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The study involved three groups of six broodstock with a 1:1 male-to-female ratio. They were injected with 13 µg/kg LHRHa to stimulate spawning. We fed the broodstock three diets: a control diet without selenium, a diet containing 0.3 mg of nano-selenium /kg (N-Se), and a diet containing 4 mg of organic selenium /kg (O-Se). The broodstock diet consisted of equal parts of dry feed (45% protein), sardines, and squid. After being laid, the eggs were obtained from the collection ponds at the General Authority for Fisheries Development's fish hatchery and incubated until hatching. The larvae were given a micro diet containing 51.7% crude protein and live food (Rotifer and Artemia). Rotifer density increased from 5/ml to 15/ml by day 22 dph, Artemia nauplii increased from 0.2 to 4 ind./ml, from 7 to 35 dph then decreased to 0 at 55 dph, and micro-diets increased from 100-200 µ at 16 dph to 200-400 µ at 23-40 dph to 300-500 µ at 55 dph, and 500-1000 µ until the experiment ended. Three different diets in three replicates were tested: A micro diet free of selenium as a control diet (C), A micro diet with 0.3 mg of nano selenium (N-Se) kg-1, and A micro diet supplemented with organic selenium 4 mg (O-Se). Each group was taken from the three Broodstock groups respectively. Sixteen days after hatching, the three experimental micro diets were introduced to the larvae and continued for 76 days post-hatch. Larvae (260,000 per tank) were placed in fiberglass tanks with 4 m3 of water at a temperature of 19±2°C for optimal conditions. The larvae fed the N-Se diet had significantly better survival rates (75.0 ± 1.2 %), final body weight (240.0 ± 5.8 mg), weight gain (239.00 ± 5.8 mg), average daily gain (3.98±0.1mg), total length (39.0±0.06 mm), specific growth rate (9.133±0.04 %/day), feed intake (471.67±0.01 mg), and better feed conversion ratio (1.97±0.01) than the other groups (P < 0.05). The group provided with N-Se also had the highest levels of glutathione peroxidase enzyme (GPx) content in the whole larval body, whereas the control diet without Se supplementation recorded the lowest value of (14.8 ± 0.1 U/mg protein). The number and length of folds in the stomach and esophagus of sea bass post-larvae fed on diets fortified with selenium in both forms, nanoparticles or organic, showed a significant (P < 0.05) enhancement on the larval gastrointestinal (GI) tract. Moreover, selenium has an anti-inflammatory action in sea bass post-larvae. This study concluded that using N-Se as an antioxidant supports the growth and survival of European seabass D. labrax, gastrointestinal development and antioxidant efficacy during critical weaning. [ABSTRACT FROM AUTHOR]

Estuaries are considered as key habitats for the early life stages of fish. However, in the face of massive destruction of many estuarine intertidal areas, management and conservation measures are needed. Fish condition indicators may be used as a proxy of habitat quality and provide valuable information for management of coastal areas. In this study, the larvae of golden mullet (Chelon auratus) and European glass eels (Anguilla anguilla) were sampled in three sites of the Gironde Estuary. Different lipid classes and fatty acids were quantified: phospholipids (globally, phosphatidylethanolamine and phosphatidylcholine), triglycerides, omega‐3 (particularly docosahexaenoic and eicosapentaenoic acids), omega‐6 and C18:1. These biomarkers provide information on the nutritional status of the larvae as well as on prey availability and larvae diet between sites. One site significantly differed from the others as it seemed to offer abundant and better‐quality prey. The very high levels of omega‐3 contained in mullet larvae suggested that this site provided a high amount of diatoms. However, the mullet larvae that colonized this site also showed physiological stress that could be explained by exposure to pollutants through their prey. This work constitutes an essential baseline for developing biomarkers to assess the quality of habitats in a global change context. [ABSTRACT FROM AUTHOR]

In September 2023, several hatcheries in Latin America experienced significant mortality rates, up to 90%, in zoea stage 2 of Penaeus vannamei. Observations of fresh mounts revealed structures resembling lipid droplets, similar to those seen in a condition known as "las bolitas syndrome". Routine histopathological examinations identified detached cells and tissues in the digestive tracts of affected zoea, contrasting with the typical algal cell contents seen in healthy zoea. Polymerase chain reaction (PCR) testing for over 20 known shrimp pathogens indicated minimal differences between diseased and healthy batches. Both groups tested negative for acute hepatopancreatic necrosis disease (AHPND) but positive for Vibrio species and Rickettsia-like bacteria in the diseased samples. Histological analyses of the affected zoea revealed characteristic tissue degeneration in the hepatopancreas, forming spheres that eventually migrated into the upper gut, midgut, and midgut caeca, a pathology identified as bolitas syndrome (BS). Microbiological assessments revealed Vibrio species at concentrations of 106 CFU zoea/g in affected zoea, approximately two orders of magnitude higher than in healthy zoea. Bacterial isolation from both healthy and BS-affected zoea on thiosulphate–citrate–bile salts–sucrose (TCBS) agar and CHROMagar™ (Paris, France), followed by identification using API 20E, identified six strains of Vibrio alginolyticus. Despite similarities to "las bolitas syndrome" in fresh mounts, distinct histopathological differences were noted, particularly the presence of sloughed cells in the intestines and variations in hepatopancreatic lobes. This study highlights the critical need for further research to fully understand the etiology and pathology of bolitas syndrome in zoea stage 2 of P. vannamei to develop effective mitigation strategies for hatchery operations. [ABSTRACT FROM AUTHOR]

