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USE OF SURROGATE SPECIES IN ASSESSING CONTAMINANT RISK TO ENDANGERED AND THREATENED FISHES
Citation:
Dwyer, F. J., L. C. Sappington, D. R. Buckler, AND S. B. Jones. USE OF SURROGATE SPECIES IN ASSESSING CONTAMINANT RISK TO ENDANGERED AND THREATENED FISHES. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-96/029, 1995.
Impact/Purpose:
The tests conducted in this study were static acute toxicity tests with six listed species.
Description:
Surrogate species used in toxicity assessments must be carefully selected in order to be protective of listed species. At present, the rainbow trout is considered to be an acceptable surrogate for coldwater fishes. Similarly, the fathead minnow is considered to be an acceptable surrogate for warmwater fishes. This research project was designed to determine the applicability of using rainbow trout and fathead minnows as surrogate species for several endangered fishes. Coldwater static acute toxicity tests were conducted with rainbow trout and three listed species of salmonids - Apache trout (Oncorhynchus apache), Lahontan cutthroat trout (Oncorhynchus clarki henshawi), and greenback cutthroat trout (Oncorhynchus clarki stomias). Warmwater static acute toxicity tests were conducted with fathead minnow and two listed species of cyprinids - bonytail chub (Gila elegans) and Colorado squawfish (Ptychocheilus lucius). In addition, warmwater static tests were conducted with the razorback sucker (Xyrauchen texanus). Chemicals used in these toxicity assessments were selected in consultation with EPA to represent different chemical classes and toxic modes of action. Chemicals used in testing were: carbaryl, copper, 4-nonylphenol, pentachlorophenol, and permethrin. Results from the current studies indicated that the standard test organisms (rainbow trout and fathead minnows) often had a similar sensitivity to toxicant exposure as the listed salmonid and cyprinid species. The fathead minnow and the razorback sucker responses were generally similar. However, for 30% (8 of 27) of the possible surrogate/listed species comparisons, the standard 96-h LC50 for the listed species was lower than the surrogate species. After 96-h of exposure, warmwater listed species were more sensitive than fathead minnows 33 percent of the time. However, the listed warmwater species were always less sensitive than rainbow trout. Hazard assessments using rainbow trout would be protective of the warmwater species tested in this study. After 96-h of exposure, the listed salmonids were more sensitive than the rainbow trout for 25% of the comparisons. Environmental protection procedures usually focus on protection of populations or communities and not specific species or individuals of a species as may be necessary for endangered and threatened species. These data indicate an additional margin of safety may need to be included to protect listed salmonid species when toxicity assessments utilize data obtained from studies with rainbow trout.