Candidate For Aquaculture Research Articles

Sowing Machine for Scallop Seedling in Bottom-culture

The scallop is among the most important shellfish resource and is a proven candidate for aquaculture in many countries. In China, the scallop is generally bottom culture and artificial seeding. Artificial seeding on scallops is a difficult process with low production efficiency, high labor intensity, excessive cost low profit, and high rate of mortality and damage. In this paper, a sowing machine is developed for the bottom-sowing culture of the scallop. It consists of a transmission module, sows slide module, and buoyancy module. The structure and working mechanism of this machine are presented and analyzed in detail. The tests of experiments were conducted as well with the development machine. Through the simulation analysis of flow field of bottom-sown machine. The results show that the vortex area below the platform makes the scallop seedlings seedlings spread more evenly. In addition, the boat-shaped fairing at the head of the platform effectively reduces the water flow rate inside the platform, allowing the scallop seedlings to successfully leave the platform through the grille at the bottom of the platform after sowing. The control group efficiency is 26.67%; however, the optimized group efficiency average value is 57.97%. The cost of bottom sowing 1t scallop seedling was reduced from 1260 RMB to 124.4 RMB. It is proven that the design of the machine is feasible.

Evaluation of larviculture protocols for the Pacific blue tang (Paracanthurus hepatus)

Aquaculture of marine ornamental fish is an important tool that may help to provide sustainable alternatives to wild caught individuals. Many challenges are associated with marine ornamental aquaculture, especially during the larviculture process. Newly hatched marine larvae are often underdeveloped at hatch and require specific nutritional and environmental parameters for successful morphogenesis and ultimate metamorphosis into the juvenile stage. The Pacific blue tang (Paracanthurus hepatus) is a promising candidate for ornamental aquaculture due to its popularity in the aquarium trade and prior captive breeding success. However, improvements in culture methodologies, especially environmental and nutritional factors, is critical to viable commercial production. Seven experiments were conducted to determine appropriate green water culture conditions, photoperiod, and feeding protocols that best promoted survival, growth, and ingestion rate in early-stage P. hepatus larvae. Larval survival and feeding incidence were significantly increased when live microalgae was added to the culture system. The survival and feeding incidence of 3 days post hatch (DPH) P. hepatus larvae was greatest when the algae species Tisochrysis lutea was incorporated at a density of 300,000 cells/mL. The feeding incidence of 3 DPH larvae was not affected by prey type or prey density. When free amino acid feeding stimulants were added to the culture water, neither larval survival nor feeding incidence were improved. Lastly, the photoperiod that best promoted larval growth and survival was 16-h light: 8-h dark. Together, these results provide for improved larval survival in aquaculture and help move P. hepatus towards viable commercial production.

Candidate Species for Florida Aquaculture: Almaco Jack, Seriola rivoliana

Almaco jack, Seriola rivoliana, is a perciform within the order Perciformes, family Carangidae; which includes jacks and pompanos. They are members of the genus Seriola, a species of interest for aquaculture diversification worldwide. Like other commercially farmed Seriola species, almaco jack (also known as longfin yellowtail and kampachi) are fast growers, have a high market value, and are increasingly well-regarded among chefs for their versatility in both cooked and raw preparations. These characteristics, among others, have made them favorable candidates for both land-based and offshore aquaculture.

Integrating indoor and outdoor breeding systems to achieve year‐round seed production in Pearlspot cichlid, Etroplus suratensis

