Recruitment of Yellow Perch ( Perca flavescens) Affected by Stock Size and Water Temperature in Lakes Erie and St. Clair, 1965–85

Abstract

Two influences on recruitment of yellow perch ( Perca flavescens) were considered: parental stock size and spring water temperatures. The data for this analysis were obtained from two sources. First, from samples of trawl catches (near bottom) from April to October (1965–85) in the western, central, and eastern basins of Lake Erie, and from Lake St. Clair and second, from gillnet catches from April to July in the three basins of Lake Erie (1978–86). The relative abundances (CPUE) of stocks in these study areas were as follows: western > St. Clair > eastern > central basin. Degree-days and mean water temperatures of the basins were ranked as follows: St. Clair > western > central > eastern basin. Rates of warming of water were greatest in the western basin, followed by St. Clair, central basin, and eastern basin. The rates of increase in water temperature (April to June) were positively related to average water temperatures and total degree-days (above 0°C. Only in the western basin of Lake Erie could the variations in recruitment to age 1+ be apportioned to the effect of parental stock size (12%) and water warming in the spring (51%). Recruitment at age 0+ (young-of-year(YOY)) was explained also by both warming rate (17%) and parental stock size (12%) for the samples from the western basin. The pooled data obtained from samples of catches in the gillnets indicated that only parental stock size (19%) determined the abundance of perch at age 1+ yrs-old. The relative abundance of yearlings was related to the abundance of YOY perch in the previous year in only the central and western basins (trawl sample). The dependence of recruitment on the density of the parental stock was evident from the regression of the ratio of recruits (age 1 +) to spawners on parental stock size in the combined trawl samples from Lakes Erie and St. Clair, and in the separate samples from the eastern and central basins of Lake Erie and Lake St. Clair. Similarly, recruitment at age 0+ (YOY) was also shown to be density-dependent in all but the western basin of Lake Erie. The coefficients obtained by regressing recruitment (0 +, 1 + years) on stock size were significant and less than 1 in the pooled sample from the western basin and St. Clair, indicating density-dependent recruitment.