Diel vertical migration in the Lake Superior pelagic community. II. Modeling trade-offs at an intermediate trophic level

Abstract

Several hypotheses have been proposed to explain diel vertical migration (DVM); however, they have generally been applied to DVM behavior of a single trophic level. We evaluate the costs (predation risk) and benefits (foraging rate and growth rate potential) of different hypothetical and observed DVM trajectories for a three-level pelagic food chain in Lake Superior containing opossum shrimp (Mysis relicta), deepwater ciscoes (Coregonus spp.), and lake trout (Salvelinus namaycush). Lake trout appear to be maximizing foraging and growth rates by tracking vertically migrating ciscoes, while the DVM trajectories of ciscoes suggests a trade-off between predation risk and growth. For ciscoes, two alternative DVM trajectories both minimize the ratio of risk to growth: a shallow trajectory that follows low light levels down to 80 m during the day and a deep trajectory (below 150 m) that tracks highest Mysis densities. Observed cisco DVM trajectories appear to follow the shallow high risk – high growth trajectory in 2001, but switch to the deep, low risk – low growth trajectory in 2004 when lake trout density was higher and the density of ciscoes was lower.

Differentiation of deep-water lake charr Salvelinus namaycush in North American lakes

“…2c), like that of Lake Superior, inhabited deeper water than the lean, and was fatter than the lean as evidenced by its lower percentage buoyancy. The high fat levels in Lake Superior siscowets are hypothesized to be an adaptation for reducing the energetic cost of extensive vertical migration (Henderson and Anderson 2002;Hrabik et al 2006;Jensen et al 2006). A siscowet-like, fat (low percent buoyancy) lake charr was not observed by the author during field surveys of the McTavish (northeast) arm of Great Bear Lake during 2004.…”

Laboratory-derived light and temperature preferences of juvenile mysid shrimp, Mysis diluviana

“…The most frequently observed pattern is for smaller individuals to select for warmer, higher light habitats than larger adults, particularly in those systems in which the largest members of the population are at the highest risk of planktivorous fish predation (Lythgoe, 1979) or in those species with high rates of cannibalism (Bonnet et al, 2004;Eiane and Ohman, 2004). Smaller individuals also typically maximize growth rates at higher temperatures than their adult counterparts (e.g., Fiksen and Giske, 1995); thus, the ratio between mortality risk and growth gains in juveniles tends to be minimized at depths nearer to the surface than adults (e.g., Clark and Levy, 1988;Jensen et al, 2006).…”

Importance of light, temperature, zooplankton and fish in predicting the nighttime vertical distribution of Mysis diluviana

“…Werner & Gilliam 1984) to mortality risk (μ). Ratios between gain and risk have been used to predict both the timing and amplitude of migration in a variety of fish (Scheuerell & Schindler 2003, Jensen et al 2006) and invertebrate species (Fiksen 1997, Liu et al 2003). These models assume that an organism will always choose a depth that minimizes the ratio between growth gains and perceived mortality risks.…”