Aquaculture Production Research Articles

Influence of Water Temperature on Fish Reproduction in Bangladesh

Purpose: The aim of the study was to analyze the influence of water temperature on fish reproduction in Bangladesh. Methodology: This study adopted a desk methodology. A desk study research design is commonly known as secondary data collection. This is basically collecting data from existing resources preferably because of its low cost advantage as compared to a field research. Our current study looked into already published studies and reports as the data was easily accessed through online journals and libraries. Findings: The study found that water temperature significantly impacts fish reproduction in Bangladesh, with optimal breeding occurring at 25–30°C. Higher temperatures (>32°C) reduced sperm motility and hatch rates, while lower temperatures (<20°C) delayed spawning. Climate change-induced temperature shifts may disrupt fish breeding patterns, affecting aquaculture productivity. Temperature regulation and seasonal monitoring are recommended for sustainable fisheries. Unique Contribution to Theory, Practice and Policy: Metabolic theory of ecology (MTE), thermal bottleneck hypothesis & brain-pituitary-gonad (BPG) axis theory may be used to anchor future studies on the influence of water temperature on fish reproduction in Bangladesh. Fisheries and aquaculture should select and breed fish species with higher thermal tolerance, ensuring stable reproductive success despite temperature changes. Governments must revise fisheries policies to integrate climate adaptation strategies, ensuring that breeding habitats and spawning seasons are protected from rising temperatures and extreme weather events.

Farmers’ knowledge of using flood forecast information in fish farming: A case of rural Bangladesh

The effects of global climate change and extreme weather events are threatening Bangladesh's fish and aquaculture productivity. Given the negative consequences of climate change, both the national and international societies concur that mitigating the effects of climatic unpredictability and change requires the development of weather and climate services. Additionally, if forecasting data is expertly adapted to fish farmers' requirements, they may be better able to handle and adjust to climatic and climatic-induced stressors. The primary goal of the study was to determine how much fish farmers knew about using flood forecast information regarding fish farming. Three villages in the Union Islampur upazila, which is part of the Jamalpur district, were the sites of the study: Kulkandi, Chinaduli, and North-Bamna. A sample of 95 randomly chosen fish farmers (about 25% of the total population) out of 380 fish farmers provided the data. Focus groups, matrix ranking, and key informant interviews were among the qualitative and quantitative techniques used in the study's research methodology. In order to collect both quantitative and qualitative data, formal and semi-structured questionnaires were created. The majority of farmers (53.90%) had a medium level of knowledge, followed by high knowledge (31.57%), and poor knowledge (14.74%) about the use of forecast information in fish farming. Therefore, through a variety of interventions, including training, group discussions, demonstrations, and the distribution of printed materials, concerned authorities like the Department of Fisheries (DOF) should provide chances to increase the knowledge of fish farmers. Regression study revealed that farmers' knowledge regarding using forecast information in fish farming is positively impacted by their level of education, annual earnings from fish farming, organizational participation, and sources of flood forecast information. Therefore, while creating programs and making decisions, legislators, development practitioners, extension specialists, and others should consider these aspects. Int. J. Agril. Res. Innov. Tech. 14(2): 9-19, December 2024

