Do Predators Influence the Distribution of Age-0 Kokanee in a Colorado Reservoir?

Abstract

Seasonal changes in reservoir conditions such as productivity, light, and temperature create spatiotemporal variation in habitat that may segregate or aggregate predators and prey, producing implications for the distribution, growth, and survival of fishes. We used hydroacoustics to document the diel vertical distribution of age‐0 kokanee Oncorhynchus nerka relative to environmental gradients at Blue Mesa Reservoir, Colorado, during May–August of 2002. Temperature, light, and zooplankton density profiles were examined relative to foraging conditions for kokanee and their primary predator, lake trout Salvelinus namaycush. Age‐0 kokanee displayed large diel vertical migrations in May despite the lack of an energetic advantage before reservoir stratification. Age‐0 kokanee minimized near‐surface foraging at this time, perhaps to avoid predation by visual predators, such as lake trout, in the well‐lit surface waters. Strong reservoir stratification in midsummer appeared to provide a thermal refuge from lake trout that the kokanee exploited. By August vertical migrations were shallow and most kokanee remained in the epilimnion throughout the day. Although the energetic implications of the late‐summer strategy are unclear, it appears that kokanee were responding to changes in their predator environment. A robust model for kokanee diel vertical migration across a range of systems should include a predator avoidance component.

The effects of temperature and predator—prey interactions on the migration behavior and vertical distribution of Mysis relicta

“…Functions used temporally stratified environment (Hardiman et al 2004). Annual, seasonal, and diurnal changes in exogenous factors such as light, temperature, and prey and predator density gradients can influence the organization and movement of a population through space and, consequently, the degree of spatial overlap with its prey and predators.…”

“…Modeling how changes in an organism's environment affect the organization and movement of a population through space is an important tool for understanding food web dynamics (Gotelli 2001;Hardiman et al 2004). The influence of different exogenous factors such as light, temperature, and predator/prey densities on the spatial distribution and movement patterns of zooplankton during diel vertical migration (DVM) has received considerable research attention (see reviews in Lampert 1989 andHays 2003); however, much of this DVM research has focused on conditions affecting the movements and spatial distributions of the ''average'' zooplankton in a migrating population and offers little insight into how these factors are impacting the entire vertical distribution.…”

Predator–prey overlap induced Holling type III functional response in the North Sea fish assemblage

“…A reduced area of prey distribution during the 1st quarter, however, could be also the consequence of a predator avoidance strategy (e.g. Hardiman et al 2004). …”

Vertical movements of coastal pike (Esox lucius)—On the role of sun basking

“…This behaviour is widespread among aquatic organisms, has been extensively studied in zooplankton (Rhode et al, 2001;Stich & Lampert, 1981) and fish (reviewed by Mehner, 2012), and has been explained in terms of predator avoidance (Stich & Lampert, 1981), optimising food intake, avoiding harmful UV-light (Rhode et al, 2001) and thermoregulation (Loose & Dawidowicz, 1994;Sims et al, 2006). The reverse pattern whereby individuals ascend at sunset and spend daytime at the surface before returning to deeper water at sunset also occurs (Hardiman, Johnson, & Martinez, 2004; here called reversed DVM and abbreviated rDVM), sometimes along with DVM in the same population (Hardiman et al, 2004). Most studies on DVM and rDVM have focused on pelagic species performing large shifts in depth, and less is known about the occurrence of DVM/rDVM in shallow and sheltered waters.…”