Standardization of Thunnus tonggol Bleeker, 1851 (Longtail tuna)surface gillnet mesh size in order to come up with the sustainable fishing pattern in Northern of the Persian Gulf and Oman Sea (Hormuzgan Province)

In order to come up with the sustainable fishing pattern of longtail tuna, there was a need to the gillnet mesh size designed to allows immature fishes escape and provide an opportunity for them to spawn at least once. In this review original gillnet mesh size (140 mm stretched), 114 and 132 mm mesh size nets were examined. The percentage of immature species in 140, 132 and 140 mm nets were 97%, 84% and 78% respectively. The linear relationships between fork length and head (in pre gill), gill, body (in first dorsal fin) and second dorsal fin perimeters were (HP=0.48FL+0.83), (GP=0.51FL+2.35), (BP=0.60FL+0.87) and (SDP=0.49FL+3.89) respectively. There was significant coefficient between linear equations and perimeter in first dorsal fin was maximum body perimeter. The elastic ratio were 24% in first dorsal fin and 19% in head and gill. The optimum standard gillnet mesh size based on relationship between fork length - body and length at first maturity was 170 mm stretched.