Pearlspot, Etroplus suratensis naturally thrives in the estuarine reaches of Southern peninsular India and Srilanka. The relative ease of adaptation to diverse habitats makes it a promising candidate for climate-resilient aquaculture. This potential remains underexplored due to limitations in the current seed production practices. The present study focused on sustainable seed production of this species in the freshwater environment. Brooders were simultaneously maintained inside the hatchery and also in outdoor cement tanks. The breeding tanks were devoid of bottom substrate and planter pots were kept for egg attachment. The indoor fibreglass tank had an internal airlift filtration and outdoor tanks had an external filter connected to the filter bed. The modified captive breeding approaches employed were successful in obtaining 178 spawning from 44 pairs in 2 years. The indoor facility yielded 56 spawning from 15 pairs and the outdoor system yielded 122 spawning from 29 pairs. Pearlspot was found to spawn throughout the year with two distinct peaks, a minor peak in July–August and a major peak during December–January. Subsequently, spawning declined from February to June with an intermittent spurt in March. The peak spawning period distinctly differed between the breeding systems employed. The interval between successive spawning ranged from 10 to 308 days, with 46% of repetitive spawning occurring within 10 to 30 days. Pairs exhibited parental care by cleaning the substratum, protecting territory, caring for eggs and young ones. The clutch size varied from 347 to 2548, depending on the size, spawning frequency and inter-spawning interval. The indoor tank gave an average egg count of 1104 ± 192 (mean ± SD) and that was 747 ± 21 (mean ± SD), in the outdoor system. The hatching rate with ex-situ incubation was 88.6% ± 2% for outdoor and 77.4% ± 4.6% for indoor breeding tanks. The eggs hatch in about 66 to 72 h post spawning at a water temperature of 26 to 30°C. The water temperature and photoperiod are found to be important physical factors influencing spawning in Pearlspot. The water temperature of 27 to 30°C with a shorter day length of 11:30 to 12:00 are ideal for getting continuous spawning. Adopting an integrated breeding approach can achieve year round production cost effectively.

Effects of feed transition on digestive tract digestive enzyme, morphology and intestinal community in cuttlefish (Sepia pharaonis)

Sepia pharaonis is an excellent candidate for aquaculture in China. However, the low survival rate during early feed transition is a bottleneck restricting industrial development. Understanding the changes in digestive physiology and intestinal microflora during feed transition should enable us to meet their nutritional needs to improve production. In this study, we investigate the digestive enzyme of S. pharaonis and undertake histological observations of the digestive gland and intestine. The intestinal microflora 16S rRNA genes were also analyzed using high-throughput sequencing of the pre, mid, and post-feed transition stages (20, 40, and 60 days post-hatching (DPH), respectively). The digestive enzymes from the digestive gland (trypsin and chymotrypsin) rapidly decrease at 40 DPH when compared to their levels at 20 DPH, but mostly recovered by 60 DPH. The alkaline phosphatase and lipase increased sharply by 40 DPH, then peaked at 60 DPH. The intestinal digestive enzymes followed similar trends during feed transition, except for lipase activity, which decreased after 20 DPH and remained low, even at 60 DPH. Feed transition affects the morphogenesis of the digestive tract and feed transition stress leads to the impairment of the digestive gland and intestinal morphology, which reduces the digestive capacity, but almost totally recovers by 60 DPH. Moreover, the comparison of the intestinal microbial composition during feed transition revealed that the dominant phylum Bacteroidetes gradually increased to a peak at 40 DPH and then decreased until 60 DPH. The microbial composition changed with the most abundant genus Pseudomonas being replaced by Acinetobacter. The phylum and family level investigation suggested the microbiota in the rearing water had limited influence on the intestinal microbiota. The intestinal microbiota diversity increased during feed transition. This study improves our understanding of changes and adaptations in cuttlefish during feed transition.

Probiotic properties of Bacillus strains isolated from the gastrointestinal tract against pathogenic Vibriosis

Vibriosis is one of the major diseases leading to massive fish mortality. Probiotics may provide a potential alternative method to protect fish from pathogens and to promote a balanced environment minimizing the use of antibiotics and chemotherapy. The aims of this study were to (i) isolate and purify marine spore-former strains from Sardine and shrimp intestine, (ii) screen for bacteria with potential probiotic properties, and (iii) carry out theirin vitrosafety assessment using a subtractive procedure. Among 108 spore-former strains, five strains exhibited a strong antibacterial activity against Vibriosis such asVibrio harveyiandVibrio anguillarum. These selected strains were unaffected by high-temperature and gastrointestinal conditions; produced amylase, protease, and lipase activities; and showed high percentages of auto-aggregation and co-aggregation with pathogens, as well as a strong adhesion to fish mucus. Partial 16S rDNA gene sequencing and MALDI-TOF MS revealed that isolates areBacillus amyloliquefaciensorBacillus subtilis. All of them were susceptible to antibiotics, while hydrolic enzymes and virulence factors were not detected forB. subtilisS17. In conclusion, based on their proprieties and their safety assessment,B. subtilisS17 could serve as a potential probiotic candidate for aquaculture.

