The hypotheses postulate that most recruits to 

 the eastern Pacific fishery result from spawning 

 in the equatorial central Pacific. This recruit- 

 ment stock remains in the fishery for several 

 months, begins to attain sexual maturity, and 

 leaves the eastern Pacific for the equatorial 

 central Pacific where spawning takes place. 

 Some of the evidence upon which the hypotheses 

 are based, and its major features are summa- 

 rized as follows: 



1. It appears that skipjack spawning in the 

 eastern Pacific Ocean is only incidental whereas 

 in the central Pacific spawning is relatively in- 

 tense. This suggests that the skipjack in the 

 eastern Pacific come from the central Pacific. 



2. It was hypothesized from immunogenetic 

 studies and the lack of uniformity in the time- 

 space distribution of skipjack spawning that the 

 skipjack of the central Pacific are not a single 

 homogeneous population unit. 



3. The central Pacific was divided into three 

 arbitrarily designated, but likely, zones of origin 

 for skipjack taken in eastern Pacific. These 

 zones are the Hawaiian Zone, the Equatorial 

 Zone, and the Marquesas Zone. 



4. It was speculated that skipjack from the 

 Marquesas Zone do not enter the eastern Pacific 

 fishery areas because an unlikely northward 

 component would be required for their migratory 

 path, the Marquesas Zone fish comprise different 

 subpopulations than any of the other areas stud- 

 ied, and a size difference between Tahitian and 

 Hawaiian Zone fish suggests the possibility that 

 fish from the Marquesas Zone may not undergo 

 a relatively high degree of exploitation. 



5. A consideration of the relative merits of 

 the Hawaiian and Equatorial Zones as loci for the 

 origin of eastern Pacific exploited fish involved 

 establishing that emigration from the eastern 

 Pacific was spawning-associated. It appears 

 that skipjack samples in the eastern Pacific ex- 

 hibit relatively high maturity indices for about 

 9 months each year. This period extends well 

 into the fall suggesting an equatorial destination 

 for the eastern Pacific emigrants. 



6. Length-frequency distributions taken from 

 some regions of the eastern Pacific show quar- 

 ter-to-quarter changes which may be indicative 

 of a more-or-less continual movement of skip- 

 jack through the fishery. It appears that this 

 size replacement is of a duration such that it is 

 unlikely that these fish are solely generated in 

 the Hawaiian Islands, thus again suggesting an 

 Equatorial Zone origin for a majority of these 

 fish. 



7. There have been three long-distance tag 

 recoveries to date. All three resulted from fish 

 tagged oft the Mexican coast. Two were recov- 

 ered in Hawaiian waters, one in equatorial 

 waters. When compared with the rest of the 



central Pacific, the Hawaiian region maintains a 

 relatively intense fishery, and therefore the re- 

 covery in equatorial waters is more likely to 

 represent a large movement of fish than the two 

 recoveries in Hawaiian waters. 



8. It is postulated that as the adolescent skip- 

 jack approach the coast of the Americas they are 

 split into a northern and southern contingent; 

 the northern contingent is harvested off the 

 Mexican coast and the southern contingent off 

 Central and South America. 



9. Length-frequency distributions from the 

 Hawaiian fishery do not exhibit typical trends 

 such as consistent growth increases; these dis- 

 tributions do, however, show a consistent pattern 

 for adjacent months. Only 3 years of data were 

 available to compare the essentially bimodal 

 Hawaiian length frequencies with the essentially 

 unimodal eastern Pacific length frequencies. 

 For two of the years it appears that skipjack in 

 the small size Hawaiian group have common 

 elements with eastern Pacific size frequencies. 



10. The observations of equal numbers of 

 large and small fish in the Hawaiian fishery, a 

 tremendous seasonality in catch, and the exist- 

 ence of at least two subpopulations in Hawaiian 

 waters suggest that there is a component of fish 

 enteringthe fishery that doesn't originate in the 

 Hawaiian Zone. 



11. A prediction of skipjack tuna catch in the 

 Hawaiian Islands has been utilized over the past 

 several years. Large components of variability 

 are not associated with the availability-associ- 

 ated predictive index, and it seems likely that 

 year-class associated phenomena play an im- 

 portant role in controlling the abundance of skip- 

 jack in Hawaiian waters. 



12. In some years when apparent abundance 

 in Hawaiian waters is high there is a smaller 

 size component of fish in the Hawaiian fishery. 

 This component may be evident as early as Feb- 

 ruary and may in itself serve as a predictive 

 index. An implication is that if year class phe- 

 nomena can be predicted from the Hawaiian 

 fishery and if the Hawaiian and eastern Pacific 

 fisheries catch skipjack of common origin then 

 it should be possible to predict the abundances of 

 year classes that enter the eastern Pacific fish- 

 eries. 



13. There is some time interval prior to 

 spawning during which skipjack are unavailable 

 to capture. This has a bearing on sampling 

 problems. 



14. The hypothetical nature of this work was 

 emphasized. 



15. A critical line for testing the hypotheses 

 in this paper was established among the Hawaiian 

 Islands, the Line Islands, and the Marquesas 

 Islands. 



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