Increase Fish Production Research Articles

Growth and survival assessment from African lungfish (Clarias gariepinus) and its hybrid with two species of heterobranchus

Obtaining good quality and quantity of fish seeds for increasing fish production is a major quest by fish farmers. This study examined the growth responses and survival of Clarias gariepinus and two species of heterobranchus. One thousand five hundred (1500) fry (28-day after hatched) were randomly selected from each of the three crosses of Clarias gariepinus (T1), C. gariepinus x Heterobranchus longifilis (T2) and C. gariepinus x Heterobranchus bidorsalis (T3) broodstocks. They were stocked separately in triplicate at a stocking rate of 500 fish per replicate and reared for 90 days. The data were analysed for significant differences (P<0.05) by Analysis of Variance (ANOVA). There was no significant difference in the growth parameters but fish in T3 had the highest value of mean weight gain while T1 had the least. No significant difference (p>0.05) was observed in the body weight gains from day 40 to day 90 except at day 70 where T3 had the highest weight gain (18.97 g) which was significantly different (p<0.05) to the value recorded in T1 (18.20 g) but not significantly different (p>0.05) to the value recorded in T3 (18.97 g). The results of length increment showed that the growth pattern from day 0 to day 80 were similar. A little difference was observed at day 90 with T3 >T2>T1. The fish in T1 (Clarias gariepinus) had the highest significant percentage survival (89.60%). The results of water quality parameters showed that the mean temperature was 28oC, pH 6.8, dissolved oxygen 5.6 mg/l and turbidity 5.45 NYU. The culture of C. gariepinus by farmers will improve their output and consequentially increase in profit.Keywords: aquaculture; fish breeding; hybrids; weight gain

Increasing fish production in recirculating aquaculture system by integrating a biofloc-worm reactor for protein recovery

Aquaculture, producing half of global fish production, offers a high-quality protein source for humans. Improving nitrogen use efficiency (NUE) through microbial protein recovery is crucial for increasing fish production and reducing environmental footprint. However, the poor palatability and high moisture content of microbial protein make its utilization challenging. Here, a biofloc-worm reactor was integrated into a recirculating aquaculture system (BW_RAS) for the first time to convert microbial protein into Tubificidae (Oligochaeta) biomass, which was used as direct feed for culturing fish. Batch experiments indicated that an aeration rate of 0.132 m3L−1h−1 and a worm density of 0.3 g cm−2 on the carrier were optimal for microbial biomass growth and worm predation, respectively. Compared to the biofloc reactor-based recirculating aquaculture system (B_RAS), the BW_RAS improved water quality, NUE, and fish production by 17.1 % during a 120-day aquaculture period. The abundance of heterotrophic aerobic denitrifier Deinococcus in BW_RAS was one order of magnitude higher than in B_RAS, while heterotrophic bacteria Mycobacterium was more abundant in B_RAS. Denitrifiers cooperated with organic matter degraders and nitrogen assimilation bacteria for protein recovery and gaseous nitrogen loss while competing with predatory bacteria. Function prediction and qPCR indicated greater aerobic respiration, nitrate assimilation, nitrification (AOB-amoA), and denitrification (napA, nirK, nirS, nosZI), but lower fermentation in BWR compared to BR. This study demonstrated that BW_RAS increased microbial protein production and aerobic nitrogen cycling through ongoing worm predation, further enhancing fish production to a commercially viable level.

Cost-benefit analysis of large-scale recycling of treated wastewater for indirect groundwater recharge in a semi-arid region

