A Preseason Simulation Model for Fisheries on Fraser River Sockeye Salmon (Oncorhynchus nerka)

Abstract

Using a preseason fishery simulation model that refines previous reconstruction models, we explored the effects of various fishing regimes on annual catch and escapement of the major stocks of Fraser River sockeye salmon (Oncorhynchus nerka). To obtain harvest rate parameters for the model, we analyzed historical fishery catches to develop a theory of fish movement through time and space. Harvest parameters were then calculated using run reconstruction techniques. The model uses a daily time step to move fish sequentially through the major fishing areas. Fishing scenarios may be examined in the preseason to aid in developing annual management plans. Inputs of run size, timing, and diversion rate via Johnstone Strait are used to calculate run-timing curves which are normally distributed. The proportion of sockeye migrating via the northern approach or Johnstone Strait diversion, is shown to be a major factor in the sensitivity of fishing plans to altered input parameters. Clearly stated goals and objectives for spawning escapement and allocation of catch by stock groups are essential in the modelling process. The model permits managers to examine underlying assumptions and biological, economic, and social requirements centred on the harvest of these stocks.