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The aim of this study was to develop a feeding protocol for the larviculture of Apistogramma cacatuoides, using the histological approach to larval nutrition conditions. For this, three experiments were carried out. Experiment 1 was carried out in a randomized design to determine the optimal amount of Artemia nauplii (AN) per larva, and three treatments were evaluated: P1—feeding with 25 A. nauplii per larva (AN/L) during the first 5 days, followed by 50 AN/L from the 6th to the 10th day and 100 AN/L from the 11th to the 20th day; P2 and P3—37 and 50 AN/L during the first 5 days, 75 and 100 AN/L from the 6th to the 10th day and 150 and 200 AN/L from the 11th to the 20th day. Experiment 2 was carried out in a randomized design to determine the daily frequency of feeding and evaluated four feeding frequencies: F1—feeding only once a day (09:00); (F2)—feeding twice a day (09:00 and 17:00); F3—feeding three times a day (09:00, 11:30 and 17:00); and F4—feeding four times a day (09:00, 11: 30, 14:00 and 17:00). Experiment 3 lasted 40 days and was conducted in a randomized design to evaluate three periods for the beginning of the feeding transition: WE10:AN for 10 days, followed by 3 days of co‐feeding and commercial feed until the end of the experimental period; WE15:AN for 15 days, followed by 3 days of co‐feeding and commercial feed; WE20:AN for 20 days, followed by 3 days of co‐feeding and commercial feed. The results of this study showed that, for the best development of the larvae, they should receive the feeding protocol 50−100−200 AN/L (P3) until the 20th day of exogenous feeding. From the 21st day, the transition to inert food should begin with 3 days of co‐feeding, and feeding during larviculture should be carried out at a frequency of twice a day; this protocol provided a good nutritional status for the larvae, as shown by the histological approach. [ABSTRACT FROM AUTHOR]

Over the past decade, an increasing number of studies have emphasized the importance of the host microbiome in influencing organismal health and development. Aligned with this understanding, our study aimed to investigate the potential association between the turbot (Scophthalmus maximus) phenotypic traits and the post-larval bacteriome. Turbot post-larvae were sampled from twenty randomly selected production cycles thirty days after hatching (DAH) across multiple post-larval production batches over a three-month period (April to June). Fish were selectively sampled based on five phenotypic traits, namely, normal, large, small, malformed, and depigmented. Our results showed that small-sized post-larvae had significantly higher bacterial phylogenetic diversity in their bacterial communities than all other phenotypes. A more in-depth compositional analysis also revealed specific associations between certain bacterial taxa and fish phenotypes. For example, the genera Aliivibrio and Sulfitobacter were enriched in small-sized post-larvae, while the family Micrococcaceae were predominantly found in larger post-larvae. Furthermore, genus Exiguobacterium was linked to depigmented larvae, and genus Pantoea was more prevalent in normal post-larvae. These observations underscore the importance of further research to understand the roles of these bacterial taxa in larval growth and phenotypic differentiation. Such insights could contribute to developing microbiome modulation strategies, which may enhance turbot post-larval health and quality and improve larviculture production. [ABSTRACT FROM AUTHOR]

Live food in the initial life stages of neotropical fish is essential for their development and health; however, it can significantly increase production costs. This study uses complete diets with varying moisture contents (47%, 35%, 24%, and 8%) as a cost-effective alternative in the co-feeding phase of surubim larvae, assessing their influence on development, digestive enzymes, and liver metabolism. In a completely randomized design, 3200 three-day-old Pseudoplatystoma sp. larvae (0.001 g) were distributed evenly among 16 aquariums (20 L), with 200 individuals per aquarium. For the first five days, all larvae were fed Artemia exclusively, after which they were fed experimental diets with varying levels of humidity (47%, 35%, 24%, and 8%) six times a day across four treatments and four replicates. The 21-day feeding trial demonstrated that larvae fed with 24% and 8% moisture diets exhibited increased (p < 0.05) weight gain, final length, and protein efficiency rate. The remaining growth parameters (i.e., specific growth rate and condition factor) did not show significant differences (p > 0.05) among the dietary treatments. Enzymatic analysis revealed that the 47% moisture diet enhanced the amylase and alkaline phosphatase activities, whereas the 24% and 35% moisture diets elevated the lipase and protease activities. The 47% moisture diet also resulted in increased alanine aminotransferase, aspartate aminotransferase, and albumin levels, along with visible hepatic histopathologies in samples, such as visible lipid vacuoles, displacement of the nucleus of the hepatocyte, and increased sinusoid spaces. No significant liver changes were observed in fish fed with other diets. Principal component analysis showed that diets with 8–24% moisture content were the most beneficial during the co-feeding phase of surubim larviculture. [ABSTRACT FROM AUTHOR]

The Lebranche mullet Mugil liza is a marine fish of great importance for artisanal and industrial fishing, as well as aquaculture. The use of live feeds during the larviculture phase of marine fish is a significant component of production costs. The present study evaluated the effects of the feeding transition on different larval stages of M. liza, from the combined supply of live feed (Brachionus rotundiformis + Artemia franciscana) and live + inert feed (Artemia franciscana + inert diet) until the weaning phase to only the inert diet. A total of 3240 M. liza larvae (weight 0.0133 ± 0.0062 g and length 0.793 ± 0.160 cm) were distributed among the 12 experimental units (n = 270), resulting in four groups with three replicates each. Treatment groups consisted of feed transition with A. franciscana (enriched metanauplii) to commercial inert feed starting weaning at four different larval ages: 28, 31, 34, and 37 days post hatching. Zootechnical performance indexes and intestinal histomorphometry were evaluated. Mortality, condition factor, and length variation coefficient did not show significant differences between treatments. Final weight, final length, weight gain, and length gain were significantly greater in larvae that started weaning at 31, 34, and 37 days post hatching. Weight coefficient of variation was significantly higher in larvae that started weaning at 28 days (67.51 ± 11.70) compared to 37 days (34.40 ± 7.30). In intestinal histology, villi height (180.3 ± 4.4) was significantly higher in larvae that started weaning at 37 days post hatching. Considering the evidence found in the present study, it is recommended to start weaning M. liza on the 31st day post‐hatching, using a 2‐day co‐feeding protocol (31st and 32nd days). From the 33rd day after hatching, M. liza larvae can receive only commercial feed. [ABSTRACT FROM AUTHOR]

The river prawn Macrobrachium vollenhovenii (Herklots, 1857) and the brackish river prawn M. macrobrachion (Herklots, 1851) are economically and ecologically significant West African species. Recent molecular studies suggest they might be different ecotypes of the same species, complicating taxonomy and sustainable aquaculture practices. Both species face significant threats from human exploitation, leading to high exploitation rates and smaller average sizes within populations. Seasonal variations affect their abundance, with M. macrobrachion more prevalent during the rainy season and M. vollenhovenii thriving in the dry season. Their omnivorous detritivorous feeding habits involve consuming detritus, diatoms, phytoplankton, and insect larvae during juvenile stages. Aquaculture of M. vollenhovenii and M. macrobrachion encounters difficulties such as limited hatchery technology and low larval survival rates. Efforts to cultivate juveniles or adults in captivity face obstacles like high mortality rates due to moulting stress, handling, feeding, and cannibalism. Reintroducing captive-bred prawns into the wild offers dual benefits: controlling snail populations that host parasite causing schistosomiasis and restoring ecological balance while enhancing local fisheries and providing socio-economic benefits. To achieve sustainable aquaculture, it is crucial to address taxonomic complexities, implement management measures to mitigate overexploitation, improve hatchery technology, optimise feeding strategies, reduce stress during moulting and handling, and engage local communities through capacity building and awareness programs. This review aims to contribute to a better understanding of these prawns, promoting informed decision-making for sustainable management, conservation, and socio-economic benefits in West Africa. [ABSTRACT FROM AUTHOR]