The large-scale recycling of treated wastewater plays a pivotal role in promoting groundwater sustainability, addressing water scarcity, and ensuring efficient resource utilization to achieve sustainable development goals. This study aimed to conduct a cost-benefit analysis of an innovative large-scale treated wastewater recycling project for indirect groundwater recharge in the Kolar district of Karnataka, India. Data regarding project and cultivation costs were obtained from multiple government organizations. Analysis was based on nine years of agricultural production data (2014–2022). A linear extrapolation was conducted on total production data, using 2018 as a reference point for a business-as-usual case, to quantify the benefits resulting from the project. The study's findings indicated a significant expansion in cultivated land and improved productivity due to the water security, leading to an increase in revenues. There was a significant 3-time increase in raw cocoon production and related revenues. Year-round filled tanks resulted in >24-times increase in fish production and revenues. The cost-benefit analysis confirmed that the project's benefits exceeded the costs, with a net present value of US$ 159.97 million at 8 % interest rates on fixed capital cost and a benefit-cost ratio (BCR) was 4.34. The BCR in the context of the cost of crop cultivation, raw cocoon, and fish production was 3.14. This indicates substantial economic benefits due to the water recycling project. Furthermore, the recycling project has potential to improve employment opportunities, boost local economy and promote sustainability. Results provide evidence for policymakers to design an integrated framework that includes treated wastewater reuse for groundwater recharge and achieve multiple Sustainable Development goal (SDG), mainly SDG - 2 (Zero hunger), 3 (Good health and well-being) and 6 (water and sanitation for all). This approach encourages circular economies, enhances agro-economic systems, and ensures a sustainable balance between development, agriculture, and resource responsibility in developing countries.

Evaluation of Knowledge Level of Farmers on Package of Practices for Composite Fish Culture in Papum Pare District of Arunachal Pradesh, India

An investigation on impact of training and demonstration programme on composite fish culture (CFC), for farmers of Papum Pare district Arunachal Pradesh, were undertaken to ascertain technical knowhow on standard package of practices for successful CFC with six parameters viz, 1. Fish species selection, 2. Fish species ratio combination, 3. Fish seed stocking stages (fry and fingerling) 4. Fry/fingerling treatment (NaCl), 5. Fish stocking density, 6. Pre and post-stocking management. Six villages were selected namely: Mani, Midpu, Chiputa, Balapu, Emchi and Upper Jumi.; 30 fish farmers from each village comprising 180 farmers were part of investigation. As per the baseline survey in the beginning on average 80% of farmers had a low level of knowledge about fish species selection followed by 12% medium and 8 % high. 82% had a low level of knowledge about, fish species ratio combination, 10% medium and only 8% had high knowledge on CFC. 81% had a low level of knowledge on fish seed stocking stages (fry and fingerling) followed by 10% and 9% respectively for medium and high. 91% had a low level of knowledge on fry/fingerling treatment (NaCl), followed by 6% medium and 3% high. 78% had low knowledge on fish stocking density followed by 13% and 9% for medium and high. 86% had low knowledge on pre- and post stocking management followed by 8% and 6% for medium and high respectively. After imparting training and Front line demonstration (FLD) programme at farmers door step on successive year, knowledge on fish species selection for low medium and high was 9%, 11% and 80 % respectively. 20%, 41% and 39% for low, medium and high on fish species ratio combination, 9%, 13% and 78% on fish seed stocking stages. 16%, 36% and 48% for low, medium and high knowledge on fry/fingerling treatment (NaCl), 11%, 19% and 70 % for low, medium and high knowledge on fish stocking density and 15%, 21% and 64% for low, medium and high knowledge on Pre and post-stocking management. Average fish production increase from 0.78 tone/ha/yr to 1.54 tone/ha/yr (97.4% increase) after imparting training and demonstration, which implies training and demonstration on CFC has significant impact on increase fish production per hectare of pond, through the power of knowledge gained by farmers on technical knowhow on CFC.

Assessing the Conservation Value of Artificial and Natural Reefs via Ichthyoplankton Spatio-Temporal Dynamics

The distribution of fish eggs and larvae (ichthyoplankton) reflects spawning and nursery areas as well as dispersal routes. This study’s goal is to demonstrate how the identification of ichthyoplankton species and stages and their spatial distribution among natural reefs (NRs) and artificial reefs (ARs) may serve as decision-making tools in conservation and fishery management. Natural reefs exhibited an eight-times higher abundance of eggs, as well as the highest abundance of larvae in the yolk-sac and preflexion phases. In contrast, ARs had the highest abundance of larvae in the flexion and postflexion phases. Natural reefs may serve as breeding grounds for Scaridae, Labridae, and Mugilidae; whereas, ARs may serve as breeding sites for Lutjanidae, Synodontidae, Carangidae, Fistularidae, and Haemulidae. Our study revealed differences between ARs and NRs, which demonstrate the potential of artificial reefs to expand the supply and settlement options of reef fishes and consequently can lead to increased fish production with potential benefits to adjacent fishing areas through connectivity. Thus, ARs as no-take sites can be effective tools for both fishery management and biodiversity conservation. The findings highlight the potential use of ichthyoplankton tools and the importance of considering both types of reefs in marine conservation and management efforts.