Recent Developments and Applications of Vegetable Oil in Fish Feed

ABSTRACTDietary lipids play a vital role in providing essential fatty acids that are crucial for the regulation of growth, health, reproduction, and overall physiological functions of fish. Traditionally, fish oil (FO) has served as the primary lipid source in commercial fish feed. However, due to the dwindling availability and escalating costs of FO, the sustainable growth of aquaculture has been hindered. On the other hand, vegetable oil (VO) has emerged as a promising alternative lipid source for fish diets, owing to its abundance, cost‐effectiveness, and rich content of essential C18 fatty acids. While numerous studies have explored the impact of VO on fish growth and health, it has been noted that most VO cannot entirely replace FO in the diet due to its adverse effects. Hence, current research suggests that innovative strategies such as genetic modification, nutritional programming, and supplementation with functional compounds may help alleviate the negative effects associated with dietary VO. Given the critical need to seek alternative lipid sources in fish feed to address the limited global supply of FO, coupled with the cost‐effectiveness and nutrient content of VO, it is imperative to further investigate their application in fish feed formulations to support sustainable fish production.Practical Applications: This review highlights the importance of finding alternative lipid sources for fish feed in order to support sustainable aquaculture growth. Incorporating vegetable oil (VO) into fish diets can help alleviate the reliance on fish oil, which is becoming increasingly scarce and expensive. However, it is essential to consider the potential negative effects of VO and explore innovative strategies to mitigate these effects. By continuing to research and develop new techniques, such as genetic modification and nutritional programming, we can optimize the use of VO in fish feed formulations to promote healthy growth and reproduction in fish. Overall, this review emphasizes the significance of exploring alternative lipid sources in fish feed to ensure the long‐term viability of aquaculture production.

Temporal and small‐scale spatial variation in standing stock phenology and reproduction of Australian hijiki analogues informs aquaculture potential

SUMMARYExploration of Australian fucoids for aquaculture has been limited, despite their high diversity and endemism. Sargassum fusiforme (hijiki in Japanese) is a highly‐valued seaweed worldwide for human consumption, but concerns about high arsenic concentrations limit importation into countries with strict safe‐food regulations. We investigated the temporal and small‐scale spatial variation in distribution, abundance, thallus length, reproduction and biofouling of two Australian fucoids, Cystophora torulosa and Caulocystis uvifera, as candidates for aquaculture production and alternatives to hijiki. Temporal variation was assessed quarterly over a 12‐month period at a single site for each species, while small‐scale spatial variation was assessed at a single site for each species, comparing high‐shore and low‐shore for intertidal C. torulosa, and distance from the shore for subtidal C. uvifera. For C. torulosa, no significant variation in distribution, abundance or reproduction was observed; however, thallus lengths peaked in June (winter). Moreover, biofouling was minimal overall. Significant temporal variation was observed for C. uvifera with peaks in thallus lengths and reproduction in November (spring), and biofouling in February (summer). The temporal and spatial consistency in reproduction and minimal biofouling may render cultivation of C. torulosa more practical for successful commercialization than C. uvifera. Further investigation of these two Australian hijiki analogues is warranted to inform aquaculture investment.

Mitigating oxidative stress in oyster larvae: Curcumin promotes enhanced redox balance, antioxidant capacity, development, and resistance to antifouling compounds.

Curcumin (CUR) is a natural compound recognized for stimulating the expression of antioxidant genes. This characteristic has been used to promote animal health and production in aquaculture settings. We hypothesized that supplementing embryos of Crassostrea gigas oysters with CUR would improve their antioxidant capacity, development, and resilience to stress. Embryos were exposed to CUR ranging from 0.03 to 30 µM for 24 h. Their development was assessed, along with measurements of glutathione levels, glutathione S-transferase activity, antioxidant capacity, production of reactive oxygen species (ROS), metabolic activity, and resistance to organic hydroperoxide and the antifouling compound dichlorooctylisothiazolinone (DCOIT). Low curcumin concentrations (up to 1 μM) activated the d-larvae antioxidant system, with a significant threefold increase in glutathione levels and a 50 % decrease in ROS production. This enhancement in antioxidant defense improved the ability of larvae to detoxify organic hydroperoxide. It also resulted in larger larval size and increased survival rates, whether under normal conditions or exposure to peroxide or DCOIT. CUR shows great promise in supporting larval development, but high concentrations were toxic (EC50 = 2.90 μM), probably due to excessive antioxidant activation. Our results indicate that the antioxidant system may play a role in controlling bivalve early development. Understanding how antioxidants influence redox balance and gene expression during early life can enhance our knowledge of stress response mechanisms in marine organisms, offering insights into how they cope with pollutants and environmental challenges. Integrating CUR and antioxidant defense pathway approaches into aquaculture practices could boost productivity and sustainability in oyster aquaculture.

