Forecasting Abundance of Quality-Size Yellow Perch in Indiana Waters of Lake Michigan

Abstract

Because the yellow perch Perca flavescens is a valuable sport and commercial species in southern Lake Michigan, forecasts for abundance of quality-size fish would be beneficial. We analyzed a time series of annual index trawl catch per unit effort (CPUE) in order to identify a model that could be used in forecasting. Relative abundance of stock-size (≥130 mm) and quality-size (≥200 mm) fish in Indiana waters of Lake Michigan varied by about two orders of magnitude from 1975 to 1996 and declined to a low level during the 1990s. Cross-correlation was used to identify a strong positive relation between CPUE of stock-size fish (S) in year t and quality-size fish (Q) in year t + 2. This relation was described by the linear model, √Qt+2 = 2.68 + 0.00572·St, and was due to survival and growth of sub-quality–stock-size fish from t to t + 2. The CPUE of quality fish predicted by the model closely approximated the trend in observed values. The model predicted that relative abundance of quality-size yellow perch in Indiana waters of Lake Michigan would remain extremely low in 1997 and 1998. This method of forecasting may be applicable to other populations for which adequate data are available.