In September 2023, several hatcheries in Latin America experienced significant mortality rates, up to 90%, in zoea stage 2 of Penaeus vannamei. Observations of fresh mounts revealed structures resembling lipid droplets, similar to those seen in a condition known as “las bolitas syndrome”. Routine histopathological examinations identified detached cells and tissues in the digestive tracts of affected zoea, contrasting with the typical algal cell contents seen in healthy zoea. Polymerase chain reaction (PCR) testing for over 20 known shrimp pathogens indicated minimal differences between diseased and healthy batches. Both groups tested negative for acute hepatopancreatic necrosis disease (AHPND) but positive for Vibrio species and Rickettsia-like bacteria in the diseased samples. Histological analyses of the affected zoea revealed characteristic tissue degeneration in the hepatopancreas, forming spheres that eventually migrated into the upper gut, midgut, and midgut caeca, a pathology identified as bolitas syndrome (BS). Microbiological assessments revealed Vibrio species at concentrations of 106 CFU zoea/g in affected zoea, approximately two orders of magnitude higher than in healthy zoea. Bacterial isolation from both healthy and BS-affected zoea on thiosulphate–citrate–bile salts–sucrose (TCBS) agar and CHROMagar™ (Paris, France), followed by identification using API 20E, identified six strains of Vibrio alginolyticus. Despite similarities to “las bolitas syndrome” in fresh mounts, distinct histopathological differences were noted, particularly the presence of sloughed cells in the intestines and variations in hepatopancreatic lobes. This study highlights the critical need for further research to fully understand the etiology and pathology of bolitas syndrome in zoea stage 2 of P. vannamei to develop effective mitigation strategies for hatchery operations.

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Whiteleg shrimp Penaeus vannamei farming in clear water recirculating aquaculture systems (RAS) is relatively recent, and consequently, knowledge on the shrimp dietary demands is still insufficient, particularly in the initial developmental stages. This study aimed at assessing the dietary protein requirement of whiteleg shrimp post-larvae (PL) in a clear-water recirculating aquaculture system (RAS). Six microdiets were formulated to contain 34%, 44%, 49%, 54%, 58%, and 63% crude protein (P34, P44, P49, P54, P58 and P63, respectively) and were evaluated in triplicates. Whiteleg shrimp PL (3.2 mg wet weight) were reared for 21 days in a clear-water RAS at Riasearch Lda. At the end of the feeding period, the optimal protein requirement was estimated at 47.1%, 46.4%, 47.2%, and 44.0% for weight gain, relative growth rate (RGR), feed conversion ratio (FCR), and survival, respectively. PL fed the P54, P58, and P63 diets achieved significantly higher final body weights than those fed P34. PL fed P34 showed significantly lower RGR and survival and significantly higher FCR values than those fed the remaining diets, suggesting that low protein diets may not be adequate to be used in this stage of shrimp development and/or for the clear-water RAS husbandry conditions. Moreover, diet P34 seemingly reduced the overall antioxidant status of the PL when compared to P44, P49, and P54. However, the P34 diet seems to have stimulated the PL immune mechanisms when compared to P44, P49, and P54, possibly due to increased levels of fish and algae oil. Similarly, despite the good growth performances, a diet containing 63% of protein also seemed to have compromised the overall shrimp PL antioxidant status and stimulate their immune system. Shrimp fed diet P54 showed an apparent overall superior antioxidant status when compared to the remaining diets, evidencing that using protein inclusion levels up to 54% in aquafeeds not only potentiates growth performances and survival but also can potentially be beneficial to the health status of P. vannamei PL grown in a clear-water RAS. Hence, results from this study suggest that a minimum of approximately 47% of protein should be considered when tailoring microdiets for whiteleg shrimp PL grown in a clear-water RAS, but inclusion levels up to 54% can be used with benefits to the PL antioxidant status.

Fish seed are important for the growth of aquaculture in Bangladesh, but there are many challenges associated with supplying quality fish seed. This review evaluated the current level of production, issues and challenges that are affecting the production of fish seed in Bangladesh. The fish hatchery was found to be the major contributor in terms of fish seed production. Out of 671 metric tons of fish seed produced in 2020–2021, above 99% were from hatcheries. Freshwater finfish hatcheries have expanded over the last 30 yr, and are distributed throughout the country, but there is no commercial hatchery for coastal and marine water finfish species in the country. Shrimp and prawn hatcheries are concentrated in Cox's Bazar and the greater Jassore regions, respectively, while crab culture is entirely dependent on wild capture. Crablets are collected from nature, which has a devastating impact on biodiversity and wild stocks. The fish seed value chain is multidirectional and interlinked, and intermediaries dominate the supply chain. Disease outbreaks and indiscriminate use of chemicals are major concerns in fish seed production. Management strategies such as the introduction of certification, training programs, technology transfer, access to credit, and implementation of the law could improve the quality and productivity of fish seed in Bangladesh. [ABSTRACT FROM AUTHOR]

Paracentrotus lividus gonads, often referred to as "roe" or "uni" for gastronomical purposes, are among the most appreciated seafood delicacies in the Mediterranean area and worldwide. However, the increasing demand for human consumption has caused a growing pressure on its wild stocks, prompting the need to develop efficient aquaculture systems for its production. The set-up of effective feeds for various life stages and optimal procedures for breeding post-larvae and adult sea urchins still need to be improved. Here, for the first time, we aim at developing artificial feeds for the post-larvae of P. lividus because a critical step to improve our productive skills is post-larval growth. We tested various natural and prepared components to speed up the growth and enhance the survival rates of post-larvae, while taking into account the abiotic and biotic factors influencing the culture conditions in three replicate sets of tanks, characterized by different volumes. We tested formulated feeds and compared them with the effect of fresh foods in the frame of canonical culture practices. Our results indicated the efficiency of a feed composed of spirulina and Ulva rigida. Statistical analyses demonstrated the positive impact of this diet on the growth of post-larvae, behavior and survival rates. In addition, we demonstrated the efficacy of prepared feeds in the sea urchin aquaculture system, because they facilitated manipulation and control of the culture procedures for the satisfactory growth of P. lividus post-larvae. [ABSTRACT FROM AUTHOR]

