POPULATION DYNAMICS AND EXPLOITATION STATUS OF TWO HIGHLY VALUED SCOMBRIDS (RASTRELLIGER KANAGURTA AND THUNNUS TONGGOL) ALONG THE BALOCHISTAN COAST, PAKISTAN

Abstract

This study investigates the population dynamics of the Indian mackerel (Rastrelliger kanagurta) and the longtail tuna (Thunnus tonggol), two commercially vital species of the Scombridae family. A total of 207 R. kanagurta (16–30 cm TL; 18–250 g) and 132 T. tonggol (40–133 cm TL; 1600–11200 g) specimens were collected from commercial landings at Gwadar and Pishokan, Balochistan. Growth parameters, length-weight relationships (LWRs), mortality rates, recruitment patterns, and virtual population analysis (VPA) were estimated using FiSAT II software and Excel. High correlation coefficients (R2) were observed in the LWRs for both species. For R. kanagurta, the estimated parameters were asymptotic length (L∞) = 27.30 cm, growth coefficient (K) = 0.460 yr-1 natural mortality (M) = 0.763, and fishing mortality (F) = 0.768. For T. tonggol, L∞ was 63 cm, K was 0.540 yr-1, M was 0.936, and F was 0.534. Recruitment patterns for both species indicate continuous, year-round recruitment with distinct cohorts appearing in both summer and winter seasons. In order to sustainably manage and conserve the Scombrid stocks in North Arabian Sea, these findings provide the necessary biological benchmarks.