FISHERY BULLETIN: VOL. 75, NO. 2 



20- 



10 



20- 

 10- 



0- 



20- 

 10 



20- 



10 



20 



- 10 



20 

 10 

 



20- 



10- 

 



20- 



10- 

 



20- 



10 



20- 

 10 

 



N.499I746) _^fj| | [^ 







N = I644(349) 



!!4ifrrrffTTK. 



"^mnrm^ 



!!!Utitt1T1 1 IT-i-^ 



N=3633(420) 



^T^tTTTlh^ 



"^^fTfTlTlTk. . 



^rfTTTTffJTK 



^^mTrm^! 1 



N-- 2240(291) 



N=2 762 (376) 



-^-rrTTTTrrrfTTTT-u , 



N=2I73(469) 



^^rrrrrrnTn-h_ 



^-r-rfTTTT 



N=3504(5I6) 



TflfTlTK. . 



N=280l(561 





20 25 30 35 40 45 20 25 30 35 40 45 50 



Length (cm) Length (cm) 



FIGURE 6. — Size composition of 1967-71 Pacific ocean perch 

 catches from Queen Charlotte Sound, by month. Mean numbers 

 caught per hour during 1967-71 are shown in parentheses. 



Previous work (Gunderson 1972) has shown that 

 these aggregations are faster growing, but only 

 slightly older, than the rest of the stock. 



Pacific ocean perch move into progressively 

 deeper water during October-December, as they 

 return to deepwater spawning areas. Catch per 

 hour remains high during this period, but de- 

 teriorating weather conditions force a decline in 

 trawling effort and landings. 



Because catch, CPUE, sex ratio, length compo- 

 sition, and age composition all varied with season, 

 the data from different time periods were treated 

 independently in much of the later analysis. The 



time periods utilized were January-April, May, 

 June-August, and September-December. 



Seasonal Patterns for Specific Grounds 



The geographic distribution of the catch varied 

 from month to month (Figure 7) and there is a 

 possibility that between-ground variations in size 

 composition could contribute to the results shown 

 in Figure 6. Length and age composition data were 

 analyzed by fishing ground (Figure 8) to examine 

 this point further. To insure that the data used 

 were as typical as possible of the grounds in ques- 

 tion, only samples from characteristic fishing 

 depths were chosen for this analysis. The 1967-71 

 mean depth of catch was computed for each month 

 and ground in question, and only those samples 

 whose range was within 15 fm (27 m) of this mean 

 were analyzed. 



The results (Figure 9) show that within a given 

 time period, length composition differed some- 

 what between grounds, but the differences showed 

 no consistent, predictable pattern. There was no 

 ground that could always be characterized as hav- 

 ing larger or smaller fish than the other grounds. 

 Size composition data for SE Corner, SW Corner, 

 and Triangle grounds, the three major fishing 

 grounds, showed only slight between-ground 

 heterogeneity within any given time period. 



Washington-Vancouver Island 



Unlike Queen Charlotte Sound where the con- 

 tinental shelf drops off abruptly past 150 fm (274 

 m), a wide range of depths can be fished off 

 Washington and Vancouver Island (Figure 5). 

 Trawlers can follow fish in this area into deep- 

 water spawning areas, and exploit them year 

 around. The year can be divided into a 



10 30 50 70 90 



Percent 



10 30 10 30 



10 30 10 30 10 30 50 



Tnonqle 



374 



Toloh 



rzzn 



Jan-Mar 



Apr May Jun 



Jul 



Aug Sep 



Oct 



LA 



Nov 



Dec 



FIGURE 7.— Distribution of 1967-71 

 Pacific ocean perch catch from Queen 

 Charlotte Sound by month and fishing 

 ground. Data on distribution by ground 

 were derived from the portion of the 

 catch for which fishermen interviews 

 were available. The Virgin Rocks- 

 Mexicana ground includes Virgin Rocks 

 and all grounds east of the Cape Scott 

 ground. 



