Use of Sodium Pentachlorophenate and Dehydroabietic Acid as Reference Toxicants for Salmonid Bioassays

Abstract

Results of an interlaboratory bioassay standardization exercise involving seven independent fish bioassay laboratories in British Columbia are presented. Toxicity of standard solutions of sodium pentachlorophenate and dehydroabietic acid was determined in freshwater static bioassays with underyearling rainbow trout (Salmo gairdneri), coho salmon (Oncorhynchus kisutch), and sockeye (Oncorhynchus nerka) salmon. Reported LC50s for the three species ranged from 37 to 130 ppb for sodium pentachlorophenate and 1.03–2.14 ppm for dehydroabietic acid. In general, test results for individual species and toxicants were fairly consistent and major disparities could be explained in some instances by variations in physical and chemical characteristics of the bioassay such as water temperature, hardness, or pH. Fish size and condition factor appeared to have little effect on apparent toxicity over the ranges tested.The usefulness of reference toxicants for standardizing bioassays is emphasized and suggestions are made for improved test procedures and increasing accuracy of results. Guidelines for toxicity tests should include the use of reference toxicants as a means of standardizing bioassay results.