Improvement of Immune Defense and Survival of Grouper Fish (Ephinepelus sp.) Using the Immuno-Probiosirkulasi System (SI-PBR) Method in Semi-Intensive Ponds in Brondong, Lamongan

Grouper (Epinephelus sp.) is a marine fishery commodity that is widely cultivated in marine cages and ponds. The export market demand for grouper fish continues to increase every year by 30.75% every year, so there is a need for improvement, through various technological applications. The main obstacle in cultivating grouper fish in ponds is the decline in water quality and disease attacks, which can cause up to 100% crop failure, just 3 – 5 days after infection. One effort that can be implemented is the cultivation method with the Immuno-Probiocirculation System (SIPBR). Brondong sub-district is one of the areas in Lamongan which has large fisheries potential, especially for breakwater water pools, which are the top among other districts. There have been many cases of grouper deaths in ponds to date, which are caused by disease attacks and water quality. The aim of this community service activity is to apply the Immuno-Probioculation System fish aquaculture technology in traditional plus pattern ponds (SI-PBR), increasing grouper fish production in Lamongan Regency, East Java. Observational method which includes socialization / counseling, planning and guidance for implementing SI-PBR technology in one period (three months). These results show positive indications. There is an increase in farmer knowledge, the SI-PBR method can reduce ectoparasite infestation and increase grouper yields from 272.43 kg / ha to 87.66 kg / ha, meaning an increase of 334%. The conclusion from this activity is that the SI-PBR model can increase fish production and can be applied in wider areas in the Lamongan region.

The Replacement of Fish Meal with Poultry By-Product Meal and Insect Exuviae: Effects on Growth Performance, Gut Health and Microbiota of the European Seabass, Dicentrarchus labrax.

This study addressed the urgent need for sustainable protein sources in aquaculture due to the depletion of marine resources and rising costs. Animal protein sources, particularly poultry by-product meal (PBM) and insect exuviae meal, were investigated as viable alternatives to fishmeal (FM). The research study confirmed the successful replacement of FM with a combination of PBM and insect exuviae meal (up to 50%) in the diet of European seabass without compromising growth, feed conversion, gut health, and liver fat content. In particular, growth was robust with both PBM formulations, with the 25% PBM diet showing better results. Histological examinations showed good gut and liver health, contradicting the concerns of previous studies. This paper emphasizes the importance of holistic analyzes that go beyond growth parameters and include histomorphological investigations. The results show that PBM in combination with insect/exuviae meal is well tolerated by seabass, which is consistent with reports in the literature of it mitigating negative effects on gut health. A detailed analysis of the microbiota revealed a decrease in the Firmicutes/Proteobacteria ratio due to an increase in potentially pathogenic bacteria. However, the formulation containing insect exuviae partially counteracted this effect by preserving the beneficial Lactobacillus and promoting the synthesis of short-chain fatty acids (SCFAs), particularly butyrate. Chitin-rich components from insect exuviae were associated with improved gut health, which was supported by the increased production of SCFAs, which are known for their anti-inflammatory properties. This paper concludes that a combination of PBM and insect/exuviae meal can replace up to 50% of FM in the diet of seabass, supporting sustainable aquaculture practices. Despite some changes in the microbiota, the negative effects are mitigated by the addition of insect exuviae, highlighting their potential as a prebiotic to increase fish productivity and contribute to a circular economy in aquaculture.