Photoperiod manipulation leads to successful voluntary captive spawning of butter catfish Ompok bimaculatus during the non‐spawning breeding season

The catfish Ompok bimaculatus (butter catfish) has recently gained importance as an aquaculture candidate species because of its delicious taste, higher nutritional value and market demand. A significant problem in butter catfish aquaculture is its inability to voluntarily spawn in captivity. This experiment was conducted to study the impact of photoperiod on the voluntary spawning of O. bimaculatus in the pre-spawning season (April) in captivity. A total of 80 broodfish were equally distributed (n = 20; F = 10 and M = 10) into four photoperiod treatments: natural condition (control), 12:12 light:dark (L:D), 15L:9D and 9L:15D were stocked in rectangular tanks, and the experiment was carried out for 45 days. Light intensity was maintained at 1000 lx throughout the study for all treatments, except the control. The fish were fed a commercial diet (40% crude protein and 6% crude lipid) at a rate of 3% of body weight, twice a day, for 45 days. Ovasis™ was used for hormone induction to study induced breeding. Broodfish reared under natural photoperiod (control) did not respond to voluntary captive spawning. A complete voluntary captive spawning response was observed in the 12L:12D broodfish, and partial success was observed in the 15L:9D and 9L:15D broodfish. The fertilization rate, hatching rate and survival were significantly (p < 0.05) higher in the 12L:12D broodfish group than those in the broodfish group. Hence, the photoperiod regime of 12L:12D with 1000 lx light intensity would be ideal for voluntary captive spawning and can be elected for maximum seed production in the pre-spawning season. The present study showed that photoperiod manipulation and fixed light intensity stimulate advanced gonadal maturation and voluntary captive spawning of butter catfish, which can help seed production throughout the year.

Dysbiosis and Restoration Dynamics of the Gut Microbiome Following Therapeutic Exposure to Florfenicol in Snubnose Pompano (Trachinotus blochii) to Aid in Sustainable Aquaculture Production Strategies.

Information on unintended effects of therapeutic exposure of antibiotics on the fish gut microbiome is a vital prerequisite for ensuring fish and environmental health during sustainable aquaculture production strategies. The present study forms the first report on the impact of florfenicol (FFC), a recommended antibiotic for aquaculture, on the gut microbiome of snubnose pompano (Trachinotus blochii), a high-value marine aquaculture candidate. Both culture-dependent and independent techniques were applied to identify the possible dysbiosis and restoration dynamics, pointing out the probable risks to the host and environment health. The results revealed the critical transient dysbiotic events in the taxonomic and functional metagenomic profiles and significant reductions in the bacterial load and diversity measures. More importantly, there was a complete restoration of gut microbiome density, diversity, functional metagenomic profiles, and taxonomic composition (up to class level) within 10–15 days of antibiotic withdrawal, establishing the required period for applying proper management measures to ensure animal and environment health, following FFC treatment. The observed transient increase in the relative abundance of opportunistic pathogens suggested the need to apply proper stress management measures and probiotics during the period. Simultaneously, the results demonstrated the inhibitory potential of FFC against marine pathogens (vibrios) and ampicillin-resistant microbes. The study pointed out the possible microbial signatures of stress in fish and possible probiotic microbes (Serratia sp., Methanobrevibacter sp., Acinetobacter sp., and Bacillus sp.) that can be explored to design fish health improvisation strategies. Strikingly, the therapeutic exposure of FFC neither caused any irreversible increase in antibiotic resistance nor promoted the FFC resistant microbes in the gut. The significant transient increase in the numbers of kanamycin-resistant bacteria and abundance of two multidrug resistance encoding genes (K03327 and K03585) in the treated fish gut during the initial 10 days post-withdrawal suggested the need for implementing proper aquaculture effluent processing measures during the period, thus, helps to reduce the spillover of antibiotic-resistant microbes from the gut of the treated fish to the environment. In brief, the paper generates interesting and first-hand insights on the implications of FFC treatment in the gut microbiome of a marine aquaculture candidate targeting its safe and efficient application in unavoidable circumstances. Implementation of mitigation strategies against the identified risks during the initial 15 days of withdrawal period is warranted to ensure cleaner and sustainable aquaculture production from aquatic animal and ecosystem health perspectives.

