Investigation of some morphometric characteristics of Frigate tuna Auxis thazard (Lacepede, 1800) caught with drift gillnets in Chabahar waters

Abstract

Introduction: Since baby yolk fish is one of the most important commercial fishes in the
Oman Sea, it seems necessary to investigate the stocks of this species in order to achieve
optimal and integrated management of these stocks in order to achieve sustainable fishing.
Materials & Methods: In the present study, some biological characteristics of Frigate tuna
Auxis thazard (Lacepede, 1800) species caught with drift gillnets in Chabahar fishing ports
from October 2019 to March 2020, were studied and measured. Fishing operations were
performed by multifilament surface drift gillnets with hanging ratio 50% and mesh size 70,
79 and 101 mm from knot to opposite knot (STR).
Result: In total, 299 fish samples were bioassayed that the Mean±SD of fork length in
autumn and winter 38.02±4.94 cm and 37.58±4.84 cm and in total sampling duration
37.80±4.89 cm was obtained. Length range of caught fishes was from 30 to 50 cm, that the
length ranges of 37-36 and 35-34 cm had the highest relative frequency with 21.74% and
18.39%, respectively. The exponential equation of fork length and weight was calculated
as W=0.0102 FL3.1077 and logarithmic data exhibited the exponent value of b>3, showed
that A. thazard has positive allometric growth. Also in total fish, between fork length and
weight and fork length and girth were a high significant correlation (P<0.01).
Conclusion: According to the Lm50 of A. thazard reported in previous research 29.7 cm,
the findings of the present study showed that A. thazard caught on the shores of Chabahar
have a standard size, which is very effective in managing successful fishing of this species
in the region.