Complexities and opportunities: A review of the trajectory of fish farming in Zimbabwe

AbstractZimbabwe is currently rated as one of the top 10 fish producers in Sub‐Saharan Africa. Fish farming in Zimbabwe is dominated by the culture of Nile tilapia (Oreochromis niloticus) followed by rainbow trout (Oncorhynchus mykiss). Over 90% of the cultured fish is O. niloticus, which comes from Lake Kariba. Since the first decade of the 21st century, there has been a significant increase in fish production from two tons to eight tons annually. The increase in fish production has been attributed to the government and donor‐funded fishery programs. In this review, current practices, opportunities, and challenges for aquaculture in Zimbabwe are highlighted. The current practices include intensive, semi‐intensive, and extensive aquaculture systems. Consistent high market demand for fish and numerous water bodies with potential for cage culture are some of the drivers for aquaculture. Despite the industry's significant growth, there are still a number of management and production issues that need to be resolved. Weaknesses in structural issues and operational frameworks in Non‐Governmental Organizations, lack of credit facilities, subsidies, limited technology, obfuscated governance, weak fish disease surveillance mechanisms and legal frameworks, and constrained human resources capacity are some of the challenges plaguing fish culture in Zimbabwe. Cogent aquaculture policies, sustainable subsidies, intensive training of human resources and fisheries experts, strengthened disease surveillance, cheaper alternative fish feeds, reliable viable fingerling production, concerted value chain efforts, and exploration of lucrative export markets is a panacea for the fledgling aquaculture industry in Zimbabwe.

FAKTOR-FAKTOR YANG MEMPENGARUHI PRODUKSI IKAN DI DESA NANGADHERO KECAMATAN AESESA KABUPATEN ENDE

This study aims to determine and explain the factors that influence fish production in the Nangadhero village, Aesesa District, Nagekeo Regency. The population in this study were all members of the fishing community who work as fisherman in the Nangadhero Village. Totaling 129 people. The sample in this study amounted to 98 people using simple random sampling technique in this research is by distributing questionnaires to fisherman. The data analysis technique uses Multiple Linear Regression analysis with calcutions using the SPSS 21 program. Based on the results of the analysis that has been done, this study shows that education has a negative and insignificant effect on fish production, while skillsin using fishinggear have a positive and significant effect on fish production. The results of this study can be used to formulare effective policies and strategies for activities to increase fish production and income of fishing communities in Nangadhero Village, and itis hoped that the local government can provide fishing equipment and education to improve the skills of fisherman through training programs.

Adfluvial migration and passage of Steelhead before and after dam removal at a major Great Lakes tributary

Despite the importance of Great Lakes fisheries and the increasing popularity of dam removal as a method to restore river connectivity and increase fish passage, the adfluvial migration of Steelhead (Oncorhynchus mykiss) has been drastically understudied and only relatively few published studies have examined the impacts of dam removal on fish movement and timing. To help fill these knowledge gaps, spawning migrations of Great Lakes adfluvial Steelhead tagged in spring and fall were monitored for two years before and three years after removal of a dam that partially blocked upstream movement for 100 years. Removal of the dam not only reduced downstream delay and increased passage at the site of the dam removal itself, but increased travel speeds and increased passage at remaining upstream dams for both spring and fall run fish, underscoring the cumulative impact of successive dam passage on fish migration. Fall fish were most impacted by the dam removal and were able to pass not only the dam footprint, but, for the first time, were also able to pass both remaining upstream dams, allowing them to overwinter at locations closer to known spawning areas. For these fish, delay at the footprint was reduced from the order of 100+ days to < 1 hour and the number of days passage occurred compared to the number of days fish were present and blocked increased from 2% to 82%. The benefits of dam removal should ultimately equate to increases in fish production, as more critical habitat becomes reconnected and more fish are able to pass dams and arrive at spawning beds. The observation that fish are likely able to remain in better condition and retain more energy for continued migration and reproduction warrants further study.

The Applications of Mamdani Fuzzy in Water Selection of Pangas Catfish Ponds

In the field of fisheries, the selection of ponds water for Pangas catfish is very important because it affect the production and quality of fish. The purpose of this research is to apply the Mamdani fuzzy method in selecting suitable ponds water for Pangas catfish. The method used includes collecting data on water quality and environmental conditions, constructing the Mamdani fuzzy system and evaluating the results of selecting ponds water. The results of the study show that the Mamdani fuzzy method is able to provide a good solution in selecting ponds water for Pangas catfish by combining several factors such as temperature, pH and oxygen solubility. This concept can be used as a consideration in selecting the right ponds water for Pangas catfish so as to increase fish production and quality.