Reproductive characteristics of the giant gurami sago strain ( Osphronemus goramy Lacepède, 1801): basic knowledge for a future hatchery development strategy.

Background: The giant gourami sago strain ( Osphronemus goramy Lacepède) has been approved in 2018 as a candidate for freshwater aquaculture in Indonesia. However, information on the species' reproduction is minimal. This study analyzed the reproductive characteristics of the gourami sago strain broodfish to provide basic knowledge for a future hatchery development strategy. Methods: A total of 10 female and 10 male mature gourami sago strain broodfish were measured for body weight and length, and were evaluated for their reproductive characteristics. Breeding fish were spawned naturally in a 2×1×0.6 m concrete pond with a male-female sex ratio of 1:1. Egg weight and diameter were measured in 25 eggs per female using, respectively, ACIS AD- 600i scales with 0.01 g accuracy, and a microscope (Labo model L-711) using Canon Digital Camera Software 3 . Semen was collected using plastic syringes in 3 mL aliquots, then placed in an insulated ice-cooled container, and analyzed within two hours of collection. Results: Average weights of female and male broodfish before spawning were 2180±159.78 g and 3060±134.99 g, respectively. The relative fecundity and egg diameter were 1029±36 eggs kg -1 and 2.42±0.05 mm, respectively. The hatching rate and embryo survival to an eyed-egg stage were respectively 76.40±2.27% and 94.76±0.42%. Sperm characteristics showed that volume was 0.60±0.12 ml kg -1 and percentage of motile sperm was 70.04±2.27%. Female broodfish weight after spawning was strongly correlated with the weight before spawned ( r2 = 0.999) and absolute fecundity was also strongly correlated with female broodfish weight before spawning ( r2= 0.921). Sperm concentration was moderately correlated with sperm motility ( r2 = 0.556) and duration of sperm motility ( r2 = 0.502). Conclusions: The gourami sago strain broodfish has suitable reproductive characteristics for the development of hatcheries. Successful natural spawning should be followed by larval weaning and feeding technology to increase growth and survival.

Embryonic Development and Fecundity of the Pacific Pygmy Octopus, Paroctopus digueti

The life history including embryonic development of most species of octopus is still poorly understood. This makes the identification of eggs and juveniles difficult, hampering distribution and dispersal studies. The Pacific pygmy octopus, Paroctopus digueti (Perrier & Rocheburne 1894), exhibits features, including its direct embryonic development, that make it an ideal candidate for aquaculture. This study provides detailed information on the embryonic development, the morphological characteristics of eggs, and the fecundity of wild female P. digueti maintained under laboratory conditions that replicate natural environmental conditions. The Pacific pygmy octopus showed a monocyclic spawning pattern that takes place in time-separated batches, leading to asynchronous embryonic development in the batch. Eggs are between 7 and 10 mm (8.9 ± 0.71 mm) in total length. During the embryonic development, 31 distinct stages were identified with a total duration of 38 days. The distribution of chromatophores showed a specific pattern, with dorsal chromatophores being more abundant and larger than ventral ones. An observed fecundity of 300 eggs per female was twice as high as the value previously reported for this species in Bahia Choya, Sonora. This study contributes to the better understanding of the life cycle of P. digueti. Besides being a basic reproductive aspect, fecundity is a key element for studies on the reproductive potential and population dynamics of the species.

