Sexual and spatio-temporal variation of Lake Erie Walleye growth and maturity: A consequence of multiple impacting factors

Abstract

Sexual and spatio-temporal variations have been observed in the life history parameters of many aquatic species and their causes have been related to harvesting pressure and environmental changes. This study aims to explore sexual, spatial and temporal variation in the growth and maturity through weight-at-length, length-at-age, and maturity-at-length relationships for Lake Erie Walleye (Sander vitreus) as a case to test some hypotheses. Hypotheses on whether harvest pressure and environmental changes (both local and global scale) caused the temporal changes of these life history traits were further diagnosed. Sexual and spatio-temporal variations in these life history traits were formulated using mixed-effects models. Our study found that geographic basin, sex, year and cohort all have substantial effects on the growth and maturity of Walleye based on survey data from 1989 to 2015. Multiple factors including water supply of Lake Erie, temperature, fishing pressure of Walleye, and global climate factors were found to correlate with the temporal variations of growth and maturity of Walleye significantly. Our findings should contribute to the future interpretation of Walleye life history variations and population dynamics. The methodology constructed in this study could be applied to explore the heterogeneity and impacting factors for other species in aquatic ecosystems.