Fish cage culture in Lake Victoria (Kenya): Fisher community perspectives on the impacts and benefits for better sustainable management

The findings of this study provide useful insights into the key aspects of fish cage farming to be considered during setting and overall management of multi-purpose water resources so as to maximise their aquacultural potential. The study was conducted in Machakos District, Kenya, to characterise limnochemistry and algal composition of three small man-made reservoirs Ngeki, Ngei and Kavovi, used for cage culture of Nile tilapia (Oreochromis niloticus). In Ngeki, the open water was compared with areas in between the cages and significant differences in dissolved oxygen were found. For N, P and chlorophyll-a, no differences were noticed. In all the reservoirs, temporal variations were noticed for all parameters except NO3N and NH4N. Peak concentrations of nutrients occurred during the rainy season with lower values in the dry season (below detectable limits for SRP). All reservoirs were classified as hyper-eutrophic with a strong positive correlation between chlorophyll-a and TP. Algal abundances changed with season. Chlorophyta dominated at the start of the rainy season, while cyanobacteria prevailed at the onset of thermal stratification. Diatoms prevailed in the dry season but were notably absent in the rainy season. It was concluded that all the reservoirs are suitable for cage culture of Nile tilapia, but this should be undertaken with caution considering critical periods when anoxic conditions may occur.

Beach Management Units (BMUs) in Kenya were established to ensure sustainable utilization and management of the fishery resource. BMUs as co-management institutions were conceptualized after the failed state-controlled fisheries management. Sustainable management by the BMUs has however not been realized, years after the institution’s inception. The study aimed to assess the management of Migingo BMUs; establish the effects of management of BMUs on the implementation of the regulations; and assess the implementation of regulations with regards to fish stocks. The study was done in Migingo Island, Lake Victoria which borders Kenya and Uganda. Data was collected from the BMU committee members and stakeholders at the fish landing site along the island’s shores. This was done through a questionnaire based survey; semi structured interviews from key informants and; focus discussion groups. Results revealed that the three out of seven functions were performed satisfactorily by the Migingo BMU. These were revenue collection, confiscation of illegal gears and arrest of offenders, as depicted by the satisfaction of respondents at 42%, 38%, and 68%, respectively. The other functions - conducting meetings, patrol of the lake, formulation of bylaws and inventory keeping had poor performance. Migingo’s BMU structure was found to be wanting as it lacked the assembly branch. Implementation of regulations by the BMU faced various challenges; lack of support from the government, inadequate funds and equipment and inadequate knowledge to operate its functions. This study shows that BMUs are viable institutions however the poor structure and management of Migingo’s BMU along with the challenges faced in implementing the stipulated regulations led to its ineffectiveness. Capacity building is therefore needed on the BMU’s management and governance at large, provision of relevant skills, equipment and funds and improved support from the government for the BMU to be efficient and effective.

Nutrient release from fish cage aquaculture and mitigation strategies in Daya Bay, southern China

Removing nutrients in recirculating aquaculture system wastewater from Nile tilapia culture via Spirulina cultivation: Optimizing sodium bicarbonate concentration and micronutrient supplementation

This study examined the efficacy of community‐level fishery co‐management organizations called Beach Management Units (BMUs) along the Kenyan shores of Lake Victoria. BMUs were established to enhance sustainable Lake Victoria fishery management through increasing the level of community participation to assist in the administration of fisheries rules and regulations by, and for, the fishers. Inefficiencies have emerged, however, inhibiting the effective execution of sustainable fisheries management by the BMUs. Data were collected from 36 BMUs along the Kenyan shores of Lake Victoria. Descriptive and inferential analyses were performed using SPSS Version 20.0. The results indicated that BMUs are successful at educating fishers and that they are aware of fishing rules and regulations. Nevertheless, high violation rates were also observed, suggesting BMUs have limited impact on fisher decisions to comply with regulations. Data suggest that the failure to comply may be due to lack of adequate financial and equipment resources for monitoring, control and surveillance (MCS) operations, making them unable to control illegal fishing in their areas of jurisdiction. Furthermore, financial mechanisms, which would allow BMUs to sustainably fund their administrative and MCS operations, are weak, thereby reducing the BMUs ability to effectively function. The data from this study highlight two activities illustrating significant indices of good performance, namely resolving disputes and receiving visitors. The data also suggest the creation of BMUs has not ensured successful implementation of co‐management of Lake Victoria fisheries. BMUs are successful at activities of a social nature, but have poorly undertaken their core functions related to enforcement and compliance with fishing rules.

