Assessment of the impacts of artisanal fishing gears on nearshore fish stocks along coastal waters off the Kilwa–Mafia seascape in Tanzania

Abstract

Small-scale fisheries (SSF) in many parts of the worlds are known to support the livelihoods of millions of coastal communities. Also, SSF are characterized by being multispecies and multi-gear, a fact that poses management and conservation challenges to this critical natural capital. Little is known about the catch composition and the impact of the artisanal fishing gears to the fishery in Tanzania. The current study assessed catch composition and effects of three major fishing gears namely handlines, gillnets, and traps using data collected from 2008 to 2011 along the Kilwa–Mafia seascape in Tanzania. A total of 214 species, belonging to 46 families, were recorded of which 15 species accounted for 82% of the catch in all gears combined. The most common species recorded were halfbeaks (Hemiramphus far), marbled parrotfish (Leptoscarus vaigiensis), sky emperor (Lethrinus mahsena), pink ear emperor (Lethrinus lentjan) and shoemaker spinefoot (Siganus sutor). Lethrinidae was the overall dominant group, contributing to more than 30% of the total catches. The findings suggest the presence of gear selectivity on individual species, particularly Leptoscarus vaigiensis (20.4%), H. far (59.53%) and L. mahsena (31.8%) which dominated catches from traps, gillnets, and handlines, respectively. Furthermore, productivity and susceptibility analysis (PSA) indicates that L. lentjan is at high risk of depletion, suggesting a gear-based management approach is needed.