Fishery and biological characteristics of the spadenose shark Scoliodon laticaudus Müller & Henle, 1838 from the Eastern Arabian Sea

Abstract

The relative abundance and biological characteristics of the spadenose shark Scoliodon laticaudus, from the south eastern Arabian Sea along Karnataka, India was studied. The average annual catch of the species during the period 2012–2017 was estimated at 112 t which formed about 13% of the total shark landing in the region. The species is landed mostly by trawl nets. Monthly abundance estimates showed that highest landing of the spadenose shark was observed in January. A total of 852 specimens were studied for biological characteristics. The length range of 19–63 cm was observed and length group of 45–55 cm formed the mainstay of the fishery. The length weight relationship for male and female and sexes pooled were 0.06588 L2.2386; 0.01118 L2.7497 and 0.01396 L2.6840 respectively. Analysis of covariance showed significant differences between the male and female (p<0.05). In the present analysis, the regression co-efficient (b value) for the species differs significantly from the value 3 indicating allometric growth. Lm50 for female and male were estimated as 32 and 33 cm. Chi-square-test on monthly sex ratio for the period showed that there was significant difference in sex ratio only in the months of January, October and November. S. laticaudus was found to be predominantly piscivorous in diet. The fishery is declining and efforts have to be taken for sustainable exploitation of resources.