Length Based Growth Estimation of Most Commercially Important Scombridae from Offshore Water of Pakistan Coast in the Arabian Sea

Seasonal growth pattern of skipjack tuna (Katsuwonus pelamis), longtail tuna (Thunnus tonggol), kawakawa (Euthynnus affinis) and king mackerel (Scomberomorus guttatus) were studied during five years period (between August 2006 and December 2011). Seasonal samplings of the species were collected from offshore water of Pakistan coast in the Arabian Sea. The weight - length relationships (WLRs) among the species except E. affinis demonstrated that the growth is allometric type (Pauly's t test, P < 0.005). The seasonal von Bertalanffy growth model parameters computed from seasonal length - frequency distributions, were estimated as L[infinity] = 67.1 cm TL, K = 1.055 year?1, C = 0.990 for E. affinis, as L[infinity] = 66.8 cm TL, K = 1.378 year?1 and C = 0.950 for K. pelamis, as L[infinity] = 71.7 cm TL, K = 0.916 year?1 and C = 0.849 for T. tonggol, as L[infinity] = 55.7 cm TL, K = 1.049 year?1 and C = 0.980 for S. guttatus. The seasonal oscillation in growth rate was determined for the species (C > 0.8). The slowest period of growth corresponded to in September (WP = 0.7) for E. affinis, (WP = 0.6) in August for K. pelamis, (WP = 0.4) in May for T. tonggol and (WP = 0.0) in January for S. guttatus