ABSTRACT The continued use of prohibited fishing gear in inland waters around the world poses a direct threat to the sound management of global fish stocks. This is also the case in Benin, where there has been a drastic decline in shrimp production since 2002, particularly in the Nokoué lagoon. This study aimed to compare the capture capacity (in space and time) of two types of fishing gear (traps and nets) that are less destructive on shrimp catches in the Nokoué lagoon and its inlet complex (North, South, Centre, East and West), as part of a sustainable exploitation strategy. In total, two genera of shrimp were sampled: Macrobrachium Spence Bate, 1868 and Penaeus Fabricius, 1798. Analysis of variance (ANOVA) analyses and Tukey's post hoc tests revealed a pronounced seasonal pattern in catches, particularly for Macrobrachium , with a peak in September and a low‐catch period from March to June. Nets showed a prolonged period of low catches, whereas traps revealed four seasonal catch levels. For Penaeus , five seasonal catch levels were identified, corresponding to prolonged peaks in catches between January and June, followed by a gradual decline to the annual minimum in October and November. The spatial distribution of catches reflects significant heterogeneity between stations. For Macrobrachium , traps caught mainly at Western station, characterized by a high density of ‘Acadja’, whereas nets showed a peak at Eastern station. For Penaeus , Western station had the highest catches for both types of gear, whereas the other stations had intermediate or low yields, highlighting the importance of spatial configuration and artificial habitats in the distribution of populations. Kolmogorov–Smirnov tests confirmed that there were no significant differences between the seasonal effectiveness of traps and nets for both genera, indicating comparable overall performance. However, the chi‐square test revealed a moderate but significant difference in the size frequencies of Penaeus , with nets capturing proportionally larger individuals 150–180 mm, whereas traps favoured intermediate sizes 90–120 mm. For Macrobrachium , no significant difference was observed, reflecting a population dominated by juveniles and adults. Chi‐square residual analysis corroborated these observations, showing an overrepresentation of large Penaeus sizes in nets and intermediate sizes in traps. For Macrobrachium , differences in catch according to size class remain limited to individuals measuring 90–120 mm, mainly caught by traps. These results highlight the complex interaction between gear selectivity, seasonal dynamics, and spatial heterogeneity, underscoring the importance of these factors for the sustainable management of shrimp populations in the Nokoué lagoon.
ABSTRACT Seaweed is a vital food and livelihood resource in Tanzania, with potential to strengthen and diversify food systems. It enables the production of high‐value products while delivering environmental benefits. Tanzania has witnessed promising research and advances in the seaweed value chain (VC), particularly in Zanzibar. However, critical gaps remain, including weak value chain mapping, limited analyses of constraints and potential solutions, poorly understood value distribution and insufficient attention to gender‐differentiated outcomes. This study developed a seaweed VC map, characterised stage‐specific constraints and identified potential opportunities for inclusive growth in the Kilwa and Mtwara Districts of Tanzania. We collected data from 25 purposively selected key informants and six focus group discussions involving 58 participants, and thematically analysed them. We found that the seaweed VC spans preparation to marketing, involving women producers cum processors, private input suppliers, traders, traditional drying and export‐oriented trade. Approximately 90% of national production is exported, while drying accounts for 40% of total losses. It faces systemic constraints, including weak seed systems, poor inputs and infrastructure, climate stressors, limited buyer competition, asymmetries in market power, limited finance, post‐harvest inefficiencies, skills and knowledge gaps and issues of equity, youth participation and innovation. The analysis identified value addition as the key upgrade lever, aligning with policy priorities, strengthening supply chains and markets, enabling policy incentives, adopting climate‐smart technologies, fostering public–private investment, and embedding inclusive, gender‐responsive and youth‐engaged development. This study provides critical evidence to inform targeted interventions that enhance market access, smallholder incomes, efficient resource utilisation, product availability and livelihood resilience.
