| Summary: | This work describes the formulation of a model system designed to estimate the impacts of offshore oil spills on a commercially fished stock. A fishery model of the cod (Gadus morhua) on Georges Bank is implemented on a computer in conjunction with an ocean transport model to simulate the distribution of eggs and larvae, and an oil spill behavior and fates model. The fishery model is unusual in that explicit estimates of spatial and temporal ichthyoplankton distributions are made, necessitating detailed biological resolution during the early developmental stages. The ocean transport model is composed of a drifter--inferred long term advective component superimposed on a wind--driven component input through a two dimensional analytic model, and isotropic dispersion simulated via a statistical random walk process. Modeled events include a tanker accident and an oilwell blowout. Using a parameter variation approach, ranges of impacts in terms of reduced catch in the long term are estimated, and primary sources of error are analyzed. Impact estimates for a 30 day oilwell blowout are below $7 million U.S. (1979) at current exvessel prices of cod. Sensitivity of model predictions to values of oil entrainment rates, toxicity threshold coefficient, and pre-recruit mortality rates are compared, the latter being of greatest importance. It is demonstrated that, given a passive constituent analogy for ichthyoplankton transport, the time rate of density reduction due to mortality must be two to four orders of magnitude greater than that due to disersion over a three month pelagic period. Directions for furture research are discussed.
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