Early life stages of fish are insufficiently studied in most regions around the globe, and consequently, there is an important gap in knowledge on the life cycle of most teleosts. In the Canary Islands (Eastern Central Atlantic), most studies on ichthyoplankton communities are based on traditional net tows in open waters that provide information about early larval stages of pelagic species in the area, while nearshore benthic fish remain highly understudied. In this study, light traps were employed for the first time to assess post-larval stages of neritic fish in this archipelago. A two-year survey was carried out to collect nearshore fish larvae every 6 months at 11 localities from El Hierro, Tenerife and Lanzarote. A total of 3940 fish larvae classified into 13 orders, 28 families and 44 species were collected. These results provide a wide description of the composition of the inshore ichthyoplankton off the Canary Islands, across islands and seasons. Main environmental factors (SST, sea floor orography, oceanographic phenomena ...) influencing the population dynamics of this community are discussed. Additionally, the ichthyoplankton assemblages were assessed from the intra-annual perspective, analyzing the species composition and abundances by months and seasons, and providing new insights into reproduction cycles of many common benthic fishes at shallow marine ecosystems of the islands. This study is important to further understand the life cycles of some of the most common fish species in the Canary Islands, unraveling main environmental factors that affect the success of their offspring that sustain populations. • Inshore ichthyoplankton community of the Canary Islands assessed by light traps. • Smaller coastal shelves off an island meant larger densities of fish post-larvae. • Changes in ichthyoplankton composition through months and seasons described. • New insights on life cycles of common fish species in the region. [ABSTRACT FROM AUTHOR]

Lipids are essential nutrients for organisms, and high-fat feeds for shrimp may cause oxidative stress. This study evaluated the effects of feeding high fat in the diet on the growth, antioxidant, immunity, and liver fat accumulation of Macrobrachium rosenbergii post-larvae. Five groups with an initial body weight of 0.0084 ± 0.001 g were fed five isonitrogenous and isoenergetic diets (47.01% crude protein and 18.40 kJ/g gross energy) containing 8%, 10%, 12%, 14% and 16% (named L8, L10, L12, L14 and L16) lipid for 8 weeks, respectively. The results showed that the weight gain rate (WGR) and specific growth rate (SGR) of L8 group were significantly higher than those of L10, L12, L14 and L16 group (P < 0.05), and the feed coefficient (FCR) of L8 group was significantly lower than that of other groups (P < 0.05). With the increase of dietary fat level, the content of MDA and the activity of SOD increased significantly, and the activities of T-AOC and CAT decreased significantly (P < 0.05). H&E staining clearly revealed the occurrence of hepatocyte swelling, hepatocyte vacuolization and nucleus displacement to the peripheral cell vacuolization in the L16 group, and hepatic lipid accumulation was further observed in the L14 and L16 group by Oil red O staining. In addition, high-fat diet significantly upregulated the expression of Dorsal , Relish and IκBα mRNA, and also upregulated the expression of fat synthesis-related genes FAS , ACC , DGAT and fat transport-related gene FABP (P < 0.05), and significantly downregulated the expression of fat metabolism-related genes AMPK and CPT-1 (P < 0.05) compared to that of the L8 group. In conclusion, this study showed that feeding a high-fat diet could induce oxidative stress, inhibit growth performance, alter antioxidant capacity, cause hepatic fat deposition and affect the immune system of M. rosenbergii post-larvae. • High-fat diet inhibits growth performance in post-larvae of M. rosenbergii. • High-fat diet causes oxidative stress in post-larvae of M. rosenbergii. • High-fat diet causes liver fat deposition in post-larvae of M. rosenbergii. • High-fat diets lead to lipid metabolism disorders in post-larvae of M. rosenbergii. [ABSTRACT FROM AUTHOR]

Galaxiid post-larvae constitute five of the six species in New Zealand's iconic whitebait fishery. Distinguishing the five species needs to occur at a younger age than is convenient for easy identification. Traditional identification uses subjective characteristics such as colouration of fresh specimens and fin position, but supervised classification methods could be more accurate and less labour-intensive. We compared the accuracy of six methods (multinomial logistic regression, linear discriminant analysis, quadratic discriminant analysis, naive Bayes, decision tree, and random forest) using total length, wet weight, body depth, and date, latitude and longitude of capture as predictive variables. Four of the galaxiid species were represented in 17,546 observations, but the other species was too rare to analyse. The best method, determined using 10-fold cross-validation classification accuracy (95.2% overall), was random forest across all species. The most difficult species to classify correctly (giant kōkopu) was the rarest species included in data with 66.1% accuracy at best. In addition to examining overall accuracy, we show how use of a cost function can improve classification performance with respect to rare species. This research could improve the efficiency of monitoring the composition of the whitebait fishery, and thus management of this occasionally overfished group of fish. [ABSTRACT FROM AUTHOR]

This study aimed to isolate a yeast strain and evaluate its potential to be inoculated in the biofloc technology culture of Pacific white shrimp employing in vitro and in vivo assays. A yeast strain identified as Meyerozyma guilliermondii (CPQBA 1459/17 DRM‐01) was isolated from the soil of an estuary. Its growth kinetics under different salinities (0%, 1.0%, 2.0%, 3.0% NaCl) and Vibrio alginolyticus inhibition were evaluated in vitro. For the in vivo assay, a factorial design was employed to evaluate the effects of yeast addition and biofloc management strategy in the nursery culture of Litopenaeus vannamei as regards shrimp growth performance, water quality and water microbiology. The two factors evaluated were biofloc (mature and heterotrophic) and yeast (addition or no addition), totaling four treatments. In the in vitro trials, the yeast strain was capable of growing under all salinities evaluated, but no pathogen inhibition was observed. In the in vivo experiment, the addition of yeast significantly reduced the concentration of total suspended solids (p < 0.05), in addition to promoting a higher post‐larvae survival when considering only the two mature biofloc treatments (p < 0.05). No significant effects on water Vibrio spp. and total heterotrophic bacteria counts were found (p ≥ 0.05). In conclusion, the inoculation of yeast in the biofloc culture of L. vannamei exhibited bioremediation potential and improvement in shrimp survival, the latter being modulated by the biofloc management strategy. [ABSTRACT FROM AUTHOR]

