The selectivity of gillnets for Katsuwonus pelamis (Linnaeus, 1758) in the Oman Sea (Sistan and Baluchistan province)

Abstract

Introduction: One of the solutions for the management of fish resources, including
Katsuwonus pelamis as an economic species, is to determine the source of the tour standard
and implement it. Since Muscat Hoover fish is one of the target species in the composition
of surface fish catch in Sistan and Baluchistan province and it includes a relatively high
amount of catch in the fisheries of this province, the present study can provide useful
information about the catch status of this exploited species in the investigated area should
be presented, which seems to be necessary from the point of view of ecology and proper
management in the exploitation of reserves.
Materials & Methods: The selectivity of surface drift gillnets for Katsuwonus pelamis
(Linnaeus, 1758) in the fishing ports of Sistan and Baluchistan province from October 2019
to June 2020 with the meshes size of 145, 165 and 197 mm was assessed using Sechin
method. Morphometric data including fork length, total length and weight of specimens,
as well as the size of the opercula girth (enmeshed point) and the maximum girth in the
first dorsal fin to calculate the selectivity curve and the optimal selection length of K.
pelamis by net mesh, was measured.
Result: The results of measuring 719 fish showed that the length of the fork length ranged
from 46 to 80 cm (with an average of 55.87 cm) and also their weight range varied between
1980 and 10820 g (with an average of 3811.71 g). The length of sexual maturity (Lm50)
of K. pelamis was calculated to be 45.3 cm by microscopic observation using the least
squares method. Using selectivity by Sechin method, the optimal selection length was
obtained for the surface drift gillnets of K. pelamis with 145, 165 and 197 mm meshes size,
46, 53 and 60 cm, respectively. Also, the selectivity coefficient (net mesh size divided by
the optimal selection length) varied from 0.315 to 0.328. Using the selectivity coefficients
and the length of sexual maturity of K. pelamis, the optimal mesh size for catching K.
pelamis was determined to be 173 mm.
Conclusion: According to the results, immature fish were not caught in all the meshes used
and these meshes are no problem for fishing this species, but the standard mesh for this
species is 173 mm.