Fishery Laboratory (Rybecki and Keller 1978). Of greatest concern initially 

 was the problem of toxic substances. The fish were known to contain sub- 

 stantial residues of DDT and its metabolites and of PCBs (Reinert 1970; 

 Stalling and Mayer 1972). Concentrations of each of these contaminants ex- 

 ceeded 10 yg/g in adult lake trout (Willford 1975) and 4 ug/g in their eggs 

 (Reinert and Bergman 1974). Published reports on the effects of DDTs (DDT, 

 DDD, and DDE) and PCBs indicated that the concentrations of these contami- 

 nants in lake trout and their eggs were sufficient to interfere with repro- 

 duction. For example, Burdick et a_l_. (1964) reported that concentrations of 

 DDTs in excess of 2.9 yg/g in the eggs of lake trout resulted in increased 

 mortality of fry. This effect was later confirmed by Macek (1968) who 

 studied brook trout ( Salvelinus fontinalis ) fed DDT. Unusually high morta- 

 lity of fry of coho salmon ( Oncorhynchus kisutch ) hatched from eggs of Lake 

 Michigan fish, and possible correlation of that mortality with elevated 

 levels of DDTs and other chlorinated hydrocarbons were also reported 

 (Johnson and Pecor 1969; Willford et aj[. 1969). In addition, reduced hatch- 

 ability of salmon eggs in Sweden was reported as correlated with elevated 

 PCB residues (Jensen et a/[. 1970), Nevertheless, hatchery records showed 

 that when eggs of planted Lake Michigan lake tro"t were manually stripped, 

 fertilized, and hatched, and the fry were reared in hatcheries, survival was 

 "normal" or "satisfactory" (Stauffer 1979). 



HATCHABILITY OF EGGS 



In 1972-73, researchers at the Great Lakes Fishery Laboratory performed 

 studies to investigate further the hatchability of eggs from Lake Michigan 

 lake trout under three sets of incubation conditions: normal hatchery con- 

 ditions; a thermal regime similar to that of winter and spring in Lake 

 Michigan; and the thermal and chemical conditions characteristic of water 

 from the Hammond Bay Biological Station's intake on Lake Huron. Related 

 studies were carried out by the MDNR at the Marquette State Fish Hatchery, 

 at the Thompson State Fish Hatchery, and at two locations (in egg-holding 

 enclosures) in Lake Michigan's Grand Traverse Bay from 1973 to 1976 

 (Stauffer 1979). In all of these studies, the survival of contaminated eggs 

 and fry from Lake Michigan lake trout was compared with that of relatively 

 uncontami nated eggs and fry from hatchery brood stock. Although occasional 

 differences in survival were noted between groups of eggs and fry reared 

 under the various experimental conditions, no consistent relation between 

 hatching success and the concentrations of DDTs or PCBs in the eggs was ap- 

 parent. The conclusion reached in the studies performed at the several lo- 

 cations by the two agencies was that existing levels of DDTs and PCBs in 

 eggs of Lake Michigan lake trout did not significantly affect survival in 

 eggs or of early stages of the fry. 



The reproductive failure of lake trout in th" lake was nevertheless 

 still apparent in the mid 1970's. We then speculated that although the eggs 

 could hatch and the fry survive in a clean (hatchery or laboratory) environ- 

 ment, the additional chronic exposure to PCBs and DDE in the water and food 

 of Lake Michigan might reduce the stamina, strength, or wariness of the fry 

 sufficiently to preclude their survival in the rigorous lake environment. 



78 