Lipids are essential nutrients for animal. Oxidized lipid might induce injury stress for prawns. This study was conducted to evaluate the oxidized fish oil on growth, digestive enzymes activities, antioxidant system of giant freshwater prawn (Macrobrachium rosenbergii) post-larvae for 21 days with the initial body weight of 1.13 ± 0.04 mg. Three trial diets were with fed the basal diet (C), basal diet supplemented 4% fish oil (4F), basal diet supplemented 4% oxidized fish oil (4OF), respectively (feeding 0 d, 7 d and 14 d, denoted as T7, T14 and T21, respectively). The results showed that the final body weight (FBW) and weight gain ratio (WGR) was increased in the group of 4F and decreased in the group of 4OF. After feeding fish oil or oxidized fish oil, the proteinase activity of T14, T21 post-larvae in 4OF group was significantly higher than T7 post-larvae (P

Paracentrotus lividus gonads, often referred to as “roe” or “uni” for gastronomical purposes, are among the most appreciated seafood delicacies in the Mediterranean area and worldwide. However, the increasing demand for human consumption has caused a growing pressure on its wild stocks, prompting the need to develop efficient aquaculture systems for its production. The set-up of effective feeds for various life stages and optimal procedures for breeding post-larvae and adult sea urchins still need to be improved. Here, for the first time, we aim at developing artificial feeds for the post-larvae of P. lividus because a critical step to improve our productive skills is post-larval growth. We tested various natural and prepared components to speed up the growth and enhance the survival rates of post-larvae, while taking into account the abiotic and biotic factors influencing the culture conditions in three replicate sets of tanks, characterized by different volumes. We tested formulated feeds and compared them with the effect of fresh foods in the frame of canonical culture practices. Our results indicated the efficiency of a feed composed of spirulina and Ulva rigida. Statistical analyses demonstrated the positive impact of this diet on the growth of post-larvae, behavior and survival rates. In addition, we demonstrated the efficacy of prepared feeds in the sea urchin aquaculture system, because they facilitated manipulation and control of the culture procedures for the satisfactory growth of P. lividus post-larvae.

The results of wild mullet Mugil liza post-larval growth are presented, using 0.1 ha fish pens in El Ciego coastal lagoon at Tunas de Zaza, Cuba. A total of 3,633 post-larvae were cached, with a mortality of less than 2% during their capture and transportation. Before their stocking in the fish pens, the post-larvae were transferred directly to fresh water to segregate alive those of the mullet from the others mullet species, and their total length (TL) and their body weight (BW) determined. One thousand post-larvae (23.5 mm of TL and 0.23 g of BW) were introduced in each fish pen. Post-larvae fed on bottom detritus and once every day fish meal enriched with 2% of cod liver oil was supplied. After rearing for 90 days, survival was 86 ± 4 %, with 70.4 mm of TL and 3.25 g of BW, ready to be transferred to grow-out facilities. The relative growth rate in TL and BW, as well as their condition factor were significantly different (P < 0.05) between fish pens. Growth obtained were similar to those of Mediterranean mullets, but lower than those of chucumite snook (Centropomus parallelus) intensively reared. In conclusion, wild mullet post-larvae could be reared in fish pens in coastal lagoons up to a size which allow their grow-out, reaching growth rates of ≈ 6 g/day in one year or less of culture. [ABSTRACT FROM AUTHOR]

Sustainable development of Vaname shrimp aquaculture in the future depends on several things, one of which is the availability of the male parent in a sufficient quantity. Regarding this problem, sex reversal can be performed as the solution. Sex reversal is a technique of sex genetic differentiation to change sexes artificially from males genetically into phenotype females or vice versa. This research was intended to obtain the maximal mono-sex (single sex) male of Vaname shrimp using 17α-methyltestosterone (MT) hormone through sex reversal technology to the limited sex change in Vaname shrimp, in which to date the Vaname male parent gained is still dependent on natural selection. This research used a descriptive and experimental method. The experimental research design used was a completely randomized design (RAL – Rancangan Acak Lengkap). The treatment given was immersing the shrimp larvae in 17α-methyltestosterone (MT) for 8 hours at different doses of 0 mg/L, 5 mg/L, 8 mg/L, and 12 mg/L. The immersion of the post-larvae (PL1) of Vaname shrimp using the 17α-methyltestosterone hormone gave a significant result (P < 0.05) on all of the treatments and control in which the highest percentage of male Vaname shrimp was obtained from the treatments with 8 mg/L and 12 mg/L doses, respectively reaching 64% and 66.7%. As for the weight growth, the immersion of the post-larvae (LP1) growth of Vaname shrimp using 17α-methyltestosterone hormone provided a very significant result (P < 0.05) on all the treatments and control in which the highest weight growth (weight gain) and Specific Growth Rate of Body Weight (SGR BW) were shown by the treatments with 8 mg/L and 12 mg/L doses, respectively reaching 1.5415 grams and 1.5871 grams.

Whitebait comprise a culturally, commercially and recreationally important fishery in New Zealand, where post-larvae are netted while returning from their marine phase. In this study, we expanded an historical (1964) sampling programme to gain a contemporary understanding of the species composition of the whitebait fishery; 87 rivers were sampled over six months in 2015. Over the entire country, >12 species were found in samples and 87.6% of these were īnanga (Galaxias maculatus). Kōaro (G. brevipinnis) and banded kōkopu (G. fasciatus) were abundant in some rivers and regions at particular times of the year. Buller was the most variable region, spatially and temporally, for species composition; Canterbury was the least variable. Banded kōkopu whitebait migrated one month earlier north of Cook Strait than in the south. There was a positive association between the abundance of kōaro and banded kōkopu in samples and the level of indigenous forest cover in catchments. Compared to samples from 50 years ago, there was a greater proportion of kōaro and banded kōkopu whitebait throughout the country. This spatio-temporal variability requires fishery regulations to be more tailored and flexible if they are to conserve the diversity of life-histories present in the catch and sustain the whitebait fishery. [ABSTRACT FROM AUTHOR]

Fish hatcheries must adapt larval feeding protocols to feeding behavior and metabolism patterns to obtain more efficient feed utilization. Fish larvae exhibit daily ingesting rhythms rather than ingesting food continuously throughout the day. The aim of this study was to determine the daily patterns of feed intake, protein digestibility, protein retention and catabolism in Senegalese sole post-larvae (Solea senegalensis; 33 days post-hatching) using 14C-labeled Artemia protein and incubation in metabolic chambers. Sole post-larvae were fed at 09:00, 15:00, 21:00, 03:00 and 09:00+1 day; and those fed at 09:00, 21:00, 03:00 and 09:00+1 day showed significantly higher feed intake than post-larvae fed at 15:00 h (P=0.000). Digestibility and evacuation rate of ingested protein did not change during the whole cycle (P=0.114); however, post-larvae fed at 21:00 and 03:00 h showed the significantly highest protein retention efficiency and lowest catabolism (P=0.002). Therefore, results confirm the existence of daily rhythmicity in feeding activity and in the utilization of the ingested nutrients in Senegalese sole post-larvae.

