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Low-fishmeal and protein-saving diets are two prominent nutritional strategies utilized to address challenges related to the scarcity and sustainability of protein sources in aquaculture. However, these diets have been associated with adverse effects on the growth performance, feed utilization, and disease resistance of aquatic animals. To mitigate these challenges, exogenous protease has been applied to enhance the quality of diets with lower protein contents or fishmeal alternatives, thereby improving the bioavailability of nutritional ingredients. Additionally, protease preparations were also used to enzymatically hydrolyze fishmeal alternatives, thus enhancing their nutritional utilization. The present review aims to consolidate recent research progress on the use of protease in aquaculture and conclude the benefits and limitations of its application, thereby providing a comprehensive understanding of the subject and identifying opportunities for future research.

The term ‘tea polyphenols’ (TPs) comprises a broad range of polyphenol compounds present in tea, demonstrating positive health effects such as antioxidant activity, etc. in animals. This study investigated the effects of TPs supplementation in juvenile genetically improved farmed tilapia (GIFT); Oreochromis niloticus). Fifteen fish (weight: 13.46 ± 1.25 g) were distributed in six tanks and randomly assigned with diets containing graded levels of TPs (mg/kg): 0.00 (control), 100, 200, 300, 400 and 500 in quadruplicate for 8 weeks. After the trial, the fish fed 500 mg/kg TPs exhibited a significant reduction (p

AbstractDermestes maculatus accounts for about 71.5% of dried fish infestation in most of the producing areas with a substantial loss in both dry weight and nutritional value. The study aimed to evaluate the repellent effect of oils extracted from Garlic (Allium sativum), Coconut (Cocos nucifera), Ginger (Zingiber officinale), Jatropha (Jatropha curcas), and Neema (Azadirachta indica) on Dermestes maculatus larvae in smoke-dried Protopterus annectens. The extracted oils from each plant were applied to the fish at varying concentrations of 0.001, 0.004, 0.016, 0.064, and 0.256 ml/g fish in triplicates. Late instar larvae of D. maculatus were introduced into Kilner jars containing fish treated with these oils and repellency was monitored for 24 hrs. Repellency was highest (87%) in A. sativum oil and lowest (59%) in A. indica oil at the highest concentration (0.256 ml/g of fish) within 24 hrs. of exposure. Furthermore, an increasing trend in repellency was observed with increasing concentrations of oils from all the plants used. The order of repellency performance was A. sativum > C. nucifera > Z. officinale > J. curcas > A. indica, starting with the highest to the lowest. Therefore, this study demonstrates the repellent properties of the oils in offering effective protection against infestation and damage by D. maculatus, suggesting that the oils can be utilized in post-harvest preservation of smoke-dried fish.

AbstractAquaculture is crucial for global food and nutrition security due to the inability of wild harvests to meet increasing demand. Africa’s contribution to aquaculture is generally low, despite its potential for economic development, food security, and reduced unemployment. The study focuses on the African catfish (Clarias gariepinus) a freshwater fish species that is widely farmed for food in Africa and other parts of the world. Proper nutrition is essential for the growth and development of the fish, and understanding their nutritional requirements is critical for producing healthy and high-quality fish. This review article provides an overview of the knowledge on the nutritional requirement of the African catfish, including protein, lipids, carbohydrates, vitamins, minerals, and amino acids. The recommended protein content for juvenile fish is between 40 and 50% and for adult fish is between 30 and 40%. Based on the reviewed studies, the recommended amount of methionine in C. gariepinus diets ranges from 18.7 to 29.7 g/kg of protein while the lysine requirement ranges from 44.9 to 62.2 g/kg protein). The recommended lipid content in the diet is between 5–15% for juvenile fish and 5–10% for adult fish. The African catfish requires a low-carbohydrate diet, with recommended carbohydrate content between 26 and 32%. They require a variety of vitamins, including vitamin A, vitamin D, vitamin E, and vitamin C, as well as minerals, such as calcium, phosphorus, and potassium. Clarias gariepinus also require a variety of essential and non-essential amino acids. Besides the nutritional requirements, culture conditions also have a significant effect on the feed performance. The recommended conditions include temperature ranging from 28 to 32 °C, Light intensity of 150 Lx, 12D:12L photoperiod, and stocking density in earthen of 7 fish m−3. Overall, understanding the nutritional requirements of C. gariepinus is crucial for the successful fish farming and sustainable aquaculture. Information in this review will be built to further guide the development of feeds for C. gariepinus.