One of the most persistent challenges in walleye larviculture is the high rate of unobserved mortality occurring within the first 30 days post-hatch. Walleye larviculture is characterized by high mortality rates, but oftentimes, only a fraction of the total mortality in walleye larviculture is observed. Unobserved mortality is frequently attributed to a high rate of cannibalism, but decomposition of larvae and other factors may also be important contributors. Unobserved mortality can make walleye larviculture especially challenging as accurately estimating daily feed rations and forecasting larval production rely on accurate counts of surviving fish. Despite the importance of unobserved mortality, there is little empirical evidence available that assesses the temporal occurrence and causes of unobserved mortality in walleye larviculture. This study assessed when unobserved mortality occurs during walleye larviculture by examining survival at three timepoints (8, 15, and 30 days post-stocking). Tanks were cleaned daily and dead fry were enumerated to account for observed mortality. At the end of each treatment period, the tanks were drained, all remaining fry were enumerated, and the unobserved mortality rate was calculated. While observed mortality trended higher as trial duration increased, unobserved mortality did not increase significantly from the 8-day treatment suggesting that the bulk of unobserved mortality occurs during the first 8 days of walleye larviculture. [ABSTRACT FROM AUTHOR]

Arachidonic acid (AA) is an essential fatty acid that has vital influences on early development in marine fish larvae. In this regard, a 30-day research was run to examine the effects of live food enrichment with graded levels of AA on some physiological responses of Acanthopagrus latus larvae. Four experimental emulsions containing four levels of AA were used to enrich live foods (rotifer and Artemia), including very low (6%, N), low (12%, L), medium (24%, M), and high (37.8%, H) AA levels. Newly hatched larvae were distributed into twelve 250-L cylindrical tanks with initial density 15,000 larvae in each tank supplied with seawater (23 ± 1 °C; 40.0 ± 1.0 g L−1). Nannochloropsis oculata was used in a green water system and live foods were offered to larvae two times daily. Larvae in the H group had lower total length (7.24 ± 0.6 mm) than those in other treatments. The highest survival rate after air exposure and osmotic stress challenges was in the H group. The level of n-6 polyunsaturated fatty acids, mainly AA, was enhanced in the larval whole body with increasing AA level in the emulsion. The highest and lowest alkaline phosphatase activities were in the H and N groups, respectively. The aminopeptidase N and leucine-alanine peptidase activities in the N group were lower than those in the other treatments. The trypsin activity gradually increased with the increment of AA in the emulsions. The highest and lowest chymotrypsin, amylase, and pepsin activities were in H and N groups, respectively. The highest and lowest phospholipase A2 activity was in the M and N groups, respectively. The activity of catalase in the whole body of the M group was greater than that in the rest of the treatments. The highest and lowest superoxide dismutase activities were in M and N groups, respectively. The activity of glutathione reductase in the L and M groups was higher than that in the rest. Total antioxidant capacity in the whole body of larvae in the N group was lower than that in the other treatments and the H group showed the highest value. The whole body malondialdehyde level in the L group was lower than that in N and H groups and M showed intermediate value. Based on the findings of the present study, moderate levels of AA suggested for the enrichment of live foods in A. latus by considering n-3 long-chain polyunsaturated fatty acid content in the enrichment solution. [ABSTRACT FROM AUTHOR]

The Florida pompano, Trachinotus carolinus, is an ideal species for commercial aquaculture because of its rapid growth, tolerance to a range of environmental parameters, and high demand in the seafood market. This study detailed embryonic and early larval development of this species. Florida pompano followed similar developmental sequences to those observed in other marine teleosts, and embryos hatched between 22 and 28 h post‐fertilization. Significant brain lobe differentiation occurred prior to hatching. Pectoral fins were functional within 1‐day post‐hatch (dph). Substantial eye development occurred within 3 dph, indicating visual acuity prior to the onset of exogenous live feeding. Intestinal segments were differentiated by 3 dph, and rotifers were seen in the digestive tract by 4 dph. Digestive functions were limited through the first 7 dph because of the absence of functional gastric glands and gastric mucous cells in the rudimentary stomach, lipid vacuoles in the anterior intestines, and the persistence of acidophilic supranuclear vesicles in the posterior intestines. Within 7 dph, the pharyngeal arches differentiated, and hematopoietic tissue and mesonephric tubules were visible in the larval kidney. Their rapid larval development and organogenesis are additional factors that make Florida pompano an ideal species for aquaculture production and should encourage continued efforts toward commercialization. [ABSTRACT FROM AUTHOR]

The aim of the present study was to determine the optimal time to start weaning from Moina minuta to inert diet, assessing its effects on growth performance, stress resistance, feeding cost and intestinal histomorphometry of angelfish and severum during larviculture. Two separate 30-day experiments were conducted with 200 post-larvae each of angelfish (Pterophyllum scalare) and severum (Heros severus). At five days post-hatching, angelfish and severum had an average initial length and weight of 5.58 ± 0.13 mm and 1.72 ± 0.26 mg, and 6.38 ± 0.25 mm and 3.02 ± 0.27 mg, respectively. The larvae were distributed in twenty 1 L aquariums at a density of 10 post-larvae per liter. The experiments included five treatments with four replications, consisting of five supply periods of M. minuta for 0, 5, 10, 15 and 20 days (T0, T5, T10, T15 and T20), followed by a three-day weaning period (50 % M. minuta and inert diet) and then feeding only inert diet. The highest values of final length, length gain, final weight, weight gain, specific growth rate for both length and weight were observed in both species in T15 and T20. Only angelfish post-larvae had a higher value of survival rate when submitted to T15 and T20, and a higher stress resistance to air exposure when submitted to T10, T15 and T20. Both species had the lowest feeding costs in T20. Angelfish and severum post-larvae in T15 and T20 showed the highest value of intestinal villus height and perimeter. Severum post-larvae in T10, T15 and T20 had the best value of villus width. Angelfish post-larvae in T0 and T5 had the highest proportions of goblet cells, while severum post-larvae exhibited this only in T0. It is recommended that angelfish and severum post-larvae be fed with M. minuta for 15 days before weaning.

In a time of unprecedented coral reef decline, improved aquaculture protocols and high-quality live feeds may contribute to the sustainability of the ornamentals industry producing new valuable and stronger specimens bred under controlled conditions, mitigating the pressure on wild natural stocks. In the present study, the effect of microalgae enriched live feed diets (15 ind. mL−1), the copepod Acartia tonsa and the rotifer Brachionus plicatilis, were tested on early larvae stages (0–15 days post hatch) of the orchid dottyback Pseudochromis fridmani. Enriched A. tonsa significantly improved P. fridmani larval growth, survival, biochemical composition, as well as the morphological development of liver, intestine and skeletal system, compared to rotifers treatment. The results obtained showed that is feasible to totally replace the enriched rotifer B. plicatilis with the enriched copepod A. tonsa during first larval feeding of orchid dottybacks, resulting in a more robust larvae with better culture performance. Indeed, feeding larvae with enriched A. tonsa avoid the different negative effects when used enriched rotifers diets, which led to liver steatosis and nuclear pyknosis, delays in intestine and skeletal development, altered proximate composition and FA content. This study provided valuable information about rearing and breeding under controlled conditions of P. fridmani, contributing to its mass scale production and to the implementation of new hatchery protocols employing high quality live feeds.

Scallop cultivation on the coasts of Peru and Chile is continuously expanding, leading to increased larval production and the mounting need to enhance efficiency to boost sector productivity. This study focused on investigating how the water exchange system affects the development, survival, and performance of Argopecten purpuratus larvae. Three static water exchange systems (T1 [12-h exchange], T2 [24-h exchange], and T3 [48-h exchange]) and 2 recirculation systems (RAS 1 and RAS 2) were evaluated, with 3 replicates per treatment. The feed supplied in each treatment consisted of a mixture of the microalgae Isochrysis galbana, Diacronema lutheri, Chaetoceros calcitrans, Chaetoceros gracilis, and Nannochloropsis sp. at a concentration of 5 × 104 cell·mL–1·d–1. The results showed that survival was higher in T1 (80.49%) than in T2 (68.49%) or T3 (67.17%); lower survival was observed in RAS 2 (52.94%) and RAS 1 (6.34%). Furthermore, T1 resulted in significantly greater growth (shell height: 192.2 ± 9.03 μm; growth rate: 3.7 μm·d–1) than that of T2 or T3. Although RAS 1 was discarded due to high mortality, RAS 2 showed similar performance to that of T1 with regard to larval growth. Considering commercial factors and energy efficiency, T2 and T3 yielded the most favorable results in terms of larval survival and growth.

