Modeling yellow perch (Perca flavescens) abundance in inner Saginaw Bay, Lake Huron, 1971--2001: The importance of density independent and density dependent processes

Yellow perch (Perca flavescens) in Inner Saginaw Bay, Lake Huron, have exhibited wide variations in total abundance over the last thirty years. Abundance was low in the 1970s, high in the 1980s, and low in the 1990s. Abundance increased gradually from the late 1970s to the early 1980s, but decreased abruptly at the end of the 1980s. Fifteen competing hypotheses involving density independent survival, density dependent survival, and/or density dependent growth from age 0 through age 5 were modeled and evaluated using a method that minimized residual summed squares between observed and modeled catch per unit effort at age, 1971–2001. Model strength was measured using Akaike Information Criteria and Akaike weights. The top-ranking models showed the following processes to be important in determining the abundance of this yellow perch population: (1) compensatory survival at age 2–4, (2) compensatory survival at age 0, and (3) compensatory survival at age 1; however, a model with constant survival and growth rates ranked the highest. Compensatory survival at age 2–4 ranked second and is supported by other studies; however, compensatory survival at age 1 is best supported by auxiliary data in this study. In addition, the modeling process itself indicated that the dramatic drop in abundance in 1991 could only be accurately simulated if all age groups experienced a significant reduction in survival, suggesting the shift in abundance at this time was caused by a mortality event that affected all age groups. The top four models also predict total abundance to gradually increase in the future, an increase that could be hastened with a reduction in fishing mortality.