ABSTRACT 



An oil spill fishery impact assessment model composed of an oil spill fates 

 model, a continental shelf hydrodynamics model, an ichthyoplankton transport and 

 fate model, and a fishery population model has been applied to the Georges Bank — 

 Gulf of Maine region to assess the probable impact of oil spills on several im- 

 portant commercial fisheries. The model addresses direct impacts of oil on a 

 commercial fishery through hydrocarbon-induced egg and larval mortality. This 

 early life stage mortality is estimated by mapping the dynamic spatial/temporal 

 intersection of the surface and subsurface oil concentrations resulting from 

 the spill, and juxtaposing dynamic maps of the developing eggs and larvae. 

 Ichthyoplankton entering an area with hydrocarbon concentrations in excess of a 

 specified threshold are assumed lost. Model output is given in terms of 

 differential catch, comparing the non-impacted and the hydrocarbon impacted 

 fisheries. 



Simulations of the impacts of monthly oil well blowouts at a site in the 

 North Atlantic Outer Continental Shelf (OCS) lease area have been completed for 

 Atlantic herring and Atlantic cod. Results of these case studies clearly show 

 the importance of spill timing and location, spatial and temporal spawning 

 patterns, and details in the hydrodynamic transport field as critical factors 

 in determining spill impact. Model system sensitivity studies to incremental 

 losses of a given year class and the influence of the Georges Bank gyre on 

 impact are also presented. 



INTRODUCTION 



One of the major concerns associated with Outer Continental Shelf (OCS) 

 hydrocarbon exploration and development, is the release of oil into the marine 

 environment, and the resulting short- and long-term effects on the ecosystem. 

 Of particular concern in productive fishing areas such as Georges Bank, is the 

 impact of spills on the higher trophic levels, and more specifically on com- 

 mercially important fish species. Realistic assessments of the impact of spills 

 on these species are essential if the fish and mineral resources of these shelf 

 regions are to be managed rationally. 



An objective assessment methodology is clearly needed to support a rational 

 resource management policy. The methodology selected should be able to (1) 

 reliably quantify impacts, (2) appropriately represent the space and time scales 

 of the pollutant events of interest, (3) take advantage of existing environmental 

 data and therefore minimize the need for additional data, (4) be formulated 

 within the framework of management needs, (5) address a well-defined ecological 

 unit, (6) limit the number of empirical formulations and, (7) be trans ferrable 

 to other geographical areas and species. These requirements are intended to 

 assure that the approach to impact assessment is credible, useful, and affordable. 



Scientists addressing biological impact assessment problems have developed 

 three major model methodologies, characterized here as the statistical, the 

 indicator species, and the ecosystem dynamics approaches. 



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