AGE AND GROWTH OF SKIPJACK TUNA, KATSUWONUS PELAMIS, AND 



YELLOWFIN TUNA, THUNNUS ALBACARES, AS INDICATED 



BY DAILY GROWTH INCREMENTS OF SAGITTAE 



James H. Uchiyama* and Paul Struhsaker^ 



ABSTRACT 



Counts of the daily growth increments on otoliths provided the means for establishing growth curves 

 for central Pacific skipjack tuna, Katsuwonus pelamis , up to 3 years old and for central Pacific yellowfin 

 tuna, Thunnus albacares. up to 2 years old. The data indicated three stanzas of linear growth for 51 

 skipjack tuna ranging in size from 3 to 80 cm fork length. Estimated daily growth rates were 1.6 

 mm/day for fish up to a length of about 27.0 cm; 0.8 mm/day for fish between 27.0 and 71.4 cm; and 0.3 

 mm/day for fish between 71.4 and 80.3 cm. Growth data for 20 eastern Pacific skipjack tuna ranging in 

 size from 38 to 65 cm fork length suggested that skipjack tuna in the eastern Pacific grew at a slower 

 rate than those from the central Pacific. 



Age determinations of 14 central Pacific yellowfin tuna suggested possibly two stanzas of linear 

 growth. Estimated growth rates are 1.4 mm/day for fish up to a length of 64.2 cm and 0.9 mm/day for fish 

 between 64.2 and 93.0 cm. Growth curves from this study were compared with published growth curves 

 based on other methods. 



The validity of daily growth increments was tentatively determined by observations on skipjack and 

 yellowfin tunas held in captivity. Agreement of our growth curves with those of previous studies on the 

 same stock of tunas using other growth estimating techniques also suggests that our aging technique is 

 acceptable. However, the day-to-growth increment relation and the effect of various variables on the 

 formation of growth increments of tunas need to be investigated further. 



The many studies on age and growth of skipjack 

 tuna, Katsuwonus pelamis, have primarily 

 utilized three basic methods. Brock (1954), 

 Schaefer (1961), Kawasaki (1965), Joseph and 

 Calkins (1969), Yoshida (1971), Marcille and 

 Stequert (1976a), and Diaz^ determined growth 

 rate and estimated the age of skipjack tuna by 

 examining modal progression in length-frequency 

 distributions. Yamashita and Waldron (1959), 

 Shaefer et al. (1961), Clemens and Roedel (1964), 

 Rothschild (1967), and Joseph and Calkins (1969) 

 used data from tagged skipjack tuna to determine 

 growth rates. Wild and Foreman (1980) estimated 

 the growth rate of eastern Pacific skipjack tuna 

 from the recapture fork length, the known period 

 of growth, and the linear change in an otolith 

 dimension following a tetracycline injection which 

 was used to estimate length at marking. Marks on 



'Southwest Fisheries Center Honolulu Laboratory, National 

 Marine Fisheries Service, NOAA, Honolulu, HI 96812. 



^Southwest Fisheries Center Honolulu Laboratory, National 

 Marine Fisheries Service, NOAA, Honolulu, Hawaii; present 

 address: Easy Rider Corporation, 1050 Koloa Street, Honolulu, 

 HI 96816. 



^Diaz, E. L. 1966. Growth of skipjack tuna, Katsuwonus 

 pelamis, in the eastern Pacific Ocean. Unpubl. rep., 18 p. 

 Inter-Am. Trop. Tuna Comm., La Jolla, Calif. 



hard parts such as vertebrae and dorsal spines 

 were interpreted to determine age and growth of 

 skipjack tuna by Aikawa and Kato (1938), Yokota 

 et al. (1961), Shabotiniets (1968), Batts (1972), and 

 Chi and Yang (1973). Numerous reviews have been 

 written on the subject and the lack of agreement 

 on the aging and growth rate of skipjack tuna has 

 frequently been noted. 



Likewise, many studies have been conducted on 

 age and growth of yellowfin tuna, Thunnus alba- 

 cares. Moore (1951), Yabuta and Yukinawa (1957), 

 Hennemuth (1961), Davidoff (1963), Diaz (1963), 

 Le Guen et al. (1969), Yang et al. (1969), Le Guen 

 and Sakagawa (1973), and Marcille and Stequert 

 (1976b) have estimated age and growth rate by the 

 analysis of modal progression in either length or 

 weight frequencies. Blunt and Messersmith 

 (1960), Schafer et al. (1961), and Bayliff^ used re- 

 sults of their tagging experiments to determine 

 the growth rate of yellowfin tuna in the eastern 

 Pacific. Wild and Foreman (1980) estimated the 

 growth rate of eastern Pacific yellowfin tuna by 



" Bayliff, W. H. 1973. Observations on the growth of yellow- 

 fin tuna in the eastern Pacific Ocean derived from tagging exper- 

 iments. Unpubl. rep., 26 p. Inter-Am. Trop. Tuna Comm., La 

 Jolla, Calif 



Manuscript accepted August 1980. 

 FISHERY BULLETIN: VOL. 79, NO. 1, 1981. 



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