MONDAY, February 13, 2006
3:00 - 4:00 p.m.
CAB 657

Caroline Bampfylde

Biological control through intraguild predation: a case study in the dynamics of rusty crayfish and smallmouth bass.

Rusty crayfish are aggressive invaders of the Great Lakes ecosystem. When introduced into new lakes, they drive down native crayfish populations, reduce the density and abundance of aquatic plants, interfere with fish recruitment, and overgraze algae and eliminate snails. Recently, the population density of rusty crayfish in some lakes has far exceeded previously recorded levels. Management of this nuisance species is necessary.

The interaction between rusty crayfish and indigenous smallmouth bass fish involves a mixture of competitive and predator-prey relationships. Juvenile smallmouth bass compete with many life stages of the invasive rusty crayfish. However mature smallmouth bass are major predators of rusty crayfish. Intraspecific interactions for rusty crayfish also include cannibalism and resource competition.

We used mathematical models to investigate possible biological control of rusty crayfish by smallmouth bass. The method is to apply perturbations to shift the dominance in a competitive bottleneck from rusty crayfish to smallmouth bass. The perturbations include crayfish trapping and changes to lake fishing regulations.

The modelling approach included a spatially independent and a spatially explicit model. We use bifurcation analysis and travelling waves to investigate the dynamics of the system, which suggests methods for effective control.

The combination of predation and competition for resources is characterised as intraguild predation (IGP). We will provide further examples where the mathematical framework for IGP can be applied to understand the control of invasive species, pest species and range expansions.

Refreshments will be served following the seminar from 4:00 to 5:00 p.m. in CAB 549