A condition known as "broken-back syndrome" has been reported by other 

 investigators in pond-reared channel catfish, as well as in natural popula- 

 tions. Studies with fingerling channel catfish showed that exposures for 

 90 days to concentrations ranging between 0.044 and 0.535 ug/liter signifi- 

 cantly decreased collagen and increased calcium in their backbones. Resi- 

 dues in the affected fingerlings ranged upward from 3 ug/g. X-ray analyses 

 of these fish revealed aberrations in backbone structure (Figure 4). 

 Studies to determine the mechanism of action as well as the possibility 

 that other contaminants could also induce this condition are now in 

 progress. 



TFM Investigations 



The lampricide 3-trif luoromethyl-4-nitrophenol (TFM) was registered in 

 1964 for control of larval sea lampreys ( Petromyzon marinus ) in selected 

 tributaries of the Great Lakes. The EPA is presently renewing registration 

 of TFM on a year-to-year basis while research is being conducted on poten- 

 tial adverse effects and residues in non-target species. Brook trout are 

 an important and indigenous sport fish in many of the streams treated with 

 TFM. 



Chronic exposures of adult brook trout to concentrations ranging from 

 0.7 to 14 mg/liter of TFM formulation (35.7% active ingredient) were begun 

 in 1973. The adults were exposed for 120 days before spawning, and their 

 offspring for 90 days. Growth of adults exposed to the highest concentra- 

 tion was reduced, and all died during spawning. Many of the adults exposed 

 to 14 mg/liter and a few of those exposed to 8 mg/liter developed blindness. 

 Concentrations of 3.3 mg/liter or higher reduced egg viability (as measured 

 by the percentage reaching the neutal keel stage) and hatchability and 

 growth rates of fry. 



Although TFM has a significant chronic effect on brook trout at concen- 

 trations well below those used to control lamprey larvae, it is not likely 

 that use patterns for TFM would result in such long and continuous expo- 

 sures. Therefore, we repeated the study, but exposed two groups of adult 

 trout in a light- and temperature-controlled flow-through diluter, in 

 simulation of a typical stream treatment. Because such treatments 

 generally take place during the summer or early fall, one group of fish was 

 exposed to TFM during the summer at 15 C and the second during the fall at 

 9 C. Both groups were exposed to 16-18 mg/liter of TFM for 12 hr. About 

 19% of the adults in the first group died shortly after exposure, probably 

 because TFM was more toxic at the higher temperature, but those in the 

 second group were not affected. None of the treated adults showed signs of 

 blindness, and all spawned normally in November. Viability and hatch- 

 ability of the eggs were similar in the treated and control fish (Figure 5), 

 and growth of the young was not affected. 



The results of these investigations serve to illustrate the utility and 

 versatility of chronic and partial chronic toxicity tests in estimating 

 potential impact or non-impact of pesticides on aquatic organisms. At pre- 

 sent, there are about 30,000 registered pesticide formulations that must be 



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