First evidence of WW superfemale for hybrid sturgeon, the bester (Huso huso × Acipenser ruthenus)

Sex control offers a promising strategy for cost-effective aquaculture in certain fish species. Sturgeons, which utilize the ZZ/ZW sex determination system, are particularly valuable for producing high-priced black caviar derived from female roes, making all-female production highly desirable. However, this goal has yet to be fully realized. In this study, we identified a short genomic region specific to the Z and W genomic scaffolds of Acipenser ruthenus and developed a polymerase chain reaction (PCR) method to distinguish between the Z and W alleles. Using PCR, 1280 A. ruthenus, 66 A. baerii baerii, and 31 F2 hybrids of besters (Huso huso × A. ruthenus) were genotyped, revealing either a single Z amplicon or dual Z plus W amplicons in an approximately 1:1 ratio. This indicates successful discrimination of the ZZ/ZW genotypes. Additionally, gonadal sex was identified in 145 of the genotyped individuals, all of which corresponded to their genetic sex. Gynogenetic individuals of the F3 bester hybrid were also genotyped, with 25 of 112 (22.3 %) exhibiting only W amplicons, identifying them as WW superfemales. These findings contribute to the advancement of all-female sturgeon production for aquaculture, facilitating the efficient farming of these highly prized species.

Genome-Assisted Gene-Flow Rescued Genetic Diversity Without Hindering Growth Performance in an Inbred Coho Salmon (Oncorhynchus kisutch) Population Selected for High Growth Phenotype

Selective breeding is a powerful tool for improving aquaculture production. A well-managed breeding program is essential, as populations can otherwise lose genetic diversity, leading to reduced selection response and inbreeding excesses. In such cases, genetic diversity in broodstock must be restored by introducing individuals from external populations. However, this can reduce the accumulated genetic gains from selective breeding. However, the selective introduction of individuals with superior phenotypes will allow the restoration of genetic diversity without sacrificing these gains. In this study, we demonstrated this possibility using a selectively bred (SB) and a randomly bred (RB) population of coho salmon (Oncorhynchus kisutch). Forty males with superior growth were selected from the RB population using genomic selection and crossed with 127 randomly collected females from the SB population, producing a newly bred (NB) population. Genetic diversity, assessed from population statistics such as effective number of alleles, allele richness, and observed heterozygosity of 11 microsatellite markers, was higher in NB than in SB and RB. Additionally, fork length and body weight were compared among the three populations after 12 months of growth post-fertilization in common tanks. The least-squares means of fork length and body weight were similar between NB (164.9 mm and 57.9 g) and SB (161.1 mm and 53.7 g), while both were significantly greater than RB (150.4 mm and 43.0 g). Our results highlight the effectiveness of genome-assisted gene flow in restoring the genetic diversity of a population without compromising accumulated genetic gain in growth.

Truncation-Enhanced Aptamer Binding Affinity and Its Potential as a Sensor for Macrobrachium rosenbergii Nodavirus Detection.

White tail disease in Macrobrachium rosenbergii is caused by M. rosenbergii nodavirus (MrNV) infection, resulting in up to 100% mortality in larvae and post-larvae stages, severely impacting aquaculture production. Existing genome-based detection methods for MrNV are costly and time-consuming, highlighting the need for rapid and cost-effective diagnostic tests. This study evaluated the effects of truncating selected aptamer on its binding affinity to the MrNV capsid protein. The previously isolated and identified aptamer through magnetic-capture SELEX and Next Generation Sequencing demonstrated high binding affinity to the MrNV capsid protein. Truncation at the primer overhang was found to improve binding affinity, reducing the dissociation constant from 347 nM to 30.1 nM. The calculated limit of detection for the truncated aptamer decreased from 5.64 nM to 1.7 nM, while the limit of quantification decreased from 17.1 nM to 5.16 nM. These reductions indicate that the truncated aptamer has higher sensitivity compared to the full-length aptamer. In tests with MrNV-infected M. rosenbergii samples, both the enzyme-linked aptamer assay and the gold nanoparticle aptasensor assay showed consistent results when 0.5 μg of total protein lysate was used. This indicates that the prawn protein concentration interferes with the detection of the viral protein. These findings suggest the potential application of the truncated aptamer as a sensor in the development of a practical aptamer-based diagnostic kit. For instance, an aptamer-based lateral flow assay test kit could provide a user-friendly, cost-effective solution that eliminates the need for sophisticated instrumentation for diagnosis or data interpretation, making it ideal for detecting MrNV infection in M. rosenbergii aquaculture.