The potential impact of aquaculture on the genetic diversity and conservation of wild fish in sub‐Saharan Africa

Abstract An increasing focus on aquaculture using introduced strains or species poses a serious threat to native wild species in sub‐Saharan Africa, yet almost no policies have been enacted or regulations put in place to address this environmental challenge. Aquaculture in these regions has traditionally been conducted on a relatively small scale but is currently expanding rapidly and is projected to continue increasing in the coming decades, with increasing use of genetically improved strains. This expansion is occurring in a region known for its high biodiversity, creating challenges for increasing fish production without damaging wild fish populations. However, few studies have yet assessed the impacts of changes in aquaculture practice on the genetic composition and diversity of wild populations. The use of non‐native improved strains for aquaculture could cause competition, gene introgression when there is interbreeding with native populations or species, displacement of species and possible extinction of the native wild populations. After providing historical context on African aquaculture, this review describes the current methods of fish breeding and genetic improvement programmes for the main species of cultured fishes, focusing on the potential conservation impacts of the use of introduced (and selectively bred) farmed species. Existing aquaculture policies, legislation and regulations regarding the import and farming of fish are then compared across the main fish‐producing countries. We recommend a regional policy framework considering fish introduction, risk analysis and risk management, human resources development and genetic monitoring that could be drafted into the existing policies to strengthen conservation efforts. We conclude by making recommendations for refining existing regulations and for future research aimed at minimizing the impacts of aquaculture on wild fish populations in sub‐Saharan Africa. Aquaculture in this region needs implementation of responsible guidelines to avoid genetic impacts on native populations of high conservation value.

ASSESSING THE PERFORMANCE OF A POND SLUDGE REMOVER SET AND SLUDGE COMPOSITION

Bangladesh, a leading fish-producing country, relies on fish as a primary protein source, but poor management has led to a decline in fish quality. Ammonia and low dissolved oxygen levels adversely affect fish production and taste. Leftover pellet feed accumulating at the pond bottom decomposes releasing ammonia and forming sludge, the primary source of water pollution. High fish density exacerbates sludge buildup, necessitating effective removal for pond water preservation. The study addresses the critical issue of sludge accumulation in fish ponds, contributing to elevated gas and ammonia levels. A sludge remover set was constructed in Kaharole Upazila, Dinajpur, utilizing local materials and an electric motor. Testing three sludge collectors with perforated holes of 10 mm, 15 mm, and 20 mm revealed that the 15 mm perforated pipe was the most cost-effective, with a collection rate of 1.85 kg of sludge-water mixture per 5L. The sludge composition, analyzed at the Soil Resources Development Institute (SRDI), Dinajpur, indicated valuable nutrients like nitrogen (0.179%), phosphorus (54.05 ppm), potassium (0.28 meq/100g), and micronutrients, potentially beneficial for plant growth and agricultural fertilizer. The findings emphasize the vital role of sludge remover sets in increasing fish production by effectively managing sludge accumulation.

The Potential for Increasing Corn (Zea mays) Production to Support Agricultural Self-sufficiency in the Bangkunat District of West Pesisir Regency, Lampung Province

This study aims to understand the potential of increasing fish production in Bangkunat district of the Pesisir Barat, based on internal and external factors, using qualitative research methods, purposive sampling, and SWOT analysis. The study found that the potential increase in fish production in Bangkunat district is influenced by internal factors such as human participation, government budget, fish production, subsidies, and government support, as well as external factors like technology development.

Biofloc technology: A sustainable approach towards wastewater utilization and fish production

AbstractBiofloc technology (BFT) has gained popularity recently as the aquaculture industry faces significant economic losses due to water pollution creating various pathogens. Many bacterial, viral and fungal diseases in fish cause a decrease in annual world fish production. Therefore, owing to a growing demand for healthy fish, zero‐water exchange is widely practiced in fish and shellfish production. It minimizes the release of aquaculture wastewater into the aquatic ecosystem, which contains nutrients, organic matter and pathogens. It uses a minimal amount of land, which provides an impartial cost–benefit ratio to maintain socio‐economic sustainability. Besides sustainability, fish cultured in the BFT have also expressed better health status after being challenged by different pathogens. However, this review explores the use of BFT as a sustainable approach to wastewater utilization and fish and shellfish production. Apart from this, the review highlights the potential of BFT to enhance fish production in aquaculture systems and discusses various factors that affect the performance of systems, such as carbon‐to‐nitrogen ratios, aeration and the use of probiotics. It also investigates the role of biofloc in improving water quality, fish and shellfish health prophylactic properties, and its effect on gut microflora. The review further examines the economic feasibility of BFT and discusses about the cost‐effectiveness of implementing systems and the potential for generating additional revenue through the sale of bioflocs as a value‐added product. Overall, this review highlights the potential of BFT as a sustainable solution for wastewater utilization and increasing fish production. It provides valuable insights into the factors affecting the performance of BFT systems and suggests areas for further research and development in this field.

