APPLYING SURVIVAL CURVES 

 TO ASSESSMENT OF FISH LARVAL 

 ENTRAINMENT IMPACT 



MICHAEL D. DAHLBERG 



Ecological Sciences Division, NUS Corporation, 



Pittsburgh, Pennsylvania 



ABSTRACT 



The equivalent-adults model for approximating numbers of fish larvae entrained 

 at povirer plants and survival rates from larva to adult is assessed in regard to 

 predicting the numbers of adults represented by entrained larvae. The accuracy 

 of this model, in relation to other proposed approaches, depends on the proper 

 selection of methods for calculating larval losses, lifetime fecundity, and 

 larva-to-adult survival. Additional approaches are recommended when sufficient 

 population data are available. Until questionable assumptions can be resolved, a 

 reasonable approach is to calculate a possible range for the number of equivalent 

 adults lost. These numbers can be compared to a reference of acceptability, such 

 as year-to-year variability of stock size. 



Entrainment of fish eggs and larvae is one of the major impacts of 

 power-plant operation. Potential effects are generally assessed by 

 translating entrained eggs and larvae to the potential number of 

 adults they represent. The calculations are accomplished with 

 complex models and a simplistic equivalent-adults method proposed 

 by Horst (1975). Horst's method has been recommended by the 

 Environmental Protection Agency (1976) and is widely applied in 

 impact calculations. This paper examines problems encountered in 

 applying the Horst model and discusses alternative procedures. Data 

 for the walleye population of Oneida Lake, New York (Forney, 

 1976a; 1976b) are used as an example. 



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