Are the Laurentian Great Lakes great enough for Hjort?

Abstract

Hjort's insights on marine fish recruitment and larval fish advection are presumed not applicable to freshwater lakes because most freshwater lakes are small. The Laurentian Great Lakes (LGL), however, are large enough for certain oceanic-type hydrodynamics, such as strong currents and upwelling, to affect the distribution and survival of larval fish and thus fall under Hjort's purview. However, there are evolutionary constraints because LGL species underwent an evolutionary bottleneck during glaciation, ∼10 000 years BP. We consider three narratives pertinent to both the spatial scale and the evolutionary time-scale of the LGL. The first reviews recent evidence of offshore advection and subsequent cross-lake dispersal of larval and juvenile yellow perch, a coastal demersal species in Lake Michigan. The second narrative suggests that biotic interactions, rather than spatial scale itself, could account for the transition in the critical period of Lake Michigan yellow perch period from a juvenile to a larval critical period. In the third narrative, we consider whether the deep LGL lack a significant native pelagic larval fish predator. We propose that the LGL, in combination with the older World's Great Lakes, present an opportunity to explore evolution and adaptation of fish to oceanic type physical conditions.