Item 



3. Examination of the data indicates violation of several assumptions 



including temporary outmigration and perhaps equal catchability of 



marked fish by sex or size. 



Comment 



Similar findings were made by Worobec (1981) in a study patterned 

 after the Niantic River surveys. Some violation of assumptions invariably 

 occur in capture-recapture studies with differing effects on precision 

 and reliability of the estimates, depending upon the intent of the 

 investigation (Begon 1979). The effect of assumption violations here 

 are not yet known. It is recommended that the data be re-examined to 

 minimize these errors and to obtain more accurate if not precise estimates 

 for use in impact analysis. Pollock (1981, 1982) recommended the POPAN- 

 2 computer program package (Arnason and Baniuk 1978) for very powerful 

 and flexible analyses of studies using the Jolly method. It has strong 

 data manipulation capabilities such as the ability to stratify by age or 

 sex. It can carry out various tests of fit to models and assess the 

 influence of assumption failure on estimates. Recent steps have been 

 taken to obtain this program and implement it on the data processing 

 system. This program should greatly increase the reliability of the 

 population estimate program data. 



Other recommendations to assess the assumptions of the Jolly method 

 include measuring all fish branded and recaptured. Although this would 

 increase the labor involved in the field, it would result in much more 

 information available for data analysis including the ability to stratify 

 by age (through an age-length key) and would allow the examination for 

 size selectivity in recaptures. Data collected among many categories 



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