In vitro hemocyte phagocytosis activation after experimental infection of common octopus, Octopus vulgaris (Cuvier, 1797) with Photobacterium damselae subsp. piscicida or Vibrio alginolyticus at different temperatures and infection routes

Due to the fast growth rate, the short life cycle, the high market price and the high food conversion efficiency, O. vulgaris is considered as a good candidate for aquaculture. One of the prerequisites for the successful integration of new species, such as octopi, into industrial-scale production, is the knowledge of the pathological conditions that may arise, with emphasis on infectious diseases caused by microorganisms and para-sites transmitted through wild populations, especially for the farmed organisms cul-tured in cages in proximity to teleost fish. The main objectives of this study were to investigate the sensitivity of common octopus to experimental infection with pathogenic bacteria, to assess the activation of hemocytes and more specifically their phagocytic activity after infection and to associate sensitivity of the species and phagocytic activity of hemocytes to temperature changes, route of infection and pathogen. Common octopus individuals were intramuscularly and intravenously infected with either Photobacterium damselae subsp. piscicida or Vibrio alginolyticus. The hemocyte phagocytosis activation in vitro at two temperatures (21 ± 0.5 °C and 24 ± 0.5 °C) was studied, in an effort to relate these aspects to climate change. Hemolymph was withdrawn on days 0, 3 and 7 post infections/injections. Number of circulating hemocytes/ml hemolymph, phagocytosis ability and Phagocytosis Particle Binding Intensity index were determined. Correlations between hemocytes and bodyweight and between hemocytes and phagocytosis ability were also determined.No mortalities were recorded irrespective of pathogen, route of infection and temperature employed. Circulating hemocytes in control specimens ranged between 1.60x105 hemocytes ml−1 hemolymph to 20.02x105 hemocytes/ml hemolymph at both experiments and temperatures. The interrelation between octopi weight and circulating hemocytes showed that natural fluctuations, age, maturity stage and temperature may affect this relationship.Rise of temperature influenced phagocytosis which seemed to be route of infection, time-point and pathogen related. Specimens infected with Photobacterium damselae subsp. piscicida showed decreased phagocytosis with rise of temperature while when Vibrio alginolyticus was used, phagocytosis activity increased, in most cases. Temperature also played an important role in the correlation between the circulating hemocytes and phagocytosis activity, as at lower temperatures a negative strong correlation was observed. The results prompted us to calculate the activation index. This index showed that temperature is an important factor in hemocyte activation since for Photobacterium damselae subsp. piscicida infected specimens, hemocytes were more activated at 21 ± 0.5℃ instead of 24 ± 0.5℃, and the opposite observed for Vibrio alginolyticus samples and only later post-infection.Comparing the phagocytosis ability results with those obtained from Particle Binding Intensity index important differences concerned mainly confidence levels. The use of phagocytosis ability instead of PBI index provides more accurate results.

Reproductive characteristics of the giant gurami sago strain ( Osphronemus goramy Lacepède, 1801): basic knowledge for a future hatchery development strategy

Background: The giant gourami sago strain ( Osphronemus goramy Lacepède) has been approved in 2018 as a candidate for freshwater aquaculture in Indonesia. However, information on the species’ reproduction is minimal. This study analyzed the reproductive characteristics of the gourami sago strain broodfish to provide basic knowledge for a future hatchery development strategy. Methods: A total of 10 female and 10 male mature gourami sago strain broodfish were measured for body weight and length, and were evaluated for their reproductive characteristics. Breeding fish were spawned naturally in a 2×1×0.6 m concrete pond with a male-female sex ratio of 1:1. Egg weight and diameter were measured in 25 eggs per female using, respectively, ACIS AD- 600i scales with 0.01 g accuracy, and a microscope (Labo model L-711) using Canon Digital Camera Software 3 . Semen was collected using plastic syringes in 3 mL aliquots, then placed in an insulated ice-cooled container, and analyzed within two hours of collection. Results: Average weights of female and male broodfish before spawning were 2180±159.78 g and 3060±134.99 g, respectively. The relative fecundity and egg diameter were 1029±36 eggs kg -1 and 2.42±0.05 mm, respectively. The hatching rate and embryo survival to an eyed-egg stage were respectively 76.40±2.27% and 94.76±0.42%. Sperm characteristics showed that volume was 0.60±0.12 ml kg -1 and percentage of motile sperm was 70.04±2.27%. Female broodfish weight after spawning was strongly correlated with the weight before spawned ( r 2 = 0.999) and absolute fecundity was also strongly correlated with female broodfish weight before spawning ( r 2= 0.921). Sperm concentration was moderately correlated with sperm motility ( r 2 = 0.556) and duration of sperm motility ( r 2 = 0.502). Conclusions: The gourami sago strain broodfish has suitable reproductive characteristics for the development of hatcheries. Successful natural spawning should be followed by larval weaning and feeding technology to increase growth and survival.