This study aimed to evaluate the effectiveness of the supplementation of Pseudoalteromonas piscisida 1UBthrough Artemia sp. to enhance the growth performance, immune response and the resistance of white shrimp (Litopenaeus vannamei) larvae to the infection of Vibrio harveyi. The natural feed given to the white shrimp larvae was Artemia sp. enriched with P. piscisida 1UBR at concentrations of 106 CFU mL-1, 107 CFU mL-1, 108 CFU mL-1 and a control (Artemia sp. without any enrichment). The experimental shrimps (0.25±0.02 mg shrimp-1) were reared in the aquarium (25 × 20 × 30 cm) containing 4 L sea water with a stocking density of 30 shrimps L-1. The experimental shrimps were fed the experimental feed from mysis 3 to PL12, and after that they were challenged with V. harveyi (107 CFU mL-1)through an immersion method. The results of this study revealed that the administration of Artemia sp. enriched with P. piscisida 1UB could improve the survival, daily growth rate and absolute growth of length of white shrimp larvae. The activities of protease, lipase and amylase of white shrimp larvae treated with probiotic were higher (p

Seed production of freshwater prawns requires brackishwater of varying salinity to complete their larval cycle in river mouths (estuaries). Though, the hatchery technology for seed production of freshwater prawn Macrobrachium gangeticum has been developed and standardized, the activity is mostly concentrated in coastal regions as huge quantity of seawater is required for larval development. Attempts were made to operate the hatcheries for seed production of the freshwater prawn in interior area with the chemically reconstituted seawater as well as natural seawater transported from the sea, the procedure is complicated and involves high cost. An attempt has, therefore, been made to reuse the hatchery wastewater for the seed production of M. gangeticum after proper treatment and aging. PL production was documented during the two years which was 5,577, 5,299 and 5,056 with PL/L 21.29, 17.66 and 16.82 in trials 1, 2 and 3, respectively during the first year. PL production recorded during second year was 5,167, 5,070 and 4,748 with PL/L 17.3, 16.9 and 15.8 in trials 1, 2 and 3, respectively. The average post-larvae production of three trials was 5,367 during the first year and 4,995 the second year. [ABSTRACT FROM AUTHOR]

Enterocytozoon hepatopenaei (EHP) is a microsporidian parasite that causes hepatopancreatic microsporidiosis (HPM) in penaeid shrimp. HPM was observed in several countries, including Thailand and India; it has become a prominent pathogen in shrimp culture. Based on observations on EHP infection in the wild, the route of transmission has been hypothesized. Identification of artificial EHP infection procedures can facilitate our understanding of EHP transmission. Experimental transmission of EHP was attempted using the immersion and oral infections of infection. In the immersion mode, post‐larvae (PL) were exposed to an EHP tissue homogenate (0.2%) by immersion for 48 hr. Experimental samples were collected at various time points, and infection was confirmed using polymerase chain reaction, haematoxylin and eosin staining, transmission electron microscopy and modified trichrome staining. All test results revealed successful EHP transmission. Similar results were obtained through oral infection (oral infection). Innate immune gene expression patterns during infection were analysed; prophenoloxidase, crustin and superoxide dismutase were upregulated at 6, 6 and 48 hr post‐challenge, respectively. Experimental infection procedures facilitate the development of diagnostic and prevention strategies. This is the first study demonstrating the experimental transmission of EHP in shrimp PL. [ABSTRACT FROM AUTHOR]

Our previous work confirmed that the higher survival, growth, and commercial performance of a mussel stock collected from a specific lagoon have been maintained over the last 25 years at a microgeographic scale despite intensive transfers of its spat to other local mussel sites. The objective of this study was to identify potential selection mechanisms supporting the quality of this stock. We used a mesocosm approach to examine the effect of maximum seawater temperature measured in the field on the different ontogenic stages of Mytilus edulis to simulate similar patterns in the laboratory. We demonstrated that thermal selection did not affect the development of peri-metamorphic stages (< 1 mm) since no effects were observed on growth, survival, or prodissoconch II size under natural thermal variations. However, our experimental results clearly indicated the existence of a thermal selective pressure (24 °C for 85 h) on 4.5–7 mm juvenile mussels, with growth performance enhanced in surviving individuals. Mortality was 37% higher compared to the control group, suggesting the elimination of more sensitive and less performant mussels. Interestingly, surviving individuals showed improved shell and tissue growth rates, by 22 and 51%, respectively. Our results support the hypothesis that the thermal selection of highly performant stock is size-dependent. The selective pressure demonstrated in this study along with our previous work highlighting the physiological and genetic differences between local stocks constitute the key mechanisms leading to the observed stable production performance over decades at a microgeographic scale. • A selective pressure affecting late post-larval mussels (> 4.5 mm) was induced by thermal peak. • The thermal selection eliminated sensitive spat but led to enhanced growth of surviving individuals. • The development of early post-larvae (< 1 mm) appears not to be affected by this thermal selection. [ABSTRACT FROM AUTHOR]

We tested the suitability of three different kinds of artificial collectors designed for quantitative assessment of echinoid settlement rates: (1) nylon nets containing plastic biofilter balls, (2) vertical scrub brushes with vegetal bristles and (3) horizontal triangular mats of coconut fibre. We measured the collecting efficiency by counting the number of post-larvae of two sea urchin species (Paracentrotus lividus and Arbacia lixula) gathered by each collector and deployed in two geographic areas: Tenerife (Canary Islands, eastern Atlantic) and Tossa de Mar (Costa Brava, northwestern Mediterranean). The plastic biofilter ball collector proved to be the most efficient design, collecting more settlers of both sea urchin species under all assayed conditions and showing a higher reproducibility than the other two designs. We therefore suggest using plastic biofilter balls in future studies aimed at quantifying echinoid settlement rates.

