Estimating fish production potentials using a temporally explicit model

A temporally explicit model is developed to predict the growth rate potential of fish in response to temporal fluctuations in both prey availability and temperature structure of the water column at both long (seasonal) and short (daily) time scales. The model was tested in a 20 m water column in Lake Ontario using chinook salmon (Oncorhynchus tshawytcsha) and alewife (Alosa pseudoharengus) as predator and prey species, respectively. Prey availability was assessed using acoustic techniques, while temperature was measured with a temperature–depth profiler. Chinook growth rate potential was significantly greater during June than during other sampled months. The latter months supported little to no chinook growth potential as a result of low overlap in conditions supporting growth. On a diel scale, chinook growth rate potential was typically greater during crepuscular and night periods than during the day. Results reveal that both short and long term variability of prey density and thermal structure impose stringent limits to fish growth potential and production, and that fish grow well only over finite periods. The temporally explicit model provides quantitative predictions of fish production potential as influenced by temporal changes in habitat quality and/or climatic conditions. In light of recent modifications to both local and regional climate conditions, and the localised nature of fish harvesting practices, this model can assist in setting realistic production estimates and future potential harvesting quotas.