HUNTSMAN ET AL.: YIELD PER RECRUIT MODELS 



Black Sea Bass M = 5 



Yield Per Recruit in Weight 



at 



w 5h 



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4 - 



3- 



2 - 



1 - 



_L 



J_ 



_L 



_L 



J_ 



_L 



J_ 



_L 



-L 



20g 



-L 



0.2 0.4 0.6 0.8 1.0 1.2 14 16 18 2 



F 

 FIGURE 12. — Yield per recruit in weight of black sea bass where M = 0.5. 



Regardless of the M estimates chosen, of the recruit- 

 ment ages specified, or of whether the recreational or 

 commercial fishery is discussed, it is apparent that 

 most of the important species in the headboat fishery 

 were providing the bulk of their readily available 

 yield per recruit (Table 3). At the lowestM estimates 

 all species studied (except deep water black sea bass) 

 were subjected to sufficient fishing mortality on the 

 headboat grounds to provide at least 707c (mean = 

 877c) of the maximal yield per recruit. Even at the 

 estimates provided by the highest M values and least 

 favorable recruitment ages, 50% or more (mean = 

 687c) of the maximal yield per recruit was taken for all 

 species except red snapper (407c). 



Stocks available to the commercial fishery (includ- 

 ing those on the headboat grounds) were similarly 

 exploited. At the lowestM estimates, at least 707c of 

 the maximal yield per recruit was harvested for all 

 species (black sea bass and white grunt were not 

 taken commercially) except speckled hind for which 

 507 was taken. The mean for all species was 8 17c. At 

 the high M estimates, 407c was the minimum taken 



(for red snapper) and the mean for all commercial 



species was 677c 



It appears that by the late 1970's most of the prac- 

 tically available yield was being taken from the 

 grounds fished at that time. Several species were 

 incurring sufficient F to provide virtually all the yield 

 per recruit possible while F for most others was at the 

 level beyond which increased yield per recruit comes 

 only with very large increases in effort and concomi- 

 tant large decreases in CPUE. 



DISCUSSION 



Any value of our models lies in their utility to 

 management of reef fish stocks. Some information 

 about management can be derived directly from the 

 models without resort to adjunct information; for 

 instance, the models alone reveal that if recruitment 

 age can be kept moderately high, yield per recruit will 

 stay high regardless of how great F becomes. Thus 

 protection of yield per recruit can be obtained 

 without having to know what F is, or without having to 



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