Restricted genetic connectivity and conservation prospects of Bagrid catfish, Bagrus orientalis, populations in the Rufiji River basin, Tanzania

Abstract

The Bagrid catfish, Bagrus orientalis, historically sustained communities in the Rufiji River basin (RRB), Tanzania, but has rapidly declined due to high consumer demand and unsustainable fishing. Consequently, a Ramsar site was designated within the RRB, although its potential to revitalize overexploited populations beyond its boundaries is uncertain because of limited information on genetic connectivity. To address this uncertainty, 158 partial cytochrome oxidase subunit I sequences of B. orientalis were analyzed to quantify genetic connectivity in the RRB. We observed significant genetic differentiation, indicating limited connectivity among populations. Populations in the Ramsar site were genetically connected to those in the Kilombero Valley Floodplain (KVFP), but were distinct from those in Ruaha and Rufiji, which clustered separately. Our findings suggested the Ramsar site could revitalize overexploited KVFP populations, and emphasized the need for sustained efforts against its encroachment. However, limited genetic connectivity with Ruaha and Rufiji implied that conservation measures in the site might have restricted effect in these areas. Conservation efforts should extend beyond the Ramsar site, by promoting sustainable fishing and enhancing habitat connectivity in Ruaha and Rufiji.