Genome editing by manipulating the embryos of Pacific bluefin tuna (PBT) was recently proposed for improving the breeding and aquaculture production of PBT. However, the yield of genome-edited eggs is limited due to the narrow timing of genome editing of embryos and the labor-intensive process. Therefore, the development of a small-scale larviculture method is necessary for efficient evaluation of the phenotype and traits of genome-edited PBT larvae. The plankton-kreisel tank can form a vertical rotating flow that may prevent the sinking syndrome of PBT larvae. In this study, we applied a plankton-kreisel tank (8-L) for PBT larviculture up to 10 days post-hatch (dph). We compared the survival rate and growth of PBT larvae reared in the 8-L plankton-kreisel tank and an 8-L cylindrical tank (CT). The survival rate in the plankton-kreisel tank at 10 dph (58.9 ± 4.8%) was significantly higher than that in the CT (4.8 ± 3.6%). Larval growth was not significantly different between these tanks. We observed that the larvae that sank to the tank bottom drifted with the strong vertical rotating flow along the tank wall during the night. This flow in the plankton-kreisel tank prevents the sinking syndrome. Thus, this apparatus is proposed for small-scale larviculture experiments in PBT. [ABSTRACT FROM AUTHOR]

Objective: The White‐barred Goby Amblygobius phalaena is a popular ornamental fish in the marine aquarium market. To achieve successful commercial production, efficient larval rearing techniques are crucial. Previous studies have achieved successful cultivation of White‐barred Goby larvae by using a combination of three live feed organisms—the ciliate Euplotes sp., the rotifer Brachionus rotundiformis, and the copepod Apocyclops royi nauplii—during the first feeding stage. However, the specific contributions of these live feed organisms to larval survival and growth remain unclear. Moreover, the optimal feeding density for the critical initial live feed organism has not been determined experimentally. In this study, we aimed to enhance the larviculture protocol for White‐barred Goby by introducing Portuguese oyster Crassostrea angulata trochophores and by addressing these knowledge gaps. Methods: Larvae were initially cultured through individual and combined feeding with four live feed organisms: Euplotes sp., Portuguese oyster trochophores, B. rotundiformis, and A. royi nauplii. The objective was to identify the optimal initial live feed organism during the first feeding stage by assessing the survival and growth performance of larvae. Subsequently, using this optimal live feed organism, larvae were cultured at four feeding densities (2, 5, 10, and 20 individuals/mL). Through evaluating feeding incidence, feeding intensity, survival, and growth performance, the aim was to determine the optimal feeding density for the selected live prey. Result: Our experiments revealed that White‐barred Goby larvae could consume both oyster trochophores and Euplotes sp. during the first feeding stage. However, larvae exhibited superior survival and growth performance when fed oyster trochophores. The optimal feeding density of oyster trochophores was determined to be 10 individuals/mL, while a feeding density as high as 20 individuals/mL resulted in decreased larval feeding incidence. Conclusion: These findings have significant implications for enhancing larval production programs for marine ornamental gobies and promoting their sustainable commercialization. Impact statementOur study enhances the larval rearing of the popular marine ornamental fish, the White‐barred Goby. Feeding them with oyster trochophores at appropriate densities improves their survival and growth. This leads to more efficient commercial production, alleviating fishing pressure on wild populations. It marks a significant stride in preserving the diversity of coral reef fish and fostering a sustainable aquarium industry. [ABSTRACT FROM AUTHOR]

Abstract The Florida pompano, Trachinotus carolinus, is an ideal species for commercial aquaculture because of its rapid growth, tolerance to a range of environmental parameters, and high demand in the seafood market. This study detailed embryonic and early larval development of this species. Florida pompano followed similar developmental sequences to those observed in other marine teleosts, and embryos hatched between 22 and 28 h post‐fertilization. Significant brain lobe differentiation occurred prior to hatching. Pectoral fins were functional within 1‐day post‐hatch (dph). Substantial eye development occurred within 3 dph, indicating visual acuity prior to the onset of exogenous live feeding. Intestinal segments were differentiated by 3 dph, and rotifers were seen in the digestive tract by 4 dph. Digestive functions were limited through the first 7 dph because of the absence of functional gastric glands and gastric mucous cells in the rudimentary stomach, lipid vacuoles in the anterior intestines, and the persistence of acidophilic supranuclear vesicles in the posterior intestines. Within 7 dph, the pharyngeal arches differentiated, and hematopoietic tissue and mesonephric tubules were visible in the larval kidney. Their rapid larval development and organogenesis are additional factors that make Florida pompano an ideal species for aquaculture production and should encourage continued efforts toward commercialization.

ABSTRACT This study evaluated the effect of co-feeding with commercial feed and live food (enriched or not with microalgae) on the growth and survival of Trachelyopterus galeatus larvae. Five treatments were carried out: commercial feed as a control (F); brine shrimp nauplii (BS); brine shrimp nauplii enriched with Chaetoceros sp. Microalgae (BSM); combined feed with brine shrimp nauplii (F+BS) and combined feed with brine shrimp nauplii enriched with microalgae (FBSM). The larvae (5.00±0.02 mg and 5.95±0.33mm) were reared for 30 days. There were no significant differences (P>0.05) in water quality between treatments, but there were significant differences in weight, weight gain and survival. The F+BS and F+BSM treatments, which involved co-feeding, showed the best results in final weight (0.168±0.004g and 0.169±0.007g) and weight gain (0.1278±0.004 g and 0.1294±0.007g), respectively. The treatments with live food, enriched or not, showed high survival rates of over 73%, with no significant differences between them. On the other hand, the exclusive use of feed resulted in low survival (36.7 ± 9.53%), indicating that this may result in low growth and make the production of T. galeatus larvae unfeasible.

Over the past decade, an increasing number of studies have emphasized the importance of the host microbiome in influencing organismal health and development. Aligned with this understanding, our study aimed to investigate the potential association between the turbot (Scophthalmus maximus) phenotypic traits and the post-larval bacteriome. Turbot post-larvae were sampled from twenty randomly selected production cycles thirty days after hatching (DAH) across multiple post-larval production batches over a three-month period (April to June). Fish were selectively sampled based on five phenotypic traits, namely, normal, large, small, malformed, and depigmented. Our results showed that small-sized post-larvae had significantly higher bacterial phylogenetic diversity in their bacterial communities than all other phenotypes. A more in-depth compositional analysis also revealed specific associations between certain bacterial taxa and fish phenotypes. For example, the genera Aliivibrio and Sulfitobacter were enriched in small-sized post-larvae, while the family Micrococcaceae were predominantly found in larger post-larvae. Furthermore, genus Exiguobacterium was linked to depigmented larvae, and genus Pantoea was more prevalent in normal post-larvae. These observations underscore the importance of further research to understand the roles of these bacterial taxa in larval growth and phenotypic differentiation. Such insights could contribute to developing microbiome modulation strategies, which may enhance turbot post-larval health and quality and improve larviculture production.

