Yellow Perch Dynamics in Southwestern Lake Michigan during 1986–2002

Abstract

We examined the role of harvest in the collapse of the population of yellow perch Perca flavescens in southwestern Lake Michigan during the mid to late 1990s. After the great decrease in this population at that time, commercial fisheries in Illinois and Wisconsin were closed during 1996-1997 (and have remained closed), and stricter regulations were placed on recreational fisheries. Reproductive failure has been implicated as the primary cause of the population collapse, but the role of fishing in the collapse was not rigorously investigated in previous studies. We conducted an age-, size-, and sex-structured stock assessment of yellow perch to estimate population size and examine historical trends in fishing mortality in Illinois and Wisconsin waters of southwestern Lake Michigan. Model estimates indicated that yellow perch abundance in 2002 was less than 10% of the 1986 abundance in Wisconsin and about 20% of the respective population in Illinois. Annual mortality rates for females age 4 and older averaged 69% during 1986-1996 in Wisconsin and 60% in Illinois during 1986-1997, rates that are quite high for a species like yellow perch, which can live longer than 10 years. The estimated fishing mortality rates of adult females during 1986-1996 exceeded widely used reference points, suggesting that overfishing may have occurred. Fishing mortality rates decreased substantially in the late 1990s after stricter regulations were imposed on recreational fisheries and commercial fisheries were closed. We believe that unsustainably high mortality rates from fishing were a substantial contributing cause of the rapid decline of mature females in the mid-1990s. Spawning stock biomass in 2002 was at its highest level since the early 1990s despite relatively poor recruitment during the past decade. In part, this development reflects the fact that management actions have successfully reduced fishing mortality.

Measures of larval lake whitefish length and abundance as early predictors of year-class strength in Lake Michigan

“…Population models that recreate stocks and analyze changes in demographics have also been developed (Allen 2000;Wilberg et al 2005). For example, Wilberg et al (2005) found that fishing mortality rates were very high from the mid-1980s to the closure of the commercial fishery in 1997.…”

Reproductive health of yellow perch Perca flavescens in selected tributaries of the Chesapeake Bay

“…Historically, YP populations in Chesapeake Bay and the Great Lakes supported major recreational and commercial fisheries (Piavis, 1991;Wells, 1977). However, at selected sites or tributaries in both geographic regions, major population declines and a lack of recruitment have occurred (Yellow Perch Work Group, 2002;Clapp and Dettmers, 2004;Wilberg et al, 2005).…”

Gill net selectivity of yellow perch

“…Higher deviance residuals indicate that more fish were caught than would be expected by the model and lower deviance residuals indicate that fewer fish were caught than would be expected by the model. Because yellow perch growth rates are sexually dimorphic (Wilberg et al 2005), large mesh gill net selectivity was estimated separately for males and females as well as in a combined sex analysis. Selectivity in the micromesh was only fit to combined sex, as gender was difficult to determine with these smaller fish.…”

“…Mesh sizes are believed to be length-selective (Jensen 1986) and selectivity could be related to morphometric differences in the anterior portion of the fish. Yellow perch growth rates are also known to be sexually dimorphic (Wilberg et al 2005) and if these differences extend to those portions of the fish typically entangled in a gill net, we believe it may influence selectivity curves.…”