Aquaculture plays a critical role in Zambia's food and nutrition security. However, aquaculture is highly vulnerable to the effects of a changing climate which can lead to economic losses, and food and nutrition insecurity. In this study, we investigated the perceived effects of climate change on aquaculture production in Zambia, vulnerability factors, and adaptation strategies. We used semi-structured and structured questionnaires to collect data from aquaculture producers in all provinces across the country. Results revealed high (over 80%) awareness of climate change, primarily attributed to literacy levels and access to media. Producers perceived occurrence of climate-related changes such as rising temperature, altered rainfall patterns, cyclones frequency, and disease outbreaks, impacting production costs. Generally, the results indicate a high to medium perception of rising temperature and increased frequency of flooding and droughts across the country. Although rising temperature did not appear to affect aquaculture production cost, the frequency of droughts, floods, cyclones, and disease outbreaks showed a significant association with production costs. Identified vulnerability factors include reliance on a limited range of fish species, absence of insurance coverage, and low adoption of adaptation practices. Vulnerability levels vary across regions, with provinces in agroecological zone I (Eastern, Lusaka, Southern, and Western) showing higher vulnerability. Despite this, many producers aren't implementing adaptation measures due to financial limitations, species diversity constraints, and insufficient knowledge of alternative economic pursuits. Main adaptation strategies involve livelihood diversification and adjustments in fish cultivation periods and infrastructure. To foster aquaculture sustainability amid climate change, critical interventions such as farm insurance, research diversification in aquaculture species, and enhancing producer resilience are necessary.

AbstractIn the fourth industrial revolution, achieving sustainable agricultural development while feeding a growing world population and maintaining a balanced interrelationship between the economy, society, and the environment has been a significant challenge. However, COVID-19 disrupted agricultural extension and advisory systems, affecting all market participants. The complexity of the pandemic has impacted the private sector, public sector, extension staff, donor funding, education, and research systems, subsequently affecting human nutrition. This paper aims to expertly review COVID-19’s effects on the sustainability of gender-specific agricultural extension service systems. Demand and supply market stakeholders in the extension system are thematically discussed. The findings reveal various consequences of COVID-19 for market actors on both the demand and supply sides of the extension system. Private-sector players often support expansion directly or indirectly, with multi-sectorial support and funding strategies existing for sustainability. In many developing nations, the comprehensive extension system was disrupted by COVID-19, impacting household incomes and nutrition. The pandemic accelerated the adoption of digital technologies in many developing nations, transitioning from a centralized to a decentralized and pluralistic extension model. Multi-sector coordination and execution, especially from health and other sectors, are crucial in managing complex crises that disrupt the market system.

AbstractThis study investigated the application of anaesthetics in 23 private and government-owned hatcheries in 10 provinces of Zambia. The study employed both qualitative and quantitative research designs and used a structured questionnaire to collect data from the respondents. The results showed that most hatcheries (65%) were not using anaesthetics in handling fish and all (100%) that were using anaesthetics (35%) used clove powder as the only type. Most respondents (61%) were not sure or did not have information about the availability of the anaesthetic substances in their localities while only 26% reported wider availability but 13% had a divergent claim. The mortality rate for fingerlings in hatcheries that applied anaesthetics ranged between 15–30% with consistently high demand while those that did not use anaesthetics reported mortality rates of more than 50% and had low demand. The majority of the respondents (53%) had received training up to certificate level, followed by those who had attained up to a diploma qualification (27%) while those that attained up to a degree (13%) and general skills (7%) levels were in the minority. Furthermore, most respondents (35%) did not know the importance of fish anaesthetics. We conclude that the use of fish anaesthetics in Zambian hatcheries is very low and could partly be the cause of high fingerling mortalities, and there is an urgent need to address the situation.

