- Personal harvest consumption was distributed evenly 

 over the time interval since the last successful trip 



• Fishing interval 



- Fishing frequency (days) is related to seasonal fisheries; 

 that is, interviewees did not report average time interval 

 for entire year but only for recent past. Therefore, cal- 

 culated consumption rates cannot be directly extrapo- 

 lated to a yearly basis. Fishing interval was set to 1 day if 

 unreported (Landolt et al. 1985). 



Despite the hmitation noted in the last item above, calculated con- 

 sumption rates can be extrapolated to an annual average rate by 

 multiplying the liju by 365 days and by a species-specific factor equal 

 to the fraction of the year a fishery is available. Determination of this 

 species-specific factor is somewhat subjective because of large 

 seasonal fluctuations of the harvest (e.g.. Appendix E of Landoh et al. 

 1985). These factors should be determined on a case-specific basis. 



In many cases, comprehensive data on fisheries catch and consumption 

 patterns are not available. For some risk assessment problems (e.g., 

 ranking of potential problem chemicals in aquatic organisms or 

 development of consumption advisories) extensive catch/consumption 

 data are not needed. Moreover, catch/consumption patterns undoub- 

 tedly vary over time. Extensive long-term monitoring of catch/con- 

 sumption for all areas of interest within a large water body may not be 

 warranted. Despite its obvious limitations, extrapolating consumption 

 data from one area (or time) to another may be a suitable approach 

 when: 



• Site-specific data are unavailable 



• Differences among areas (or times) are expected to be small 



• Precise estimation of average fish or shellfish consumption is 

 unnecessary to meet the study objectives. 



In the past, many risk analysts have simply assumed standard values for 

 food consumption rates based on previous analyses of dietary patterns 

 of the U.S. population (U.S. EPA 1980b; SRI 1980). Average values 

 for fish and shellfish consumption for the U.S. population generally 

 range from 6.5 to 20.4 g/day (Nash 1971; National Marine Fisheries 

 Service 1976, 1984; SRI 1980; U.S. Department of Agriculture (USDA) 

 1984; also see Appendix F). Most estimates include fish and shellfish 

 (molluscs, crustaceans) in marine, estuarine, and fresh waters, but 

 saltwater species form the bulk of consumed items. Most estimates also 

 include commercially harvested fisheries products. Also, estimates of 

 average U.S. consumption do not account for subpopulations in areas 

 such as the Great Lakes that consume large quantities (20 g/day) of 

 locally caught sport fish. 



An estimate of 6.5 g/day for consumption of commercially and recrea- 

 tionally harvested fish and shellfish from estuarine and fresh waters 

 was used by U.S. EPA (1980b) to develop water quality criteria based 

 on human health guidelines. The value of 6.5 g/day is an average 

 per-capita consumption rate for the U.S. population, including non- 



Assumed Consumption Rate 



57 



