albacore swim through the area of the longline 

 fishery, but are. for the most part, not vulner- 

 able to capture). Our belief that a large pro- 

 portion of the albacore that emigrate from the 

 North American fishery first enter the pole- 

 and-line fishery is based on several lines of 

 evidence: (1) size distribution. (2) size distri- 

 bution combined with estimates of growth rate 

 and the time interval between middates for the 

 various fisheries, (3) the correlation between 

 apparent abundance in the longline fishery and 

 in the pole-and-line fishery, and (4) tagging 

 data. 



influence of recruitment directly from the 

 spawning grounds has a negligible effect on the 

 difference between the average lengths of the 

 longline fish and the pole-and-line fish. A 

 second point is that the discrepance in average 

 length between the fish in the two fisheries 

 should not preclude an interpretation that some 

 of the albacore may be captured in the longline 

 fishery before reaching the pole-and-line fish- 

 ery. Clearly the difference in average age of 

 the fish in the two fisheries is a function of, 

 among other things, the proportion of fish that 

 enter either fishery. 



Size Distribution 



We note that the average size of the albacore 

 taken in the pole-and-line fishery is consistent- 

 ly less than the average size of albacore taken 

 in the longline fishery (fig. 5). The difference 

 in size implies that the fish in the longline 

 fishery are, on the average, older than the fish 

 in the pole-and-line fishery. This difference by 

 itself might be taken to indicate that the alba- 

 core enter the longline fishery only after pass- 

 ing through the pole-and-line fishery. Two 

 qualifications to this interpretation are neces- 

 sary. First, young albacore are taken along 

 the Japanese coast (see, for example, Otsu and 

 Uchida, 1963). It is unlikely these young alba- 

 core are emigrants from the North American 

 fishery. They are probably recruited directly 

 into Japanese coastal waters from the place of 

 their birth, probably the equatorial western 

 Pacific. If the eastern Pacific emigrants were 

 partitioned equally between the pole-and-line 

 and the longline fishery then, ceteris paribus, 

 the average length of the albacore in the two 

 fisheries would be roughly equal (actually the 

 albacore taken by the longline fishery would be 

 slightly smaller than the albacore taken by the 

 pole-and-line fishery, owing to the temporal 

 difference in the peak fishing period). But it 

 young albacore, directly from the spawning 

 grounds, were taken in the pole-and-line catch 

 then the average length of the pole-and-line 

 fish would be less than that of the fish on the 

 longline grounds. Thus, the observed differ- 

 ence in average size between the fish taken on 

 the longline grounds and the pole-and-line 

 grounds may be the result of the pole-and-line 

 fishery's having a significant recruitment of 

 young, small fish that have never passed 

 through the eastern Pacific fishery. Our opin- 

 ion, however, based on examination of length 

 frequencies given by Suda (1963a), is that the 



Size Distributions, Growth Rate, and the Time 

 Interval Between the Middates of the 

 Various Fisheries 



The California fishery is centered on mid- 

 August (for timing of the various fisheries we 

 use data from Suda (1963b)), and the modal size 

 of fish taken in this fishery appears to be about 

 65 cm. (Clemens and Craig, 1965). The longline 

 fishery peaks 5 months after the California 

 fishery at the end of January, and the pole-and- 

 line fishery peaks about 4 months after the 

 longline fishery, at the end of May. If we use 

 the VBGF (von Bertalanffy growth function) for 

 albacore computed by Shomura (1966) with 

 Otsu's (1960) data as havingparameters Lao= 119, 

 K = 0.25, then the 65 cm. albacore would be 

 74cm. after 5 months and 78 cm. after an addi- 

 tional 4 months. Thus, if the albacore simply 

 moved from coastal North America to the long- 

 line grounds, to the pole-and-line grounds, then 

 we should expect that the fish in each fishery 

 should have modal lengths of 65 cm., 74 cm., 

 and 78 cm., respectively. This expectation is 

 not met, however, because the data given by 

 Suda (1963a) show that the albacore taken in the 

 pole-and-line fishery average several centi- 

 meters smaller than those taken in the longline 

 fishery. This difference suggests considering 

 an alternative, viz, that the albacore move from 

 the coastal North American fishery to the pole- 

 and-line fishery to the longline fishery. If the 

 predominant movement was indeed from the 

 North American, to the pole-and-line, to the 

 longline fisheries, then the 65 cm. fish would, 

 according to the same VBGF as before, appear 

 as 78 cm. fish 9 months later in the Japanese 

 pole-and-line fishery and as 85 cm. fish in the 

 Japanese longline fishery 8 months after ap- 

 pearing in the Japanese pole-and-line fishery. 

 An average size of 78 cm. in the pole-and-line 

 fishery and of 85 cm. in the longline fishery is 



25 



