POLOVINA and RALSTON: MSY FOR DEEP SLOPE FISHES 



Table 11.— Annual sustainable yield in metric tons (t) and yield in kilograms 

 (kg) per nautical mile (nmi) of 200 m contour for the age at entry which max- 

 imizes the yield per recruit at a level of fishery mortality of F = 1.0. 



those species to the catch with the high MIK values, 

 particularly P. flavipinnis andE 1 . carbunculus tends 

 to increase (Table 12). A form of succession is, 

 therefore, predicted as exploitation proceeds. 



There are two approximations which have been 

 used to determine MSY which express it as a frac- 

 tion of the unexploited biomass. Gulland's formula 

 estimates MSY as 0.5 MB, where M is the instan- 

 taneous rate of natural mortality and B is the unex- 



ploited biomass. An approach proposed by Pauly 

 estimates MSY as B 2.3w~ 02S , where w is the mean 

 of the weight (in grams) at sexual maturity and the 

 asymptotic weight (Gulland 1983; Pauly 1983). A 

 comparison of these two estimators with the values 

 obtained here shows that for four out of seven 

 species the YIB values estimated with the Bever- 

 ton and Holt equation lie between the values ob- 

 tained from the Pauly and Gulland approximations. 



Table 12.— The percentage of annual sustainable yield by species groups for two ages 

 at entry with two levels of fishing mortality. 



769 



