AHRENHOLZ ET AL.: ATLANTIC MENHADEN POPULATION AND FISHERY 



160- 



140 



120 



w 



< 100 



o 



m 

 > 



80 



< 60 



40 



20- 



1970 



1975 



_L 



_L 



J I L 



_L 



J I L 



_J 



5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6 



AGE IN YEARS 



Figure 24. — Age-specific relative biomass estimates of a hypothetical year 

 class of Atlantic menhaden in the absence of fishing, with growth parameters 

 estimated for the 1970 and 1975 year classes. If harvesting occurred instanta- 

 neously at any given age, the corresponding ordinate value would represent 

 yield per recruit in grams. 



w 



< 

 o 



I 



z 

 < 



600 



500 



400 



300 



200- 



100- 



/^ 



/\. 



:, Age 3 



Age 2 



\ 



/ 



\.-v /^./\ 



A_ge I'^Xxv 



A • — /•■ \ Age "^---^ 



I  I  I  I  I  I ' I  I ' I ' I ' "^ 



1955 57 59 61 63 65 67 69 71 73 75 77 79 81 

 YEARS 



Figure 25. — Weighted mean annual weight of purse seine landed 

 Atlantic menhaden, ages 0-3, for years 1955-81. 



solution shown earlier may be more realistic than 

 first impressions would indicate. However, to at- 

 tain that level of harvest would require a restruc- 

 turing of the fishery, and continued moderate to 

 high levels of recruitment to sustain it. 



GENERAL DISCUSSION 



With estimates of year-class sizes, exploitation 



rates, and an understanding of the interaction of 

 population size and effort relative to rates of fish- 

 ing mortality, the trends observed in the fishery 

 since 1955 are more readily explained. Addition- 

 ally, this information permits inferences to be 

 drawn about the earlier presampling period of the 

 1940's and early 1950's. The major premise of this 

 discussion is that harvest levels and effort of the 

 earlier presampling period were probably near 



595 