Gonadal miRNomes and transcriptomes in infected fish reveal sexually dimorphic patterns of the immune response.

Fish disease outbreaks caused by bacterial burdens are responsible for decreasing productivity in aquaculture. Unraveling the molecular mechanisms activated in the gonads after infections is pivotal for enhancing husbandry techniques in fish farms, ensuring disease management, and selecting the most resilience phenotype. The present study, with an important commercial species the European sea bass (Dicentrarchus labrax), an important commercial species in Europe, examined changes in the miRNome and transcriptome 48h after an intraperitoneal infection with Vibrio anguillarum. The findings indicate that following infection, testes exhibited more pronounced alterations in both the miRNome and transcriptome. Specifically, males showed approximately 26% more differentially expressed genes in testicular genes compared to females (2,624 vs. 101 DEGs). Additionally, four miRNAs (miR-183-5p, miR-191-3p, miR-451-5p, and miR-724-5p) were significantly expressed post-infection in males, while none were identified in females. Interestingly, upon deep analysis of sexual dimorphic gene modules, a larger number of miRNAs were identified in infected females targeting genes related to the immune system compared to infected males. These results suggest that fish ovaries demonstrate greater resilience in response to infections by suppressing genes related to the immune system through a post-transcriptional mechanism performed by miRNAs. In contrast, testes activate genes related to the immune system and repress genes related to cellular processes to cope with the infection. In particular, the crosstalk between the miRNome and transcriptome in infected males revealed a pivotal gene, namely, insulin-like growth factor binding protein (igfbp), acting as a gene network hub in which miR-192-3p was connected. The current study elucidated the need to comprehend the basic immune regulatory responses associated with miRNAs and gene regulation networks that depend on fish sex. The data reveal the importance of considering sex as a factor in interpreting the immune system in fish to generate efficient protocols to prevent outbreaks in fish farms.

Probiotic-based adsorbent mitigates aflatoxin B1 toxicity in Piaractus mesopotamicus: assessing well-being via changes in tissue architecture and digestive enzyme activity.

Aflatoxin is a mycotoxin produced by fungi of the genus Aspergillus that is present in various foods. Probiotics are well-established products in aquaculture, and due to their effective contribution to the intestine, they can be used as an aflatoxin adsorbent. This study evaluated the effects of aflatoxin B1 (AFB1) on enzymatic activity and intestinal function in Piaractus mesopotamicus (pacu) fingerlings fed diets containing a probiotic-based adsorbent (PBA). Seventy-two fish with an average weight of 12 ± 1.30g were used in the study. The experiment was conducted over 15 days using a completely randomized design with six diet treatments (AFB1 per kg of formulated diet) and two replicates. These treatments were: control without AFB1; 25.0µg of AFB1; 400.0µg of AFB1; control diet without AFB1 + PBA; 25.0µg of AFB1 + PBA; and 400.0µg of AFB1 + PBA. After the experimental period, the digestive enzymes protease, amylase, and lipase from the stomach, pyloric caeca, and intestine were quantified. The height and width of the intestinal villi, pyloric caeca, and stomach wall were measured. Fish fed the 400.0µg of AFB1 diet showed reduced feed consumption, even though they ingested higher amounts of AFB1 compared to those fed the other experimental diets. The best zootechnical performance parameters were observed in fish fed the control diet without AFB1 + PBA. Changes (p < 0.05) were observed in the amount of protease in the stomach, pyloric caeca, and intestine; in the amount of amylase in the intestine; and the amount of lipase in the pyloric caeca and intestine. Changes were observed (p < 0.05) in the length of the stomach wall and the anterior and posterior intestines. Changes in the width of the stomach and anterior intestine walls were observed as a result of diet. Our results suggest that the use of probiotics as an aflatoxin adsorbent in pacu diets is beneficial from a physiological perspective and may also enhance growth.