ABSTRACT The expansion of aquaculture has intensified the search for sustainable alternatives to fishmeal. The mopane worm, Gonimbrasia belina (syn. Imbrasia belina ), is a traditionally consumed southern African insect whose protein, lipid and micronutrient contents have prompted interest in its use as an aquafeed ingredient. This semi‐systematic review evaluates the nutritional value and digestibility of mopane worm meal and its effects on growth, feed utilisation and physiological responses in fish. Several experimental studies on mopane worm meal in fish diets, reviews and related insect‐meal research used to examine its nutritional potential were identified. The available evidence suggests species‐specific and inclusion‐dependent responses. Mozambique tilapia ( Oreochromis mossambicus ) tolerated partial fishmeal replacement and exhibited increased activity of some digestive enzymes, although the fishmeal‐based control achieved the highest growth. By contrast, increasing replacement levels reduced growth, protein utilisation and digestibility in African catfish ( Clarias gariepinus ) and were associated with greater hepatic alteration. Dusky kob ( Argyrosomus japonicus ) showed favourable growth and feed‐utilisation responses at moderate inclusion levels without major changes in digestive enzymes or haematological variables. Overall, the evidence supports mopane worm meal as a potentially valuable supplementary protein, particularly in locally formulated diets and when replaced in moderate proportions (18% for Dusky kob). Although there are studies suggesting replacements up to 60% for Mozambique tilapia, there is no scientific evidence regarding the optimal range. However, the small number of short‐term feeding trials, variability in ingredient composition and processing, incomplete digestibility data and uncertain sustainability of wild harvesting prevent broad commercial recommendations. Standardised, long‐term and independently replicated studies are required to establish species‐specific inclusion thresholds and evaluate physiological, economic and ecological outcomes.
ABSTRACT The ornamental fish trade is one of the fastest‐growing sectors of the global aquatic animal industry, involving more than 7900 fish species. Global demand for ornamental fish has increased substantially over the past few decades, with millions of fish traded annually to supply the expanding aquarium industry. The industry in Tanzania is also expanding rapidly, yet information on traded species, trade practices and associated conservation risks remains limited. This study assessed freshwater (FW) ornamental fish trade practices and their conservation risks in Tanzania through a cross‐sectional survey involving 124 respondents, including 70 fishers, 31 importers, 20 exporters and 3 law enforcers across Kigoma, Dar es Salaam, Morogoro and Arusha regions. Data on FW ornamental fish species, trade pathways and regulatory practices were collected through questionnaires, interviews and field surveys, whereas species conservation status and invasion history were obtained from FishBase, the IUCN Red List and published literature. Data were analysed using descriptive statistics and inferential statistics. Results revealed a well‐organized trade network dominated by exporters linking local collectors and breeders to international markets. Export trade mainly relied on wild‐caught endemic cichlids (70%) from Lake Tanganyika, with Cyphotilapia frontosa being the most frequently traded species. Imported ornamental fishes were recorded under 113 unique trade names, representing multiple taxonomic species across 14 families, with imports originating predominantly from Asian countries. Several imported species previously reported as invasive in introduced environments globally were recorded, including Carassius auratus with 100% frequency of occurrence from all importers, followed by Poecilia reticulata (83.8%) and Cyprinus rubrofuscus (78.6%). Respondents also reported permit‐related difficulties and awareness of unofficial trade routes, indicating regulatory and compliance challenges within the sector. The study highlights the need for improved species‐level monitoring, stronger regulatory enforcement, and enhanced biosecurity measures to support sustainable ornamental fish trade while minimizing ecological risks to native aquatic ecosystems.
ABSTRACT Pesticides have become an integral part of agricultural crop production for growing more food. However, the excessive use of pesticides ultimately reaches the aquatic ecosystems and demonstrates pernicious impacts on non‐target aquatic organisms, including fish. Hence, the current study aimed at unravelling the chronic toxicity of an organophosphate insecticide, chlorpyrifos (CPF), on a battery of blood biomarkers, somatic indices and histopathological aberrations of liver and kidney in banded gourami ( Trichogaster fasciata ). Fish were subjected to different sub‐lethal concentrations (0, 15, 50, 150 and 500 µg/L) of CPF for 75 days, and sampling was done at each 15‐day interval. Results indicated a significant rise ( p < 0.05) in glucose, white blood cell levels, mean corpuscular volume and mean corpuscular haemoglobin, and a subsequent decrease in haemoglobin, red blood cell count and packed cell volume. Hepatosomatic index exhibited an increasing pattern, whereas the kidney somatic index followed the opposite trend. Vacuolation, fatty degeneration, dilation of sinusoids and haemorrhage were evident in the liver, whereas kidney histopathology revealed occlusion of the tubular lumen, widened intertubular space, vacuolation, melanomacrophage centre and haemorrhage. Overall, chronic CPF exposure exerted concentration‐ and time‐dependent alterations resulting in anaemia, hepatotoxicity and nephrotoxicity in banded gourami. However, more in‐depth studies are required to understand the changes in fish at the molecular level, such as oxidative stress, gene expression, metabolomic profiling and so forth. The study encourages research for pesticide alternatives and interdisciplinary actions to conserve the aquatic environment as well as the aquatic biota.
