Analysis and forecast of Pontic shad (Alosa immaculata) catch in Danube River

The relationship between annual water level of Danube and annual catches of Pontic shad (Alosa immaculata, Bennett 1835) in Romania were analyzed. For analysis of long term data on the Danube water level and Pontic shad catch (1920-2013), combinations of different methods were applied using programs Statistica, SPSS 13.0 and MATLAB 6. Periodograms, containing cyclic patterns, were obtained using Fourier analysis. Significant oscillations were determined with Fisher-Whittle’s tests and residuals were calculated after subtracting these significant oscillations from the original signals. Autoregressive moving average (ARMA) models of residuals were finally acquired. Results indicated that water levels, and specially those in the May, greatly explained the fluctuations of Pontic shad catch. Annual landings vary greatly and appear to be cyclic. Varying river flow is considered to be one of the most important factors that cause fluctuations in the size of populations. Forecast indicates gradually increase of the catch in next decade. Towards 2033, the catch will decrease. Estimated as vulnerable species of fish by the IUCN, development of the forecasting model of the future catch oscillations could be very helpful to regulate fishing effort.