Captive Broodstock Research Articles

Ova lipid profiling and egg quality in wild and captive lumpfish, Cyclopterus lumpus (Linnaeus, 1758)

Lumpfish (Cyclopterus lumpus) serves an important role as cleaner fish for removing salmon lice in salmon aquaculture. For this use, cultivated lumpfish are preferred over wild-caught fish to avoid overexploitation of natural stocks and provide a stable production of good quality eggs and larvae. To support this, high quality eggs containing the necessary building blocks to support high fertilization success, development into a normal embryo and high hatching success is needed. Ova from wild-caught and captive lumpfish females were collected and assessed to identify how wild and domesticated lumpfish differ in terms of ova lipid profiles, egg and larvae quality. Wild-caught lumpfish displayed higher fertilization and hatching success compared to captive lumpfish, whereas other biological variables like egg size, egg/larvae dry weight and respiration, and larval morphometry, were not significantly different between wild and captive lumpfish. Ova lipid profiles (total lipid, lipid classes, fatty acid composition and lipidomics) can separate egg batches based on their geographic origin of wild-caught females and composition of diets used for captive broodstock (lipid and carbohydrate content). Multivariate statistics were applied to identify lipid markers that can be used to predict the quality of lumpfish ova. Lumpfish ova lipidomic profiles covaried with several biological parameters, indicating that the former can be used to predict the latter. Lumpfish eggs were mostly composed of triacylglycerides (TAGs) with some phosphatidylethanolamines (PEs) and phosphatidylcholines (PCs), and their lipid profiles were more sensitive to the different origins, mother weight/size and fertilization success than variables such as eggs size or larvae morphometric measures. PC and PE content of lumpfish eggs were positively correlated to both hatching success and fertilization rates, thus the lipidomic profiles, with some key highlighted lipid species were putative predictors of egg quality.

Comparative proximate analysis of wild and captive lumpfish (Cyclopterus lumpus) eggs show deficiencies in captive eggs and possible egg quality determinants

The production of lumpfish (Cyclopterus lumpus) is increasing rapidly due to their use as a cleaner fish for sea lice infections in Atlantic salmon farming. The sustainable development of captive broodstocks is reliant on good egg quality however this remains unknown. The present study assessed the hatching success and nutritional composition of eggs collected from two wild groups, at the start and end of the Norwegian fishing season (2018–2019), and one captive broodstock population (2019). Eggs from the farmed broodstock, used in this study, showed significantly lower fertilisation rates, eyeing rates and survival to hatching than eggs from wild broodstock. There was significantly less overall lipid content in the captive eggs when compared to the wild group as well as significantly lower levels of lipid fractions such as total N-3 PUFAs, minerals such as sodium and phosphorus and overall egg pigment levels. A principal component analysis of all 139 measured nutritional components within fatty acids, minerals and pigments was conducted to identify those associated with egg quality in lumpfish. A total of 51 components was identified as being positively (31) and negatively (20) correlated with hatching rate including essential fatty acids such as EPA, DHA and ARA, total pigment levels and calcium levels. Overall, this study clearly showed a reduction in egg quality from captive broodstock and suggested nutritional deficiencies in the current broodstock diets. As such, this study provides a foundation for further work into the optimisation of lumpfish broodstock management with a number of nutritional factors to be further investigated.

Reproductive Biology of the Sea Cucumber Holothuria mammata (Echinodermata: Holothuroidea).

Simple SummaryHolothuria mammata is one of the sea cucumber species with high commercial value and great demand in Asian markets; however, the existent knowledge about the biology and ecology of this species is scarce. This study aims to describe the reproductive cycle of H. mammata in a coastal area of southwest Portugal through monthly collections of biometric data and environmental data. The sex ratio of H. mammata was 1:1.2 (male:female), and the size at first sexual maturity was 142 mm for males and 167 mm for females. Gonad development began when days had a shorter photoperiod and lower seawater temperature, and spawning occurred later, with longer photoperiod and higher seawater temperature and chlorophyll-a concentrations. This study is essential to increase the biological and ecological knowledge of the populations of H. mammata, create conditions for the domestication of broodstock in captivity and create precise measures for the conservation of ecosystems.Holothuria mammata is one of the most valuable species of sea cucumber, as well as one of the main target species harvested in the Mediterranean and NE-Atlantic regions. This study aims to describe the reproductive cycle of H. mammata in a coastal area of southwest Portugal. Monthly samplings were carried out for 19 months, with the concomitant collection of environmental data and biometric data. H. mammata had a sex ratio of 1:1.2 (male:female) and a size at first maturity of 142 mm for males and 167 mm for females. The gonadosomatic index (GI) peaked between April and May for both sexes. Gonad development started when days had a shorter photoperiod (9 to 13 h of sunlight) and lower seawater temperature (<15 °C), and spawning occurred later, with longer photoperiod (13 to 15 h of sunlight) and higher seawater temperature (>15 °C) and chlorophyll-a concentrations. The development of new studies to increase the biological and ecological knowledge of the populations of H. mammata is essential to create conditions for the domestication of broodstock in captivity, to allow the development of fishing regulations based on informed decisions and to create precise measures for the conservation of ecosystems.

