Prey selection and vulnerability to predation in age-0 pallid sturgeon (Scaphiryncus albus).

William E French

            Two of the most important parameters of population dynamics in fishes are recruitment and mortality (Ricker 1975).  Mortality during the early life histories of fish is especially important (Rice et. al. 1987), and the majority of mortality during this period can be attributed to predation and starvation.  As fish grow, they often undergo ontogenetic diet shifts where the preferred prey type changes.  These shifts are often related to changes in body morphology and habitat of juvenile fishes.  Predation on young fish is primarily controlled by size ratios between predators and prey, as well as predator gape.  However, other factors such as the development of predator avoidance behavior and environmental conditions also affect predation vulnerability of young fishes.  The pallid sturgeon Scaphiryncus albus is a federally listed endangered species native to the Missouri River system.  Little is known about the population dynamics of pallid sturgeon, particularly factors affecting survival during the early life history.  I will conduct a series of laboratory experiments to examine patterns of juvenile pallid sturgeon prey selection and predation vulnerability.  I will identify ontogenetic diet shifts in young pallid sturgeon through prey selection experiments using invertebrates and fish taxa as prey.  Prey selection will be quantified using Chesson’s α index of selectivity.  I will examine the vulnerability of age-0 pallid sturgeon to predation by three common Missouri River predators.  I will also examine the effects of velocity and turbidity on pallid sturgeon predation vulnerability.  These experiments will be conducted in living stream arenas (simulated pool and riffle habitat) that allow me to manipulate both velocity and turbidity.  Results from these experiments will allow managers to better direct habitat restoration, identify appropriate habitats for supplemental stocking, and predict effects of water management alternatives on the survival of young pallid sturgeon.

Rice, J. A., L. B. Crowder, M. E. Holey.  1987.  Exploration of mechanisms regulating larval survival in Lake Michigan bloater: a recruitment analysis based on characteristics   of individual larvae.  Transactions of the American Fisheries Society 116:703-718

Ricker,W. E. 1975. Computation and interpretation of biological statistics of fish populations.  Bulletin of the Fisheries Research Board of Canada 191: 382.