Spatial and temporal differences in life history parameters of Rastrineobola argentea (Pellegrin, 1904) in the Lake Victoria basin in relation to fishing intensity

Abstract

The small pelagic cyprinid, Rastrineobola argentea (Pellegrin), commonly known as dagaa, accounted for 60% of the total fish biomass and 40% of the commercial catches in Lake Victoria in 2015. However, some aspects of the biology of species (from which management interventions are based) have changed since 1970s; and yet harvest regulations have remained the same. In this study, spatial and temporal variations in life history traits of dagaa in the northern portion of Lake Victoria were examined in relation to fishing intensity to offer guidance on possible adjustments in managing the fishery. The mean standard length halved, whilst the length at 50% maturity (Lm50) reduced by 27%, between the 1970s and 2015; however, the decline in Lm50 was more pronounced in males than females. Data collected between 2014 and 2015 showed that immature individuals are largely harvested from inshore and mid‐island areas, whilst most of the fishes caught in open water areas are largely mature irrespective of the size of the gear used. The causes of the changes in these biological aspects, and the need for policy adjustment, are discussed in the context of changes in fishing pressure.