July. This appears even more pronounced 

 because the values in April through June 1970 

 are smaller in comparison to the values in 

 these same months of 1969 and 1968. 



Surprisingly, this catch-effort value in August 

 1970 is smaller than the one for July of that 

 year. This is the first year during the sampling 

 survey for this to occur. A partial explanation 

 is the tremendous increase in trap-hauls and 

 trap-haul-set-over-days in July and August 1970 

 as compared to these months in 1969 and 



1968 (Table 4). In addition, the peak shedding 

 percentages by month were later in 1970 than 

 in previous years. 



This combination of factors, different from 



1969 and 1968, could account for the changed 

 relationship by month between catch in num- 

 bers per trap-haul-set-over-day and water tem- 

 perature in 1970. 



I reasoned that other than a shift of specific 

 months between the three periods of 1970, we 

 have not destroyed the hypotheses that we had 

 developed for each of these periods in 1969 

 and 1968. 



Relationship Between Catch in Numbers 

 per Trap-Haul and Set-Over-Days 



We compared the catch in numbers per trap- 

 haul (TH) with the number of set-over-days 

 (SOD) as another means of studying the de- 

 scribed catch and effort situation in 1970. This 

 type of analysis could also be used to evaluate 

 the intricacies of catch in numbers per THSOD 

 because we hypothesize using it as an index 

 of stock density. 



To analyze these data, we compiled the 

 information by month and year in two categories : 



(1) the catch in numbers per trap-haul, and 



(2) the associated number of set-over-days. 

 The values for these categories were calculated 

 by dividing that total catch in numbers by 

 that total number of trap-hauls from the fisher- 

 men who said their traps were hauled the day 

 before (1 SOD), then the same procedure for 

 those fishermen who hauled with a 2 SOD, 

 and so on through 5 SOD. We omitted data 

 from any fisherman who had a mixed number 

 of SOD for the group of traps that he hauled 

 for the day; such as a fisherman who hauled 

 300 traps for the day and of those, 150 had 

 been set-over for 1 day, while the remaining 



150 traps had been set-over for 2 days. These 

 modified data were compiled by month and 

 year from 1968 through 1970 (Table 8). 



The relationship between the catch in num- 

 bers per trap-haul and the number of set- 

 over-days in 1970 reveals a higher increasing 

 trend line than for 1969 and 1968 (Fig. 14). 

 I attribute this to the same reason that I have 

 already discussed: that is, an earlier and higher 

 percent of shedders starting in June 1970, 

 resulting in higher recruitment and vulnera- 

 bility starting in July and continuing through 



SET OVER DAYS 



SET OVER DAYS 



SET OVER DAYS 



Fig-tire 14. — The relationship between catch in num- 

 bers per trap-haul and set-over-days by year, 1968 

 through 1970. 



37 



