SURVIVAL OF FRY 



To test this hypothesis, we began a 6-month study in the winter of 1975- 

 76 on the effects of chronic exposure of fry of Lake Michigan lake trout to 

 PCBs and DDE. In addition to routine observations on mortality and growth 

 of the fry, we also evaluated methodology for, and made measurements of, 

 their temperature preference, swimming performance, predator avoidance, and 

 metabolism. About 27,000 eggs were manually stripped and fertilized with 

 milt from lake trout (about 10 females and 20 males) gillnetted in south- 

 eastern Lake Michigan near Saugatuck, Michigan in the fall of 1975. Con- 

 taminant levels in adult lake trout from this area had been monitored for 

 several years and the fish were known to contain average whole-body concen- 

 trations of about 22 yg/g PCBs, 7.5 yg/g total DDT, and 0.3 yg/g dieldrin 

 (Great Lakes Fishery Laboratory, unpublished data). Our analysis of eyed 

 eggs sampled from those collected for this study revealed 7.6 yg/g PCBs and 

 4.7 yg/g total DDT. Samples of 1 -day-old sac fry hatched from these eggs 

 and analyzed at the USFWS Columbia National Fishery Research Laboratory were 

 shown to contain 3.8 yg/g PCBs (Aroclor 1254), 2.3 yg/g total DDT, 0.06 yg/g 

 dieldrin, 0.12 yg/g cis-chlordane, and about 5.7 yg/g of a chemical re- 

 sembling toxaphene. Later analysis showed that the toxaphene-like residue 

 was actually composed of several chlorinated camphenes of undetermined ori- 

 gin. 



The fry were then exposed for 6 months to 10.0 ng/1 PCBs (Aroclor 1254) 

 and 1.0 ng/1 DDE in water, and 1.0 yg/g PCBs and 0.1 yg/g DDE in food. 

 These values approximate the exposure received by fish in the lake as 

 determined by analyses of water and plankton collected offshore in south- 

 eastern Lake Michigan. Concentrations 5 and 25 times these values were also 

 tested to allow dose-effect interpretation and prediction of potential 

 effects on fry hatched in the more contaminated, nearshore areas of the 

 lake. 



About a week after the eggs hatched, grossly deformed fry were discarded 

 and the rest were equally divided among 30 tanks (650 fish per tank) in a 

 constant-flow bioassay system. Serial diluters supplied the appropriate 

 concentrations (Ix, 5x, 25x, and control) of the contaminants singly or in 

 combination in 9 C well water. The experimental design thus provided for 10 

 different treatments (including the controls) and three replicates of each. 

 Following 11 days of exposure, the fry began to exhibit feeding behavior and 

 were fed the corresponding dosage of either or both contaminants that had 

 been added to their food. Analyses of water during the study showed that 

 the actual average exposures received by the fry corresponding to Ix, 5x, 

 25x were 20.8, 64.7, and 327 ng/1 PCBs and 1.8, 6.3, and 32.7 ng/1 DDE. 

 Analyses of the food showed that actual concentrations were all within 28% 

 of agreement with nominal concentrations. 



During the first 16 days of exposure to the three levels of PCBs, DDE, 

 and PCBs plus DDE in water, the percentages of fry that died ranged from 1.9 

 to 3.7% across all treatments. Mortalities of fry among the nine exposed 

 groups were not significantly different from the percentage that died among 

 the controls. During the next 40 days (days 17-56), when exposed fry began 

 receiving contaminants in their food as well as from the water, the morta- 



79 