The anaesthetic effect of sodium bicarbonate (NaHCO3) on male and female three spotted tilapia (Oreochromis andersonii) was investigated. A total of 210 broodstock O. andersonii (weight: 160 ± 10 g) of different sexes were immersed in NaHCO3 at concentrations of 0, 5, 10, 15, 20, 25 and 30.0 g/L in triplicates. The induction and recovery times were monitored using a stopwatch. The induction and recovery times at all stages of anaesthesia for both sexes were significantly higher at concentrations ≥10 g/L. The induction times were significantly longer in the male fish than in the female at concentrations of 15 g/L for stages 1, 20 g/L for stages 1 and 2, 25 g/L for all the stages and 30 g/L for stage 2. The recovery time for male fish was significantly longer than that of the female fish at concentrations of 10 g/L for stages 2 and 3, 15 g/L for stage 1 and 20–30 g/L for stages 1 and 2. Overall, the induction and recovery times of the three spotted tilapia broodstock exposed to different concentrations of NaHCO3 could be affected by sex. Therefore, 30 and 25 g/L of NaHCO3 concentrations are recommended for use in male and female broodstock, respectively.

The aquafeed industry continues to expand in response to the rapidly growing aquaculture sector. However, the identification of alternative protein sources in aquatic animal diets to replace conventional sources due to cost and sustainability issues remains a major challenge. Recently, insects have shown tremendous results as potential replacers of fishmeal in aquafeed. The present study aimed to review the utilization of insects in aquafeeds and their effects on aquatic animals' growth and feed utilization, immune response and disease resistance, and fish flesh quality and safety. While many insect species have been investigated in aquaculture, the black soldier fly (Hermetia illucens), and the mealworm (Tenebrio molitor) are the most studied and most promising insects to replace fishmeal in aquafeed. Generally, insect rearing conditions and biomass processing methods may affect the product's nutritional composition, digestibility, shelf life and required insect inclusion level by aquatic animals. Also, insect-recommended inclusion levels for aquatic animals vary depending on the insect species used, biomass processing method, and test organism. Overall, while an appropriate inclusion level of insects in aquafeed provides several nutritional and health benefits to aquatic animals, more studies are needed to establish optimum requirements levels for different aquaculture species at different stages of development and under different culture systems.

As a land-locked country in Southern Africa, Zambia is rich in natural resources suitable for fish production. However, aquaculture is still in its infancy with enormous potential as most of Zambia’s fish now comes from capture fisheries. The aim of this study was to review the recent progress, status, challenges, and opportunities in Zambia’s aquaculture industry while drawing some lessons from China’s aquaculture experience, focusing on policy instruments, external support, quality seeds, and the investment environment for possible adaptation. To achieve this, we reviewed the existing literature about aquaculture in Zambia. This paper starts by reviewing the overall fishery sector’s developments based on the analysis of relevant statistics over decades before narrowing down to the aquaculture sub-sector. The review shows that aquaculture production has continued to expand significantly and will soon play a leading role in food and nutrition security in Zambia. However, the industry still faces major challenges relating to investments, science and technology, fish seed and feed, and an underdeveloped value chain besides the increasing demand for fish products. Nevertheless, great potential still exists to further develop the aquaculture sub-sector and meet the ever-growing demand for fish products caused mainly by the rapid population increase.

Aquaculture is a significant industry in food production, and its contribution to food and nutrition security is well acknowledged. Zambia’s aquaculture production has continued to increase significantly, thus playing a key role in supplying animal protein sources for human consumption. However, recent estimates show that 75% of the national aquaculture production comes from large-scale commercial producers despite being by far the minority while the majority of small-scale producers contribute the remaining 25% of the total annual production. This low production by small-scale producers is attributed to insufficient financial resources, poor management and utilization of farm resources, lack of access to competitive markets, and more recently a changing climate. In this research, we examine the viability of integrated agriculture-aquaculture (IAA) as a means for small-scale producers in Zambia to boost their aquaculture output despite the numerous obstacles they face. In addition, the obstacles that could prevent small-scale farmers from adopting IAA have been emphasized. We conclude that IAA has the potential to dramatically boost small-scale aquaculture production in Zambia, but information and understanding must be improved to make it a more feasible alternative.

