Adaptive strategies of Nile Tilapia (Oreochromis Niloticus L.) to changing habitat

Abstract

Environmental changes are some of the factors that affect fisheries and biological characteristics of fishes. The Nile tilapia has biological characteristics that enable it to continue existing under various stressful environmental conditions. However, limited studies have examined the influence of habitat shrinkage on the morphological parameters and feeding behaviour of the Nile tilapia. The study examined some of the biological characteristics of Nile tilapia in lakes Wamala and Victoria (Uganda) to provide an understanding of their response to changing habitat conditions due to climate variability and changes. A total of 64 archived specimens were used in the study. Diet data of O. niloticus from Lake Victoria was obtained from Njiru et al., 2008. The study observed significant morphological differences between Nile tilapia from the two lakes with specimens from Lake Victoria being larger than those from Lake Wamala. The eye depth, cheek depth, snout length, lower jaw length, lower jaw width and dorsal fin base length were the key morphological parameters that seemed to adjust faster to the changing environment. These differences were attributed either to genetic or environmental factors, which seemed to play a major role in influencing morphology of Nile tilapia populations. With regard to feeding, O. niloticus in both lakes are still phytoplanktivorous. Nonetheless, specimens from Lake Wamala have included more zooplankton and higher plant material whereas Lake Victoria dwelling specimens included insects and mollusks in the diet. The results reflect an adjustment to the available dietary components that occur in habitat specific conditions. Therefore, the Nile tilapia has the capacity to adjust appropriately under conditions created by climate variability and changes in order to adapt to such environments. Proper management of the fish species can sustain the fisheries of Lakes Wamala and Victoria.