Abstract. Tania NJ, Hossain MB, Habib, A, Musa N. 2020. Effects of fish cage culture on macrobenthic communities in a subtropical river. Biodiversitas 21: 3583-3589. The present study described the impact of freshwater fish cage culture on macrobenthic faunal assemblages in the Dakatia River, Chandpur, Bangladesh. The experimental design involved the establishment of four stations in two study sites, two stations near the culture area, and two stations away from culture area. A total of 23 macrobenthic taxa belonging to annelids, molluscs, arthropods, and other minor phyla were recorded from study sites. Oligochaetes were found to be dominant at all four stations composing 42.34% of the total macrobenthos. Pollution indicator benthic organisms i.e., Naididae (30.32%), Tubificidae (20.16%), and Chironomidae (3.54%) were found most in the cage culture area. The density of benthic macrofauna was higher (28,134 inds./m²) in the cage culture site than the non-cage culture site (4,358 inds./m²) due to high abundance of certain pollution tolerant species. However, the values of diversity indices i.e., Species Richness (SR), Shannon-Wiener (S-W) diversity (H´), Pielou’s evenness (E), and Margalef (J) were consistently higher in non-cage culture area than the cage culture area. One-way ANOVA showed no significant variation (P > 0.05) in diversity values between the sites. The results of the present study revealed effects of cage culture on the abundance, diversity, and composition of benthic macrofauna.

Fish catches in Lake Victoria have been on the decline, while demand for fish has been increasing because of rapid human population growth and awareness of the health benefits of fish. This decline is attributed to socioeconomic activities around the lake and climate change effects. To bridge the gap, cage culture has presented itself as a new socioeconomic frontier with good prospects for income in Lake Victoria, besides conserving declining wild fish stocks. However, these cages are greatly influencing the biodiversity of the lake both negative and positive. The study adopted a descriptive survey research where a total of 200 cage fish farmers were targeted. A sample of 60 fish farmers was selected using purposive and simple random sampling methods. Interview schedules and self-administered questionnaires were the main tools for data collection. Both primary and secondary data were collected and analyzed using Statistical Package for Social Sciences. The results were: the majority of cage fish farmers were male (87%) while the female was 13%, with a majority (75%) of the secondary and tertiary level of education. The beach management units and fish farmers were responsible for siting of cages. The fish farmers experienced several challenges including high cost of feeds leading to the use of poor quality feeds that sink and increase eutrophication, which enhances the growth of algae and water hyacinth in the lake. Overstocking leads to the emergence of diseases and fish kills, and fish theft resulting in economic loss. Most (80%) of respondents were not aware of policy guidelines on cage culture in Lake Victoria, while (75%) were not aware if cage culture was promoting climate change effects in Lake Victoria. This paper recommends the government to create awareness of policy guidelines on cage fish farming.

The study aims to determine suitability of floating cage (KJA) culture of grouper fish in Ringgung waters of Lampung. Data were analysed using GIS for spatial analysis at five stations. There were 10 water quality parameters measured, such as bathimetry, current velocity, water transparency, temperature, salinity, pH, dissolved oxygen, nitrate, ammonia, and phosphate. Three suitability criteria, i.e very suitable, suitable, and not suitable were used to determine the suitability of floating cage culture of grouper fish. The results show that from 99.168,5 ha of the total area used for floating cage culture of grouper fish, about 85,94% covering 8522,16 ha were classified as very suitable, 5,64% covering 559,69 ha classified as suitable, and 8,42% covering 835 ha classified as not suitable. Keywords : grouper culture, suitability, Ringgung waters, Lampung Province, GIS

Fish catches in Lake Victoria have been on the decline while demand for fish has been increasing. Cage culture with >3,000 cages, over 3 million tilapias and valued at US$ 12 million is trying to fill the gap. This study reviews the development of cages and the need to develop a decision support tool for effective management. Existing literature and data on fisheries and cage culture held by the Kenya Marine and Fisheries Research Institute (KMFRI) were used in the analysis. Cage culture is a promising venture that may increase productivity, offer employment and enhance economic well‐being. However, site suitability for the installation of cages is poorly regulated with most developments (>45%) located within 200 m of the shoreline that are breeding grounds of fish and conflict with other lake users. Waste feed increases eutrophication, and enhances growth of algae and water hyacinth in the lake. Recent isolated fish kills were attributed to low dissolved oxygen concentrations (<0.64 mg/L), and an increasing occurrence of fish disease are signs of poor management practices among cage farmers. Cage culture may turn into an environmental disaster if not managed well, and there is need for robust policies and increased awareness to reduce environmental impacts.

Editorial

Cage culture plays an important role in achieving higher output and generating more export earnings in Malaysia. However, the cost of fingerlings, feed and labour have increased substantially for cage culture in the coastal areas in Peninsular Malaysia. This paper uses farm level data gathered from Manjung, Perak and Kota Tinggi, Johor to investigate the technical efficiency of brackish water fish cage culture using the stochastic frontier approach. The technical efficiency was estimated and specifically the factors affecting technical inefficiencies of fish cage culture system in Malaysia was investigated. On average, 37 percent of the sampled fish cage farms are technically efficient. The results suggest very high degrees of technical inefficiency exist among the cage culturists. This implies that great potential exists to increase fish production through improved efficiency in cage culture management in Peninsular Malaysia. The results indicate that farmers obtained grouper fingerlings from other neighboring countries due to scarcity of fingerlings from wild sources. The cost of feeding for grouper (Epinephelus fuscoguttatus) requires relatively higher costs compared to seabass (Lates calcarifer) production in cage farms in the study areas. Initiatives to undertake extension programmes at the farm level are needed to help cage culturists in utilizing their resources more efficiently in order to substantially enhance their fish production.