Oocyte growth, gonadosomatic index, hepatosomatic index and levels of reproductive hormones in goldspot mullet Planiliza parsia (Hamilton, 1822) reared in captivity

Goldspot mullet Planiliza parsia (Hamilton, 1822) is a commercial food fish in South-east Asian countries. Availability of hatchery produced seed is the major bottleneck in the development of aquaculture of this species. Therefore, an attempt was made to develop captive broodstock of P. parsia and understand its reproductive maturation. Broodstock reared for eighteen months were sampled and six maturation stages were defined (I-VI) in both the sexes. Ovarian biopsy, gonad histology, gonadosomatic index (GSI), hepatosomatic index (HSI) and reproductive hormones assay were performed in different maturation stages. Diameter of pre-vitellogenic, vitellogenic, post-vitellogenic and ripe oocytes was less than 369.80, 444.38, 477.41 and 665.5 µm, respectively. In the female, the highest value (p&lt;0.05) of GSI (18.31±1.15), HSI (1.84±0.84), 17 β-estradiol (E2) (898.45±0.35 pg ml-1), follicle stimulating hormone (FSH) (81.14±40.48 ml U ml-1) and vitellogenin (Vtg) were found at stage IV, whereas luteinising hormone (LH) attained its peak at V stage. In males, the concentration of testosterone (T) increased gradually from stage I (7.60±0.43 pg ml-1) to VI (40±2.89 pg ml-1). Histological observations revealed synchronous type of oogenesis and cystic type of spermatogenesis. The results of this study will help in the captive seed production of this species.Keywords: Captive maturation, Histology, Ovarian stages, Reproductive hormones, Vitellogenin

Intracellular production of recombinant GnRH1 in yeast, Pichia pastoris, and its potential as oral treatment to advance gonadal development in juvenile orange-spotted grouper, Epinephelus coioides

Late maturation and large size at maturity are significant challenges when administering hormonal treatments in captive broodstock. Here, we report the potential of yeast, Pichia pastoris, as a vehicle to orally deliver a recombinant gonadotropin-releasing hormone (rGnRH1) aimed at stimulating gonadal development in juvenile orange-spotted grouper, Epinephelus coioides. Two recombinant GnRH1 constructs were designed utilizing pPIC3.5, the yeast expression vector lacking a signal sequence, hence retaining the recombinant within the yeast. The first construct (rGnRH1_1xGAP) comprised of GnRH1 decapeptide and the GnRH-associated peptide (GAP) separated by a cleavage site. The second construct (rGnRH1_10x) consisted of ten GnRH1 decapeptides, each separated by a cleavage site. Expression of the two recombinant peptides was confirmed by mass spectrometry. ELISA for the GnRH analogue (GnRHa) was validated to determine the level of rGnRH1 from the yeast extracts. Parallelism between the serially diluted GnRHa and serially diluted extracts from recombinant yeast confirmed validity of the assay. A luciferase reporter assay showed stimulation of tilapia GnRH type 3 receptor by the yeast extract, suggesting biological activity in vitro. In a short term experiment, lyophilised yeast loaded in gelatine capsules and fed once to juvenile orange-spotted grouper resulted in a significantly higher plasma GnRH compared with the control. In a 4-week experiment, lyophilized yeast containing either rGnRH1_1xGAP or rGnRH1_10x was incorporated in fish pellets and fed daily at a dose of 1 μg rGnRH1/kg fish body weight/day. The mean gonadosomatic index and oocyte diameter did not vary between the treated and control fish. The mean plasma levels of FSH, LH and GnRH in the rGnRH1-fed and control fish did not also vary significantly, however there were individuals in the rGnRH1-fed groups that had increased level of the hormones. Together with histological evidence showing oocyte development in a proportion of fish fed with the recombinant, results of the present study point to a biological activity in vivo of the rGnRH1 in yeast. With further refinement, this technology has the potential to provide a non-invasive method for broodstock management of large, late-maturing species of fish and of small, delicate endangered species that require breeding in captivity.