This study evaluated different artificial substrates during pre-nursery of Pacific white shrimp in a biofloc system. Post-larvae (PL 5–80 PL L −1 ) were raised in 60 L tanks filled with 52 L of chlorinated seawater (35‰) and 6 L of the microalga Chaetoceros muelleri . Four treatments were performed, including control (no artificial substrate), Bidim ® (geotextile), mosquito net screen (2 mm mesh) and Needlona ® (polyester fiber). The total surface area of artificial substrate comprised 100% of the tank area (0.89 m 2 ). PLs were fed nine times a day using commercial feed. Molasses was added in all treatments four times a day at an average carbon:nitrogen ratio of 14.7:1. The experiment was carried out until the PLs reached PL20, and during this time, water quality, survival, weight gain and survival to salinity stress were all evaluated. Water quality parameters remained within the accepted levels for shrimp rearing, with the exception of total suspended solids (TSS) in mosquito net screen and control, which had the highest values (507 ± 5.50 mg L −1 and 565 ± 23.46 mg L −1 , respectively). Using Needlona ® as artificial substrate increased the survival rate (91 ± 11.6%) and reduced TSS (42%) when compared to the control. No significant differences were observed in final weight and survival to salinity stress. Among the different substrates, Needlona ® was the most suitable for application in Pacific white shrimp prenursery in the biofloc system, essentially because it could maintain levels of solids suspended in water without the use of clarifiers or water exchange, resulting in higher survival. [ABSTRACT FROM AUTHOR]

The efficacy of using agar-bound microparticulate diet (A-MPD) as alternative food for abalone Haliotis asinina Linne post-larvae in large-scale culture was investigated. Larvae sourced from the hatchery-bred (HB) and wild-sourced (WS) broodstock were fed with either diatoms (TMT1-NF), agar-bound microparticulate diet (TMT2-A-MPD), or a combination of both feeds (TMT3-NF + A-MPD) in six 2-m tanks replicated over time. Three hundred thousand veliger larvae were stocked/tank containing 80 corrugated plates with mucus trails hanging on bamboo poles. Feeds were given at 0900 h starting at day 3 with seawater flow through introduced every 1400 h starting day 5. Two-way analysis of variance determined significant differences ( p < 0.05) in survival and shell length between larval sources and feed types. Tukey's post hoc test established differences among treatment means. At day 30, survival for HB- and WS-sourced larvae was significantly higher (42%) in TMT3 compared with TMT2 having 35% for HB and 38% for WS ( p < 0.05). Larvae fed with TMT1 had significantly lowest survival among the three treatments. Survival at 60 and 90 days did not show significant difference for TMT2 and TMT3 regardless of broodstock source. Post-larval shell growth (90 days), from both sources fed with TMT2 and TMT3, was significantly higher than TMT1 ( p < 0.05). Larval performance did not show any significant interactions between HB and WS broodstock. The use of A-MPD alone or in combination may elicit improvement in survival and shell length growth in abalone larvae regardless of larval sources. A-MPD may be used as full or partial replacements to diatoms as alternative food for abalone post-larvae in large-scale culture. [ABSTRACT FROM AUTHOR]

Settlement, metamorphosis, survival, and growth of Haliotis asinina larvae exposed to settlement surfaces coated with biofilms of four local diatom species ( Navicula seminulum, Navicula parva, Nitzschia alexandria, Amphora coffeaeformis) were assessed. After 24 h and 72 h, N. alexandria induced the highest settlement rate ( p < 0.001). Larval settlement rate on slats coated with N. seminulum, and A. coffeaeformis was significantly higher after 72 h than after 24 h ( p < 0.001). Metamorphosis was not higher than control after 24 h ( p > 0.05) for any diatom treatment, but after 72 h, all diatoms induced a significantly higher metamorphosis rate than the control ( p < 0.001). N. alexandria induced the highest metamorphic rate (15.71 %). Shell length of post-larvae was not significantly different on day 4 and day 10 ( p > 0.05) in diatom film treatments, relative to control. By day 20, post-larvae survived best on slats with N. alexandria (79.86 %). Survival among treatments was the lowest on slats with N. seminulum (54.91 %), and no live larvae were found in the control. Post-larvae on slats with A. coffeaeformis showed the highest daily growth rate of shell length (DGsl) (87.44 μm d). Post-larvae on slats with N alexandria showed the lowest DGsl (55.66 μm d). Commercial nursery slats seeded with N. alexandria will result in high and consistent settlement, metamorphosis, and survival, while slats with A. coffeaeformis will ensure sufficient food for rapid growth of the H. asinina post-larvae. [ABSTRACT FROM AUTHOR]

This study aimed to assess the movement patterns of post-larvae (PL) of whiteleg shrimp and black tiger shrimp, which were linked to the epidemic of acute hepatopancreatic necrosis disease (AHPND) in Thailand in 2013, using social network analysis. Hatcheries or nurseries were assigned as origin nodes, whereas cultivated ponds were designated as destination nodes. From 376 farms, data of 1300 ponds were collected from network data using a questionnaire. We found that 1477 nodes with 1315 ties appeared in this study. These were divided into a network of cases and controls that presented 538 nodes with 436 ties and 1013 nodes with 879 ties, respectively. The top four out-degree centrality values in the entire partial network, cases, and controls were used to analyze ego-alter similarity. The results showed that each PL provider played a different role in the association with the disease sender. A simulated network using exponential random graph models presented edges as a significant microstructure. In addition, our analysis indicated that the hatchery or nursery (PL provider) is an important node for AHPND occurrence. In conclusion, this study led us to understand the source of PL, which plays a key role in the surveillance, prevention, and control of AHPND. [ABSTRACT FROM AUTHOR]

