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Habitat coupling in a large lake system: delivery of a nearshore energy subsidy by an offshore planktivore
Citation:
STOCKWELL, J. D., D. L. YULE, T. R. HRABIK, M. E. SIERSZEN, AND E. J. ISAAC. Habitat coupling in a large lake system: delivery of a nearshore energy subsidy by an offshore planktivore. FRESHWATER BIOLOGY. Blackwell Publishing, Malden, MA, 59(6):1197-1212, (2014).
Impact/Purpose:
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Description:
In ecosystems where native fish species have been greatly reduced or extirpated, ecological processes such as transport of energy and nutrients across habitats or ecosystems may be lost to the detriment of remaining native species. We hypothesized that fall spawning migrations of rehabilitated Lake Superior cisco (Coregonus artedi) provide a spatial resource subsidy from the offshore pelagic to the nearshore benthic community over winter, in the form of energy-rich cisco eggs, when alternate prey production is likely low. We tested this hypothesis using fish population demographics, diet and stable isotope analyses, and bioenergetics modeling. Our results suggest that cisco eggs represent 16% of lake whitefish (C. clupeaformis) annual consumptive demand on a biomass basis, but 35% on an energetic basis because of their high energy density (> 10 kJ·g wet-1). Stable isotope analyses corroborated these results, and suggest other nearshore fish species also may rely on cisco eggs. Cisco eggs likely play an important role for post-spawn recovery and future reproductive output of whitefish. In the other Great Lakes, where cisco populations remain very low, the offshore-to-inshore ecological link present in Lake Superior has been replaced by non-native planktivorous species which spawn in spring, havesmaller eggs, and shorter incubation periods. Our work suggests rehabilitation of native fishes may provide additional benefits beyond simple predator-prey considerations.