This study investigated the effect of replacing fishmeal with red wigglers (Eisenia fetida) worm meal (RWWM) in the diet of Nile tilapia (Oreochromis niloticus) fingerlings. Red wigglers worms (RWW) were culture on a vegetable by-product medium, harvested and dried to obtain red wigglers worm meal. The fish (average weight ± SE: 7.70 ± 0.06 g) were fed with seven diets (30% crude protein and 7.5% crude lipid), in which fishmeal was replaced with 0%, 5%, 10%, 15%, 20%, 25%, and 30% RWWM. The fish was reared in 1000 L fiberglass tanks in a recirculating aquaculture system and were hand-fed twice daily for 90 days. At the end of the experiment, the growth, feed conversion ratio, and energy utilization improved when feeding 15% and 20% RWWM compared with the control diet (P

AbstractThe contamination of heavy metals in the Largescale Yellowfish (Labeobarbus marequensis) from the Solwezi River in North-western Zambia was investigated. The fish were captured from three different sampling sites on the Solwezi River. Site I was located before the mining effluents could join the river, site II was located immediately after the entry point of the mining effluent into the river, while site III was located downstream of where the effluents from the mining company had joined the river. The water and fish organs (muscle, gills, and liver) were checked for contamination with heavy metals. The values were compared with the established permissive levels considered safe for human consumption by the World Health Organization (WHO), and the Food and Agriculture Organization. In decreasing order, the contamination levels in fish organs were: Fe > Zn > Cu (gills), Fe > Zn > Cu (liver) and Zn > Fe > Cu (muscle). Co, Mn, and Pb were not detected in all the parts of the fish investigated. In water, the concentrations were in the order Zn > Fe > CU. The Metal Pollution Index (MPI) showed that site II was the most concentrated with heavy metals, while the gills were the most concentrated part of the fish. These results showed that the levels of the heavy metals investigated in the water and fish were within permissive levels by WHO and FAO. However, future expansion of existing companies and the introduction of new ones should strictly be monitored and their risks studied to safeguard fish and other aquatic products.

Fish is a relatively cheap and accessible source of animal protein for human consumption even in rural communities. It is critical for global food and nutrition security, and its consumption continues to increase. As a highly nutritious food, fish consumption is highly recommended for children and expectant mothers for normal growth and development. The present paper explores the nutritional value of fish as approach to nutrition in children and its benefits. The findings reveal that fish is a valuable source of essential amino acids (EAA) and polyunsaturated fatty acids (PUFAs) that play important physiological functions for maintenance and development of fetuses, neonates, and infant brains. Therefore, it could be a valuable tool in the fight against food insecurity and malnutrition. However, fish and fish products are also highly susceptible to contamination by various organic and inorganic compounds that threaten public health. Particularly, heavy metals and biogenic amines (BAs) have shown adverse effects when contaminated fish is consumed, and the effects in children have been worse. Hence, while fish consumption is highly recommended for children's nutrition, the safety and quality of the product should always be checked to safeguard public health.

Fisheries and Aquaculture are among the most popular activities in coastal regions of the world. In addition, both correspond to high-risk activities within a climate change context as they are vulnerable to environmental changes that threaten the socio-economic sustainability of the fishing communities that depend on fish for food security and income generation. In 2019, the central part of Mozambique was hit by two unprecedented cyclones: Idai and Kenneth that killed over 600 people and left nearly 2.2 million people in need of urgent assistance. The aim of the present study was to investigate the impacts these cyclones had on fisheries and aquaculture in the provinces of Sofala and Zambézia in Mozambique. The study further seeks to propose strategies that could be adopted by the communities to minimize the risks in the future. For the construction of the database, both secondary and primary data collection approaches were used to characterize the cyclone events. Secondary data was collected through sector reports and previously published articles, while primary data was collected through interviews with fishers, sector employees, and aquaculture producers in the affected provinces. The results revealed that these natural events had both a direct and indirect impact on fishing, as they affected more than 1,440 fishermen that lost 590 vessels, 1,800 fishing gear, and 67 boat engines in Sofala province. In Zambézia province, aquaculture producers lost 169 fish ponds, two cages, and 606,000 lost fry, while in Sofala province, 58 fish tanks, 204 cages, and 257,500 fish fry were lost. Overall, our study reveals the vulnerability of fisheries and aquaculture to extreme events particularly the cyclones in Mozambique. Lack of knowledge regarding climate change, advanced preventive measures, and poor adaptive capacity makes the sectors more vulnerable to disasters. Therefore, it is recommended to improve awareness programs, introduce measures and policies that promote resilience and optimum adaptive efficiency.

