An evaluation of present and potential inland fisheries in dams and rivers in the uThukela and uMngeni Catchments, KwaZulu-Natal, South Africa.

Abstract

Globally, freshwater systems and their biodiversity and ecosystem services are threatened. Freshwater fisheries in South Africa are understudied despite their economic importance to fishers, especially subsistence fishers. Little is known about the potential for rivers and impoundments to support subsistent fisheries and the resilience of native fish species impacted by invasive alien fish species. The main aim of this study was to address the lack of knowledge about economically and biologically important indigenous fish species that support inland fisheries in KwaZulu-Natal Province, South Africa. The composition and contribution of native and invasive fish species and their offtake by fishers were assessed. Fishers across the uThukela and uMngeni catchments were interviewed using in-person questionnaires. In addition, assessment of fish communities and population structures in Midmar Dam and Henley Dam, two selected dams on the uMngeni River, coupled with questionnaire data, were used to determine the offtake trends by fishers (subsistence and recreational). These will contribute to a potential subsistence fisheries management plan for these dams based on the findings to guide the development of the provincial and national inland fisheries plan. Firstly, in a systematic review, the present and potential inland fisheries in dams and rivers across Africa to guide inland fisheries in KwaZulu-Natal, South Africa, were assessed. The results showed diverse inland fisheries types with distinct characteristics and shared challenges. National and regional importance of African inland fisheries was found, but there was a lack of understanding of the definitions and boundaries between the categories of inland fisheries. Subsistence fisheries, focusing on local food provision through traditional methods, face threats like overfishing. Recreational fisheries, contributing to food, income, and recreation, require effective conservation in developing nations. Small-scale fisheries showcase resilience and successful conservation, emphasising adaptive management. Commercial fisheries involving professional fish exploitation encounter challenges, especially in regions like South Africa, demanding sophisticated approaches for long-term viability. Across Africa, common challenges such as overfishing and habitat destruction persist. In KwaZulu-Natal, a significant research gap exists, impacting sustainability. Addressing issues like monitoring systems, invasive species, and species knowledge is crucial for sustainable fisheries management in the region. Secondly, to address the paucity of knowledge of economically beneficial fish species and their offtake based on the perceptions of fishers present in selected sections of the uMngeni and uThukela catchments, KwaZulu-Natal, South Africa, a questionnaire interview method was used to obtain fishers' responses during 2021-2023. Findings from this study revealed difficulties in categorising fishers because of present inland water policies similar to the “fuzzy boundary” concept for inland fisheries globally, with some individuals identifying as recreational because of nondisclosure fears. Fishers’ knowledge illustrated the ecological imbalances between native (Labeobarbus natalensis) and invasive (Cyprinus carpio, Micropterus spp.) species, as well as the economic importance of fish based on market valuations, with C. carpio having a greater market value. Additionally, the results showed that subsistence fishers preferred river fishing compared with recreational fishers that targeted impoundments. Importantly, a considerable percentage of subsistence fishers ate fish mostly once a week or once a month. These results highlighted the importance of holistic management of water regulations, fish ecology, and economics to promote sustainable inland fisheries. Thirdly, an ecological assessment of fish communities in Midmar Dam and Henley Dam during the winter and summer seasons of 2022 and 2023 was conducted. Diverse fishing methods were used to capture a broad spectrum of fish species. Additionally, questionnaires were administered in selected areas of KwaZulu-Natal to gather complementary data on fish species in inland fisheries. A total of six fish species (three native species and three invasive species) were found in the two impoundments. Midmar Dam had significantly higher total fish catch than Henley Dam, highlighting the role of environmental factors such as dam size, depth, and temperature in shaping fish populations and influencing overall productivity. The KwaZulu-Natal yellowfish (L. natalensis) was significant to local inland fisheries, while invasive fish species posed challenges to maintaining the native fish species. These results emphasised that incorporating fish catch data into decision-making processes is crucial for making informed, science-based choices that ensure the long-term viability of fish populations and promote the overall health of freshwater ecosystems. In conclusion, the findings underscore the necessity for tailored fisheries management strategies that consider the unique environmental characteristics of each dam and the structures of fish populations. By integrating water quality data, catch-per-unit-effort (CPUE) results, and insights from fishers, decision-makers can formulate science-based approaches to preserve fish populations, support local livelihoods, and safeguard vulnerable communities dependent on subsistence fishing. Ultimately, successful conservation and sustainable management of fish populations hinge on informed decision-making prioritising ecosystem health and resilience across KwaZulu-Natal's freshwater habitats.