Operational, environmental, and resource productivity factors driving spatial distribution of gillnet and longline fishers targeting Nile-perch (Lates niloticus), Lake Victoria

Operational and environmental factors limited available resource space of gillnet and longline fishers targeting Nile perch in the Speke gulf and open lake of southern Lake Victoria and drove their encounter rates with patches of fish resulting in gear specific distributional patterns. Catch-rate patterns were similar by region and gear: large (>50 cm) Nile-perch densities increased over distance from homeport and deeper in the water column while small Nile perch (<50 cm) densities decreased. Effects of season, (setting) depth and region were present but small and obscured by high variation in daily catch-rates and individual fisher strategies. Both fisheries distributed themselves over the size-productivity spectrum of Nile perch but reacted differently to patterns in size distribution of Nile perch: gillnetters focused more on numbers of productive juveniles between 30 and 60 cm at on average 5 km distance (59 min travel time) from homeport and longliners on larger sized 40-80 cm Nile perch deeper in the water column at 7 km (108 min). Sampled fishers likely were representative of most of the Nile perch fisheries. If so, this means that fishing pressure is mainly exerted on nearshore lake areas, and more lightly fished offshore areas may act as a refuge for adult Nile perch. Total catch-rates by gear were generally equalized over the resource space, increasing slightly with distance from homeport, according to ideal free distribution predictions. Nile perch fishers on Lake Victoria appear to distribute themselves according to the underlying productivity distribution of the resource within the constraints of their available resource space. (C) 2018 International Association for Great Lakes Research. Published by Elsevier B.V. All rights reserved.