In this study, we present the results of two experiments; in the first one we evaluated the effects of four larval dietary treatments on the survival and growth of the sea urchin Paracentrotus lividus , larvae and post-larvae. In the second experiment we have measured the effects of two different settlement substrates, combined with the presence of conspecifics, on metamorphosis, survival and growth of post-larvae. The microalgae dietary treatments consisted in: Dunaliella tertiolecta (Duna); 50% mixture of Isochrysis galbana and D. tertiolecta (ID); 50% mixture of Chaetoceros gracilis and D. tertiolecta (CD); 33% mixture of I. galbana , C. gracilis and D. tertiolecta (ICD). Although all dietary treatments resulted in a good survival at competence, significant difference in post-larval survival was observed between treatments, and indeed, only larvae fed Duna and CD survived to 180 days post settlement (DPS). In the second experiment, the settlement substrates consisted in a film of cultured Ulvella lens or a naturally developing biofilm of diatoms, and the employed rearing water was either natural seawater or seawater previously exposed to P. lividus adults. At 10 DPS, larger ( p < 0.05) post-larvae were observed in the natural biofilm treatment, whilst the presence of conspecifics significantly increased larval settlement in both substrates ( p < 0.01). These results indicate that it is important to consider the survival of post-larvae and juveniles to establish the efficiency of the dietary treatment on the hatchery production of P. lividus . Furthermore, it suggests that improved settlement protocols, such as the use of conspecifics, could contribute to increase hatchery outputs. Finally, it confirms the suitability of U. lens as settlement cue but also highlights that further research is required to establish its effectiveness for post-larvae first feeding. Statement of relevance Our work contributes to improving hatchery rearing methods of larvae and post-larvae of the sea urchin Paracentrotus lividus . [ABSTRACT FROM AUTHOR]

The decapod penstyldensovirus (PstDV1) is a widely spread shrimp pathogen that causes high mortalities in the shrimp Penaeus stylirostris, while in P. vannamei, it has been associated with induction of the runt deformity syndrome. Using shrimp post-larvae (PL, stages PL13-PL21) collected from 16 commercial hatcheries from Mexico, and a sensitive PCR protocol for its detection, a survey of the PstDV1 prevalence in larvae was undertaken. A high overall prevalence of PstDV1 (49.5 %) in shrimp PL from the studied hatcheries was found. This study reveals that PstDV1 occurs persistently in PL populations, which may have significant implications for its dispersal. [ABSTRACT FROM AUTHOR]

Populations of the Common European cockle ( Cerastoderma edule ) often have highly patchy distributions and variable recruitment success. One of the proposed reasons is that high densities of filter feeders and/or bioturbators are thought to reduce the success of larval settlement and post-settlement survival, but the direct causal processes driving these observations are not clearly identified and validated. Through combined field and laboratory experiments, we test the hypothesis that macrofauna cause decreases in post-larval density through feeding and movement activities. The effect of excluding the bioturbating lugworm Arenicola marina and filter-feeding adult cockles on post-larval cockle densities was estimated in separate field experiments at two locations from the time of initial larval settlement in May 2012 to late summer August 2012. Lugworm exclusion led to a significant increase in cockle post-larval densities whereas the opposite was true for adult cockles, where exclusion led to a reduction in C. edule post-larval density. Although clear effects were observed in the field, experiments conducted in the laboratory failed to detect changes in mortality or byssus drifting of post-larvae as a consequence of macrofaunal activity. This study demonstrates that the presence of macrofauna can have both positive and negative effects on post-settlement density of C. edule post-larvae. Thus the density, distribution and identity of macrofauna have significant effects on the density and spatial distribution of C. edule post-larvae during the post-settlement period. These observations have implications for conservation and fishery management of this species. [ABSTRACT FROM AUTHOR]

The effect of supplemented commercial diets with crystalline l-tryptophan (TRP-5, 10 and 20 g TRP kg) on cannibalism, survival and growth parameters of pikeperch post-larvae ( Sander lucioperca) was evaluated. Fifteen-day-old pikeperch larvae (mean weight-6.8 mg) were reared during the next 28 days (20.5 °C, 16L:8D) in glass aquaria in a recirculating aquaculture system. The enzyme-linked immunosorbent assay showed that TRP-supplemented diets were effective in increasing the levels of serotonin (5-HT) in the body tissue of pikeperch. TRP supplementation resulted in a slight decrease in both types of cannibalism, although the reduction in cannibalism impact did not amount to more than a few percent. TRP treatment had no significant influence on the final survival of pikeperch post-larvae (ranged from 20.1 ± 12.4 to 29.0 ± 12.9 %). However, contrary to the earlier studies conducted on other fish species, no significant difference in the growth rates and feeding behavior of pikeperch between TRP-fed and control group were found. The final body weight and growth rate ranged from 0.211 ± 0.014 to 0.243 ± 0.016 and from 12.19 ± 0.38 to 12.76 ± 0.35 % day, respectively. To our knowledge, this is the first study reporting the effects of TRP supplementation on the cannibalism-survival-growth relations in fish in the post-larval stage. [ABSTRACT FROM AUTHOR]