The effects of the intensification on the performance of the Amazon River prawn hatchery carried out in a simple recirculation system were investigated. Newly hatched larvae were stocked in 120 L tanks at 80, 100, 120 and 140 larvae L−1 in a closed recirculating system. The experiment used a randomized block design with five replicates. An exponential equation was adjusted to express the relationship between the stocking density and productivity (postlarvae L−1). The development, larval quality, survival and postlarval (PL) dry weight did not significantly differ among the treatments (p > 0.05). When 80 larvae were stocked, the productivity (54 ± 11 PL L−1) was lower than those at higher densities (p < 0.05). Stocking 120 and 140 larvae L−1 resulted in higher productivities (75 ± 18 and 80 ± 17 PL L−1, respectively) with a lower use of Artemia nauplii to produce each postlarvae (~1200 Artemia nauplii PL−1). The maximum mean M. amazonicum postlarval production estimated by the exponential model was 93 PL L−1. This means that despite the increase in stocking density, productivity tends to stabilize. The results showed that M. amazonicum tolerates high intensification in recirculating hatchery systems based on a crushed shell bed biofilter, and the intensification optimizes Artemia use. [ABSTRACT FROM AUTHOR]

We evaluated the potential of the euryhaline copepod Pseudodiaptomus inopinus as a prey to enhance the feeding activity of red sea bream Pagrus major larvae. Pseudodiaptomus inopinus was used to evaluate free amino acid composition and dietary effects on the rearing performance of fish larvae, in comparison to rotifers (control prey). Among free amino acids, alanine, arginine, and glycine were markedly higher in P. inopinus than in rotifers. Larvae were reared for 20 days post-hatching under three feeding treatments: rotifers (control), rotifers supplemented with copepods, and copepods only. Larvae fed copepods alone had a higher growth rate than those in the other treatments. However, the survival rates of these larvae were lower than those under control or copepod supplementation. While equivalent stocking densities of rotifers were employed in the rearing water for both larvae, whether supplemented with copepods or not, the supplemented treatment yielded diminished larval survival and failed to enhance growth rates. According to gut content analysis, larvae receiving supplemented treatment preferentially fed on copepods, and the number of ingested rotifers was reduced. As a result, total ingested mass was lower in the supplemented larvae. This study suggests that copepods containing free amino acid species negatively affect prey acceptance of fish larvae. [ABSTRACT FROM AUTHOR]

Artemia nauplii are widely used as fish larvae feed due to its beneficial nutritional characteristics for larval development; however, efficient feeding strategies are needed to balance its high costs. Therefore, we evaluated the effects of different densities of Artemia nauplii (100, 250, 500, 750, and 1000 nauplii/post-larvae) on the growth, survival, water quality, and myogenic gene expression of tambaqui (Colossoma macropomum) post-larvae cultivated in a recirculating aquaculture system. After 2 weeks of trial, there was a significant decrease in dissolved oxygen concentration with the increase in nauplii density, but it did not interfere with larval performance and survival. In the first week, larvae fed with fewer than 500 nauplii/post-larvae presented slower growth, while in the second week, larvae fed with 1000 nauplii/post-larvae had the highest final weight and length. Regression analysis suggests that the optimum feeding density of Artemia nauplii during the first week is 411 nauplii/post-larvae, while for the second week, the growth increased proportionally to the feeding densities. The relative expression of the myod, myog, and mstn genes was higher in larvae fed with fewer than 500 nauplii/post-larvae. Although low-growing larvae showed increased expression of myod and myog genes, responsible for muscle hyperplasia and hypertrophy, respectively, mstn expression may have played a significant inhibitory role in larval development. Further research is needed to better determine the effects of the live food on the zootechnical performance and the expression of the myogenic genes in the initial phase of the life cycle of the tambaqui post-larvae. [ABSTRACT FROM AUTHOR]

The objective of this study was to elucidate the effect of temperature on food intake and time for digestion in larvae of Lophiosilurus alexandri. An experiment was performed with four constant temperatures (23°C, 26°C, 29°C, and 32°C), four ages (8, 13, 18, and 23 days post-hatching (DPH)) and eight sampling times (5, 15, 30, 45, 60, 120, 180, and 300 minutes after feeding). The effect of temperature was more evident at 18 and 23 DPH. Due to the increase in age and temperature, there was a decrease in the time to reach the highest rate of digested nauplii. In addition, the larvae were estimated to ingest up to 0.30 ± 0.10 MJ/larva at 32°C in the first meal of the day. Temperatures of 29°C and 32°C provided the most satisfactory results for intake, digestion rate, and intake as percentage of live weight in one meal. [ABSTRACT FROM AUTHOR]

Aquaculture plays a crucial role in meeting the increasing global demand for food and protein sources. However, its expansion is followed by increasing challenges, such as infectious disease outbreaks and antibiotic misuse. The present study focuses on the genetic and functional analyses of two Lacticaseibacillus paracasei (BF3 and RT4) and two Lactiplantibacillus plantarum (BF12 and WT12) strains isolated from a rotifer cultivation tank used for turbot larviculture. Whole-genome sequencing (WGS) and bioinformatics analyses confirmed their probiotic potential, the absence of transferable antibiotic resistance genes, and the absence of virulence and pathogenicity factors. Bacteriocin mining identified a gene cluster encoding six plantaricins, suggesting their role in the antimicrobial activity exerted by these strains. In vitro cell-free protein synthesis (IV-CFPS) analyses was used to evaluate the expression of the plantaricin genes. The in vitro-synthesized class IIb (two-peptide bacteriocins) plantaricin E/F (PlnE/F) exerted antimicrobial activity against three indicator microorganisms, including the well-known ichthyopathogen Lactococcus garvieae. Furthermore, MALDI-TOF MS on colonies detected the presence of a major peptide that matches the dimeric form of plantaricins E (PlnE) and F (PlnF). This study emphasizes the importance of genome sequencing and bioinformatic analysis for evaluating aquaculture probiotic candidates. Moreover, it provides valuable insights into their genetic features and antimicrobial mechanisms, paving the way for their application as probiotics in larviculture, which is a major bottleneck in aquaculture. [ABSTRACT FROM AUTHOR]

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One of the most persistent challenges in walleye larviculture is the high rate of unobserved mortality occurring within the first 30 days post-hatch. Walleye larviculture is characterized by high mortality rates, but oftentimes, only a fraction of the total mortality in walleye larviculture is observed. Unobserved mortality is frequently attributed to a high rate of cannibalism, but decomposition of larvae and other factors may also be important contributors. Unobserved mortality can make walleye larviculture especially challenging as accurately estimating daily feed rations and forecasting larval production rely on accurate counts of surviving fish. Despite the importance of unobserved mortality, there is little empirical evidence available that assesses the temporal occurrence and causes of unobserved mortality in walleye larviculture. This study assessed when unobserved mortality occurs during walleye larviculture by examining survival at three timepoints (8, 15, and 30 days post-stocking). Tanks were cleaned daily and dead fry were enumerated to account for observed mortality. At the end of each treatment period, the tanks were drained, all remaining fry were enumerated, and the unobserved mortality rate was calculated. While observed mortality trended higher as trial duration increased, unobserved mortality did not increase significantly from the 8-day treatment suggesting that the bulk of unobserved mortality occurs during the first 8 days of walleye larviculture.

Abstract Patella candei d'Orbigny, 1840 is a valuable resource from the European Macaronesia. Limpet aquaculture is a recent research field that could contribute to reducing anthropogenic impact and developing appropriate restocking technologies. This study presents the results of 14 assays performed under laboratory culture conditions aimed at: (1) improving the larval production methodologies for limpets through the optimization of the artificial maturation of the oocytes and the sperm density required for fertilization and incubation, (2) validating a larviculture protocol for P. candei, and (3) evaluating rearing density effect on larvae performance until the pediveliger stage. Results obtained in the present study indicate that NH4OH is more efficient than KOH and NaOH to enhance the artificial maturation of the oocytes. The optimal combination was NH4OH at pH 9.0 for a duration of 20–30 min. The optimal sperm density was approximately 105 sperm cells mL−1 as in other limpet species. The larviculture method described hereby demonstrated to be efficient to obtain viable pediveligers, that is, the larval survival was high, and the artificial maturation did not influence negatively the posterior larval development. The rearing density, within a range from 2.5 to 30 larvae mL−1, showed minimal influence on survival and development.

