24 



COMMERCIAL FISHERIES REVIEW 



Vol. 28, No. 10 



N = 58 

 ■ BROKEN SHELL 

 D UNBROKEN SHELL 



20 -1- 



u 



Q 



O 



Pi 



10 -- 



5 -- 



CONTROL LANE 



1 



LANE 

 2 



LANE 

 3 



Fig. 7 - Pacific oyster mortalities from aU lanes of Cultivation 

 Experiment 1 separated into broken-shell and unbroken-shell 

 categories. 



The first survey and collection of sam- 

 ples for determination of oyster condition was 

 on July 8, 1964. Experimental harrowing be- 

 gan July 23 when each of the lanes 1,2, and 

 3 was dragged once. The control lane was 

 never dragged, lane 1 was dragged only once, 

 lane 2 was dragged once each week for 10 

 weeks, and lane 3 was dragged during the be- 

 ginning, middle and last week (total of 3 times). 

 A sample of 20 oysters was taken weekly from 

 each lane immediately before the dragging and, 

 after completion of experimental dragging, 

 monthly for 6 months until March 1, 1965 

 (table 2). Dragging produced some changes 

 in the condition of oysters. 



Condition of oystersi./ in all lanes was 

 similar before dragging, ranging from 7.2 in 

 lane 3 to 8.0 in the control lane. The condi- 

 tion of control-lane oysters (9.4) on August 6 

 indicated ripe, ready to spawn oysters; con- 

 dition then immediately dropped to a very low 

 value (3.8) on August 11 after spawning. Re- 

 covery was rapid but erratic and at the end of 

 the sampling period (March 1, 1965), control- 

 lane oysters had the lowest condition (3.9) 

 while all dragged lanes had an identical but 

 higher value (5.1). 



Fig. 8 - Condition indic es of Pacific oysteis for all lanes of Cultivatio n Experiment 1 from July 8, 1964, to March 1, 1965, 



Fig. B - Condition indices oi raciiic oysi.en. lui aii i^ucc wi ^u^,.., ....... .-„r- ^ -, . 



I/Classification of Pacific oysters in Willapa Bay according to condition index is a. foUows: Below 4.0, extremely poor quality; 4.0 to 

 8.0, poor quality; 8.0 to 12.0, good quality; above 12.0, excellent quality. 



