Morphometric variations associated with breeding season in obtuse barracuda, Sphyraena obtusata Cuvier, 1829 observed from the commercial fish landings at Vizhinjam, Kerala, India

Obtuse barracuda (Sphyraena obtusata Cuvier, 1829) is one of the common species available throughout the year in the landings from traditional fishing crafts and contribute much to the total landings along Thiruvananthapuram coast, Kerala. Since all size groups are available throughout, the present study was carried out to find out the morphometric variations of the species with respect to its breeding season. A total of 9 morphometric variables and weight were recorded monthly from 429 fishes, landed at Vizhinjam fish landing center (Thiruvananthapuram District, Kerala) for two years from January 2017 to December 2018. Analysis of variance (One Way ANOVA) along with post hoc comparisons (DMR test) of the morphometric variables comparing breeding seasons (pre spawning, spawning and post spawning) revealed significant (P < 0.05) variations in weight, head length, snout length, snout to pre-nostril length, inter-dorsal length and caudal peduncle length in total population (N=429). Seasonal comparison of male population (n=176) alone also showed significant difference similar to total population except head length and female population (n=253) registered significant difference in only three variables (snout length, snout to pre-dorsal length and caudal peduncle length). Morphometric ratios (TL: SL, SnL: SL, Sn-Plvc: SL, Intr-Drsl: SL and CPL: SL) showed significant variations between the seasons. Principal component analysis extracted three variables ratio, TL: SL, SnL: SL and CPL: SL as contributing factors for morphometric variations in breeding season. Rate of growth in terms of morphometric ratios showed more fluctuations than measured variables, which clearly emphasized the shift in growth rate from length to weight dependency during breeding season.