LAURS and WETHERALL; GROWTH RATES OF NORTH PACIFIC ALBACORE 



Such a comparison was recently made for bait- 

 boat-caught southern bluefin tuna, T. maccoyii, 

 by Hearn/ who found that fish caught 3 wk after 

 being tagged weighed 14% less than untagged fish 

 of the same length in the same schools. Assuming 

 the tagged bluefin tuna also grew less in length 

 than their untagged counterparts, this 14% 

 weight loss would be an underestimate. At any 

 rate, after 1 yr at liberty no difference in weight 

 was discernible. 



We found that the growth rate of North Pacific 

 albacore recaptured either off the coast of North 

 America north of lat. 40° N or in the western North 

 Pacific off Japan was significantly lower than for 

 tagged albacore recaptured off North America 

 south of lat. 40° N during 1972-78. The differences 

 in growth rate of tagged fish are remarkably 

 consistent with differences in length-frequency 

 distributions of albacore caught off North Amer- 

 ica north and south of lat. 38° N during the period 

 when most recaptures were made. These findings 

 add to a growing body of evidence (Brock 1943; 

 Laurs and Lynn 1977; Laurs et al. ; Laurs and 

 Lynn ) that North Pacific albacore are not as 

 homogeneous as usually assumed, and that there 

 may be at least two subgroups of albacore: one 

 which supported the Japanese pole-and-line fish- 

 ery and the United States and Canadian fisheries 

 in waters north of about lat. 40° N from 1972 to 

 1978, and another which did not contribute sig- 

 nificantly to the Japanese surface fishery, but 

 supported the United States coastal fishery south 

 of lat. 40° N during this period. If such a distinc- 

 tion is valid, the situation is surely more complex 

 and dynamic than we have supposed, with each 

 stock's contribution to each fishery varying from 

 year to year. Presumably such variation would be 

 tied directly to changes in oceanographic con- 

 ditions. And undoubtedly the latitudinal bound- 

 ary was not fixed exactly at lat. 40° N during 

 1972-78, as we assumed, but analyses based on 

 assumed boundaries at lat. 38° and 42° N gave the 



■'Hearn, W. S. 1979. Growth of southern bluefin tuna 

 (Thunnus maccoyii). Commonwealth Scientific and Industrial 

 Research Organization, Division of Fisheries and Oceanog- 

 raphy, Cronulla, New South Wales, Australia, Unpubl. manuscr. 



»Laurs, R. M., R. J. Lynn, and R. N. Nishimoto. 1975. Re- 

 port of joint National Marine Fisheries Service- American Fish- 

 ermen's Research Foundation albacore studies conducted during 

 1975. Southwest Fish. Cent. La Jolla Lab., Natl. Mar Fish. 

 Serv, NOAA, Admin. Rep. LJ-75-84, 49 p. 



''Laurs, R. M., and R. J. Lynn. 1976. Report of joint 

 National Marine Fisheries Service-American Fishermen's Re- 

 search Foundation albacore studies conducted during 1976. 

 Southwest Fish. Cent. La Jolla Lab., Natl. Mar. Fish. Serv., 

 NOAA, Admin. Rep. LJ-76-36, 51 p. 



same results. If an accurate assignment of tagged 

 fish to stock were possible, a more powerful test of 

 growth differences could be made. 



A finding that more than one subpopulation or 

 stock is involved in the North Pacific albacore 

 fisheries would have important consequences, of 

 course, both for stock assessment, fishery evalua- 

 tion and management policy analysis, and for 

 development of accurate catch forecasting 

 systems. It is important that further work be done 

 to identify stocks, and to elucidate their origins, 

 migratory habits, and degree of interchange. 



LITERATURE CITED 



AIKAWA, H., AND M. KATO. 



1938. Age determination offish (preliminary report 1). [In 

 Jpn., Engl, synop.] Bull. Jpn, Soc. Sci. Fish. 7:79-88. In 

 W. G. Van Campen (translator), U.S. Fish Wildl. Serv., 

 Spec. Sci. Rep. Fish. 21, 22 p., 1950. 

 Bell, R. R. 



1962. Age determination of the Pacific albacore of the 

 California coast. Calif. Fish Game 48:39-48. 



Brock, V. E. 



1943. Contribution to the biology of the albacore (Germo 

 alalunga) of the Oregon coast and other parts of the North 

 Pacific. Stanford Ichthyol. Bull. 2:199-248. 

 CLEMENS, H. B. 



1961. The migration, age, and grow^th of Pacific albacore 

 (Thunnus germo), 1951-1958. Calif Dep. Fish Game, 

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 DRAPER, N. R., AND H. SMITH. 



1966. Applied regression analysis. Wiley, N.Y., 407 p. 

 GANSSLE, D., and H. B. CLEMENS. 



1953. California-tagged albacore recovered off Japan. 

 Calif. Fish Game 39:443. 



JOSEPH, J., AND T. R Calkins. 



1969. Population dynamics of the skipjack tuna (Katsu- 

 wonus pelamis) of the eastern Pacific Ocean. [In Engl, 

 and Span.] Inter-Am. Trop. Tuna Comm., Bull. 

 13: 1-273. 



Laurs, R. M., W. H. Lenarz, and R. N. Nishimoto. 



1976. Estimates of rates of tag shedding by North Pacific 

 albacore, Thunnus alalunga. Fish. Bull., U.S. 

 74:675-678. 



LAURS, R. M., and R. J. LYNN. 



1977. Seasonal migration of North Pacific albacore, Thun- 

 nus alalunga , into North American coastal waters: Distri- 

 bution, relative abundance, and association with Tran- 

 sition Zone waters. Fish. Bull., U.S. 75: 795-822. 



NOSE, y, H. KAWATSU, and Y. HIYAMA. 



1957. Age and growth of Pacific tunas by scale reading. 

 [In Jpn., Engl, summ.] In Suisan Gaku Shusei, 

 p. 701-716. Tokyo Univ. Press. 

 OTSU, T 



1960. Albacore migration and growth in the North Pacific 

 Ocean as estimated from tag recoveries. Pac. Sci. 

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 OTSU, T, AND R. F SUMIDA. 



1970. Albacore (Thunnus alalunga) of Hawaiian waters. 

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