Comparative assessment of egg and larval quality traits of progeny from wild-collected and captive-matured brooders of endangered golden mahseer, Tor putitora: A prelude to quality broodstock development and seed production

In this study, we assessed the differences in reproductive outputs (fertilization and hatching rates); egg quality (egg size increase during hardening, biochemical composition, carotenoid content, and characteristics of ovarian fluid); and larval performance traits (growth, microanatomical development, survival, starvation response, and critical thermal tolerance) of progeny from captive-matured and wild-collected golden mahseer brooders. Fertilization and hatching rates were significantly higher in wild-collected brooders than in captive broodstock. Captive brooder eggs were significantly larger in size and weight but had significantly lower energy/nutrient (total protein, glucose, and triglyceride) reserves and total carotenoids. On the contrary, ovarian fluid from captive females had significantly higher levels of total protein, glucose, and triglycerides, possibly indicating weaker egg membrane and nutrient leakage due to membrane damage or lysis. During water hardening, the cumulative weight increase due to a higher water uptake rate was significantly higher in the wild origin eggs than captive brooder eggs. CTmax of larvae obtained from captive-matured brooders was lower during the early developmental stages (15 dph), but became similar to the CTmax of wild brooder's larvae at 35 dph. On the other hand, CTmin of captive origin larvae was higher than their wild counterparts at all examined stages. There were no differences in starvation tolerance of larvae between the two brooder types. Histological observations revealed that the intestinal nutrient absorption and hepatic nutrient accumulating efficiency during the early developmental stages was relatively lower in captive origin larvae, corresponding to the comparative growth metrics observed until 35 dph. Also, the survival percentage at 90 dph was lower in the larvae of captive brooders than their wild counterparts. Collectively, these findings indicate potential areas for improvement in the captive broodstock management of the endangered cyprinid, golden mahseer.

Effects of dietary fish oil and corn oil on gonadosomatic and hepatosomatic index, gonadal histology, 17β‐oestradiol level and fatty acids profile of mahseer ( Tor tambroides ) broodstock in captivity

The present research was conducted to investigate the effects of fish oil (FO) substitutions with corn oil (CO) on the gonad development of female Tor tambroides broodstocks, a high value freshwater fish. Three isonitrogenous (450 g kg−1 crude protein) and isolipidic (105 g kg−1 crude lipid) were formulated to contain FO and CO at a ratio of 1:0, 1:1 and 0:1, respectively, and fed to female fish (n = 10 fish × 3 replicate × 3 treatment; average weight = 910.0 ± 130.0 g) for five months. At the end of the feeding trial, there were no significant differences (p > .05) on the gonadosomatic index (GSI), hepatosomatic index, 17β-oestradiol (E2) concentration and muscle fatty acids (FA) composition. However, fish fed with diet containing FO to CO at a ratio of 1:1 demonstrated higher percentage of GSI, E2 concentration (ng ml−1) and the presence of vitellogenic oocytes in the histological data compared to the other two feeding diets. The FA composition also highlighted that T. tambroides broodstocks can elongate polyunsaturated FA to highly unsaturated FA. Based on these preliminary results, it shows that T. tambroides prefer diets with supplementation of both n3 and n6 oil source. However, more studies need to be done to strengthen this conclusion.

Early development of the Peruvian rock seabass Paralabrax humeralis (Teleostei: Serranidae): morphological description of the embryonic and yolk-sac larval stages

Describe the embryonic development of Paralabrax humeralis (Peruvian rock seabass) and the present morphology of its eggs and yolk-sac larvae using the eggs spawned by P. humeralis broodstock in captivity. The spawning occurred naturally and spontaneously in early November 2018. The egg is pelagic and round, with a diameter of 0.98 ± 0.02 mm, an oil globule, and a diameter of 0.2 ± 0.02 mm. Embryonic development started with meroblastic cleavage, reaching the first cleavage stage at 0.4 h post-fertilization (HPF), and reached 64 cells at 2.2 HPF. Blastula period, 128 cells to 30% epiboly, end at 11.3 HPF. Gastrula period, 50% epiboly to 90% epiboly, end at 19.6 HPF. In the organogenesis period, forming Kupffer’s vesicle appeared at 22.5 HPF, the separation of the caudal fin from the yolk at 30.3 HPF, and the hatching of the first larvae at 47.9 HPF. Water temperature was kept at 17.2 ± 0.2°C. The yolk-sac larvae measured 2.22 ± 0.1 mm with a pigmentation pattern of pinpoint melanophores, all along with the embryo and xanthophores in the cephalic region, trunk, and caudal region, as well as in the oil globule. The larva takes feeds from three days post-hatch-out.