Understanding the spatial structure of populations at different scales can help reveal the processes controlling abundance and distribution. For species with a pelagic larval stage and highly mobile post-larval stage, such as the common cockle Cerastoderma edule , changes in spatial distribution from settlement through to juvenile stages are likely to occur at various spatial scales influencing the population dynamics observed. To record such changes a small-scale high-resolution field survey of C. edule post-larvae over an area of 60 × 80 m of tidal mudflat was conducted using a spatially-explicit staggered-nested design in the Dee estuary, UK. The survey was repeated three times from initial settlement in June 2011 to March 2012. Changes in spatial structure were described using Moran's I correlograms and prediction mapping, with analysis of correlations between cockle cohorts and sediment composition. At the first sampling event in June 2011, when initial settlement was occurring, post-larvae were highly aggregated in patches of 10–14 m in size and 16–20 m apart. By October 2011 the post-larvae had become more evenly dispersed with some small scale (< 4 m) random patchiness and a gradient in post-larval density. This spatial structure was maintained into March 2012 but with increased patchiness. At settlement post-larval density showed no correlation with adult abundance or sediment mud content, but by October 2011 and March 2012 there was a strong positive correlation with adult abundance. Such changes in spatial structure, abundance and adult association after settlement show the likely importance of small scale (metres to tens of metres) processes on post-larval survival from predation and adult interactions, thereby potentially shaping adult distributions. Small scale patchiness in post-larvae can be created at settlement; however the distribution and association with adults change over time. [ABSTRACT FROM AUTHOR]

Despite their trophodynamic importance in many aquatic ecosystems, few studies have quantified the feeding-growth relationship of clupeid fishes. In laboratory trials, we quantified the relationship between rates of food consumption ( C, % fish energy content (Joules d)), somatic growth rate ( G, % Joules d), and swimming speed ( S body lengths ( bl) s) for post-larval (30- to 50-mm standard length) European sprat ( Sprattus sprattus L.) collected from the southwestern Baltic Sea. Measurements of G and S were also made on groups before and after an abrupt shift in prey availability. Maintenance (0-growth) and maximum food consumption rates were 5.5 and 42 % somatic energy content d, respectively. Mean ± SE gross growth efficiency ( K = 100∙ G∙ C) was 26.9 ± 3.0 %. Unfed post-larvae had markedly lower S compared to continuously-fed fish (0.1 versus 0.5 to 0.7 bl s). After 10 days of re-feeding, one group of previously unfed fish was hyperactive (mean S of 1.2 bl s) but no re-fed groups exhibited hyperphagia (based upon prey numbers), increased K, or compensatory growth. Increased competition (relatively high S) was evident during feeding in fish maintained at low to moderate but not at ad libitum prey levels. Our findings provide estimates of prey resources required to fuel in situ growth and help characterize metabolic strategies of European sprat within variable feeding environments. [ABSTRACT FROM AUTHOR]

Tripneustes ventricosus is a commercially important species of sea urchin native of the tropical Atlantic Ocean. With the purpose of providing a scientific basis for the development of its production by aquaculture, several experiments were performed under hatchery conditions, including spawning induction, larval culture, settlement and juvenile culture. The efficiency of different spawning stimuli was assessed, including the use of UV-irradiated seawater; thermal and electric shocks, and injections of potassium chloride (KCl) and acetylcholine (ACh). Growth and survival of larvae maintained at different culture conditions were compared, including culture densities (2, 6 and 12 zygotes mL−1; 0.5, 1 and 2 larvae mL−1), culture systems (9 L aquaria, 75 L and 500 L tanks), water renewal rates (total and partial), feed amount (15 and 30 cells μL−1 d−1), feeding regime (constant or increasing) and type of diet (Isochrysis galbana, and a mixture of I. galbana and Chaetoceros calcitrans). Different stimuli to induce the larval settlement were tested, including low temperature, KCl, l -glutamine and γ-aminobutyric acid (GABA), as well as different substrates (artificial and benthonic microalgae biofilms). Finally, the growth and survival of juveniles were assessed under indoor conditions. The highest percentage of spawning individuals and the shorter response times were obtained using ACh. The average fecundity was 1.5 × 106 oocytes female−1. This variable exhibited a positive correlation with the female body size. One of the most relevant results of the present study was the completion of the embryo and larval developmental stages of T. ventricosus. Higher levels of larval either survival or growth were found in the tanks with the highest volume (500 L), maintaining conditions of low culture densities and complete water renewal and a constant supply of microalgae during all the larval development stage (15 cells of I. galbana and C. calcitrans μL−1 day−1). The larval settlement was obtained using low temperatures in all the tested substrates, except the substrate with artificial biofilm containing Sargassum and Thalassia. After 9 months of culture in laboratory conditions, juveniles of 44-mm length were obtained, using a regime of complete water renewal, and feeding the larvae with artificial biofilm, benthic microalgae and macroalgae. Although the present study made possible to identify appropriate culture conditions for obtaining hatchery-reared juveniles of white sea urchin, the low survival rates observed during the larval culture and the settlement stage must be improved with further research on the feeding requirements and the optimal water quality conditions for this species. • This is the first report of fecundity, early larval development and settlement of T. ventricosus. • Acetylcholine injection was the most effective method for T. ventricosus spawning induction. • The basic culture conditions and feeding regime required for obtaining competent larvae of T. ventricosus were determined. • The larval settlement of T. ventricosus was obtained reducing the water temperature in almost all the tested substrates. • -The high growth and survival rates of T. ventricosus juveniles are promising results for its aquaculture use. [ABSTRACT FROM AUTHOR]

Fish hatcheries must adapt larval feeding protocols to feeding behavior and metabolism patterns to obtain more efficient feed utilization. Fish larvae exhibit daily ingesting rhythms rather than ingesting food continuously throughout the day. The aim of this study was to determine the daily patterns of feed intake, protein digestibility, protein retention and catabolism in Senegalese sole post-larvae (Solea senegalensis; 33 days post-hatching) using 14 C-labeled Artemia protein and incubation in metabolic chambers. Sole post-larvae were fed at 09:00, 15:00, 21:00, 03:00 and 09:00+1 day; and those fed at 09:00, 21:00, 03:00 and 09:00+1 day showed significantly higher feed intake than post-larvae fed at 15:00 h (P=0.000). Digestibility and evacuation rate of ingested protein did not change during the whole cycle (P=0.114); however, post-larvae fed at 21:00 and 03:00 h showed the significantly highest protein retention efficiency and lowest catabolism (P=0.002). Therefore, results confirm the existence of daily rhythmicity in feeding activity and in the utilization of the ingested nutrients in Senegalese sole post-larvae., Competing Interests: The authors declare no competing or financial interests., (© 2017. Published by The Company of Biologists Ltd.)