Tolerance Level of Domesticated Asian Red-Tail Catfish Hemibagrus Nemurus to Salinity, Acidity, and Temperature Variability

The Asian redtail catfish Hemibagrus nemurus is Indonesian native fish proposed for catfish culture diversification project. Prior to be commercialized and widely distributed, it is imperative to evaluate environmental tolerances of the catfish for successful breeding programs and its aquaculture development program. This research was carried out to evaluate the optimum tolerance range and physiological responses of domesticated H. nemurus exposed to different salinity, acidity, and temperature. Fish used in this experiment were the second generation of H. nemurus produced at the Research Institute for Freshwater Aquaculture and Fisheries Extension (RIFAFE), Bogor, West Java, Indonesia. A total of 12 fish for each treatment were exposed to different salinity (0 ppt (control), 5 ppt, 10 ppt, 12.5 ppt, 15 ppt and 17.5 ppt), pH (4, 5, 7 (control), 9 and 10), and temperatures (15℃, 20℃, 25℃, 28.5℃ (control), 32.5℃, 35℃, and 40℃) for 12 days observation until fish reached their Loss of Equilibrium (LOE). Cortisol, hemoglobin, and glucose were investigated to study the stress response happened. This research reveals that the domesticated Asian redtail catfish are able to be acclimated to slightly brackish-water environment (≤10 ppt), have more resilience in acidic than alkaline water (pH 5.0 to 7.35), and can adjust in wide range of temperatures (25℃ to 32.5℃). In salinity exposure, significant physiological effects existed between controls and treatments (P&lt;0.05) except glucose. For pH, cortisol was the best indicator to see the effect of exposure (P&lt;0.05). The last for temperature exposure, the only cortisol was enabled to be used as the indicator of stress response. From the study, it found that cortisol level analysis was the best indicator to detect stress responses of the catfish that would be important to mitigate unpredictable environmental events and early warnings in the changes of environmental quality in culture system. We would recommend that the domesticated H. nemurus can be developed for the new catfish aquaculture candidate as it met a requirement to tolerance evaluation on different water quality levels which its responses was commonly similar compared to other existing aquaculture species.

Differential expression analyses reveal extensive transcriptional plasticity induced by temperature in New Zealand silver trevally (Pseudocaranx georgianus).

Ectotherm species, such as marine fishes, depend on environmental temperature to regulate their vital functions. In finfish aquaculture production, being able to predict physiological responses in growth and other economic traits to temperature is crucial to address challenges inherent in the selection of grow‐out locations. This will become an even more significant issue under the various predicted future climate change scenarios. In this study, we used the marine teleost silver trevally (Pseudocaranx georgianus), a species currently being explored as a candidate for aquaculture in New Zealand, as a model to study plasticity in gene expression patterns and growth in response to different temperatures. Using a captive study population, temperature conditions were experimentally manipulated for 1 month to mimic seasonal extremes. Phenotypic differences in growth were measured in 400 individuals, and gene expression patterns of pituitary gland and liver were determined in a subset of 100 individuals. Results showed that growth increased 50% in the warmer compared with the colder condition, suggesting that temperature has a large impact on metabolic activities associated with growth. A total of 265,116,678 single‐end RNA sequence reads were aligned to the trevally genome, and 28,416 transcript models were developed (27,887 of these had GenBank accessions, and 17,980 unique gene symbols). Further filtering reduced this set to 8597 gene models. 39 and 238 differentially expressed genes (DEGs) were found in the pituitary gland and the liver, respectively (|log2FC| > 0.26, p‐value < 0.05). Of these, 6 DEGs showed a common expression pattern between both tissues, all involved in housekeeping functions. Temperature‐modulated growth responses were linked to major pathways affecting metabolism, cell regulation and signalling, previously shown to be important for temperature tolerance in other fish species. An interesting finding of this study was that genes linked to the reproductive system were up‐regulated in both tissues in the high treatment, indicating the onset of sexual maturation. Few studies have investigated the thermal plasticity of the gene expression in the main organs of the somatotropic axis simultaneously. Our findings indicate that trevally exhibit substantial growth differences and predictable plastic regulatory responses to different temperature conditions. We identified a set of genes that provide a list of candidates for further investigations for selective breeding objectives and how populations may adapt to increasing temperatures.

