exposure. Estimated LScq values for striped bass yold-sac larvae were 785 

 dynes/cm and 300 dynes/cm for 1 and 4 minute exposures, respectively. 

 White perch yolk-sac larvae were more vulnerable, their LSrn values were 415 

 dynes/cm and 125 dynes/cm for 1 and 4 minute exposures respectively. 

 Calculated average shear force in the Chesapeake and Delaware Canal, where 

 striped bass eggs occur, was only 13.8 dynes/cm , far below the estimated 

 LSrQ values. The authors (17) also related these LS^q values to expected shear 

 forces of 72-230 dynes/cm that might be present in the water box of a power 

 plant cooling system. The 230 dynes/cm shear approaches the 4 minute LScn 

 value for striped bass yolk-sac larvae and exceeds it for white perch. 



Chipman (27) reviewed literature on effects of naturally occurring ionizing 

 radiation on marine animals. He found no convincing evidence to demonstrate 

 that marine animals showed any response, functional or structural, to ionizing 

 radiation levels present in the environment. In marine animals observable 

 effects are primarily at the cellular level, and the radiation tolerance is a 

 function of the dose-rate, time patterns of exposure and metabolic rate; 

 consequently, effects would be most evident during embryonic development 

 (27). 



FUTURE RESEARCH 



Both laboratory and transitional laboratory-field studies will extend our 

 knowledge of environmental effects on larval stages of marine fish. A recent 

 colloquium on larval mortality and the recruitment problem has defined some 

 areas in need of research (48). Emphasis of that colloquium was to advocate 

 research related to starvation and predation, the two factors that probably have 

 the greatest effect on recruitment of year classes. Environmental stresses from 

 man's activities are additional threats, particularly to estuarine species or those 

 found over the continental shelf. Pollution effects on embryos can cause gross 

 functional and structural abnormalities that may produce yolk-sac larvae 

 incapable of surviving to the exogenous feeding stage (81). Larvae can be 

 equally vulnerable to deleterious effects of pollutants, and their responses to 

 this stress may be reflected in impaired predator avoidance behavior and food 

 capture efficiency. More subtle effects could involve functional disruptions of 

 metabolism, temperature and salinity tolerance, and enzyme-substrate 

 interactions. Both direct and indirect effects of environmental modification on 

 recruitment need to be determined. 



The ability to culture larvae widens the possibilities for laboratory research 

 which will help interpret results of field studies. The larval stage is a dynamic 

 one, characterized by fast growth, sometimes spectacular developmental 

 changes, and frequent shifts in behavior. Typical toxicity bioassays, where 

 times to 50 percent mortality are estimated, may not be the best approach to 



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