NOTE Gunderson et a\ : Natural mortality o\ Atheresthes stomias and Sebastes crameri 



179 



the darkblotched estimate of M appreciably from what 

 was obtained by poohng the age-length data to estimate 

 a common K, but the estimate for arrowtooth flounder 

 would increase from 0.11 to 0.21. 



All indirect methods of estimating M rely on the correla- 

 tion established in their basic data set (28 fish stocks for 

 Gunderson, 175 for Pauly, and 84 for Hoenig). As a result 

 these methods are subject to bias in the estimates of M, 

 K, maximum age, and reproductive effort in the original 

 correlation data, and in the estimates of these parameters 



being used to extrapolate the correlations to new species. 

 Although Pauly's database is the most extensive (in terms 

 of the number of stocks available), age determination and 

 stock assessment methods have improved in the years 

 since it was initially compiled, and estimates of M have 

 tended to decline. An updated database would probably 

 reduce the estimates of M based on K. 



The estimate of maximum age required by Hoenig's 

 method assumes that the age determination technique be- 

 ing employed is unbiased. Validating this assumption is of- 