Biological performance of African catfish Clarias gariepinus (Burchell, 1822) fingerlings fed with raw chicken entrails

The African catfish Clarias gariepinus (Burchell, 1822) grows fast, feeds on a large variety of agriculture by-products and can be raised in high densities resulting in high net yields. It is therefore considered as a good candidate for aquaculture. Generally, the increasing aquaculture activities worldwide led to a more expensive feed costs, thus looking for alternative and cheaper feeds coupled with optimum feeding rate is a focus in aquaculture research field. This study therefore aimed to determine the most efficient feeding rate and the potential of raw chicken entrails as feeds for C. gariepinus in terms of fish weight increment (WI), specific growth rate (SGR), feed conversion ratio (FCR) and survival rate (SR). Clarias gariepinus were fed with chopped raw chicken entrails at three different feeding rates (3%, 4% and 5%) based on the average weight for 60 days. The fish weight continually increased regardless of the feeding rate, but generally, those that were fed at 4% and 5% of the body weight showed significantly higher WG (g), SGR (% day-1) and better FCR. Regardless of the feeding rate, all fish attained 100% SR. The feeding rate of 4% is recommended due to its similar WI with those fed at 5% but showed better FCR at the end of the culture.

A potential endemic cyprinid for aquaculture and food security: The embryonic development of the Bornean spotted barb Puntius sealei (Herre, 1933)

The Bornean Spotted Barb is endemic fish species and widely distributed throughout Borneo in various freshwater bodies and can be considered as a potential aquaculture candidate for food security and the ornamental trade. However there has yet to be scientific studies on the early life history and developmental stages of this species. Thus the present study reveals the embryonic development of Puntius sealei embryo, from fertilization to post-hatching using the induced breeding method. The induced spawning on P. sealei using Ovaprim hormone at a dose of 0.5 ml/kg for females and 0.25ml/kg for males respectively was successfully conducted and the embryonic development of the fertilized eggs were observed. The zygote, cleavage, blastula, gastrula, segmentation, and larval phases were the six major stages of embryogenesis that investigated in this experiment. This study contributed major knowledge to the early developmental biology of this particular species. The information will be useful for accessing the potentiality of this species for aquaculture as well as the management, and production of the species. Asian Australas. J. Food Saf. Secur. 2021, 5 (2), 55-62

Observations on feeding behaviour of fresh water prawn Macrobrachium lamarrei (Crustacea: Decapoda)

Freshwater prawn are promising candidates for aquaculture and knowledge of food and feeding habit is must for successful culture. Present study investigates the feeding mechanism and role of appendages in feeding behaviour of freshwater prawn, Macrobrachium lamarrei. Mostly preferred food was dried prawn powder and least preferred was groundnut cake. Prawns showed cannibalistic behaviour frequently in lab. Antenna and antennules were the main sensory appendages which help in locating and orientation while I & II chelate legs were used for detection, catching and transferring of food up to the mouth. Maxillipedes, maxilla and maxillula played the supportive role. Mechanism of feeding and functional role of different appendages in feeding behaviour have been discussed.