Fishes belonging to the family Pomacentridae (clownfishes and damselfishes) dominate the marine ornamental fish trade. However, only 1.0–4.2% of marine ornamental species traded in the US are reproduced in captivity, while the vast majority are wild-caught, an environmentally damaging practice. Reproduction in captivity undoubtedly is an adequate strategy for moving in the direction of sustainability. Among ornamental marine fish species, the most spectacular advances in captive breeding have been made for clownfishes. Twenty-five species of clownfishes have been captive-bred for commercial purposes. Furthermore, numerous clownfish varieties or color morphs have been developed through selective breeding and hybridization between species has been achieved. Of at least thirty-nine damselfish species that have been reproduced in captivity, only nine are currently commercially available. This is related to the small size of eggs and to the underdeveloped state of altricial damselfish larvae. In addition, long larval periods (up to 50 dph) and low survival rates (typically less than 10%) create barriers to the success in commercial aquaculture of damselfishes. Improvements in the low survival of damselfish larvae can be expected as zootechnical aspects for larviculture are perfected (especially improved nutrition). [ABSTRACT FROM AUTHOR]

Objective: The color of the environment positively influences the development of some fish species. Thus, we evaluated whether different aquarium colors affected the metamorphosis process of Tomato Clownfish Amphiprion frenatus. Methods: Operationally, we distributed the Tomato Clownfish larvae into white, yellow, blue, or black aquaria and monitored the larval development until 61 days posthatch. Result: We found that environmental color influenced the early development of Tomato Clownfish and their metamorphosis process. In the black aquarium treatment, 87.2% of the larvae in block I completed metamorphosis and reached the juvenile stage, and 59.3% of larvae in block II completed metamorphosis (blocks represented two successive spawns). These high percentiles of metamorphosed larvae were not observed in the other tank color treatments. Conclusion: Thus, our results suggest that the metamorphosis of Tomato Clownfish could be accelerated if the larviculture occurs in darker‐color conditions, especially black aquaria. This result has practical and economic implications since Tomato Clownfish specimens are commercialized at the juvenile stage. Impact statementWe showed that the metamorphosis of Tomato Clownfish could be accelerated if the larviculture occurs in darker color conditions, especially black aquaria. This result has practical and economic implications since the Tomato Clownfish specimens are commercialized at the juvenile stage. [ABSTRACT FROM AUTHOR]

The trade of aquarium organisms is growing worldwide. This market depends on a continuous supply of healthy and colorful aquatic animals, but this sector has few initiatives. However, in the last decade, there has been a growing interest in researching captive breeding of these animals, aiming to develop a more sustainable aquarium hobby. Larviculture is an important phase in the cultivation process because the larvae are more sensitive to stress and variations in the bulk of variables, such as temperature, salinity, nutritional management, light intensity and spectrum, and environmental background colors. Because background color could be a promoter variable of proper welfare, we tested whether it affects the endocrine response of tomato clownfish Amphiprion frenatus larvae to an acute stress challenge. We show that background color influences the endocrine stress axis responsiveness in tomato clownfish. When fish were subjected to a standard acute stressor of 61 days after hatching, only fish adapted to white walls increased the whole-body cortisol levels. From the results presented herein, we recommend that white tanks be avoided for A. frenatus larviculture. Both, the less stress level and the good welfare condition of larvae reared in colored tanks may have robust, practical applications since almost all clownfish in the ornamental aquarium trade come from captive breeding. [ABSTRACT FROM AUTHOR]

Patella candei d'Orbigny, 1840 is a valuable resource from the European Macaronesia. Limpet aquaculture is a recent research field that could contribute to reducing anthropogenic impact and developing appropriate restocking technologies. This study presents the results of 14 assays performed under laboratory culture conditions aimed at: (1) improving the larval production methodologies for limpets through the optimization of the artificial maturation of the oocytes and the sperm density required for fertilization and incubation, (2) validating a larviculture protocol for P. candei, and (3) evaluating rearing density effect on larvae performance until the pediveliger stage. Results obtained in the present study indicate that NH4OH is more efficient than KOH and NaOH to enhance the artificial maturation of the oocytes. The optimal combination was NH4OH at pH 9.0 for a duration of 20–30 min. The optimal sperm density was approximately 105 sperm cells mL−1 as in other limpet species. The larviculture method described hereby demonstrated to be efficient to obtain viable pediveligers, that is, the larval survival was high, and the artificial maturation did not influence negatively the posterior larval development. The rearing density, within a range from 2.5 to 30 larvae mL−1, showed minimal influence on survival and development. [ABSTRACT FROM AUTHOR]

Context: Balistes capriscus is relevant for fishing worldwide, but there is no consistent information on the maintenance of the species in a captive environment. Aims: Develop protocols for the reproduction of the species in aquaculture systems, contributing to the maintenance of the supply in the commerce through captive breeding. Methods: A Balistes capriscus couple was selected on the basis of behavioural observations. Nutritional and environmental stimuli were invested in obtaining natural spawning. After reproduction, the larvae were regularly observed under an microscope to monitor the ontogenic development. In larviculture, feeds based on Brachionus plicatilis (10 mL−1) and Nannochloropsis oculata (150 000 cells mL−1) and pate formulated with Artemia salina , Nannochloropsis oculata , sardines and commercial feed were evaluated. Key results: The eggs had a diameter of 667.5 μm (±21.66) and formed a mass adhered to the substrate. Newly hatched larvae had a total length of 1653.63 μm (±213.97). The first food intake was evidenced 72 h after hatching; however, larvae did not survive more than 6 days. Conclusions: The reproduction in laboratory of the species is viable; however, larviculture remains a limiting factor. Implications: The success in captive breeding is essential for the introduction of B. capriscus in aquaculture, and for the conservation of the species. This study observed the formation of a pair within a group of grey triggerfish (Balistes capriscus) in the laboratory, culminating in reproduction and enabling studies on the larviculture of the species. The results indicated that it is possible to keep small groups of breeders in captivity, but the individualisation of couples may be necessary, because of the aggressiveness towards other individuals. The hatchery phase is still a strong limiting factor for the artificial propagation of the species, because it demonstrates specificity regarding the first exogenous food. [ABSTRACT FROM AUTHOR]

Summary: Brazilian basslet Gramma brasiliensis is a fish highly appreciated by the marine ornamental industry. There is an increasing interest in the development of a breeding protocol for this species. However, descriptions of the reproductive biology, eggs and larval development are scarce. This study was the first to describe the spawning, eggs and larvae of G. brasiliensis in captivity, including mouth size information. Six spawning events produced egg masses with 27, 127, 600, 750, 850, and 950 eggs. Larger egg masses showed embryos with at least two different developmental stages. Eggs are spherical (∼1.0 mm diameter), held together by filaments entangling chorionic projections. Larvae with fewer than 12 hph (hours post-hatch) presented 3.55 mm standard-length, well developed eyes, fully absorbed yolk sac, an inflated swim bladder and mouth opened. Exogenous feeding on rotifers began within 12 hph. The average mouth width at first feeding was 0.38 mm. The first settled larva was noted by day 21. This information should help to determine appropriate diets and prey-shift time during the larviculture of the species. [ABSTRACT FROM AUTHOR]

The primary aim of this study was to comprehensively evaluate the welfare of Nile tilapia (Oreochromis niloticus) throughout their entire life cycle within aquaculture, spanning from reproduction to slaughter. The methodology was structured to identify welfare indicators closely aligned with the principles of animal freedoms defined by the Farm Animal Council, encompassing environmental, health, nutritional, behavioral, and psychological freedom. Notably, psychological freedom was inherently considered within the behavioral and physical analyses of the animals. To accomplish this, an integrative systematic literature review was conducted to define precise indicators and their corresponding reference values for each stage of tilapia cultivation. These reference values were subsequently categorized using a scoring system that assessed the deviation of each indicator from established ideal (score 1), tolerable (score 2), and critical (score 3) ranges for the welfare of the target species. Subsequently, a laboratory experiment was executed to validate the pre-selected health indicators, specifically tailored for the early life stages of tilapia. This test facilitated an assessment of the applicability of these indicators under operational conditions. Building on the insights gained from this experimentation, partial welfare indices (PWIs) were computed for each assessed freedom, culminating in the derivation of a general welfare index (GWI). Mathematical equations were employed to calculate these indices, offering a quantitative and standardized measure of welfare. This approach equips tilapia farmers and processors with the tools necessary for the continuous monitoring and enhancement of their production systems and stimulate the adoption of more sustainable and ethical practices within the tilapia farming.