Understanding the variability of heavy metals in surface sediments and how they accumulate is important not only in ecology and biodiversity conservation but also in aquatic natural resources management. This study investigated the level of some heavy metal contaminants in the Kifubwa and Solwezi Rivers in the Northwestern Province of Zambia. We used an atomic absorption spectrophotometer (AAS) to determine the levels of heavy metals in the surface sediments. Six sites known to be associated with heavy metal anthropogenic activities were sampled. In these sites, six elements, namely Cu, Co, Fe, Mn, Pb, and Zn, were targeted and measured in surface sediments from these two rivers. The mean values of these elements in each river were determined. To understand the ecological risk related to heavy metal contamination, we calculated the contamination factor (CF), the contamination degree (CD), as well as the pollution load index (PLI) for each element at each site in each river. These indices showed little contamination in the surface sediments of these rivers. This, therefore, implies that there are few ecological risks posed by heavy metal pollution to the ecosystems of the Solwezi and Kifubwa Rivers from sediments. However, follow-up studies should be carried out to monitor the levels of heavy metals in the fauna and flora of these rivers. Additionally, a follow-up study for the determination of other heavy metals such as arsenic, mercury, cadmium, and nickel must be conducted.

Cage aquaculture is among the recent innovations that have attracted great attention in fish production in most African countries. In Zambia, cage aquaculture has recorded significant growth to even emerge as the largest contributor to the total national aquaculture production annually. Our study was aimed at assessing cage aquaculture production in Siavonga district of Zambia. We targeted the aquaculture and feed manufacturing companies, their production, challenges, and opportunities. This study revealed that there were five main aquaculture production companies with fish cages ranging from 96 m3 to 135,534 m3 in size. Oreochromis niloticus was found to be the only cultured species. Lack of quality fish seed and feed were the major challenges faced by the aquaculture production companies in Siavonga district. The study further revealed that there were two major aquafeed manufacturing companies within the district with a production capacity ranging from 50 tons to 200 tons per day. Lack of readily available raw material for feed making was the major challenge facing the aquafeed manufacturing companies. There are huge potentials for cage aquaculture in Siavonga district, which can significantly contribute to the nation's aquaculture production. These include the availability of large fish feed manufacturing companies and huge water resources. Keywords: Cage, Aquaculture, Technology, Production, Capacity, Zambia

Aquaculture continues to significantly expand its production, making it the fastest-growing food production sector globally. However, the sustainability of the sector is at stake due to the predicted effects of climate change that are not only a future but also a present reality. In this paper, we review the potential effects of climate change on aquaculture production and its implications on the sector's sustainability. Various elements of a changing climate, such as rising temperatures, sea-level rise, diseases and harmful algal blooms, changes in rainfall patterns, the uncertainty of external inputs supplies, changes in sea surface salinity, and severe climatic events have been discussed. Furthermore, several adaptation options have been presented as well as some gaps in existing knowledge that require further investigations. Overall, climate change effects and implications on aquaculture production sustainability are expected to be both negative and positive although, the negative effects outweigh the positive ones. Adapting to the predicted changes in the short-term while taking mitigation measures in the long-term could be the only way toward sustaining the sector's production. However, successful adaptation will depend on the adaptive capacity of the producers in different regions of the world.

The ever increasing demand for fish and fishery products in Zambia has resulted in the culture of many tilapia species including greenhead tilapia (Oreochromis macrochir). This increase in aquaculture entails an increase in routine procedures being performed which require anaesthetizing fish to reduce stress. In this study, we examined the efficacy of sodium bicarbonate commonly known as ‘baking soda’ as an anaesthetic agent for greenhead tilapia juveniles (7.2 ± 1.10 g weight and 27.64 ± 4.44 mm length). The juvenile fish were subjected to different concentrations of baking soda namely 0 (control), 5, 10, 15, 20, 25 and 30 g/L of sodium bicarbonate solution. In each of these different concentrations of the anaesthetic agent, fish were bath-immersed. Generally, the time of induction decreased while the time of recovery from anaesthesia increased with an increase in sodium bicarbonate concentration. The time of induction and recovery depended significantly (p

