fisheries are provided by Landolt et al. (1985), McCalium (1985), and 

 National Marine Fisheries Service (1986). Details of methods will not 

 be presented here, except to emphasize some important considerations 

 for calculating consumption rates. Examples of analyses of catch/con- 

 sumption data can be found in Puffer et al. (1982) for coastal waters of 

 southern California, in Landolt et al. (1985, 1987) for Puget Sound, in 

 Belton et al. (1986) for New York Bay and Newark Bay, and in National 

 Marine Fisheries Service (1986) and companion documents for other 

 areas of the U.S. 



Lindsay (1986) reviewed alternatives to field survey methods, including 

 use of food diaries and dietary recall. Gartrell et al. (1986a,b) described 

 methods used by FDA in their total diet studies to estimate rates of 

 consumption of various foods. Note that the results of the FDA total 

 diet studies are of limited use in the present context because fish are 

 grouped with meat and poultry. Estimates of seafood consumption 

 used by FDA to calculate average intake of methylmercury for exposed 

 portions of the U.S. population were based on a diary survey sponsored 

 by the Tuna Research Foundation (Tollefson and Cordle 1986). Sup- 

 plementary information on analysis of fisheries consumption data can 

 be found in SRI (1980). 



The average rate of consumption of fish or shellfish is the key exposure 

 variable for use in subsequent steps of risk assessment. Consumption 

 rates should be expressed in terms of g/day and meals/year [meals/year 

 may be calculated from g/day by assuming an average meal of fish or 

 shellfish equals about 150 g (0.331b) if the average meal size is un- 

 known]. Average consumption rate for each harvest species is calcu- 

 lated from field data according to the following steps: 



• For each successful angler trip, calculate the weight of harvest 

 by species based on number and total weight harvested per 

 household 



• Calculate mean harvest weight consumed per person per time 

 by: 



- Dividing the total harvest weight for each species by the 

 number of consumers in household and by the days 

 elapsed since last meal from the same area 



- Multiplying the value obtained in the preceding com- 

 putation by a factor to account for the proportion of 

 cleaned weight to total weight [according to Landolt et 

 al. (1985), this factor equals about 0.5 for squid and 

 crabs, 0.3 for fish, and 1.0 for shucked clams; these 

 estimates should be verified or replaced by local data] 



• Calculate mean consumption rate per person by geographic 

 harvest area, by subpopulation, and by total exposed popula- 

 tion. 



Note that the above method (cf. Landolt et al. 1985, 1987) may provide 

 a biased estimate of average consumption rate due to its dependence 

 on a short-term observation (i.e., time since last meal). Averaging of 

 data over a longer time period might be preferable, but such data may 

 be more susceptible to biases from inaccurate recall of consumers 

 (interviewees). Harvest weights should generally be determined direct- 

 ly rather than from length measurements. However, for shellfish and 



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