The effects of the intensification on the performance of the Amazon River prawn hatchery carried out in a simple recirculation system were investigated. Newly hatched larvae were stocked in 120 L tanks at 80, 100, 120 and 140 larvae L−1 in a closed recirculating system. The experiment used a randomized block design with five replicates. An exponential equation was adjusted to express the relationship between the stocking density and productivity (postlarvae L−1). The development, larval quality, survival and postlarval (PL) dry weight did not significantly differ among the treatments (p > 0.05). When 80 larvae were stocked, the productivity (54 ± 11 PL L−1) was lower than those at higher densities (p < 0.05). Stocking 120 and 140 larvae L−1 resulted in higher productivities (75 ± 18 and 80 ± 17 PL L−1, respectively) with a lower use of Artemia nauplii to produce each postlarvae (~1200 Artemia nauplii PL−1). The maximum mean M. amazonicum postlarval production estimated by the exponential model was 93 PL L−1. This means that despite the increase in stocking density, productivity tends to stabilize. The results showed that M. amazonicum tolerates high intensification in recirculating hatchery systems based on a crushed shell bed biofilter, and the intensification optimizes Artemia use.

A common problem in marine fish hatcheries is the lack of functional embryonic parameters reliably predicting favorable larval outcomes. Embryos characterized as high-quality by typical assessment methods frequently result in weak larvae with high mortality during the endo-exotrophic transition. Thus, because there is no universal consensus on what parameters are most associated with successful larval survivability, this study aims to determine the most reliable, practical, and real-time predictor of vitality at the earliest developmental stage for first-feeding larvae of L. guttatus. From 18 mass volitional spawnings, the reproductive performance and quality of embryos and larvae were assessed by following quality parameters: total fecundity per spawning, percentage of floating eggs, fertilization rate, blastomere morphology score (at 8–32 cell stages), egg and oil globule volumes, coefficient of variation of eggs and oil globule diameters, percentage of poly-globular eggs, oil globule-to-egg volume percentage, morphological appearance and survival rates at 24 (hatching), 48 and 72 h post-spawning, larvae transition rate, and survival activity index (SAI). SAI was used as a larval vitality benchmark to determine the predictive capacity of the abovementioned parameters. Our results show that blastomere morphology score was the only parameter positively correlated with SAI. However, when examining each component of blastomere morphology to SAI prediction, only the presence of cell inclusions, but not size, symmetry, margins, or adhesions of blastomeres, predict the SAI. This reveals that embryos with defective blastomeres can develop into normal-appearing larvae but are weak to starvation. Therefore, cell inclusions are the best real-time, early, reliable, and functional predictor of first-feeding larvae vitality in L. guttatus.

The microalgae effect on population performance and fatty acid composition of Apocyclops panamensis was studied in two independent experiments (E), with starting densities of 4,000 (E1) and 8,000 nauplii L-1 (E2). In both experiments, copepods were fed once a day for 20 days in 0.4 L triplicates with a single-species diet containing Isochrysis galbana at 1 105 cells mL-1 day-1 (ISO), a two-species diet containing Nannochloropsis sp. at 1 105 cells mL-1 day-1 and I. galbana at 0.5 105 cells mL-1 day-1 (N + I), and a single-species diet containing Nannochloropsis sp. at 2 105 cells mL-1 day-1 (NAN). In E1, the highest final total animal density was reached with diet ISO (11,000 ind. L-1) and N + I (14,000 ind. L-1). In E2, the highest final densities were also found with ISO (8,000 ind. L-1) and N + I (6,000 ind. L-1). At day 20, 90 % of the copepods belonged to nauplii and copepodite stages, except for NAN in E2. In E1, the number of eggs per females was higher when the diet included I. galbana in both experiments. Thus, copepods fed with diets containing I. galbana had the best performance. Exclusive feeding with Nannochloropsis sp. yielded copepods with higher omega-6 fatty acids (n-6) percentage, while those fed with I. galbana had a higher omega 3 (n-3)/n-6 ratio. The docosahexaenoic acid (DHA) content and the DHA/EPA ratio were higher in copepods fed exclusively I. galbana. Our data indicate that I. galbana provides a suitable nutritional profile for A. panamensis with 0.5–1.0 105 I. galbana cells mL-1 day-1, reaching high densities of 6,000–14,000 copepods L-1, a 1.8–2.6 % of DHA and a DHA/EPA ratio of 1.6–2.9. We conclude that A. panamensis has the potential for intensive cultivation and therefore is suitable as live feed for finfish larviculture requiring a fatty acid profile rich diet in omega-3 fatty acids and DHA.

This work aimed to develop a methodology for marking Artemia with different markers and evaluating their passage rate and digestibility in Lophiosilurus alexandri larvae of different ages. In the first phase, Artemia nauplii were marked 28 h after hatching with chromium oxide, titanium dioxide and NANOLIPE®. Contact times with the markers were 30, 60, 90 min at a concentration of 500 mg/L. Titanium dioxide had a higher concentration in Artemia than the other markers. The passage rate did not differ significantly between titanium and NANOLIPE®. In the second phase, the apparent digestibility of the protein in Artemia nauplii was evaluated for L. alexandri larvae at three ages. Average real protein digestibility at the three ages was 95.08%, demonstrating Artemia as a good quality food. All ages exhibited the same final time of fecal excretion of 30 min after feeding. Artemia nauplii presented satisfactory results for assimilation for all markers tested. In determining the digestibility of Artemia protein, we can conclude that chromium oxide and NANOLIPE® were good markers of animal metabolism and titanium dioxide was the worst marker of Artemia digestibility for the initial stages of L. alexandri. [ABSTRACT FROM AUTHOR]

Simple Summary: High flesh quality, along with a good potential for intensive farming in a Recirculating Aquaculture System (RAS), make the pike-perch (Sander lucioperca) a valuable fish species both from the industry and the research point of view. Although high electricity demands have been attributed to it, fish farming in a RAS is recognized as the key strategy for sustainable fish farming, given its minimal usage of natural resources as well as its independence of outdoor weather conditions. Although the older juvenile stages of pike-perch are well adapted to indoor rearing conditions, the larval and early juvenile stages seem to be particularly sensitive to indoor rearing. Switching to the indoor production of pike-perch larvae would support the continuous, weather-independent, production of fish throughout the year. Hence, our study aimed to identify the pros and cons of rearing pike-perch larvae and early juveniles (nursing period) in indoor versus outdoor systems. For this purpose, we compared the effects of pike-perch nursing in both systems on the later growth and survival of the fish. Our results show that, although nursing indoors increases fish mortality, it provides a basis for improved fish growth later in life. This can eventually shorten the period for the production of market-size fish, and, along with the advantages related to the year-round production of larvae, provide higher yields to fish farmers in the long run. This study aimed to estimate the efficacy of two pike-perch juvenile production technologies: exclusive Recirculating Aquaculture System (RAS) culture (the RAS group) and pond larviculture with a transfer to the RAS at the 42nd day post-hatch (DPH). Both direct weaning on dry feed (the Pond-D group) and 10-day gradual weaning using bloodworms (the Pond-B group) after transfer to the RAS were evaluated in pond-nursed fry. Their survival and morphometric indices were monitored after the RAS habituation period (first 10 days), after the 18-day post-habituation period and after an additional 30 days of on-grow. Our results indicate a negative allometric growth of the pond-nursed fish during the nursing period, which was slower (p < 0.0001) in comparison to the RAS-nursed fry (16.3 ± 0.4 vs. 17.8 ± 0.7%/day). After transfer, these fish grew faster than the RAS-nursed fry (7.7 ± 0.1, 4.9 ± 0.5 and 6.1 ± 0.6 during habituation, 8.5 ± 0.6, 9.3 ± 0.5 and 6.7 ± 0.1%/day during post-habituation period, in the Pond-B, Pond-D and RAS groups, respectively). However, four weeks afterwards, the RAS-nursed fry were again superior in terms of growth (4.0 ± 0.1, 3.6 ± 0.2 and 4.6 ± 0.2%/day, for the Pond-B, Pond-D and RAS groups, respectively), and this was accompanied by a significantly lower feed conversion ratio in this group. Although the survival of the RAS-nursed fry during the nursing period was lower in comparison to the pond-reared fry (11.3 vs. 67.3%), the RAS seems to provide a long-term growth advantage. [ABSTRACT FROM AUTHOR]

