A summary of indicator species recommended by Tetra Tech (1985b) 

 for monitoring of chemical residues in tissues of marine and estuarine 

 organisms is shown in Figure 4. Many of the recommended indicator 

 species are associated with soft-sediment substrates. Contact with 

 sediments by such species may lead to body burdens of contaminants 

 that are high relative to those in pelagic organisms of similar lipid 

 content and size. However, the relationship of contaminant concentra- 

 tions in demersal (bottom-dwelling) vs. pelagic (open-water) or- 

 ganisms is difficult to predict without extensive data. As shown by Tetra 

 Tech (1986c), English sole may be used as an indicator of the order- 

 of-magnitude contaminant concentrations that would be expected in 

 edible tissues of pelagic fish species in Puget Sound, WA. However, 

 relative contamination among species may vary among bays within 

 Puget Sound. For example, in Commencement Bay, the average PCB 

 concentration in muscle of English sole was about twice that in recrea- 

 tionally harvested pelagic species (Pacific cod. Pacific hake. Pacific 

 tomcod, rockfish, walleye pollock, and white-spotted greenling; based 

 on data from Gahler et al. 1982). In Elliott Bay, the average PCB 

 concentration in angler-caught English sole was about 0.4 times that in 

 harvested pelagic species (sablefish, squid. Pacific cod, Pacific hake. 

 Pacific tomcod, rock sole, and rockfish; based on data from Landolt et 

 al.l985). Site-specific data are needed to evaluate contamination of 

 potential indicator species relative to contamination in other species 

 of interest. 



Apparently, no comprehensive review of target species for bioac- 

 cumulation studies in lakes and streams has been conducted. Salmon 

 and trout (Salmonidae), perch (Percidae), and sunfish (Centrar- 

 chidae) species may be preferred for tissue analysis in many cases 

 because they constitute the bulk of the fisheries harvest. However, 

 perch and sunfish species will generally have the lowest concentrations 

 of organic contaminants in edible tissues because of their low lipid 

 content. Freshwater mussels, especially /l/iaJo/ira spp. and Corbicida 

 spp., crayfish, sculpins (Cottidae), and catfishes (Ictaluridae) may be 

 preferred as target species for site-specific analyses. 



Size ClasseS"A study design for analysis of chemical residues should 

 incorporate stratified random sampling of a selected size class or 

 various size classes within each target species. Stratification by size is 

 extremely important, since both lipid content and contaminant con- 

 centrations can vary greatly among different sized organisms of the 

 same species (Phillips 1980). Moreover, the nature of the relationship 

 between body size and contaminant concentration varies among 

 chemicals, among species, and possibly among sampling stations and 

 seasons (Phillips 1980; Strong and Luoma 1981; Sloan et al. 1985; 

 Johnson 1987). The size classes of each species selected for analysis 

 should be representative of those in the diet of the potentially exposed 

 human population. For persistent chlorinated organic compounds and 

 organic mercury complexes, the largest (i.e., oldest) individuals within 

 an aquatic species are expected to be the most contaminated. If organic 

 compounds are of concern and a limited analysis is planned, the study 

 should focus on the largest individuals likely to be harvested by the 

 exposed human population. If contamination of relatively large in- 

 dividuals is high, sampling and analysis of all size classes typically 

 harvested should be performed to develop specific advisories. For 



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