Testicular maturation of thin-lipped grey mullet during the annual reproductive cycle in captivity

ABSTRACTIntroduction: Continuous maintenance of mullet broodstock in captivity and the control of testicular development are important, particularly when linked to mass propagation of juveniles in the hatcheries, however, the complete description of testes maturation still lacking.Aim of the work: The main goal of our study to present a complete description for the testes and the obtaining of mature thin-lipped mullet, Liza ramada, males suitable for breeding in captivity.Material and methods: We performed morphological and histological techniques to describe the testicular cycle of developmental stages of male mullet reared in freshwater and captivity. Results: In general, the testes of L. ramada exhibit remarkable seasonal variations in shape, size, color and texture. Indeed, five developmental stages were characterized during testicular cycle in L. ramada in freshwater based on the histomorphology and gonadosomatic index. These stages include immature testis, stimulating spermatogenesis, rapid spermatogenesis, mature (ripe) testis and spawning (running) testis. Importantly, the testis development started when the day length and water temperature begun to decrease in September while the gradual decrease in both photoperiod and water temperatures ensure complete gonad maturation (September-December). However, induction of successful spawning in L. ramada occurs when photoperiod and water temperatures decline to their minimum values during December.Conclusion: The present study provides the morphological and histological description for testes of L. ramada during gonad maturaion in captivity and able to obtain a ripe mullet male suitable for hormonal induced reproduction in these species especially in captivity. In spite of attaining the ripe stage of L. ramada males in freshwater, the spawning can only possible with hormonal and environmental stimulation.

Recent advances in artificial breeding and larval rearing of silver pomfret Pampus argenteus (Euphrasen 1788) in Kuwait.

During last several years, Kuwait Institute for Scientific Research (KISR), Kuwait has been trying to develop a sustainable culture technique for silver pomfret (Pampus argenteus). This paper reports the recent research advances in the breeding and rearing of silver pomfret fry at KISR. The eggs collected from wild silver pomfret during spawning seasons of 2012 to 2015 were artificially fertilized under laboratory condition. The average hatching rates of artificially fertilized eggs collected from wild silver pomfrets were 25.6%, 44.8%, 76.7%, and 53.5.0% and average survival rates of metamorphosed fry produced from these eggs were 3.7%, 5.7%, 4.4% and 3.8% for the spawning seasons 2012, 2013, 2014, and 2015, respectively. For captive brood stocks, observation on the spawning time at hourly interval by collecting eggs from the nets set at out-flow of brood tanks showed that the spawning time for captive silver pomfret starts at the time of sunset. In 2012, two groups of captive silver pomfret broods spawned a total of 62x103 and 66x103 eggs, but the eggs were unfertilized. No captive spawning occurred during 2013 and 2014 spawning season. In 2015, captive silver pomfret broods in three tanks spawned about 653x103, 673x103 and 270x103 eggs, and in 2016, the broods in four tanks spawned about 669x103, 22x103, 3x103 and 366x103 eggs. However, from these eggs only 1,400 and 1,000 fertilized eggs were collected which produced 300 and 123 hatched larvae in July 2015 and June 2016, respectively. The larvae produced from the 2015 broods did not survive beyond 56 days of metamorphosed stage while larvae produced from 2016 captive broods survived for 9 days only. The mortality of the larvae from captive brood could be related to the poor egg or milt quality. However, efforts are continued to improve the eggs and sperm quality through proper brood management.

Blood Analyte Changes of Wild-Caught Adult Almaco Jack in Response to Acclimation to Recirculating Aquaculture Systems and Hyposalinity Treatment.

