speed, tide, wind, and other factors. Annual means in tow time ranged 

 from 8.0 min in 1975 to 17.5 min in 1980 (Table 15). Mean duration 

 varied among stations with tows at the channel stations (1 and 2) longer 

 than those at other areas. For simplicity each tow was standardized to 

 a 10-min duration for the calculation of CPUE without regard for the 

 additional variability this might have introduced into the data. 



Another source of variability examined which may have affected CPUE 

 was the various research vessels used throughout the studies. Although 

 the same model 9.1-m otter trawl was used for sampling from year to 

 year, the type of boats used generally changed every 1 or 2 years. Each 

 boat used may have caused the trawl to fish differently due to its size, 

 rigging, and towing speed. Where sufficient data existed, the catch of 

 the two or three vessels used were compared within a year at a particular 

 station by one-way analysis of variance. No between-year or between- 

 station comparisons were made since the variability contributed by years 

 and stations was thought to be much greater than that for boat and 

 because most boats were only used during 1 year. A total of 21 boat- 

 station-year combinations were examined; 18 of these were not significant, 

 In 1979, the vessel Sisu had significantly greater catches than the 

 vessel Mya at stations 1 and 4. Although it was a much smaller boat it 

 may have fished better than the larger Mya which couldn't maintain 

 steady towing speeds (J. Castleman, personal communication). In 1981, 

 the vessel Northeast I had significantly greater catches at station 1 

 than Northeast II . Although otherwise identical, the trawl rigging for 

 these two boats is different with the former more properly rigged for 

 trawling. Even though some differences due to boat were indicated, the 

 variation in CPUE as a function of vessel cannot be quanitified because 

 little direct comparative data exists among all the boats used. 



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