360 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



Table 2. — Albacore tag recoveries reported by POFI and the California Department of Fish and Game 



1 The data for the California tag recoveries are derived from the reports of Ganssle and Clemens (1953), Blunt (1954), and Anonymous (1955). 



2 Department of Fish and Game, Sacramento, California. 



3 Pacific Oceanic Fisheries Investigations, U. S. Fish and Wildlife Service. 



Variable growth is indicated, ranging from 2 cm. 

 in about 6 months to 37 cm. in 16 months (4 to 

 28 cm. per year). The weights indicated in 

 figure 8, with the exception of the last two recov- 

 eries (Nos. 8 and 9, table 2), are estimated weights 

 based on the following length-weight relation : 



Log Weight= -7.0239 + 2.87912 Log Length ' 



In terms of weight, a rough estimate of growth 

 amounted to 6, 9, 27, 6, and 10 pounds per year, 

 respectively, for the 5 fish shown from top to 

 bottom in figure 8. Clearly, no conclusions can 

 be drawn from these data. It is to be noted, 

 however, that there are indications here of a 

 moderately rapid growth rate, somewhat greater 

 than the various estimates provided by the 

 vertebral method of age determination. 



It is possible, of course, that the rings on the 

 centra are associated with growth but not neces- 

 sarily with age of the fish. Unlike many of the 

 fishes of the north temperate zone, it appears that 

 albacore live under fairly uniform conditions by 

 migrating to areas where food is available and 

 where water temperature is suitable. They are 

 not subject to extremes of winter and summer 

 conditions as are certain fishes that occupy a more 

 limited range. In the absence of any environ- 

 mental extremes that might produce marked 

 changes in the metabolic activity of the fish, it is 

 quite possible that "winter" rings do not appear 

 on the albacore's scales and vertebrae. 



We have concluded that the rings on the verte- 

 brae are probably not age rings which are laid- 

 dowo annually or at such regular intervals that 

 they can be used to tell the age of the fish; how- 



i Computed by POFI based on 77 fish (51-119 cm.) taken in the central 

 North Pacific. 



ever, even if the rings were laid down randomly 

 with respect to time, older fish in general would 

 be expected to possess more rings than the younger 

 ones. Assuming this applies to the albacore, the 

 number of rings in relation to the size of fish 

 might be used to differentiate rapidly growing 

 fish from slower growing individuals. Counts of 

 rings in albacore separated by sex show that among 

 larger fish, the females, at a given ring count are 

 smaller than the males (fig. 9). The number of 

 rings in the counts ranged from 3 to 12, and the 

 females were represented for each count up to 

 11 rings. Although the female albacore ap- 

 parently do not grow so large as the males, 

 having reached their maximum size at around 

 112 cm. (fig. 10, alsoOtsu and Uchida, 1959), the 

 ring counts indicate that the largest females may 

 be about as old as the largest males. 



A great predominance of males has been noted 

 among the larger sizes of several species of tunas 

 (e. g. Shomura and Murphy 1955). This unequal 

 sex ratio among the larger sizes has been attrib- 

 uted to "either differential mortality or differential 

 growth, or to combinations of the two factors." 

 Differential availability has also been suggested. 

 For albacore there is a similar situation, but 

 somewhat more pronounced, for the males attain 

 a markedly larger size than females (fig. 10). 

 Returning to figure 9, fish having 7 or more 

 rings show growth differentiation by sex, the 

 males being the larger for each ring class. This 

 bit of evidence suggests that after about the 

 seventh ring, the males have a faster growth 

 rate than females. It is interesting to note that 

 this apparent differentiation in growth commences 

 when the fish attain a length of about 90 cm., 

 which is the size at which albacore are believed 