Despite the utility of blood analyte evaluation as a diagnostic tool to assist in monitoring the health of marine fishes, baseline data are often lacking for many commercially important finfish species. The objective of this study was to compare hematology and plasma chemistry data for adult wild-caught Almaco Jack Seriola rivoliana at time of capture and again following a period of acclimation to a recirculating aquaculture system and hyposalinity treatment. A total of 30 clinically healthy adult fish were caught via hook and line in the eastern Gulf of Mexico, approximately 120 mi offshore from Madeira Beach, Florida. Blood was collected from a subset of these fish (n = 13) immediately after capture and again at 16 weeks postcapture from another subset (n = 12) following a 45-d antiparasitic hyposalinity treatment. A 19% increase in fish body weight was observed during the study period (16 weeks) and no overt health issues or mortality were noted. Compared to fish that were sampled immediately following capture, several significant differences (P < 0.05) were observed. Absolute white blood cells were lower in captive held fish, suggesting biological variation, antigenic stimulation in wild fish, and/or immunosuppression associated with stress in captive held fish. Lower sodium, chloride, and calculated osmolality indicate osmoregulatory adjustments following the hyposalinity treatment by 16 weeks postcapture. Other observed plasma biochemical differences presumptively reflect dietary and/or environmental changes, or physiological variation following acclimation to captive culture conditions. This study reports baseline blood analyte data of wild-caught Almaco Jack and documents hematological and plasma biochemical responses to their new environment as captive broodstock. Baseline hematological and plasma biochemistry data obtained during this study are the first reported for this species.

Fatty acid composition and spawning quality in wild and captive broodstock of Pacific red snapper Lutjanus peru

The Pacific red snapper (Lutjanus peru) is very popular fishery that reaches high prices in the market that is distributed in tropical and subtropical climates. Most studies in fatty acid requirements for larval production are done in temperate species; in general, warm-water fish are given the same levels of DHA and EPA than cold-water fish, which increases considerably the costs of production, without apparent benefit. We analyzed spawns during lecithotrophic development, with emphasis on fatty acids, of L. peru. Three origins were compared, Wild spawns, used as the standard of better-quality larvae, Laboratory and Pond, each with some differences in the inductions of maturation and broodstock diet: Lab and Pond broodstock were fed sardines and squids and DHA-rich oil capsules were added once a week. A total of 87 spawns were sampled throughout three years of sampling. Egg and oil globule diameters before fertilization, in 1-h embryo (E) and before hatching (LE); larval total length and oil globule diameter at hatching (LH), and after 24 (L24h) and 48 h (L48h) were measured. Hatching and survival percentages were measured in triplicate for each spawn. Hatching were significantly higher from Pond spawns (75.7%) compared to Wild (60.8%). Survival at L48 hours was not significantly different among origins. Wild spawns had significantly more carbohydrates, but less phospholipids during development, compared to Lab and Pond spawns. ARA, EPA and DHA concentrations decreased in total lipids and triglycerides, but in Lab spawns they were accumulated in phospholipids. There was a more variable fatty acid composition in Pond spawns compared to Lab spawns, a result of more diversified diet in ponds. Viable eggs had two-fold higher proportion of ARA compared to non-viable eggs. A principal factor analysis revealed three positive associations between 1) female weight, egg oil globule diameter, and EPA:ARA in egg PL; 2) hatching, LH length, and DHA:ARA in egg PL; 3) L48h survival, TG and PL content in eggs. According to our results, subtropical L. peru needs less DHA and more ARA and monounsaturated fatty acids in their diet, compared to temperate marine fish.

