Hydroacoustic assessment of fish resources in three reservoirs: The effects of different management strategies on fish density, biomass and size

Abstract

To assess the effectiveness of different fisheries management strategies in freshwater reservoirs in China, we use hydroacoustic techniques to quantify the density, biomass, size, and patterns in distribution of fishes in Wanyao (WY), Laohutan (LHT), and Qiaodun (QD) reservoirs (Zhejiang Province), each of which has been managed differently. Significant differences in density, biomass and size distribution are reported among these reservoirs. In the overfished WY, fish density and biomass are lower than that in LHT (P < 0.05). In QD, where fishing has been prohibited from 2011 to 2015, fish density and biomass are higher than in LHT (P < 0.05). In LHT, where the larger-size fish (>48 cm) were caught and the smaller ones were left in the reservoir, proportionally more mid-sized fish (˜11–48 cm, 84.63%) are present than smaller or larger fish. Our research improves the understanding of the relationships between fisheries management strategies and the density, size and biomass of fishes in reservoirs.We demonstrate that fisheries management strategies play an important role in maintenance of fish resources in reservoirs, and that hydroacoustics techniques can be successfully used to quantify fish density and size distributions.