94 



Fishery Bulletin 100(1) 



Total number of sampled sets and average 

 annual fishing effort by seasons 



250 



200 



150 - 



Two whale-shark 

 assocrated sets 



] Log-associaled 

 ] Whale-associated 

 I Whale-shark-associated 

 9 Ffee-swimming 



- Average effort (fishing days) 



- Average effort (sets) 



E 



100 



Winter 



Spring 



Summer 



Autumn 



Total sampled catch and average 

 annual catch (t) by seasons 



Winter 



Spnng 



Summer 



Autumn 



500 

 450 

 400 

 350 

 300 

 250 

 200 

 150 

 -I- 100 

 50 

 



B 



Figure 2 



(A) Sampled effort (by school type) and the long-term average fishing effort by season; 



(B) sampled catch (by school type) and long-term average catch by season for the Soviet 

 tuna fleet. 



believe that the observers' data are representative of the 

 catch by the Soviet purse-seine fleet in terms of sample 

 size and geographical distribution of the sets. 



The data series available for analysis was a combination 

 of samples different in size, obtained in different years and 

 seasons (Tables 1-3). Therefore the results of all analyses 

 may have been subject to interannual variability (it is im- 

 possible to evaluate the effect of interannual variability 

 from the data available), and the estimated average annu- 

 al figures may have been subject to seasonal variability as 

 well, on account of the unequal size of samples taken in dif- 

 ferent seasons. 



Because the daily radio reports, which formed the basis 

 of the database, did not include information on sets by 

 school type, it was not possible to directly extrapolate the 

 observers' data to the Soviet fleet separately by school 



types. However, I believe that the observers' data correctly 

 reflect the seasonal ratio of sets on different school types. 

 To assess the possibility of using annual averages of the 

 available samples and extrapolating them to the whole 

 catch of the Soviet fleet, the author compared the season- 

 al magnitudes of total fishing effort (fishing days, sets) 

 and catches reported by the Soviet fishing fleet (from the 

 database) with the seasonal magnitudes of effort (number 

 of sets) and catch (t) sampled by the observers (Fig. 2, A 

 and B). The seasonal distribution of the sampled catch fol- 

 lowed the same pattern as the long-term average seasonal 

 distribution of the catch by the fleet (Fig. 2B). The effort 

 did not fully agree with seasonal increase in the fishing ef- 

 fort of Soviet vessels diu'ing the autumn season (Fig. 2A), 

 which may have resulted in a slight underestimation 

 of average annual values of bycatch from log-associated 