Status of sablefish, Anoplopoma fimbria, aquaculture

AbstractSablefish, Anoplopoma fimbria (also called black cod), is a long‐lived marine species with wide distribution extending from Baja California to Alaska, the Bering Sea, and through to the eastern coast of Japan. The landed weight of sablefish in the U.S. commercial fisheries is not large compared with other species; however, the exceptional value of sablefish has ranked it high compared with other species such as pollock, sockeye salmon, and Pacific cod. Sablefish are high in omega‐3 fatty acids and have white firm flesh with superior quality and taste. Current population levels are lower relative to historic ones and harvests have decreased within the last decade. The exceptional value of sablefish and decreases in wild populations have stimulated the development of methods to commercially aquaculture this species. Over the last 20 years, significant progress has been made in addressing the production of sablefish, and while there is still research that needs to be completed, sablefish have been commercially aquacultured by a small number of Canadian companies. In the Pacific Northwest, it is relatively easy to collect sablefish broodstocks from the wild and to transition them to land‐based rearing facilities. However, they must be maintained at cold temperatures to successfully reproduce. Captive broodstocks for genetic selection are not commercially available, though producers have begun their own development. Incubation conditions for yolk‐sac larvae have been developed and currently require long incubation periods at low temperatures, elevated salinity, and light exclusion. Although incubation times are long, they do not require very much attention during this phase. Exogenously feeding larvae currently require a regimen of rotifers and Artemia prior to dry feed habituation. However, tank characteristics, water turbidity, temperature, and illumination, as well as live feed enrichments have been studied. With the research that has been accomplished so far, survival rates of 10–40% have been routinely obtained at the larval stage. Despite a scarcity of species‐specific nutritional studies, researchers have shown that sablefish can be successfully cultured from the juvenile to the adult stage on commercial salmon feeds. Off‐the‐shelf salmon feeds have been used successfully in net‐pen grow‐out trials and are used by commercial producers. In addition, sablefish have proven to be a good cold‐water marine model for alternative feeds research. Still, research is needed to optimize nutritional requirements for all life stages of sablefish, develop practical feeds with these nutrient profiles, optimize feeding schedules, and produce life‐stage specific diets since the growth of sablefish differs according to size—most likely reflective of their complex life history. Sexually dimorphic growth in sablefish occurs during the typical grow‐out period, affecting time to harvest, the proportion of undersized (male) fish, and thus overall economic return to the producer. Production of all‐female monosex offspring at semi‐commercial scale using F‐1 progeny of neomales (XX males) generated through dietary treatment with 17α‐methyltestosterone is now possible. Results of long‐term feeding trials suggest that time to harvest at 2.5 kg from stocking at 75 g may be reduced by almost 3 months when monosex stocks are used. Econometric models reveal that internal rates of return are 11–15% higher for monosex relative to mix‐sex stocks over a 10‐year period under typical cage culture conditions. Sablefish are susceptible to diseases (furunculosis and vibriosis) brought on by atypical Aeromonas salmonicida and Vibrio anguillarum. Vaccination of sablefish using commercial vaccines to A. salmonicida (typical and atypical) has demonstrated that fish can be protected against a subsequent challenge by A. salmonicida, but this has only been effective by injection of the vaccine (not immersion) and how long the protection lasts has not been studied. More research is required to develop more effective vaccines, methods for vaccine delivery, and to understand conditions (ontogenetic and environmental) that may promote or enhance pathogenesis.

Effect of hormonal stimulation on captive broodstock maturation, induced breeding and spawning performance of striped snakehead, Channa striata (Bloch, 1793)

In the present study, there was assessment of effects of gonadotropin treatments on broodstock maturation, induced breeding, and spawning outcomes of striped snakehead in captivity. The striped snakehead (n = 128) were equally distributed in four concrete tanks (15 m2) and hormone implants (500 IU human chorionic gonadotropin (hCG)/kg body weight) were inserted intramuscularly and striped snakehead broodstock administered this treatment were confined in two tanks and striped snakehead of a non-implanted group were confined in two tanks. The hormone implanted striped snakehead had a greater (P < 0.05) gonadosomatic index (GSI) and oocyte diameter in comparison to non-implanted striped snakehead. In a subsequent experiment, hCG and carp pituitary homogenate (CPH) were evaluated for inducing breeding. Dosages of hCG used were, 2,000 (TH1), 3000 (TH2), and 4000 (TH3) IU hCG/kg body weight of females. Dosages of CPH were, 20 (TP1), 30 (TP2), and 40 (TP3) mg CPH/kg body weight of females. Males were administered 0.75 of the dosage administered to females. The values for reproductive variables were estimated. Fertilization (89.0 ± 3.0 %) and hatching (92.0 ± 1.0 %) rates were greater (P < 0.05) in the TH1 group of implanted striped snakehead. Relative fecundity (19,023 ± 2211), as well as fertilization (96.2 ± 2.4 %), and hatching (96.6 ± 1.7 %) rates were greater in the TP2 group of the implanted striped snakehead. The results from the present study indicate broodstock treated with gonadotropins had greater spawning outcomes which might facilitate mass scale breeding and fertilized egg as well as juvenile production of striped snakehead in captivity.