Spatial density, externalities, and productivity of salmon aquaculture farms

This paper estimates the effect of spatial proximity to other salmon farms on aquaculture firms’ costs. Open cage salmon aquaculture farms cause and face externalities, such as various diseases and salmon lice. Hydrodynamic forces and the spatial density of farms influence the transmission of these externalities. We analyze the effects of salmon farm proximity on production cost using a translog cost function estimated from a panel data set of Norwegian aquaculture farms. We employ two indicators of the spatial density of aquaculture production. The first indicator is the mean distance to the nearest farm, and the second indicator is the number of farms within 20 km distance for all the farms. We find that increased proximity to other farms is associated with significant cost increase. The results imply that there are economic welfare effects due to the farm location structure and the spatial biological externalities between farms.

A comparative assessment of economic, social, and environmental performance of tilapia aquaculture in Nigeria and Ghana

Capture fisheries in many developing countries are overcapitalized and biologically overexploited, necessitating the promotion of aquaculture to mitigate the deficit in animal protein requirements, create jobs, reduce poverty, and improve the livelihoods of individuals and communities. Over the last two decades, total aquaculture output and its contribution to domestic fish production have surged, reaching 19% and 26% by 2021 (from 1% and 6% in 2000) in Ghana and Nigeria, respectively. The two main species cultivated are tilapia and catfish. While Nigeria is Africa’s second-largest aquaculture producer, Ghana experienced the fastest growth in aquaculture production between 2006 and 2019. Despite the potential benefits, the sectors in both countries face critical challenges, including high feed costs and a lack of technical expertise. In addition, aquaculture can impose a negative externality on aquatic and terrestrial ecosystems. As a result, aquaculture’s social, economic, and environmental sustainability benefits are context and species-specific, hence an empirical conundrum. This study employs the Aquaculture Performance Indicators (APIs) for a comparative assessment of tilapia farms in Nigeria and Ghana. We found that the overall economic sustainability score is similar for both countries, but Ghana outperforms Nigeria marginally in social and environmental performance.

Prevailing Knowledge on Aquaculture of Abalone in Southeast Asia: A Review

Abalone is a marine gastropod mollusc with significant economic importance in global fisheries and aquaculture. Currently, the abalone culture is actively engaged in Southeast Asia and has gained significant popularity among aquaculturists and aquafarmers in Indonesia, the Philippines, Thailand, Vietnam, and Malaysia. Abalone also has emerged as a highly profitable source of income for fish farmers in Asian countries. The exquisite taste of abalone has made it a sought-after delicacy, particularly in Chinese cuisine. However, scanty documentation of this marine gastropod has been reported on the development of aquaculture production in Southeast Asia. Therefore, to help bridge the gap, this review emphasised the information and collated ideas on the industrial culture of abalone in Southeast Asia. In this review paper, all issues on abalone culture will be summarised and highlighted, especially on the aquaculture industries of abalone, challenges and constraints in developing the aquaculture of Haliotis spp., and biological features of the abalone. This review paper could be a valuable reference for abalone aquaculture practices in Southeast Asia, with the aim of boosting production and conservation efforts of these marine gastropod molluscs, thereby benefiting abalone aqua farmers in Southeast Asian countries.

Replacement of fishmeal with Quinoa Husk (Chenopodium quinoa) for mitigating multiple stresses in Pangasianodon Hypophthalmus

