1 cm high and has an area of 2.0 cm 2 . The anal fin 

 is also 1 cm high and has an area of 2.2 cm 2 . The 

 combined total surface area of both sides of the sec- 

 ond dorsal and anal fins is 8.4 cm 2 , which is larger 

 than predicted (7.2 cm 2 ) by the Magnuson and 

 Weininger equation (1978, app. II). The total num- 

 ber of second dorsal and anal fin rays and dorsal and 

 ventral finlets agrees with that for other yellowfin 

 tuna (Gibbs and Collette 1967, table 1). 



Table 1 compares caudal keel area and caudal and 

 right pectoral fin dimensions of the study specimen 

 and seven SIO fish of differing L. Also shown are 

 values calculated for several of the same parameters 

 using allometric equations for T. albacares 

 (Magnuson 1978, table X; Magnuson and Weininger 

 1978, app. II). The caudal keel area of the one-finned 

 fish (6.2 cm 2 ) is smaller than the value expected 

 from the equation (6.7 cm 2 ) but is well within (i.e, 

 93%) the range of variation (77-102%) seen in the 

 SIO specimens (Table 1). Comparison of the 

 measured and the equation-derived caudal data for 

 the one-finned fish with the same set of values for 

 the next smallest (32.5 cm) and largest (37.0 cm) SIO 

 fish indicates that the caudal fin of the one-finned 

 fish has a slightly smaller span but larger area than 

 would be expected for its L. This is further reflected 



in its aspect ratio (AR; 4.63), which is lower than that 

 of any of the SIO specimens. This lower value prob- 

 ably does not represent an artifact of preservation 

 because in the other material caudal span and area 

 increased directly with L. There is also general 

 agreement between the measured and calculated 

 values for each, showing that neither preservation 

 nor measurement protocols affected caudal fin data. 

 As would be expected from the underlying formulae, 

 caudal AR calculated from the equations increases 

 with L. However, among the measured data, there 

 is no correlation between AR and L. It is also note- 

 worthy that both the mean and predicted AR values 

 of all of these small yellowfin (5.64, 5.34, Table 1) are 

 in good agreement but well below the summary 

 range (6.8-7.2) given for larger T. albacares by 

 Magnuson (1978, table IX). This serves to empha- 

 size that while AR may differ between species of 

 scombrids (Magnuson 1978), it also varies within 

 each species as a function of body size 



Both the length and area of the right pectoral fin 

 of the one-finned fish are much less than those of 

 the 37 cm SIO specimen (Table 1). When measured 

 and computed pectoral fin areas are compared, there 

 is good agreement between both values for the 37 

 and 42.5 cm L fishes but not for the 36.5 cm L one- 



Table 1.— Comparative caudal and right pectoral fin measurements for the one-finned 

 yellowfin tuna (36.5 cm L) and seven specimens of different lengths (L) from the SIO 

 collection. Data for each fish includes the actual measured values (m) and values 

 calculated (c) from equations in the footnotes (Magnuson and Weininger 1978, app. II). 



465 



