FISHERY BULLETIN: VOL. 80, NO. 1 



TABLE 7.— Comparison of mean empirical length-age data obtained by reading tomtate 



scales and otoliths. 



age-Ill, 197.1; age-IV, 213.0; age-V, 232.2; age- 

 VI, 253.1; and age- VII, 267.0 mm. 



The relative length frequencies of the mea- 

 sured distance from the focus of the scale to each 

 ring progressively increased with the number of 

 rings. Significant features of the plotted curves 

 were the occurrence of one mode for each ring, 

 the consistent location of a specific mode on the 

 X-axis for fish of different ages, the increased 

 overlap for each additional ring, and the pro- 

 gressive decrease in the distance between modes 

 for each successive year, indicating less linear 

 growth each year as the fish ages. 



Growth 



There was relatively little difference in the 

 mean annual increments of fish aged by scales 

 and those of fish aged by otoliths (Table 7). An- 

 nual growth increments for fish aged by scales 

 for ages I-V were: HI, 46.5 mm; II-III, 21.1 mm; 

 III-IV, 17.0 mm; and IV-V, 14.5 mm. After age 

 V, growth appears to be more irregular, prob- 

 ably a result of the relatively small sample sizes 

 for ages VI, VII, VIII, and IX (Table 7). 



Lengths by age for fish from all years were 

 back-calculated from a scale radius-fish length 

 regression. The prediction equation was 



TL = 1.7489 SR 09512 ; r = 0.93 and AT = 103, 



where TL = total length, and SR = scale radius. 

 By substituting the means of the distances from 

 the focus to each annulus for SR in the above 

 equation, we were able to calculate the mean fish 

 length at the time of each annulus formation, and 

 the mean annual growth increment for each age 

 (Table 8). 



The von Bertalanffy equation was used to de- 

 scribe theoretical growth. The growth param- 

 eters L x and K were first calculated by fitting a 

 Walford (1946) line to back-calculated data. The 

 equation was Itn = 90.833 + 0.6747*,, r = 0.982. 

 Our first estimate of K was L 0.6747 or 0.3935. 

 This value was used to obtain L x by solving the 

 equation L x = ^-intercept / (1 — k). The initial 

 value for L x of 289, and the subsequent value of 

 285.7 obtained by regressing annual growth in- 

 crement {X) against fish length at the beginning 

 of the incremental period (Y) (Jones 1976), 



Table 8.— Calculated total lengths (millimeters) of 346 tomtates aged by scales. 



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