Decline of zooplankton food resources of Limnothrissa miodon fishery in Lake Kariba: Global warming‐induced ecosystem disruption by Cylindrospermopsis raciborskii

Abstract

AbstractThe present study was conducted on the Lake Kariba portion of the Middle Zambezi Biosphere Reserve. Magadza (2011) previously reported the pelagic Lake Tanganyika sardine (Limnothrissa miodon) fishery introduced into Lake Kariba was declining. This phenomenon was attributed to observed climate‐change‐related warming of the lake, facilitating establishment of the invasive Cylindrospermopsis raciborskii, currently the dominant alga in the lake. Chlorophyceae contribute to less than 10% of the phytoplankton biomass. Accordingly, it was postulated that its dominance in the lake resulted in a food chain disruption because this cyanobacterium was not preferred by zooplankton grazers. Accordingly, the present study examined the feeding behaviour of L miodon with reference to available food items in the Sanyati Basin of Lake Kariba. The results highlighted a virtual absence of entomostraca zooplankton in the Sanyati Basin of Lake Kariba, in contrast to previous findings of previous studies, the avoidance of C. raciborskii in the diet of L. miodon, as measured by the Ivlev electivity index, a low stomach fullness index, the movement of L. miodon to macroinvertebrates associated with the littoral zone as a food source, and unfavourable dietary indicators of L. miodon. These results collectively suggest a food deficit for L. miodon in Lake Kariba, leading to the previously observed decline in the lake fishery.