A MODEL SIMULATING THE IMPACT OF HABITAT SUPPLY LIMITS ON NORTHERN PIKE, ESOX-LUCIUS, IN HAMILTON HARBOR, LAKE-ONTARIO

The effects of life-stage habitat supply limits on fish populations ar e examined using a simple model of northern pike (Esox lucius). The mo del has submodels for spawning, fry, and juveniles + adults (1+). The modelling approach assumes the habitat supply for life stages can be e stimated and the key population processes in each life stage are contr olled by a saturation function of habitat supply. Only one life stage can limit the population at a time. Baseline simulations show that fry and juvenile-adult habitat supplies are more limiting than spawning h abitat, contrary to conventional wisdom. Paradoxically, spawning habit at may be rarer in absolute terms but other life stages need more of t he total lake ecosystem area to be suitable for the population to succ eed. Simulations based on a simple depth-based model of suitable habit at show how lake depth and hypsographic shape can affect population si ze and structure. Population sizes generated with various habitat supp ly scenarios overlap the reported range of values. The application to Hamilton Harbour shows how a dynamic model with habitat supply limitat ions can guide restoration efforts. Habitat management and conservatio n assessments must consider the dynamic population responses to varyin g life-stage habitat supplies.