An 8-week rearing trial was designed to appraise the dietary lysine levels on intestinal antioxidant capacity and immunity of grass carp fry. Six practical diets were prepared with graded levels of lysine (1.44, 1.79, 1.97, 2.44, 2.56 and 2.87% dry matter), and these diets were fed to grass carp fry. The results showed that the activities of intestinal antioxidant factors including catalase and glutathione peroxidase were markedly improved by the 2.44% dietary lysine compared with the control diet (1.44% dietary lysine) (P < 0.05). In terms of antioxidants, compared with the control diet, the 2.44% diet markedly upregulated the mRNA expression levels of target of rapamycin, S6 kinase1 and nuclear factor erythroid 2-related factor 2 pathway-related antioxidant genes, containing catalase and glutathione peroxidase 1α (P < 0.05) and downregulated the mRNA levels of Kelch-like ECH-associated protein 1 (P > 0.05). The mRNA levels of 4E-binding protein 2 showed the opposite trend compared with those of target of rapamycin, and the minimum value was observed in the group of 1.97% dietary lysine (P < 0.05). In terms of immunity, compared with the 1.44% diet, the 2.44% diet markedly suppressed the intestinal p38 mitogen-activated protein kinase and interferon γ2 mRNA levels (P < 0.05). Moreover, nuclear factor-kappa B p65, tumor necrosis factor α, interleukin 6, interleukin 8, and interleukin 15 mRNA levels all exhibited the same trend as p38 mitogen-activated protein kinase and interferon γ2; however, the difference among all the lysine treatments groups was not significant (P > 0.05). The anti-inflammatory cytokines transforming growth factor β2 and interleukin 4/13B mRNA levels in the intestine were remarkably upregulated by high dietary lysine levels (2.56 and 2.87%) (P < 0.05), and when the dietary lysine level reached 2.44%, the interleukin 4/13A mRNA levels were strikingly increased (P < 0.05). Overall, the data suggested that 2.44% dietary lysine could strengthen the immune and antioxidant capacities of grass carp fry via activating the target of rapamycin (TOR) signaling pathway, and suppressing the p38 mitogen-activated protein kinase (p38 MAPK) signaling pathway, which then improve the survival rate.

Extension programs in rural communities play a critical role in linking farmers and other actors in rural developmental agenda. The relevance of these programs in agriculture is largely dependent on their ability to meet farmers’ needs since they are the stakeholders at the grassroots. This paper aimed to review studies on enhancing the role of rural agricultural extension programs in poverty alleviation. Various approaches and tools used in rural extension program delivery have been discussed, and ways in which their contribution to poverty alleviation can be enhanced have been highlighted. Extension programs have undergone many changes throughout the years in response to farmers’ changing needs as well as the market they operate in. Therefore, there is no “one-size-fits-all” approach recommended for effective service delivery and outcome due to different farmer needs that are affected by their geographical location, social and economic structures. We conclude that rural extension programs can provide a sustainable solution to poverty, however, the appropriate approaches should be chosen taking into account the needs of the farmers and market dynamics of a particular area.

Facilitative glucose transporter 4 (GLUT4) plays a central role in mediating insulin function to increase glucose uptake in glucose metabolism homeostasis. In this study, the function and localization of GLUT4 in blunt snout bream (Megalobrama amblycephala) were first investigated, and then, the response measured as carbohydrate level, was analyzed. The results showed that the cDNA sequence of GLUT4 in blunt snout bream (MaGLUT4, GenBank accession no: MT447093) was 2868 bp in length, and the corresponding mRNA contained a 5′-UTR region of 513 bp and a 3′-UTR region of 837 bp. MaGLUT4 had an open reading frame of 1518 bp and was encoded by 505 amino acids. Its theoretical isoelectric point and molecular weight was 6.41 and 55.47 kDa, respectively. A comparison of these characteristics with BLASTP results from the NCBI database showed that MaGLUT4 had the highest homology with Cypriniformes fish, with MaGLUT4 and GLUT4 of other Cypriniformes clustered in the phylogenetic tree with other GLUT1–4 amino acid sequences. Compared with the results from the homo_sapiens and mus_musculus data sets, some mutations were observed in the GLUT4 amino acid sequence of these aquatic animals, including an FQQI mutation to FQQL, LL mutation to MM, and TELEY mutation to TELDY. MaGLUT4 was constitutively expressed in the muscle, intestine, and liver, with the highest mRNA level observed in muscle. Furthermore, the predicted tertiary structure and results of immunohistochemical staining showed that MaGLUT4 was a transmembrane protein primarily located in the plasma membrane, where it accounts for 60.9% of the total expressed, according to an analysis of subcellular localization. Blood glucose level peaked within 1 h, and the insulin level peaked at 6 h, while the mRNA and protein levels of GLUT4 showed an upward trend with an increase in feeding time and decreased sharply after 12 h. These results confirmed that MaGLUT4 was mainly distributed in muscles and crosses the cell membrane. The changes in the insulin, mRNA, and protein levels of MaGUT4 lagged far behind changes in blood glucose levels. This delay in insulin level changes and GLUT4 activation might be the important reasons for glucose intolerance of this fish species.

