Determinatio the optimum mesh size of gillnets for Largehead hairtail (Trichiurus lepturus) fishing by Hormozgan coastal waters

Abstract

Introduction: This study was performed in order to the optimization mesh size of Trichiurus
lepturus´s gillnet-fishing in Hormozgan province.
Materials & Methods: At first linear relationships between the total length and the different
parts of the body of the Ribbonfish were obtained. In order to evaluate the efficiency and
determine the appropriate mesh size, the classification of fish caught by this method was
compared with the length at first maturity. The percentage of fish caught in different parts of
the body was investigated. By using the length at first maturity of this species and proportion
coefficient the optimal mesh size was obtained.
Results: More than 57% of the fish were caught in the head (around gill) as the highest part of
body fish. The length modes of the various parts of the ribbonfish, including head (gilled),
body, snout(snagged) circumference and entangled, were in the total length classifications of
50-55, 65-70, 65-70 and 80-85 cm, respectively. The proportion coefficient was equal to 0.036
and the optimal internal mesh (knot to knot opposite) was calculated to be 57 mm.
Conclusion: Considering that more than 71% of the ribbonfish caught with common gillnets
have been in sizes less than the length of maturity (78.7 cm total length), eliminating these
gillnets and using the optimized mesh nets that proposed this research study, reduces immature
fish in the fishing.