Morphological development and distribution of paralarvae juveniles of purple back flying squid Sthenoteuthis oualaniensis (Ommastrephidae), in the South eastern Arabian Sea

Abstract

The occurrence, distribution and morphological development of paralarvae and juveniles of Sthenoteuthis oualaniensis from the Arabian Sea (8°-17°N and 64°-76°Ee) are presented and discussed based on 32 exploratory surveys conducted during 2010-2013. The results indicated that the spawning grounds of S. oualaniensis may be in the southeastern Arabian Sea around the Lakshadweep Archipelago (09˚04’N-15˚04’N, 73˚44’E-75˚36’E). Detailed morphological studies of the planktonic paralarvae (rhynchoteuthions), revealed the presence of three stages based on the shape and relative size of the proboscis: stage 1 (1.47-1.78 mm DdML), stage 2 (2.07-5.17 mm DdML) and stage 3 (5.17-9.18 mm DdML). The observations revealed that the switch from paralarvae to juvenile occurs between 8.7 and 10 mm DdML. Aging studies using statoliths revealed that the paralarval period ends 36 to 52 days after hatching, with the growth rate ranging from 0.14 to 0.21 mm The results also indicate that the species spawns near the continental shelf edge, and that paralarvae migrate to oceanic waters thereafter.