Live feed enrichments are often used in fish larvicultures as an optimized source of essential nutrients to improve larval growth and survival. In addition to this, they may also play an important role in structuring larval-associated microbial communities and may help improve their resistance to diseases. However, there is limited information available on how larval microbial communities and larviculture water are influenced by different live feed enrichments. In the present study, we investigated the effects of two commercial rotifer enrichments (ER) on turbot (Scophthalmus maximus) larval and post-larval gut-associated bacterial communities during larviculture production. We evaluated their effects on bacterial populations related to known pathogens and beneficial bacteria and their potential influence on the composition of bacterioplankton communities during larval rearing. High-throughput 16S rRNA gene sequencing was used to assess the effects of different rotifer enrichments (ER1 and ER2) on the structural diversity of bacterial communities of the whole turbot larvae 10 days after hatching (DAH), the post-larval gut 30 DAH, and the larviculture water. Our results showed that different rotifer feed enrichments were associated with significant differences in bacterial composition of turbot larvae 10 DAH, but not with the composition of larval gut communities 30 DAH or bacterioplankton communities 10 and 30 DAH. However, a more in-depth taxonomic analysis showed that there were significant differences in the abundance of Vibrionales in both 10 DAH larvae and in the 30 DAH post-larval gut fed different RE diets. Interestingly, the ER1 diet had a higher relative abundance of specific amplicon sequence variants (ASVs) related to potential Vibrio-antagonists belonging to the Roseobacter clade (e.g., Phaeobacter and Ruegeria at 10 DAH and Sulfitobacter at 30 DAH). In line with this, the diet was also associated with a lower relative abundance of Vibrio and a lower mortality. These results suggest that rotifer diets can affect colonization by Vibrio members in the guts of post-larval turbot. Overall, this study indicates that live feed enrichments can have modulatory effects on fish bacterial communities during the early stages of development, which includes the relative abundances of pathogenic and antagonist taxa in larviculture systems. [ABSTRACT FROM AUTHOR]

Penaeus vannamei is the main species of shrimp farmed worldwide, and for Ecuador it is the first non-oil economic sector. However, various pathogens, including white spot syndrome virus (WSSV), threaten the sustainability of shrimp farming. P. vannamei larvae are susceptible to WSSV infection via vertical or horizontal transmission. To decrease the incidence of WSSV in PLs, a bioassay was performed by exposing P. vannamei shrimp (PL25), which were negative for WSSV and white spot disease (WSD), to two protective factors, water temperature (T = 24 °C and T = 31 °C), and immunestimulation using β-1,3-glucans (BG) (with and without BG added to the food), using a crossed two-factor design, for 20 days. The incidence of WSSV and WSD was modeled using generalized linear model (GLM). The strength of the association between the response and explanatory variables was estimated using the odds ratio [Exp (Beta)] and interpreted as the level of risk for the incidence of WSSV or WSD in one of the categories compared to the baseline category in the GLM. Odds ratios were considered significant if their 95 % confidence interval did not include the value 1. The results showed that BG had a significant negative effect on the number of WSSV-positive animals. In addition, a lower probability of WSSV infection was determined by combining 31 °C and BG. In this treatment, the WSD injuries were almost undetectable. Most larvae shrimps affected by WSD exhibited injuries to the antennal gland and connective tissue. In situ hybridization analysis revealed that 29 % of shrimp, initially negative by histology, were positive for WSSV. The virus was detected mainly in the nervous tissue of the head, epithelium, connective tissue of the head appendages, and the oral region surrounding the integumental glands. Apoptosis analysis showed a weak signal in nerve tissue but was more intense in epithelial cells of the head appendages, in association with cuticular damage. According to the findings, WSSV could disseminate among shrimp populations by infecting them through the TG and epithelium of the head appendage, followed by connective tissue and nervous tissue. However, applying BG at 31 °C may serve as a protective measure to reduce WSD injuries and restrict WSSV dissemination. • β-glucan protects Larvae shrimp against WSSV and WSD. • At 31 °C, β-glucans reduced WSSV infection probability and WSD tissue damage. • The WSSV would utilize various entry portals on the head appendages. • Apoptosis causes cuticle damage, raising WSSV infection risk. [ABSTRACT FROM AUTHOR]

The daily variations of temperature are one of the main synchronizers of the circadian rhythms. In addition, water temperature influences the embryonic and larval development of fish and directly affects their metabolic processes. The application of thermocycles to fish larvae has been reported to improve growth and the maturation of the digestive system, but their effects on metabolism are poorly understood. The aim of the present study was to evaluate the effect of two different temperature regimes, cycling versus constant, on the daily rhythms of metabolic factors of Nile tilapia (Oreochromis niloticus) larvae. For this purpose, fertilized eggs were divided into two groups: one reared in a 31 °C:25 °C day:night thermocycle (TCY) and another group maintained in a constant 28 °C temperature (CTE). The photoperiod was set to a 12:12 h light/dark cycle. Samples were collected every 4 h during a 24-h cycle on days 4, 8 and 13 post fertilization (dpf). The expression levels of alanine aminotransferase (alt), aspartate aminotransferase (ast), malic enzyme , glucose-6-phosphate dehydrogenase (g6pd), phosphofructokinase (pfk) and pyruvate kinase (pk) were analyzed by qPCR. Results showed that, in 13 dpf animals, most of the genes analyzed (alt , ast , malic , g6pd and pfk) showed daily rhythms in TCY, but not in the group kept at constant temperature, with most acrophases detected during the feeding period. An increase in nutrient metabolism around feeding time can improve food utilization and thus increase larval performance. Therefore, the use of thermocycles is recommended for tilapia larviculture. [Display omitted] • Temperature cycles are crucial for optimizing developmental physiology and metabolism in Nile tilapia larvae. • Tilapia larvae of 13 dpf showed daily rhythms in the gene expression of several metabolic enzymes. • Rearing larvae under thermocycles seemed to elicit a higher number of rhythmic factors than constant water temperature. • Metabolic rhythms can anticipate the time of feeding, improving the efficiency of nutrient utilization [ABSTRACT FROM AUTHOR]

Fish processing byproducts are conventionally used in live feed production for larviculture because of their low cost and high productivity. However, waste-generated bacteria may cause pathogen proliferation, and antibiotics are widely used to reduce the bacterial loads of live feeds. In this study, tilapia processing byproducts were hydrolyzed into fish protein hydrolysate (FPH). Subsequently, the FPH was used to culture Rhodopseudomonas palustris, a photosynthetic bacterium (PSB), as a nutritional source for live feed. The results of the in vitro pathogen inhibition assay indicated that R. palustris significantly inhibited the growth of Aeromonas hydrophila, Edwardsiella tarda, Lactococcus garviae, and Streptococcus iniae in the FPH supernatant (p

