Longline pelagic fishery assemblage in Kenya’s exclusive economic zone marine waters

Abstract

Fisheries catch data is important for monitoring and assessing anthropogenic and natural impacts on fish communities. Information on fish assemblages and diversity in the Western Indian Ocean region is limited complicating management of the fisheries. In this study, we determined longline catch rates, species diversity indices, species richness, and species evenness for fish assemblages of Kenya’s exclusive economic zone (EEZ) through experimental surveys conducted using a commercial Fishing Vessel (FV) between April and October 2020. A total of 110 sets were conducted where 4217 specimens of 50 species and 23 families were caught. The catches were mainly composed of Xiphias gladius (70.2%), Prionace glauca (7.8%), and Thunnus obesus (4.4%). About 15.0% of the catches were discarded of which 11.3% comprised of fish no commercial value. High levels of endangered, threatened and protected species forming 5.5% of the catches were observed. Catch rates were high for the dominant species in the three zones and differed significantly between months. Species abundance, richness, Shannon-Weiner diversity, and Simpson’s diversity indices were highest at the nearshore zone and during August. However, the diversity indices were not statistically different both for the zones and months. The nearshore zone exhibited higher species assemblages and greater species richness compared to other zones. This suggests the importance of prioritizing conservation efforts in the nearshore zone, as it serves as a critical habitat for diverse fish populations. Implementing protective measures can help preserve the biodiversity and sustainability of fish assemblages in the nearshore zone.