Biology of the spineless cuttlefish Sepiella inermis (Orbigny, 1848) from Mumbai waters

Abstract

The relationship between dorsal mantle length (DML) and body weight (TW) of Sepiella inermis was Log TW = -2.8217 + 2.4474 log DML and Log TW = -3.1712 + 2.6808 log DML for males and females respectively. The species showed allometric growth and the regression coefficients were highly significant at 5% level for both the sexes. Crustacean remains was the dominant food item in the stomach followed by fish. High value of gastrosomatic index was recorded in August (13.06%) and low value was observed in March (5.93%). Sex ratio ranged between 1:1.10 (March) to 1:2.36 (June). 50% of the males matured at 48.06 mm and females matured at 55.04 mm. Fecundity ranged between 216 and 354 ova. Ovadiameter varied between 0.38 and 3.57 mm. Matured females occurred throughout the year with a primary peak in October followed by three secondary peaks in January, April and July-August, indicating four spawning seasons.