with prey availability. Impact statementWater temperatures have been shown to trigger Striped Bass spawning and are projected to increase through time in Chesapeake Bay due to climate change. This study examined how the timing of spawning has shifted with changing water temperatures and considers how managers might best manage the stock under changing environmental conditions. [ABSTRACT FROM AUTHOR]

Simple Summary: Fish meal is commonly used as the main protein source in aquafeeds. However, the increasing global demand and the overfishing of wild fish stocks commonly used as fish meal sources have restricted supply and increased the price of fish meal in recent decades. To achieve the goal of sustainable fish culture, fish meal replacement with an alternative source that is inexpensive and year-round available in aquafeeds is highly needed. Meanwhile, more than half of the total tuna is trashed as waste in tuna-canning processing plants. In the current study, we investigated the dietary substitution effect of fish meal with tuna by-product meal on growth, feed availability, and biochemical composition of the early stage of juvenile rockfish, one of the most widely farmed marine fish species in Eastern Asia. The results indicated that up to 40% of fish meal could be substituted with tuna by-product meal in the diets of rockfish without negatively influencing the growth, feed availability, and hematological parameters of rockfish. With the dietary replacement of 40% fish meal with tuna by-product meal in practical feeding, rockfish farmers are able to produce the highest economic return. This experiment was performed to assess the substitution impact of fish meal (FM) with tuna by-product meal (TBM) in feeds on growth and feed availability of the early stage of juvenile rockfish (S. schlegeli). Six experimental feeds were prepared to be isonitrogenous and isolipidic. Fifty-five percent of FM was contained in the control (Con) diet. In the Con diet, 20, 40, 60, 80, and 100% FM were replaced by TBM, named the TBM20, TBM40, TBM60, TBM80, and TBM100 diets, respectively. A total of 540 early-stage juvenile rockfish averaging 2.4 g was divided into 18 tanks and hand-fed to satiation for 56 days. Weight gain and feed consumption of rockfish fed the TBM20 and TBM40 diets were comparable to rockfish fed the Con diet. The specific growth rate (SGR) of rockfish fed the Con diet was comparable to rockfish fed the TBM20, TBM40, and TBM60 diets. Feed efficiency, biometric indices, hematological parameters, proximate composition, and amino acid profiles of rockfish were not impacted by dietary treatments. The economic profit index (EPI) of the Con, TBM20, and TBM40 diets were higher than that of all other diets. FM up to 40% could be substitutable with TBM in the diets of rockfish without deteriorating weight gain and feed consumption, but producing the highest EPI. [ABSTRACT FROM AUTHOR]