48 



Fishery Bulletin 89(1), 1991 



CALIFORNIA 



WASHINGTON 



OREGON 



JlullJUl 



58 60 62 64 



70 72 74 76 78 80 82 84 

 YEAR 



Figure 1 1 



Combined landings of pink shrimp for the states of Califor- 

 nia, Oregon, and Washington for the years 1957-88. 



Figure 10 



Percentage of male pink shrimp for four index area-months 

 for the years 1966-88. 



o 

 u. 



UL 100000 





fl 



66 68 70 72 74 



Figure 12 



Fishing effort (single-rig equivalent hours) for pink shrimp 

 in statistical areas 18-28 for the years 1966-88. 



The pattern of growth in the index areas (Fig. 7) 

 shows a slight tendency toward improved late-season 

 growth in recent years, coincident with the season of 

 minimum shrimp density on the grounds (Fig. 13). Dur- 

 ing the fall, age-0 shrimp begin to appear in the trawl 

 catch in small numbers (Zirges et al. 1982). These data 

 suggest that the improved growth occurring prior to 

 age-13 months may be a result of decreased shrimp 

 densities created by the trawl fishery. 



The time-series of CPUE probably understates the 

 true drop in shrimp biomass since 1978 due to the gear 

 improvements mentioned previously. The difference in 



mean size at age demonstrated after 1979 may also be 

 understated by the data shown in Figure 9. Prior to 

 1969 the minimum codend mesh allowed in the Oregon 

 pink shrimp fishery was 38 mm (including one knot), 

 while from 1969 onward codend mesh size has been 

 unregulated (J.T. Golden, ODFW, Newport, 1981 

 draft). The lower curves in Figure 7, therefore, prob- 

 ably overestimate the mean size at age-1. Since 1979, 

 with larger mean size, age-1 shrimp have been more 

 completely sampled by the gear. D.R. Bernard (Oregon 

 State Univ., Corvallis, 1983 draft) estimated that pink 

 shrimp were fully recruited to the 38 mm mesh trawl 



