KEENE and PEARCY: COMPARISON OF SUCCESS OF ALBACORE TROLL FISHERMEN 



apparent abundance, the latter being a function of 

 the accessibility of the albacore to the boats, the 

 vulnerability of the fish to the lures (Marr 1951), 

 and the true abundance of albacore. 



The 10 most successful and 10 least successful 

 fishermen (highliners and lowliners, respectively) 

 of each season were selected according to their 

 boats' average fishing power estimates through- 

 out the entire season. Highliners and lowliners 

 selected had fished for at least 15 days in 1968 and 

 1969 and 8 days in 1970. Thus fishermen who fished 

 exceptionally well or poorly for only a few days in 

 a season were not considered. 



Area-Date Stratum of Apparent Abundance 



Small-scale time and space information of 

 catches and boat positions allowed a departure 

 from the traditional time-area stratum of 1 mo 

 and 1° latitude-longitude rectangle (Ayers and 

 Meehan 1963; Clemens and Craig 1965). A mobile 

 stratum was conceived to allow comparisons of 

 apparent abundance and effort regardless of 

 where the fleet moved, and without the problems 

 of fixed geographic boundaries. 



The new stratum was a circular area, the center 

 being the daily medial location of the fleet. This 

 medial point was determined such that the fleet 

 was equally divided in the north-south and east- 

 west planes. Criteria for the radius of the circular 

 area were that it should be 1) as small as possible to 

 include a homogeneous distribution of fish, but 2) 

 large enough to accommodate a sufficient number 

 of boats fishing on a given day so that catch and 

 effort could be reliably estimated, and 3) large 

 enough to give reasonable assurance that boats 

 within the area remained in the area the entire 

 day. Because of the lack of knowledge of small- 

 scale albacore distributions, there was little basis 

 for satisfying the first criterion. 



Consecutively larger concentric circles were 

 drawn around the medial point while noting the 

 ratio of boats within each circle to the number of 

 boats in the entire fleet. (Danils (1952) has pre- 

 sented theoretical considerations of sample point 

 distributions within such circles.) During much of 

 each season, over half the boats could be found 

 within 25 miles of the fleet's center. Exceptions 

 occurred in each season when the fleet was highly 

 dispersed or split into two distinct groups. Two 

 distinct groups of boats occurred on 2, 3, and 4 

 August 1968 and also 1, 2, and 8 August 1969. 

 During these days the northernmost center was 



chosen to represent the fleet center because it 

 always contained more boats. 



The third criterion suggested a radius of at least 

 31 miles to insure that vessels remained within the 

 area the entire day. This radius was determined on 

 the basis of distances traveled daily by albacore 

 boats. (This is reported later in this study.) A circle 

 with a radius of 31 miles was therefore used as the 

 area size. Figure 1 shows the percentage of boats 

 that provided catch data within 31 miles of the 

 fleet center each day during the 1968, 1969, and 

 1970 seasons. Only the time periods within the 

 vertical lines in Figure 1 will be considered for this 

 study. On days outside these periods few boats 

 reported their catch, or the fleet was small and 

 highly dispersed. The average daily percentage of 

 those boats reporting within 31 miles of the fleet 

 center was 46%, 57%, and 65% for the 1968, 1969, 

 and 1970 seasons, respectively. The differences 

 between the 1968 average and the 1969 and 1970 

 averages were highly significant (f-test, P<0.01), 

 indicating that the 1968 fleet was more dispersed 

 in general than the 1969 and 1970 fleets. (This was 

 not a result of a greater number of boats reporting 

 in 1968 because the number of boats reporting per 

 day was often greater in 1969 and 1970 than in 

 1968.) There was a tendency in both 1968 and 1969 



100% 



50% 



100% 



1969 



0% 



15 19 23 27 31 4 8 12 16 20 24 28 32 

 JUL. AUG. 



Figure l.-Daily percentage of boats within 31 miles of the 

 albacore fleet center; 1968, 1969, and 1970. Vertical lines on plots 

 indicate the time periods considered in detail in this study. 



975 



