ABRAMSON and TOMLINSON: APPLICATION OF YIELD MODELS 



Table 2. — Continued. 



1 Catches of age groups are not included. 



Table 3. — Average weight in pounds by age. From aged 

 catch landed in northern California and southern Ore- 

 gon, 1955-1968. 



Month 



Age I 



Aga II 



Age III 



Fish and Game, personal communication) indi- 

 cated that shrimp grow faster in the open season 

 than during the closed season. Hence, the em- 

 pirical curve was drawn to show seasonal dif- 

 ferences in the growth rate. A more objective 

 fit of the data could be obtained, but it would 

 not alter the results enough to change the con- 

 clusions contained herein. 



The curve shows relatively constant (linear) 

 growth in weight during the open season, but 

 slower growth during the closed period. The 

 shrimp apparently do not approach an asymp- 

 totic weight prior to reaching maximum age in 

 the fishery, and growth in weight could be de- 

 scribed as linear during the exploited phase. 

 Obviously, there was considerable variation, in- 

 creasing with age. 



Annual average count per pound for ages I, 

 II, and III combined varied from 94 in 1961 to 

 142 in 1965 (Figure 4). Monthly values varied 

 from 76 to 155 with an average for all years 

 of 114. 



B WO«lHL1 VALUES 



 SEASOMIL *ven«GE$ 



 AVCRASE 



Figure 4. — Average size of ocean shrimp in the landings 

 by month, season, and overall. 



Because of the variation exhibited by the size 

 at age data, it is possible that significant random 

 or systematic errors are contained in the age 

 composition data and that the subsequent anal- 

 yses of these data will be correspondingly af- 

 fected. 



1029 



