Influence of environmental factors on seasonal changes in clupeid catches in the Kigoma area of Lake Tanganyika

Abstract

An investigation into the relationship between the fluctuating physico-chemical environment and variability in fish catches in the Kigoma, Tanzania, area of Lake Tanganyika was conducted from January to December 2003. Catch per unit effort (kg fishing unit^–1 night^–1) showed two strong peaks in February and August–September, which followed peak catches of Stolothrissa tanganicae. Stolothrissa was the most abundant species in the pelagic catches, followed by the centropomid Lates stappersi and Limnothrissa miodon. Chlorophyll a concentrations correlated positively with high clupeid catches. Wind speed accounted for over 56.7%, of the variability in clupeid catches, while chlorophyll and phosphate, accounted for 44.0% and 55.4%, respectively. The results confirm seasonal fluctuations in pelagic fish catches and the dependence of the lake's hydrodynamics on the weather system prevailing in the lake region. However, fluctuations in nutrient concentrations in the photic zone were less apparent than in previous studies. Regression analysis indicated that environmental factors have a significant impact on the fluctuations of the pelagic fish catches. More multidisciplinary data are required to confirm the dependence of clupeid catches on environmental factors.