Fish is an extremely perishable food product which requires proper handling soon after harvest. The present study was aimed at assessing post-harvest fish losses and preservation practices in Siavonga district, Southern Zambia. Structured and semi-structured questionnaires were used to collect data on post-harvest fish losses and preservation practices from aquaculture producers, artisanal, and commercial fishers. All the fishers who landed on the lakeshore were interviewed, while aquaculture producers were randomly selected based on the information provided by the local department of fisheries. The results of the study revealed that all the fishers experienced post-harvest fish losses at varying degrees with those losing up to 10% of the total catch being in the majority. In contrast, aquaculture producers did not report any post-harvest fish losses. Most aquaculture producers commonly used chilling as preservation practice contrary to artisanal and commercial fishers who commonly used smoking and sun sun-drying respectively. Furthermore, fish product safety and quality control were poorly practiced in the district. Lack of cold storage facilities and fluctuating weather conditions were the major challenges impacting fish post-harvest activities. Therefore, to curb the loss of revenue due to post-harvest fish losses, we propose the introduction of new technology, self-development skills for fishing communities, and enhanced access to refrigeration facilities.

The blue crab, Callinectes sapidus Rathbun, 1896, is considered to be a luxury meal, especially in touristic cities. It contains more than 20 types of amino acids and provides all the needed amounts for human growth. This study describes the morphology and complex differentiation in the gonadosomatic index, morphological and ultrastructure features of the reproductive system, spermatogenesis, and spermatophores structure; this is due to the need to maintain natural and fishing stocks. Mature adult male crabs (carapace length 59 ± 7.12; width 126 ± 18.8 mm) were obtained from Abu-Qir Bay from November 2018 to October 2019 and transported alive in seawater to the laboratory. The reproductive system was dissected and weighed to the nearest 0.001g using the electronic balance, and the gonadosomatic index was subsequently calculated. The morphological analysis showed the developing testes with highly compacted seminiferous tubules. Using Periodic acid–Schiff stain, the spermatophore appeared with a zigzag-shaped wall that indicates its carbohydrate constituents. Each Spermatophore consisted of an inner spermatozoal mass embedded in a matrix, whose main components were secretions 1 and 2, and an outer thin acellular layer composed of secretions 3 and 4 from the anterior vas deferens (AVD). Secretions 5 and 6 (S5 and S6) also appeared with carbohydrate constituents using Mallory triple stain. The transverse section of the middle vas deferens (MVD) showed spermatophores with rod-shaped secretion S6 and granular secretions 7 (S7), forming a complex matrix between spermatophores. The secretion found in the MVD was granular, strongly acidophilic, and secreted by its highly columnar epithelium (S7). The ultrastructure showed that the testes were surrounded by a monolayer of myoid cells with an elongated nucleus, which also contained the following stages: spermatogonia, primary spermatocyte, secondary spermatocytes, and spermatids as well as spermatozoa. On the other hand, scanning electron microscope studies for fully formed spermatophore taken from the middle part of the vas deferens indicated that it is ellipsoidal in its outline with terminal stalk. Furthermore, the spermatophore was surrounded by a thick capsule of non-cellular substances and contained mature spermatozoa.