FISHERY BULLETIN: VOL. 71, NO. 4 

 TablE'1. — Parameters of the simulated pandalid shrimp population. 



Parameter 



Symbol 



Value 



1 . Number of year classes 



2. Instantaneous natural mortality coefficient 



3. Availability multipliers 



4. Month breeding begins 



5. Month breeding ends 



6. Year of first maturity 



7. Age (mo) at first recruitment 



8. Copulation coefficient 



9. Recruitment parameters of the Beverton 

 and Holt model 



10. Fecundity coefficients 



11. Male maturity fractions 



12. Female maturity fractions 



Figure 2. — Arbitrary growth curve exhibiting the step- 

 wise growth pattern of pandalid shrimps. 



The simulated pandalid shrimp population 

 was fished for six different season lengths, 

 from 12 to 2 mo after the hatching period (Ta- 

 ble 2). The maximum equilibrium yield for 

 each season length occurred with an annual 

 fishing mortality coefficient, F, of 1.0. This 

 means that the monthly fishing effort must in- 

 crease proportionally to the inverse of the sea- 

 son length to obtain the maximum equilibrium 

 yield (column 2, Table 2). Of those seasons 

 simulated, the greatest equilibrium yield and 



catch per unit effort were obtained with the 8- 

 mo season (columns 3 and 4, Table 2). Com- 

 pared with an annual fishery, however, the 8- 

 mo season resulted in a 5% decrease in the aver- 

 age weight of a shrimp in the catch (column 5, 

 Table 2). The 6-mo season (closure during the 

 breeding, ovigerous, and hatching periods) was 

 only slightly less than the 8-mo season in yield 

 and catch per unit effort, but it was better than 

 the annual fishery. However, there was an 11% 



IT 

 CO 



3 

 O 



2 - 



0.0 0,2 0.4 06 08 10 12 1.4 16 



FISHING EFFORT 



18 2.0 



Figure 3. — Relationship between equilibrium yield and 

 fishing effort for the simulated pandalid shrimp population. 

 Dashed line represents nonequilibrium region. 



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