Inventorying the Broodstocks of Belarusian Carp Breeds and Herbivorus Fish Species by the Genes of the Most Economically Valuable Traits to Maximize the Use of the Physiological Potential of a Fish Organism to Increase Fish Productivity in Ecological Conditions of Intensive Pond Fish Farming

One of the most promising marker genes for assessing and predicting animal meat productivity is the myostatin gene (MSTN). The protein encoded by this gene regulates the development of muscle tissue in various species of terrestrial and aquatic vertebrates. Mutations of the myostatin gene may lead to a twofold and in some cases even a threefold increase in muscle mass in the individuals of different species. Studies are underway to test the breeders of the Belarusian mirror carp and herbivorous fish species for the presence of mutations in the myostiatin gene (MSTN). When revising the broodstock of a new species of the Belarusian mirror carp, the effectiveness of using mutations of the MSTN gene associated with an economically valuable trait of fish productivity and mass accumulation has been established. The fish capacity of the juvenile mirror carp obtained during the reproduction of test breeders, where one parent was a GG homozygote and the other was an AG heterozygote with a mutation by the MSTN gene, was 1.3-1.7 times higher compared to the average productivity in the experimental and control groups and it showed a better productivity indicator for the control groups by 1.1-1.5 times. When testing silver carp and bighead carp selected for study (in Belarus and Uzbekistan), no mutations in the myostatin gene (MSTN) were found.

Stunting technique innovation for increasing milkfish production on traditional ponds in Usto Village, Mare District, Bone

Milkfish (Chanos chanos) is a fish of high economic value with nutritional content and good taste (savory) like milk, with an oblong flattened body shape which is ideal as a bait for skipjack, mackarel, and tuna fish. Various efforts were made to increase pond productivity, including changing the orientation of cultivation from the target of consumption milkfish production to feed milkfish production. One technique that can be done to increase pond productivity is stunting techniques for bait milkfish cultivation. The purpose of this study was to determine the effectiveness of stunting techniques for increasing production of bait milkfish on traditional ponds in Usto Village, Mare District, Bone Regency. The research method used is quantitative research with the type of experimental research, where the effectiveness of stunting techniques is measured through measuring fish growth starting from the initial cultivation phase (post-stunting) to the harvest phase (end cultivation). The study was conducted for three months, from August to October (early November). The results of the study found that stunting techniques can increase fish productivity, by triggering the growth rate of milkfish in the cultivation phase with an average growth of 0.85-1.5 cm per week or 0.12-0.20 cm per day. Stunting techniques also pose a high risk, especially in size and mortality inequality in fish and reduce survival rates, due to high density. The stunting technique with a stocking density of 100,000 seed per hectare, is able to produce bait milkfish measuring 100-200 grams per pieces, which is 6-8 tons per hectare with an Survival Rate (SR) rate of 80%. Thus, this technique is considered good enough to increase pond production, especially in cultivation of bait milkfish.