The fishmeal is boon for aquaculture production in this recent pollution and climate change era. However, the demand of fishmeal is enhancing in many folds which needs to find alternative to fishmeal in cheap price. The present investigation addresses these issues with quinoa husk (QH). An experiment was performed to evaluate replacement of fishmeal by QH in different proportionate at 0, 15, 20, 25, 30 and 35%. The study was designed with 12 treatments as control, stressors group (concurrent exposed to ammonia, arsenic and high temperature stress, NH3+As+T), group fed with QH at 15, 20, 25, 30 and 35% without and with stressors (NH3+As+T) in Pangasianodon hypophthalmus for 105 days. The optimization of QH dose for growth performance such as food conversion ratio, growth rate, protein efficiency ratio and specific growth rate with respect to protein percentage and obtained 26%. The oxidative enzymes such as superoxide dismutase (SOD), catalase (CAT), glutathione-s-transferase (GST) and glutathione peroxidase (GPx) in gill, kidney and liver tissues were significantly lowered by replacement of fishmeal by QH at 25% in fish reared under arsenic and ammonia toxicity and high temperature stress (NH3+As+T). The neurotransmitter enzyme (AChE) in brain tissue was noticeably enhanced by QH at 25%. The aspartate amino transferase (AST) and alanine amino transferase (ALT) as well as malate dehydrogenase (MDH) and lactate dehydrogenase (LDH) in gill and liver were significantly reduced by QH at 25% in fish reread under multiple stresses (NH3+As+T). The nitro blue tetrazolium (NBT), blood glucose, albumin, globulin, total protein, A:G ratio, myeloperoxidase (MPO) and total immunoglobulin (Ig) were noticeably improved by supplementation of QH at 25–30% in fish reared under NH3+As+T. The amylase, protease and lipase were significant improved with replacement of fishmeal by QH at 25%. The histo-pathological alterations were marked in liver and gill tissues, whereas these tissues were protected by QH at 25% in fish reared under control and stress condition (NH3+As+T). The present study revealed that replacement of fishmeal at 25% by QH could be a better replacement for improvement in anti-oxidative status, acetylcholine esterase and growth performance in fish reread under NH3+As+T stress.

Bile Imprint on Parietal Peritoneum of Gilthead Seabream and Red Seabream: Effects of Fasting Duration, Stress, and Ice Storage

The Mediterranean aquaculture industry has recently been confronted with the appearance of a bile imprint on fish filets, which to-date remains of unknown etiology. This study investigates the involvement of common procedures applied before (fasting), during (confinement), and after (ice storage) fish harvesting. Two experiments were designed, one for gilthead seabream (Sparus aurata) and one for red seabream (Pagrus major). The fish were grouped according to fasting duration (1, 2, 3 days), harvesting method (stressed, unstressed), and ice storage (0 h, 48 h). In both species, the imprint appeared in all ice-stored fish for 48 h but not in fresh fish (0 h), the color of the imprint became darker as Days of Fasting increased, stressed fish had darker imprints than unstressed fish, and plasma and bile osmolality and cholesterol were significantly affected by treatments. The histological examination of the gallbladder in red seabream showed great variability in the muscularis thickness and appearance, regardless of treatment. These results are not conclusive as to the cause of the bile imprint appearance. However, they offer a first insight into an issue that bears significant impact in the marketing of aquaculture products and may foster further investigation in the search of the underlying causes of this reoccurring issue.

Price interactions between capture fisheries and aquaculture: Evidence from India

Fish is probably the only major food product in the modern human food system for which wild harvests are still important in the market supply despite the rapid growth in production of farmed fish/aquaculture. The issue of substitution, or competitive interaction, between capture fisheries and aquaculture is of immense interest due to its role in determining market prices, livelihoods, and welfare in the two sectors. This is particularly true for a developing country like India where fisheries and aquaculture play an important role in livelihood creation, export revenues, and food security. India has also witnessed a remarkable increase in inland aquaculture production which is now the largest contributor to the country’s total fish production. In this article, we employ recursive cointegration analysis and time-varying copula estimations to analyze a novel dataset to describe the evolution in the relationship between the prices of inland capture fisheries and aquaculture products in India over time. Our results suggest an increased degree of market integration for inland fish products in India over time, though the degree of integration is lower for the capture fisheries products compared to the aquaculture products.

Identifying Bacteria Responsible for Non-Sulphate-Based Hydrogen Sulphide Production in Aquaculture.