Acceptance of cage fish farming within Volta Lake in Ghana, was assessed in the lake’s riparian sub-communities by estimating opinion case of community members generally and specifically on issues including Interference of fish culture with fishing; Cage culture interference with local boat transportation activities; Integration level of cage fish culture into other lake activities; Awareness of lake’s community of the lake as a multipurpose resource; Primary occupation of community members; Co-existence level of fish farm operators and communities and cumulative acceptance of fish culture compared to other lake uses and users currently and in the future when the lake is zoned. Methods used were Formal survey and Focus Group Discussions (FGD) in two conceptualized zones (Afram Plains and Asuogyaman) of the lake and data was analyzed by SPSS. A study was undertaken to enhance integration and acceptance of cage fish culture into activities on the Volta Lake and by extension on potential other water bodies where cage fish culture might be practiced. Results indicated that several mutually beneficial situations existed between cage fish farming operators and lake communities. However, there were also conflict flashpoints between cage fish farming practices and livelihood activities of communities at some places as well as fish culture-related outcomes, such as effluents of the culture on lake water quality for communities. The benefits of cage fish farming to communities observed in the results confirm some previous reports. Suggestions of communities to the resolution of conflict flashpoints of operations with operators of cage fish farming provide avenues for enhanced integration thus acceptance and sustainability of cage culture in riparian communities of the lake and other water bodies that could be found suitable for cage fish culture.

Char dwellers are considered poorer than the mainland population. A constant threat of riverbank failure, flooding, and seasonal cyclone, combined with lack of physical infrastructures, and employment opportunities in the Chars, makes a vulnerable, difficult, and fragile life. The aim of the present work was an initiative to improve the livelihood of Char dwellers through fish culture in the net cages. A focus group survey was conducted on Char dwellers to know about the livelihood conditions. Quantitative and qualitative analysis of plankton was performed to know the productivity of the Padma River. In the study area, there was an average of 5 household members in each family of the Charland dwellers, and the average sex ratio of males and females was 56.67% and 43.33%, respectively. The age group of below 15 to 60 years and their religion ratio of Muslim and Hindu was 45% and 55%. The total number of identified genera of phytoplankton was 41, and the total number of zooplankton genera was 20 in the Padma River. Tilapia (Oreochromis niloticus) was cultured in the net cages providing three different feeds i.e. natural feed, kitchen waste (leftover rice), and rice bran. The final weights of the experimental tilapia were 314.8 ± 24.3 g after 5 months of feeding natural food, 321.4 ± 22.8 g after 5 months of feeding natural food with kitchen waste, and 324.8 ± 29.5 g after 5 months of feeding natural food with rice bran. Considering the plankton populations and water quality parameters, the Padma River near the Charland of Munshiganj was productive for fish farming. We found the results of Genetically Improved Farmed Tilapia (GIFT) farming in net cages near the river of Char, which were almost the same (has no significant difference among the diets) by providing low-cost supplementary feed and without supplementary feed. Therefore, the result indicates that Char dwellers can culture fishes in net cages to have the fish in their daily meals and can earn extra income from selling the fish to improve their livelihood. Moreover, applied research and interdisciplinary adaptive policy framework are requisite for the Charland livelihoods sustainability in the Padma River, Munshiganj, Bangladesh. Asian J. Med. Biol. Res. 2021, 7 (2), 174-181

This study aimed to evaluate nutrients concentration and spatial-temporal changes in phytoplankton biovolume during an experimental fish culture in net cages in a lateral arm of Salto Caxias reservoir, Brazil. Two sampling stations were placed in the affected lateral arm and other two in a cageless lateral arm. Neither abiotic variables nor phytoplankton biovolume presented significant differences between the treatments. Only temporal changes were confirmed by the analysis performed. Both lateral arms were classified as oligotrophic, reflecting low influence of the net cages. Phytoplankton growth seems to be limited by nitrogen. Biovolume values were, in general, low and five major functional groups were recognized (E, F, G, K and P). In summer higher biovolume values were observed and representatives of Chlorophyceae and Cyanobacteria belonging to the functional groups F and K, respectively, were the most important. In winter phytoplankton was mainly composed by Bacillariophyceae taxa from P group. G group was also restricted to winter and E group occurred in winter and summer. The variations recorded in phytoplankton structure appear to have been mainly influenced by seasonal changes in temperature, precipitation and nutrients availability. The effects of net cages on the abiotic variables and phytoplankton biovolume appear to have been small, probably due to the small number of net cages employed and the system dilution capacity. However, a permanent monitoring of phytoplankton is recommended, since this environment has a carrying capacity, from which the trophic state may increase.

Preliminary studies on the impact of fish cage culture rainbow trout (Oncorhynchus mykiss) on zooplankton structure in the southwestern Caspian Sea