Fish Community Dynamics in Northeastern Lake Ontario with Emphasis on the Growth and Reproductive Success of Yellow Perch ( Perca flavescens) and White Perch ( Morone americana), 1978 to 1997

Abstract

Fishes were assessed in Guffin, Chaumount, and Black River bays in northeastern Lake Ontario with a 7.9-m (headrope) bottom trawl during late September and early October, 1978 to 1997. Fish density declined in the early 1990s with sharp declines in abundance of spottail shiner ( Notropis hudsonius), trout-perch ( Percopsis omiscomaycus), and johnny darter (Etheostoma nigrum) occurring in 1993 to 1995. Rising numbers of piscivores, walleye ( Stizostedion vitreum) and double-crested cormorant ( Phalacrocorax auritus), increased predation pressure, presumably acting in concert with oligotrophication to lower fish density, particularly after 1991 when large numbers of adult alewife ( Alosa pseudoharengus) no longer migrated to the northeast basin in spring. Annual mortality of yellow perch ( Perca flavescens) from age 2 to 5 rose from 33% in 1980–83 to 65% in 1992–95 and was positively related to piscivore numbers ( P = 0.01, r = 0.96, n = 5). Annual mortality of yellow perch from age 0 to 2 also peaked in 1992–95. Abundance of yellow perch YOY in fall varied 40 fold and was not related to water warming in spring ( P = 0.45, r = −0.19, n = 18) but was negatively related to the abundance of adult alewives in spring ( P = 0.04, r = −0.49, n = 18). Although yellow perch produced moderate to strong year classes each year during 1991–95, stock size failed to increase because of rapidly accelerating mortality. Fully 85% of the variation in mean length of yellow perch YOY was explained by a multiple regression model which included YOY abundance, mean total phosphorus, and cumulative degree days > 13.5°C ( P < 0.01, n = 15). Abundance of white perch ( Morone americana) YOY varied nearly 200 fold and was not related to water warming or spring alewife abundance ( P > 0.15). Variation in mean length of white perch YOY was related to cumulative degree days > 15°C ( P < 0.01, r = 0.69).