Identification, location and characterisation of spawning grounds and nurseries in the littoral zone of Lake Kivu (eastern DR Congo)

Abstract

Worldwide biodiversity is on the brink of extinction following the complete disappearance of many forest and freshwater vertebrates. This disappearance is closely linked to the reduction and disturbance of habitats, which should instead benefit from special conservation. In the case of lake ecosystems, fish spawning grounds remain the most vulnerable. This study aims to identify, characterise and locate fish spawning and nursery sites in Lake Kivu for better conservation. Sixteen sampling sites were selected along the shoreline of the Bukavu sub-basin. Physico-chemical parameters were measured in situ, and fish were captured using multi-mesh nets, identified and dissected, gonads observed and sexual maturity stages determined. Twenty-five fish species were identified, but 17 of these use the selected sampling sites as spawning and/or nursery. Eleven spawning and nine nursery sites were identified and located. Physico-chemical analyses showed that temperature (F = 2.124, p = 0.011), dissolved oxygen (F = 2.792, p < 0.001), depth (F = 5.915, p < 0.001) and transparency (F = 3.421, p = 0.004) were significantly different, which characterise each site and may be key factors in species distribution between spawning sites. Fish size–weight relationships indicate allometric growths. The results of this research contribute to empirical knowledge of fish spawning grounds.