Profiles of hemolymph antioxidant system in apparently healthy marine bivalve, Perna viridis (Linnaeus, 1758) residing in a normoxic coastal ecosystem

Dynamic interactions existing between antioxidant systems (AOS) and residing environment of marine bivalves makes practical relevance in assessing AOS of these animals for ecodiagnostics of residing water and culture practices. Among marine bivalves, Perna viridis act as an ideal aquaculture candidate and plays a pivotal role in ecomonitoring studies. Therefore, the present study was targeted to understand the responses of AOS in haemolymph of P. viridis based on their residing environmental characteristics (salinity, temperature, pH and dissolved oxygen[DO]) in a normoxic coastal environment. Results showed that profiles of all studied AOS components namely, GSH (reduced glutathione) level, GPx (glutathione peroxidase) activity and SOD (superoxide dismutase) activity, were highly influenced by inhabiting conditions, and synchronised action of these AOS maintained comparatively stable levels of oxidative metabolism in haemolymph of P. viridis. However, a uniform correlation between the studied components could not be observed, suggesting variations of AOS levels in natural ecosystem could not be attributed to single environmental factor. Accordingly, linear mixed model analysis combining predicted and unknown influences was carried out and the results indicated that GSH levels have the potential to be used as an early biomarker in P. viridis for fluctuations in DO levels of residing environment, within normoxic conditions. In short, results of present research fetch its application in domestication, culture practices, climate change research and biomonitoring studies.

Kültürü yapılan Holothuria poli (Delle Chiaje, 1823) türü deniz hıyarının deri ülserlerinden Vibrio mediterranei (Pujalte ve Garay 1986) / Vibrio shiloi (Kushmaro vd. 2001) bakterisinin gözlenmesi

Skin ulcer syndrome is frequently reported as a serious disease affecting the health, growth and mortality of stocks in sea cucumber aquaculture. In this study, bacteria isolated predominantly from skin ulcers of sea cucumber Holothuria poli (Delle Chiaje, 1823), a new candidate for aquaculture in the Mediterranean, were investigated. Morphological and biochemical tests, and molecular analysis methods were used to examine the dominant bacteria in the lesions of H. poli showing skin ulceration, peristome tumour and visceral ejection symptoms in rearing tanks. Present study is the first report for isolation and identification of Vibrio mediterranei (Pujalte and Garay 1986) (called also Vibrio shiloi Kushmaro et al. 2001) as a predominant gram-negative bacterium in the skin ulcers of H. poli. Reference data provided from the present study would lead to understand possible major pathogens causing skin ulceration syndrome and is crucial for the prophylaxis and treatment of such disease in holothuriculture.

Reproductive characteristics of the giant gurami sago strain (Osphronemus goramy Lacepède, 1801): basic knowledge for a future hatchery development strategy

Background: The giant gourami sago strain ( Osphronemus goramy Lacepède) has been approved in 2018 as a candidate for freshwater aquaculture in Indonesia. However, information on the species' reproduction is minimal. This study analyzed the reproductive characteristics of the gourami sago strain broodfish to provide basic knowledge for a future hatchery development strategy. Methods: A total of 10 female and 10 male mature gourami sago strain broodfish were measured for body weight and length, and were evaluated for their reproductive characteristics. Breeding fish were spawned naturally in a 2×1×0.6 m concrete pond with a male-female sex ratio of 1:1. Egg weight and diameter were measured in 25 eggs per female using, respectively, ACIS AD- 600i scales with 0.01 g accuracy, and a microscope (Labo model L-711) using Canon Digital Camera Software 3 . Semen was collected using plastic syringes in 3 mL aliquots, then placed in an insulated ice-cooled container, and analyzed within two hours of collection. Results: Average weights of female and male broodfish before spawning were 2180±159.78 g and 3060±134.99 g, respectively. The relative fecundity and egg diameter were 1029±36 eggs kg -1 and 2.42±0.05 mm, respectively. The hatching rate and embryo survival to an eyed-egg stage were respectively 76.40±2.27% and 94.76±0.42%. Sperm characteristics showed that volume was 0.60±0.12 ml kg -1 and percentage of motile sperm was 70.04±2.27%. Female broodfish weight after spawning was strongly correlated with the weight before spawned ( r 2 = 0.999) and absolute fecundity was also strongly correlated with female broodfish weight before spawning ( r 2= 0.921). Sperm concentration was moderately correlated with sperm motility ( r 2 = 0.556) and duration of sperm motility ( r 2 = 0.502). Conclusions: The gourami sago strain broodfish has suitable reproductive characteristics for the development of hatcheries. Successful natural spawning should be followed by larval weaning and feeding technology to increase growth and survival.