Larval mortality constitutes the major bottleneck in Centropyge species aquaculture. Marine fish eggs and larvae are sensitive to abiotic conditions variations, as salinity. Captive natural spawning of Centropyge aurantonotus were used to evaluate effects of salinity on eggs and larvae up to 72 hours post hatch (hph). Eggs were transferred from 33‰ to 10‰, 15‰, 20‰, 25‰, 30‰, 35‰ and 40‰ salinity, 27 ± 0.2°C. Buoyancy, water column distribution, incubation period and hatching rate were evaluated in eggs. For larvae, swimming behaviour, water column distribution, survival rates, standard length, yolk sac and oil drop volume, conversion rate of yolk sac in growth, pigmentation, deformities, mouth size and eye diameter were examined. The buoyancy was positive at salinities >30‰, positive to neutral at 30‰ and negative at <30‰. Neutrally buoyant eggs and larvae showed greater water column distribution than positive and negatively buoyant ones. Swimming behaviour was active in positive and neutral buoyancy. Incubation period was inversely proportional to salinity increase. Hatching rate was higher at 30‰, when compared to 10‰ and 15‰. At 10‰–25‰, deformities and high mortality rates of larvae were observed. Between 30‰ and 40‰, larvae of 72 hph showed no deformities, active swimming behaviour, higher survival rate (~87%), greater mouth size (~129.81 μm) and eye diameter (~170.1 μm) than 10‰ and 15‰. Salinities between 30‰ and 40‰ were adequate for rearing C. aurantonotus eggs and larvae up to 72 hph, 30‰ salinity increased their water column distribution and optimized hatching rate and adverse effects occurs at 10‰–25‰. [ABSTRACT FROM AUTHOR]

The present study aimed to evaluate the growth performance, batch uniformity, and survival rate of the Amazonian ornamental fish Heros severus and Pterophyllum scalare during the post-larvae growing stage, fed with diets containing levels of Euterpe oleraceae essential oil (EOO) during 30 days. In the first experiment, 160 H. severus post-larvae were distributed in 16 aquariums (1 L), and in the second, 200 P. scalare post-larvae were randomly distributed in 20 aquariums (1 L). The experiments were carried out in a completely randomized design, with four treatments for H. severus (0.0%, 0.50%, 1.00%, and 2.00% of dietary EOO) and five treatments for P. scalare (0.0%, 0.5%, 1.0%, 2.0%, and 4.0% of dietary EOO), both with four replications and dietary EOO being included in replacing soybean oil. A quadratic effect (p < 0.01) was observed for the final length, length gain, specific growth rate for length, final weight, weight gain, specific growth rate for weight, and batch uniformity for weight for both fish species. As for ornamental fish larviculture, survival rate and batch uniformity are the most important parameters to be considered. For P. scalare and H. severus post-larvae, the inclusion of dietary EOO was beneficial in up to 2.48% and 0.88%, respectively. [ABSTRACT FROM AUTHOR]

Microalgae are essential for most aquaculture hatcheries as first‐feed for larvae. Even so, high labour costs and risk of production crashes have encouraged the search for fresh culture substitutes, such as microalgae concentrates. Despite their importance as a commodity for the aquaculture sector, the concentrates are not available worldwide, and consolidated knowledge is scarce. Therefore, this bibliographic study aimed review microalgae products available for hatcheries, identifying research gaps and suggesting opportunities for development. In most studies, microalgae cultures were harvested by centrifugation, and biomass was stored chilled, frozen or dried (heat‐, spray‐ or freeze‐dried). The shelf life of microalgae products was dependent on the method of storage and microalgae species since robust species maintained their nutritional value for a longer period compared to more fragile ones, which would be sensitive to harvesting and storage. Thus, the use of concentrates in some feeding trials resulted in poor zootechnical performance. These results have four possible explanations: cell ingestion difficulty, low feed digestibility by phytoplanktivores animals, biomass degradation or inadequate choice of microalgae species. However, these limitations can be overcome by fractionating feed portions and adapting the culture tanks and aeration systems, but mainly by determining the ideal method for storing biomass and shelf life for each microalgae species. Taken together, our findings show that the application of microalgae concentrates can enhance the efficiency and profitability of aquaculture hatcheries. [ABSTRACT FROM AUTHOR]

The nutritional characteristics of microalgae affect the growth, survival and fatty acid composition of sea urchin larvae. This study aimed to evaluate the influence of nutritive characteristics of single microalgal diets in Paracentrotus lividus (Lamarck, 1816) larval development, growth, and condition. Larvae of P. lividus were fed with three monospecific microalgal diets, Rhodomonas sp. (Rho), Dunaliella tertiolecta (Duna) and the diatom Chaetoceros calcitrans (Chae), and their development and growth were analysed until competence. Additionally, the fatty acid (FA) profile of larvae was analysed at competence and compared with the FA profile of the correspondent diet. The three groups of larvae attained competence simultaneously with differences in growth performance. The larvae fed with Chae attained the largest stomach and the shortest post‐oral arm. The larvae were able to accumulate long‐chain polyunsaturated fatty acids (PUFA), such as docosahexaenoic (DHA, C22:6n − 3), eicosapentaenoic (EPA, C20:5n − 3) and arachidonic (ARA, C20:4n − 6) acids, either by assimilation and retention of dietary FA or by the synthesis from α‐linolenic acid (ALA, C18:3n − 3) and linoleic acid (LA, C18:2n − 6). Furthermore, the low DHA/EPA ratio and high EPA/ARA and n − 3/n − 6 ratios of Rho and Chae and the high levels of the β‐carotene present in Chae improved larval growth and development. In conclusion, the results indicated that of the three microalgal diets tested, C. calcitrans provided important nutritional characteristics, especially in terms of FA composition and carotenoids, improving P. lividus larval growth and condition. [ABSTRACT FROM AUTHOR]

This study evaluated the effects of four microbes, Candida parapsilosis, Pseudoalteromonas flavipulchra, Lactobacillus sakei, and Bacillus natto on suppression of Vibrio, survival rate, enzyme activity, chemical composition, and microbial longevity in the brine shrimp, Artemia franciscana. Five treatments, including four experimental groups and a control group, each with four replicates, were studied. The concentration of 108 CFU mL−1 of each mentioned strain was used to feed the nauplii for 2 weeks. The results demonstrated that the use of L. sakei, P. flavipulchra, and B. natto significantly suppressed the concentration of Vibrio over 5, 10, 15, and 20 h of enrichment respectively. From the selected microbes, B. natto and L. sakei were significantly colonized in the population and increased the enzyme activity. The longevity of B. natto in the Artemia was recorded as the best bacteria for long-term inoculation as after 8 days of starvation of Artemia, the count of B. natto was increased. The findings showed that B. natto appears to be a promising probiotic for Artemia in the suppression of Vibrio and also in increasing population growth, enzyme activity, and long-term colonization potential. [ABSTRACT FROM AUTHOR]

This study evaluated short cycles of feed deprivation on the growth performance and survival of larvae and juveniles of the ornamental fish Pyrrhulina brevis. The first experiment used larvae fed with artemia nauplii in a completely randomized design arranged in factorial (2 × 5) distributed in two feeding frequencies (two or four meals a day), five feeding deprivation protocols (7/0: seven days of continuous feeding [DCF] and no feed deprivation; 6/1: six DCF and one day of feed deprivation; 5/2: five DCF and two days of feed deprivation; 4/3: four DCF and three days of feed deprivation; Alt: alternated feeding days), and five replicates. The second experiment used juveniles arranged in a completely randomized design with five treatments (same treatments from previous experiment) and five replicates feeding commercial ration. For larviculture, the feeding deprivation resulted in the worst larvae development rate and survival. The use of feeding deprivation is not recommended for larvae because it is dependent on exogenous feed daily. For juveniles, one day of feeding deprivation a week provided lower ration consumption without negative effects on fish development. [ABSTRACT FROM AUTHOR]