Biometric characteristics of small Atlantic bluefin tuna (Thunnus thynnus, Linnaeus, 1758) of Mediterranean Sea origin

Abstract

The aim of this study was to provide a detailed description of the biometry of the juvenile Atlantic bluefin tuna (FL = 50–127 cm) of Mediterranean Sea origin. Regarding meristic features, there were 31.5 (SD = 2.1) gillrakers found on the first gill arch, 13.41 (SD = 0.494) spines in the first dorsal fin, 33.56 (SD = 2.124) soft rays in the pectoral fin, 9.86 (SD = 0.464) dorsal finlets and 8.90 (SD = 0.412) ventral finlets on the tail. Results of morphology analyses indicate that, on average, the head length contributes 28.84% (SD = 0.745); first predorsal length contributes 31.86% (SD = 0.915); preanal length contributes 61.45% (SD = 1.632); maximum body height contributes 26.90% (SD = 1.001); second dorsal fin height contributes 11.11% (SD = 1.457); pectoral fin length contributes 20.09% (SD = 1.550); and caudal fin width contributes 28.60% (SD = 1.842) of the fork length. Eye diameter comprises 13.14% (SD = 1.471), snout length 33.11% (SD = 1.332) and postorbital length 53.75% (SD = 1.354) of the head length. The significant change in body proportions, as fish grow in length, has been noted and leads to the conclusion that the juvenile bluefin body does not grow isometrically in size. Continuous decrease in the mean condition factors as body length increased, and a length–weight relationship describing negative allometric growth [ln WW (g) = −3.2965 + 2.8546 ln FL (cm)], indicate elongation of the juvenile bluefin body shape during early life, corresponding mostly to the period preceding sexual maturity.