Monitoring of common sole Solea solea (L) captive broodstock from Northern Adriatic Sea over consecutive spawning seasons

The high nutritional quality of common sole Solea solea increases its value for the fishery industry and for the aquaculture sector. To ensure the expansion of its production, it is necessary to implement farming and broodstock management technique to produce high quality eggs and larvae. This work summarizes eight years of study on reproductive performances, growth and parental contribution of a common sole broodstock from the Mediterranean-North Adriatic Sea. The broodstock (11 females and 13 males) reached the peak of fecundity after 5/6 years of captivity, with a production of 296.48 and 376.54 × 103 of total eggs kg−1 female with a fertilization rate of 31.6 ± 18.3 and 41.9 ± 23.8 %, respectively. Results shows that variations in temperature cycles are pivotal for a successful breeding season, and body condition during the first 3 years of captivity was the most important parameter positively correlated to parental contribution for both males and females. Parental contribution was assessed by eight species-specific microsatellite loci during the first 3 years of reproduction. Although the two sexes displayed different temporal trends, parentage assessment demonstrated an overall increase in the number of active breeders. However, only 13 couples out of 50 produced the 70.4 % of the larvae in year 5, confirming the same reproduction behavioural pattern in Mediterranean common sole than that observed both in Senegalese sole and in common sole of Atlantic origin.This work provides valuable data needed to understand the mechanisms behind the maturation characteristics of this species and support future strategy for the establishment and management of Mediterranean common sole aquaculture.

Captive maturation, breeding and seed production of the brackishwater ornamental fish silver moony,Monodactylus argenteus(Linnaeus, 1758)

Silver moony, Monodactylus argenteus (Linnaeus, 1758), belonging to the family Monodactylidae, has high significance in the ornamental fish industry. The present study provides the details of captive broodstock maturation, induced breeding and larval rearing of this species for the first time. Juveniles were collected from wild and raised to adults in net cages. Female with oocyte diameter =500 µm and oozing males were selected in the sex ratio of 1:2 (female: male) and induced to spawn using a single dose of LHRHa. Spontaneous spawning and fertilization were observed after 36 to 40 hr of hormonal induction. The average fertilization and hatching rates were 83.50 ± 4.37% and 70.83 ± 5.19% respectively. The incubation period was observed to be 18 to 20 hr at a temperature of 29 ± 1.8°C. Newly hatched larvae measured 1,630 ± 0.20 µm in length. Larval rearing was carried out in 500-L circular fibre reinforced plastic tanks using a green water system. Larvae were stocked at 5 L−1 in larval rearing tanks. Initial mouth opening and complete yolk absorption were observed at 48 and 96 hr post-hatching respectively. Larval feeding was done using live feeds, rotifer and Artemia nauplii. Metamorphosis began on 23 dph, and 100% larvae became juvenile on 32 dph with an average survival rate of 49.6 ± 8.73%. These findings on the development of captive seed production of silver moony would pave the way for mass scale production and reduced exploitation of wild stocks.

Broodstock development and captive maturation of hilsa (Tenualosa ilisha) in a brackishwater pond-based system.

Successful captive broodstock development of clupeid fish, hilsa, is one of the major challenges for the artificial propagation of this economically valued fish. The present study provides novel insights into the pond-reared captive broodstock development of hilsa using artificial feed. In the present study, wild collected hilsa fry (weight 1.35 ± 0.13 g, length 53.84 ± 0.95 mm) were reared in grow-out ponds for 6 months followed by maintaining them as broodstock in other ponds using formulated feed in both cases. After 6 months of pond rearing, the average body weight and length of fish were 66.76 ± 4.53 g and 184.75 ± 3.65 mm, respectively. In broodstock ponds, hilsa subadults fed with formulated feed (crude protein 41.06%) ensured significant advancement in ovarian maturity with gonado somatic index of 9.09%, enhanced secondary yolk stage oocytes of 91.66% and enlargement of oocyte diameters up to 570 μm. The broodstock reached somatic growth such as average body weight and average body length of 383.80 ± 27.38 g and 339.33 ± 9.68 mm, respectively, with a condition factor of 1.06 ± 0.15. Gut content analysis revealed the better acceptability of the artificial feed. Lipid profiling of muscle and ovary during gonadal maturation revealed mobilization of fat from muscle to ovary and selective retention of some fatty acids (i.e., C14:0, C18:0, C20:5, C22:6 and C20:4) in the ovary, which might help in gonadal maturation. STATEMENT OF SIGNIFICANCE: Successful rearing of wild-caught hilsa juvenile in captive condition using formulated feed showed its potential as aquaculture species in low saline conditions. Advance stage of maturation in low saline captive conditions showed the possibility for induced breeding of hilsa, a high priced anadromous fish. Mobilization of fat from muscle to ovary and selective retention of some fatty acids in the ovary showed the scope of dietary manipulation for broodstock development of hilsa.

