366 



Fishery Bulletin 98(2) 



Ventral 



Dorsal 



Left 



Right 



Figure t 



Profiles of an excised intact yellowfin tuna swimbladder. The actual length of the swimbladder was 165 mm, the maximum 

 width 69.1 mm, and the displacement volume 245 cc. The fish was 784 mm in length and 8.6 kg in weight. 



is situated directly adjacent to the dorsal wall of the 

 swimbladder. 



The relationship of swimbladder volume obtained 

 from volumetric displacement, to fish length for the 

 freshly caught yellowfin tuna is shown in Figure 3. 

 The relationship is described by a power function: 



0.000000005 



,.3.5715 



(r2=0.87,«=46) (1) 



where y\ - swimbladder volume at fish length x. 



The relationship of swimbladder volume, obtained 

 from volumetric displacement and expressed as a 

 percentage of the body volume (estimated from body 

 weight) to weight for freshly caught yellowfin tuna is 

 shown in Figure 4. The mean volume was 1.33% (95% 

 CI=0.16%) with minimum and maximum values of 

 0.30% and 2.84%, respectively. The relation between 

 the swimbladder volume, expressed as the percent- 

 age of body volume to body weight is described by 

 the following linear function: 



where Y,. = swimbladder volume, expressed as a 

 percentage of body volume, at weight .r. 



The relationship of swimbladder volume (esti- 

 mated from geometric reconstruction) to volume 

 obtained from volumetric displacement for freshly 

 caught yellowfin tuna is shown in Figure 5. The rela- 

 tionship was described and analyzed by the follow- 

 ing linear function, with the intercept set to zero: 



Y= 1.0735.V. 



7-=:0.96, n=46 (3) 



1.0822 -I- 0.014ar, 



(r-'=0.17,n=46) (2) 



where Y^ - swimbladder volume estimated from 

 geometric reconstruction for the corre- 

 sponding volumetric displacement .v. 



The regression coefficient is significantly different 

 from 1 (^0 0.5(21.^4=2-41; P<0.05). However, it is appar- 

 ent from Figure 5 that the two techniques produce 

 similar estimates, providing credence to the estima- 

 tion of volume from geometric reconstruction. 



Analysis of covariance applied to the log-trans- 

 formed swimbladder volumes by geometric recon- 



