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FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



DISTRIBUTION OF 1952 AND 1953 CATCHES 

 BY BIWEEKLY PERIODS 



Catches for the Entire Fishery 



Only during July and August (periods 14-17) 

 and briefly in December (period 25) did the 1952 

 skipjack catches reach the magnitude of the 1953 

 totals (fig. 9). In particular, the spring of 1953 

 and, to a lesser extent, the autumn months pro- 

 vided much larger catches than occurred in 1952. 



Effects of Small Craft Warnings 



There were 49 days with small craft warnings 

 during 1952 and 17 during 1953 (fig. 9), but only 

 6 of these fell in the interval from April through 

 September in 1952 and none in 1953. The effects 

 of rough weather, thei-efore, appear to be rela- 

 tively minor in comparison with the seasonal 

 fluctuation in the availability of skipjack. 



The immediate effects of poor weather may be 

 indicated by the relatively small catches made dur- 

 ing periods 1, 2, 5, 6, 23, and 24 of 1952, each of 

 which had several days with small craft warnings. 

 Period 25, on the other hand, shows an increase in 

 catch despite 5 days of poor weather. 



MOVEMENTS OF SKIPJACK WITHIN 

 THE FISHERY 



Local changes in the skipjack catch within the 

 entire range of the fishery may result from changes 

 in the amount of fishing effort or from changes in 

 availability. The latter may include horizontal 

 movement of the fish into or out of a particular 

 area or, within an area, a change in the vertical 

 distribution or behavior such that the catch rate 

 by live bait fishing is affected. The records of the 

 fishery, however, provide no means by which one 

 or the other cause may be determined, and it is 

 therefore assumed for the purposes of this discus- 

 sion that all changes in the catch are caused by 

 movements of fish from one area to another. 

 Thus, errors, if any, are likely to be on the side of 

 postulating a horizontal movement of fish when 

 there has been a change in vertical distribution, 

 behavior, or fishing effort. This approach seems 

 to be the most reasonable one, because tagging ex- 

 periments show that individual skipjack travel the 

 length and breadth of the fishery, while knowledge 

 of changes in availability and fishing effort, par- 

 ticularly if nonproductive, remains quite limited. 



Large Skipjack 



After an interval of low abundance throughout 

 the islands during the early part of 1952, large 

 skipjack (fig. 10) appeared simultaneously in 

 small numbers in leeward Oahu and Kaiu^i in 

 period 8. In period 10 the fish arrived in wind- 

 ward Oahu and Hawaii. This sequence suggests 

 an approach from the west. In period 12, a con- 

 centration centered in windward Oahu occurred; 

 it appears to have shifted northward to Kauai by 

 periods 15 and 16. In jieriod 17, however, the 

 catches of large skipjack ceased in Hawaii and 

 began to dwindle in Kauai, but at the same time 

 the largest catches of the year were being made in 

 leeward Oahu. All these changes seem to indicate 

 that the large skipjack had returned to the leeward 

 side of the island chain. The gradually diminish- 

 ing catches from Kauai and leeward Oahu in 

 periods 18 through 20 indicated the withdrawal of 

 season fish to the westward. After period 20, the 

 numbers of large skipjack in the catch returned to 

 the state of low variable abundance which char- 

 acterizes the off-season of the fishery. 



During the interval from period 25 (1952) until 

 period4 (1953) the number of large skipjack taken 

 in all regions of the fishery was uniformly low, a 

 condition typical of the winter season. In period 

 5, however, a sharp increase occurred in the catch 

 of large skipjack in the leeward Oahu region. To 

 judge from the variation in average weights (fig. 

 12), these fish were 1952-season fish, being some- 

 what heavier than 1953-season fish which entered 

 the fishery in period 9. These 1952-season fish ap- 

 peared in the catches during periods 5, 7, 8, and 

 9 and were the cause of the apparent early begin- 

 ning of the "season" in 1953 (fig. 9). 



In period 9 of 1953, the season fish were present 

 throughout most of the fishei-y (note the declining 

 average weights in periods 9 and 10, fig. 12) but 

 the large catches in leeward Oahu in periods 10 

 through 12 suggest that the direction of the ap- 

 proach of the main body of fish was from the lee- 

 ward. As in the previous year, a peak occurred 

 early in the season in windward Oahu (period 12, 

 1952; period 13, 1953), and in succeeding periods 

 the fish dispersed southward to leeward Oahu and 

 Hawaii where large catches were made in periods 

 15-17. Following the excellent catches of period 

 17, the best of the year, a gradual decrease in catch 

 occurred, and by period 23 the season was over. 



