Influence of Body Size and Developmental Stage of Coho Salmon (Oncorhynchus kisutch) on Lethality of Several Toxicants

Influence of Body Size and Developmental State of Cobo Salmon (Oncorhynchus kisutch) on Lethality of Several Toxicants. Hedtke, J.L., Robinson-Wilson, E. and Weber, L.J. (1982). Fundam. Appl. Toxicol. 2:67–72. Acute 96 h bioassays were conducted on coho salmon (Oncorhynchus kisutch) to determine their sensitivity to each of four toxicants during development. Alevins, swim-up fry and juveniles (up to 175 days post-hatch) were exposed to lethal concentrations of copper, zinc, nickel, or pentachlorophenol each week to monitor changes in susceptibility as the fish grew. Fish exhibited a high degree of susceptibility to all of the toxicants during the alevin stage. Swim-up fry showed drastic changes in sensitivity followed by more sustained patterns of change in the subsequent juvenile stage. Lethality could be related to both concentration of toxicant (C) and some exponential function of body weight (W) by the use of the multiple regression equation, Y = a + b(In C) + g(In W) where Y is the percent mortality expressed in probits. Through the use of this weighted expression of toxicity it was observed that coho alevins were consistently more sensitive to the toxicants than the juveniles. An exponential relationship between toxicity and weight could be calculated as −g/b. This exponent was found to be specific for each toxicant tested and changed in magnitude as the fish progressed through the various stages of development. Results indicated that lethality (LC50's) varied from one stage of development to the next, but within any defined stage, the relationship between toxicity and body weight was relatively constant.