Fishery of threadfin breams along Saurashtra coast (Gujarat), and some aspects of biology of Nemipterus japonicus (Bloch, 1791) and N. mesoprion (Bleeker, 1853)

During 1997-2002, threadfin breams contributed 10% to the annual average landings by trawlers at Veraval and Mangrol. Peak landing of 26,457 t was observed in 2000, with a catch rate of 11.6 kg per hour. Nemipterus japonicus and N. mesoprion dominated the threadfin bream fishery along this coast. The length range of N. japonicus and N. mesoprion in the landings was 60-390 mm and 80-280 mm respectively.Occurrence of larger individuals was more during October-January. Females dominated the catches. The size at first maturity was estimated as 141 mm for N. japonicus and 135 mm for N. mesoprion. The spawning peak in N. japonicus was found to occur during September-December, with a secondary peak in May. N. mesoprion had a prolonged spawning period extending from October to March. The constants of length-weight relationships derived were a = 0.0000427; b = 2.777 and a = 0.0000983; b = 2.626 for male and female N. japonicus, respectively and a = 0.0000281; b = 2.895 and a = 0.0000277; b = 2.898 for male and female N. mesoprion, respectively. The relationships were found to be significantly different between sexes in both the species.