IoT-Driven Fish Monitoring System for Enhanced Aquaculture Management

Aquaculture primarily involves cultivating aquatic organisms by providing suitable environments for various purposes, including commercial, recreational, and public uses. This paper aims to enhance fish production and maintain the aquatic environment of aquaculture in Bangladesh. It presents the use of Internet of Things (IoT) based devices to monitor the essential needs of aquaculture and support fisheries. By using these devices, various water parameters will be monitored to create a better living environment for fish. The devices include sensors that detect the Potential of Hydrogen (pH) level and water temperature. Additionally, there are sections for measuring dissolved oxygen and ammonia levels using testing kits, which are crucial for proper fish farming. An Android-based mobile application has also been developed. In this system, farmers, fishermen, and individuals involved in aquaculture will use the Android application. Through this application and with the help of the device, users will be notified about the levels of dissolved oxygen, ammonia, pH, and water temperature. This monitoring system will help fish farmers take necessary steps to prevent any disturbances in the aquatic environment. Given that Bangladesh is a riverine country and fish farming significantly impacts its economy, maintaining good health to produce more fish is essential. However, the country's fisheries may lack the expertise to understand the essential elements required for fish growth and management. This system could assist them in measuring parameters and providing the necessary resources to increase fish production.

Use of GIS‐based multicriteria evaluation for improved selection of suitable sites for cage fish farming in Mwanza Gulf, Lake Victoria

AbstractStagnating capture fisheries and increasing fish protein demand necessitate aquaculture production to bridge the gap. Lake Victoria is a potential water body for increasing fish production through cage farming. The sustainability of Lake Victoria for cage farming depends on timely and holistic site selection. However, current site selection methods involve complex, resource‐intensive field surveys that lack a holistic approach to integrate multiple factors. Accordingly, information regarding suitable sites for sustainable fish cage farming in Lake Victoria remains scarce. In this study, a transparent geographic information systems (GIS) and multicriteria evaluation (MCE) here after reffered to as GIS‐MCE was used to reveal potential sites to be permitted or avoided during cage aquaculture development in the Mwanza Gulf of Lake Victoria (Tanzania). Our analysis involved weighting and integration of sub‐models representing ecologically sensitive areas, physical environment, and socio‐economic and water quality variables into a single spatial model portraying different site suitability levels in the Mwanza Gulf. The results indicated that the sub‐models identified relatively larger suitable and most suitable sites compared to the overall model. No site maintained its status across all sub‐models. The overall model designated a small area (5.10 km2 or 1.52%) as the most suitable site, with 24.20 km2 (7.44%) as suitable, 64.47 km2 (19.82%) as less suitable, and 42.63 km2 (13.12%) as unsuitable for cage fish farming. The remaining area (188.84 km2 or 58.06%) was a constrained site to be avoided during cage aquaculture development. Taken together, the individual sub‐models are ineffective in designating potential sites for fish cage culture and thus should not be used solely. The GIS‐MCE general model provides a fast and timely method for identifying potential sites for cage farming in Lake Victoria. Fish farmers and managers should use the GIS‐MCE overall model in inland waters to facilitate site selection for complying with licensing requirements and decrease field extensive surveys.

Теория мультифизического подобия гидробионтов

In the course of studying the biomechanical characteristics of hydrobionts there appears a need to apply the theory of similarity of living objects. Along with the theory of similarity, the theory of dimensions is observed. There is considered the multiphysical similarity of hydrobionts of the same species, based on the theory of physical similarity of A. A. Nedostup. One of the tasks of studying the mechanics and hydrodynamics of living systems (hydrobionts) in the aquatic environment is to automate the collection of statistics with subsequent visualization of the characteristics of hydrobionts using augmented reality technologies. Based on the similarity theory, the rules of physical similarity have been developed, similarity criteria have been obtained with respect to geometric, mechanical, hydroacoustic, hydrodynamic, thermodynamic, and optical characteristics of hydrobionts. An important component of similarity is to preserve the physical nature of the original phenomena in the model. Based on the scale of the multiphysical similarity of hydrobionts, the criteria for the similarity of hydrobionts are determined. There is considered the solution of the problems of describing the biomechanics of hydrobionts in recirculation aquaculture systems, where only one species of hydrobionts is grown at the same time. The importance of studies of biomechanics of aquatic organisms in certain habitat conditions, in our case in an artificial enclosed space, with artificial lighting, feeding, cleaning system, etc., is explained by the need to increase fish productivity and environmental friendliness of fish farming, which requires automation of the growing process. Automation tasks require a preliminary mathematical description of processes in order to build simulation models. In turn, for a mathematical description of the growth process of a growing object, it is necessary to derive mathematical dependencies linking the target characteristics of the hydrobionts with the initial data of breeding conditions and a set of characterizing parameters of the object itself, including behavioral ones.