The Influence of Lake Level Fluctuations on Fisheries in Lake Van

Abstract

The impact of hydrological regimes on the productivity in lake ecosystems has received considerable attention in recent decades. This study tested the hypothesis that water level fluctuations influence the fisheries productivity of Lake Van. Monthly water level data from 2000 to 2014 were obtained from Hydroweb and fisheries data corresponding to the same time period were acquired from the Turkish Statistical Institute. In order to test whether water level fluctuations demonstrated significant concordance with fish landings, landings data as a dependent variable, and seasonal water level amplitude and mean annual water level as independent variables were used in a linear regression analysis. The regression analysis proved insignificant results. The general trend of a linear decline, with a rate of -575 tonnes per year, observed in the landings did not match the seasonal and inter-annual water level variations which occurred in the lake during the same period. The consistently declining yields might result from a prolonged overexploitation and/or a constant recruitment failure. The estimated values of the seasonal and inter-annual relative fluctuation index (0.402 and 0.097, respectively) were rather low indicating that Lake Van is hydrologically stable with limited aquatic/terrestrial transition zone interactions and a relatively low nutrient load.