The unintended microbiological production of hydrogen sulphide (H2S) poses a significant challenge in engineered systems, including sewage treatment plants, landfills and aquaculture systems. Although sulphur-rich amino acids and other substrates conducive to non-sulphate-based H2S production are frequently present, the capacity and potential of various microorganisms to perform sulphate-free H2S production remain unclear. In this study, we identify the identity, activity and genomic characteristics of bacteria that degrade cysteine to produce H2S in anaerobic enrichment bioreactors seeded with material from aquaculture systems. Our comparison with canonical sulphate-reducing bacteria reveals that both sulphur sources contribute to microbial H2S production, with cysteine facilitating a more rapid process compared to sulphate. 16S rRNA amplicon sequencing and metagenomic analysis identified four bacterial families-Dethiosulfatibacteraceae, Fusobacteriaceae, Vibrionaceae and Desulfovibrionaceae-as central to non-sulphate H2S production. Metagenome- and metatranscriptome-assembled genomes elucidated the primary cysteine degradation pathway mediated by cysteine desulphidase cyuA and indicated that some bacteria may also utilise cysteine as a carbon source in sulphate-based H2S production.

Enhancing the efficiency of the cultivation of cladocerans (Moina sp. and Diaphanosoma sp.) through dietary diversification strategies.

The establishment of a feeding regimen for cladocerans is crucial in contemporary aquaculture due to their significance as nutrient-rich live feeds for various aquatic species. Three experiments were conducted to optimize the growth and reproduction rates of cladocerans (Moina sp. and Diaphanosoma sp.) using various stocking densities, types of food, and feeding regimens, emphasizing the importance of Haematococcus sp. in enhancing aquaculture productivity. In the first experiment, five different initial stocking densities: 1×103 indv. L-1 (T1), 3×103 indv. L-1 (T2), 6×103 indv. L-1 (T3), 9×103 indv. L-1 (T4), and 12×103 indv. L-1 (T5) of cladocerans were tested over a 10-day culture period, where T3 demonstrated the best growth. Using the best initial stocking density from experiment 1, the second experiment assessed varying concentrations of Haematococcus sp.: 1×105, 5×105, 10×105, 15×105, and 20×105cells mL-1 in T1, T2, T3, T4 and T5, respectively as feed of cladocerans; among them, T3 exhibited the highest population density. Experiment 3 evaluated the effects of three different diets including live Haematococcus sp. (T1), baker's yeast (Saccharomyces cerevisiae) (T2), and Haematococcus sp.+baker's yeast (Saccharomyces cerevisiae) (T3) on the growth of cladocerans over 10 days. The study employed the optimal initial stocking density of cladocerans and the feeding concentration of Haematococcus sp. as determined from the prior two experiments. Notably, T3 yielded the highest zooplankton density in this investigation. These findings indicate that elevating the initial stocking density of cladocerans and increasing the concentrations of Haematococcus sp. as feed up to an optimal level can effectively enhance the population growth of cladocerans. Both very low and excessively high initial stocking density, as well as suboptimal and excessively high concentrations of Haematococcus sp., negatively impact the growth of cladocerans. Moreover, using Haematococcus sp. alone or in combination with baker's yeast (Saccharomyces cerevisiae) enhances the growth and reproduction rates of cladocerans, indicating potential benefits for aquaculture systems.

Impact of COVID-19 on Aquaculture Sector in Sabah

Abstract The COVID-19 pandemic had a direct and indirect impact on the aquaculture sector in Sabah. Therefore, a comprehensive understanding of how this epidemic affects is very important to be used as a reference. The questionnaire involved four sections which are demographics, background, issues and challenges during COVID-19 as well as the impact and knowledge related to COVID-19 on aquaculture activities. A total of 74% of respondents strongly agreed that this COVID-19 had a big impact on aquaculture-related activities in Sabah while 26% of respondents expressed a neutral stance on this issue. Therefore, survey results revealed that pandemic COVID-19 has been affected in different areas of aquaculture sector including the supply of aquaculture stocks, bureaucratic problems and the demand for aquaculture products.

Life cycle assessment of aquaculture production in Greece

Life cycle assessment of aquaculture production in Greece