Results and lessons learned after eight years of monitoring gill net catches in the Zambezi and Chobe rivers 2010-2018

Abstract

Hay, CJ, Næsje, TF, Jacobs, FJ, Simasiku, EK, Tweddle, D. 2020. Results and lessons learned after eight years of monitoring gillnet catches in the Zambezi and Chobe Rivers. NINA Report 1791. Norwegian Institute for Nature Research. Freshwater fish play an important role in the livelihood of millions of people around Africa. Despite Namibia being classified as semi-arid with very little open water sources compared to other parts of the continent, freshwater fish are vital for communities living along the Kavango, Zambezi, Chobe and Kwando Rivers in North-eastern Namibia. Recent studies have shown a decline in high-value fish species and the commercialisation of the resource that is contrary to the Inland Fisheries Policy of Namibia that states that inland fish should be for subsistence and for the benefit of the local communities. The aim of the project was to record the fishing patterns and catch rates from the fishery through the use of local fishers from the area, to provide the necessary information to manage the fish resource sustainably for the benefit of the local communities for present and future generations. The data set was analysed by dividing the data into two groups. Data were grouped into those collected between 2010 and 2013 (the period where the fisheries reserves had probably not yet had an impact on the resource) and those collected between 2015 and 2018 the period where the protected areas may have had any impact on the resource. The fishery targets certain fish species, mainly from the family Cichlidae, driven by local and regional markets. This commercialisation resulted in increased fishing effort over the years causing a decline in these targeted fish species. Selective fishing by the fishers was emphasised when comparing the catches from that fishery with those from the survey fishing by the Ministry that are considered to be representative of the fish population in these rivers due to the wide range of mesh size gillnets used. Three species, Oreochromis andersonii, O. macrochir and Coptodon rendalli dominated the gillnet catches from the fishery contrib-uting 65.3% of the total Index of Relative Importance (IRI). There has been a decline in the collection of data by the fish monitors towards the later stages of the study. The timely follow-up and validation of data received from the fish monitors are recommended to ensure high quality data. The catch per unit effort both in number and in weight declined from the first to the second sampling period, except for Kalimbeza where the catch rate in weight remained the same, perhaps indicating that the establishment of a fishery reserve in the Kalimbeza area had had some beneficial impact in stemming the decline seen in the other areas. The maximum length of selected fish species (of the more important species recorded in the catches) also declined during the study period. It is recommended that the monitoring by the fish monitors continue, but that the quality of the data be regularly evaluated.