Optimising the stocking density of Australian bass: Estimating carrying-capacity in freshwater impoundments.
There is a need for reliable ecological models for optimising the stocking of fish in Australian freshwaters. The optimal stocking density maximises the contribution of fish to a fishery and occurs at a fisherys carrying-capacity. We aim to optimise the stocking of Australian bass (Macquaria novemaculeata) in freshwater impoundments in SE Australia, using three complimentary approaches:
1) We will use ideal free distribution theory to estimate carrying-capacity by observing the rates of dispersal (also termed self-thinning) of stocked fish. We will stock patches of various habitat types with a range of densities of bass and observe and electronically-track their rates and magnitudes of movement. This will be replicated within and between impoundments.
2) We will use a general numerical predator-prey model based on the energetic needs of bass and their preys availability to estimate the optimal stocking density and predatory impact of stocked bass in select impoundments. The model incorporates published models, life-history parameters, and size-specific growth and diet data, and a spatial component, based on the spatial distribution of bass (elucidated in part 1.) and the distribution of their essential habitat.
3) We will stock bass in custom enclosures in impoundments at a range of densities in a factorial, replicated design, to estimate each impoundments carrying-capacity. Over-stocking will force density-dependent limitations, measured by decreased growth and/or survival of bass. So, by measuring the growth and survival of bass at treatment densities, we will converge on each impoundments optimal stocking density. These densities will be compared with the modeled estimates from our predictive stocking model.