Short term cold storage and sperm concentration assessment of lumpfish (Cyclopterus lumpus. L) Milt

There is increased commercial interest in the production of lumpfish (Cyclopterus lumpus) as a biological control against sea lice infections in Atlantic salmon farming. To ensure a sustainable supply of lumpfish, reliable captive reproduction is required however, optimal husbandry and conditions for captive broodstock performance remain unknown. Artificial fertilisation of gametes remains the preferred management strategy for lumpfish, but this requires an effective milt management protocol. The present study tested several milt extender solutions for short term cold storage and validated sperm concentration assessment of lumpfish milt. Results demonstrated lumpfish sperm has a long motility survival time (motile for up to 3 h) when compared to other marine teleosts. Importantly, all extenders used in the study were non-activating on dilution of the milt. Lumpfish milt was successfully stored at 4 °C in Modified Turbot Extender (MTE), Herring Ringers Solution and Aquaboost SpermCoat (Cryogenetics, Norway) for up to 14 days post stripping. MTE performed more effectively with regards to maintenance of sperm activation time in comparison to the other tested extenders. There was a significant positive correlation between sperm concentration identified through cell counts using a haemocytometer and both packed cell volume (spermatocrit) and measured optical density at 640 nm (r2 = 97.42 ± 2.14). This suggests both packed cell volume and spectrophotometric measurements can be effective methods for rapidly assessing sperm concentration in lumpfish. This study validated several options for quantifying sperm concentration and short-term cold storage of lumpfish milt that can be used for hatchery management in lumpfish aquaculture.

Thicklip (Chelon labrosus) and flathead (Mugil cephalus) grey mullets fry production in Tunisian aquaculture

For several years Tunisia has opted to breed freshwater fish in reservoirs and artificial lakes, created for irrigation, as a strategy of providing high quality aquatic protein to the interior regions and providing work opportunities for local communities. The aim of this study was to summarize the main results accumulated by the last 20 year efforts made by the members of the National Institute for Marine Science and Technology (INSTM)-Aquaculture Laboratory to develop thicklip (Chelon labrosus) and flathead (Mugil cephalus) grey mullets fry production from captive broodstocks intended for stocking inland reservoirs (artificial lakes) and grow-out purposes Administration of human chorionic gonadotropin (hCG) at a priming dose of 10.000 IU kg−1 female bw, followed by 10.000 IU hCG and (100 or 200 μg kg−1 female bw of thicklip or flathead grey mullet respectively) as resolving dose resulted at the highest egg production for both species. Mean fecundity was 494.655 eggs kg-1 bw for thicklip grey mullet and 418.945 eggs kg-1 bw for flathead grey mullet. Fertilization rate of eggs produced was high (mean rate 83 % and 63 % for thicklip and flathead grey mullet respectively) and larvae hatched from those eggs at high rates (77 % and 88 %, respectively). The green method was more efficient than clear method to produce thicklip and flathead grey mullet fry, (i.e larvae had higher growth rate and better survival rates). The results of this study demonstrate the possibility to control reproduction and produce grey mullet fry in captivity. However, further research is needed to optimize the production protocol of eggs and fry of both grey mullet species.

Evaluating Artificial Propagation Release Strategies for Recovering Endangered Snake River Sockeye Salmon

AbstractAs a growing number of aquatic organisms become imperiled due to anthropogenic and environmental threats, there is an increasing need to implement captive propagation programs to conserve some species. These captive propagation programs can aid in the recovery of species, such as for Sockeye Salmon Oncorhynchus nerka, by providing individuals that can be used to supplement wild populations. The Snake River Sockeye Salmon Captive Broodstock Program implemented a comprehensive monitoring and evaluation plan to evaluate adult recruitment using three juvenile release strategies from excess eggs of captive females. Hatchery‐produced eyed eggs, presmolts, and smolts were released into the upper Salmon River basin to increase the abundance of individuals expressing an anadromous life history as a way to support population augmentation. A mixed‐effects logistic regression model used to evaluate egg‐to‐adult returns between release strategies indicated that release strategies differed from one another. Full‐term smolt production was observed to produce the highest recruitment among the release strategies and has become the focus of recovery efforts involving juvenile releases. The estimated odds of a fish (egg) returning as an adult were 9.7 times greater for smolts reared at the Oxbow Fish Hatchery and 3.6 times greater for smolts reared at the Sawtooth Fish Hatchery relative to eggs that were hatchery reared and released as presmolts or placed into in‐lake incubator boxes. The variation observed in productivity and in expression of life history traits among release strategies indicates that juvenile releases are not one size fits all, and we recommend undertaking a similar assessment to match observed outcomes with desired objectives when initiating supplementation programs.