Long-term effects of toxaphene and depuration in lake trout and white sucker in a natural ecosystem

Individuals from lake trout (Salvelinus namaycush) and white sucker (Catast omus commersoni) populations in a small lake located in the Experimental La kes Area in northwestern Ontario, Canada, were treated with single intraper itoneal injections of toxaphene (7 mu g/g or 3.5 mu g/g) to better understa nd its potential effects on fish in their natural environment, Wild fish we re captured, tagged, weighed, measured, injected with toxaphene, and releas ed back into the lake. They were subsequently recaptured during spring (whi te sucker) and fall (lake trout) for the next 5 years. In years 2 and 3 fol lowing treatment, fish were spawned to assess reproductive success and surv ival of their offspring. Survival of adult lake trout and white sucker trea ted with toxaphene was decreased compared with controls. No changes in grow th were evident in either species due to toxaphene treatment. No difference s occurred in fertilization rate, total survival, or incidence of deformiti es in eggs and fry from female lake trout treated with toxaphene. Fertiliza tion rates and survival to swim-up of white sucker eggs and fry from female s treated with toxaphene decreased relative to controls in both years. Mate rnal transfer of toxaphene from female to eggs was observed in both white s ucker and lake trout; levels in eggs were much lower than in treated female s but were still significantly higher than in controls. Residue analyses sh owed that depuration of toxaphene was slower than expected, with estimated half-lives of 314 and 793 d in lake trout and white sucker, respectively.