PCD Risk 1: A tool for assessing and reducing ecological risks of hatchery operations in freshwater

摘要

PCD RISK 1 is a flexible computer model designed to assist in assessment and reduction of ecological risks to natural origin fish from hatchery fish releases. PCD RISK 1 simulates predation, competition, and disease impacts on naturally produced salmonids caused by hatchery smolts in fresh water as they move downstream or residualize after release. Individual- based, the model relies upon user specified inputs of up to 45 variables, such as number and size of hatchery and wild fish, and water temperature. The model generates hatchery and natural fish of specified size distributions, then randomly pairs them for interactions for a specified number of days and encounters. Wild fish are subjected to predation if they are less than 50% the length of hatchery fish, otherwise they are subjected to competition. After all of the allowable competition and predation occurs, survivors are subjected to disease risk. The model can provide either deterministic or probabilistic output. Deterministic output includes the number and proportion of wild fish that die from predation, competition, disease, and from all interactions combined. Probabilistic output includes probability distributions of the number and proportion of mortalities, based on user-specified uncertainty input either as uniform or triangular distributions for any of several variables. If desired, the model can also quantify impacts for multiple age or size classes. Simulations of a variety of hatchery programs reveal that risks are highly diverse and that a variety of options are available to reduce risks.