Project
An evaluation of whitefish recruitment limitation at the larval stage across gradients of trophic states, invasive mussels, and temperature in large lakes of North America and Europe
Whitefishes support economically and culturally valuable fisheries in North America and Europe. However, whitefish populations have exhibited alarming declines in many lakes on both continents. In the Great Lakes, long-term trends in lake whitefish year-class strength (YCS) are strongly explained by declining productivity and increasing temperature, consistent with hypotheses identified in Europe. However, the mechanism(s) for how and when these processes regulate recruitment remain unclear, leading us to test three key hypotheses at the global scale: (H1) declining pelagic productivity resulting from or exacerbated by invasive dreissenid mussels results in zooplankton resources insufficient to support larval growth and presumably survival; (H2) warmer spring temperatures increase basal metabolic rates and exacerbate slower growth due to lower prey resources under declining productivity; and (H3) YCS is positively related to larval growth rate. We are testing these hypotheses across North American and European large lakes that vary in trophic state, temperature, and invasive mussels. We are using larval coregonid foraging and bioenergetics models and in situ temperature and zooplankton data from each lake to estimate growth rate each year and then compare growth rate to corresponding YCS indices. Our cross-system, cross-continent framework contrasts larval growth rates as a function of varying abiotic and biotic conditions across lakes and within lakes over time and their relationships to whitefish YCS. Our research will help elucidate the mechanistic relationship(s) that underlie previously identified correlations among whitefish YCS, productivity, and temperature.