Fish habitat suitability and community structure in the equatorial Lake Naivasha, Kenya

D O Oyugi,P A Aloo,K M Mavuti,J R Britton,J E Ojuok

doi:10.1007/s10750-013-1785-1

Abstract

Habitat suitability indices indicate how fish species respond to different habitat types. We assessed effects of habitat characteristics on fish distribution in an equatorial lake, Lake Naivasha, Kenya, where habitats vary according to substrate, depth and turbidity. Using monthly data between 2008 and 2010 using multi-mesh gill nets, catch per unit effort was used as a relative abundance measure to identify how habitat variables drive fish distribution. The focus was on commercial fishes: two introduced species (Cyprinus carpio and Micropterus salmoides) and two naturalised species (Oreochromis leucostictus and Tilapia zillii). Analyses revealed distinct preferences for different habitat variables by all commercial species except for C. carpio. For example, O. leucostictus preferred shallow waters with silt–clay substrates whilst M. salmoides preferred deeper waters with sandy/rocky substrates. Conversely, C. carpio showed no specialised habitat requirements. Niche overlaps were significantly lower between O. leucostictus and its respective sympatric species than between other species, a likely result of its territorial behaviour. The continued environmental degradation of Lake Naivasha may imperil the preferred habitats of the niche restricted M. salmoides, O. leucostictus and T. zillii. By contrast, the ubiquity of C. carpio may facilitate their invasion, and consequently sustain their dominance in the lake’s commercial fishery.

Highlights

The spatial and temporal distribution of fish communities are determined by their functional requirements in relation to a range of abiotic factors in their environment
Distributions are often determined by niche requirements that result in the development of fish functional guilds (Noble et al, 2007)
The catch per unit effort (CPUE) of C. carpio and O. leucostictus was relatively low in the rocky lagoonal habitat at Crescent Lake, while M. salmoides was hardly recorded in the open waters and river mouth

Summary

Introduction

The spatial and temporal distribution of fish communities are determined by their functional requirements in relation to a range of abiotic factors in their environment. Distributions are often determined by niche requirements that result in the development of fish functional guilds (Noble et al, 2007). Studies suggest fish spatial distribution and habitat preferences are a function of habitat stability and migration patterns (e.g. by LoweMcConnel, 1999; Silvano et al, 2000). The net result is fish species generally developing well-defined spatial and trophic niches, and community assemblages and guilds (Hugueny & Paugy, 1995)

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