Understanding Annual Variation in Female Yellow Perch Age-At-Maturity in Lake Erie

Yellow perch Perca flavescens, an important commercial and recreational fish species in Lake Erie, exhibits high annual variability in demographic rates. For example, over the last 20 years (1990-2009), the annual percentage of age-2 female yellow perch that are mature has ranged from 6% to 94 %, and the contribution of age-2 yellow perch to population egg production has ranged from 1% to 70% of the total in a given year.  To understand what drives this temporal variation in the reproductive contribution of age-2 fish, we 1) quantified the annual variation in age and size at maturation, 2) related age at maturation to annual growth rates of young ages, and 3) used environmental data to explain age-specific annual growth rates. 

Using length, age, and maturity data collected during annual Ohio Division of Wildlife fall bottom-trawl surveys from 1990-2003, we used logistic regression to estimate both the total length and age at which 50 % of females were mature for each year class. Total length at 50 % maturity across years ranged from 151 to 172 mm (164.94   ± 1.4 mm; mean ± SE ), and age at 50% maturity ranged from 1.1 to 2.3 years (1.61 ± 0.1 years; mean ± SE). We found that percent mature at age-2 was strongly correlated to length at age-2 (r² = 0.863).  Next, we used age-specific growth increments (calculated as differences in mean total lengths) for fish of age 0 (spring hatch through October of first year), 1 (October age-0 to October age-1), and 2 (October age-1 to October age-2) to explain age at maturation.  Both age-0 (r²=0.259) and age-2 (r² = 0.568) growth explained a significant proportion of the variation in age at maturation across years. Finally, we found that age-0 growth was positively correlated to annual growing degree days while age-2 growth was negatively related to average bottom dissolved oxygen (July-October).  Our results suggest a link from abiotic effects (temperature and dissolved oxygen) through growth rate and age-at-maturation to reproductive contribution of age-2 yellow perch in Lake Erie.