Studies on the maturation and spawning of the Indian whiting (Sillago Sihama Forskal) from karwar waters

Abstract

1. A study of maturity and spawnings ofSillago sihama based on the detailed examination of 500 specimens of fish and their ovaries and also on casual observations of over a thousand females has been attempted in this paper. Preliminary observations on the condition of testes have also been made from 135 specimens. 2. The female fish have been classified as Immature, Maturing, Mature and Spent, with reference to the condition of their ovaries. The mature ovum contains a single oil globule generally measuring between 0.13 mm. and 0.15 mm. in diameter. 3. A study of the maturation cycle brought out three phases in the life of the fish: (a) Period of active maturation .. April to July. (b) Spawning Period .. August to October (c) Resting Period ..November to (following) March. 4. The spawning period in S. sihama is of short duration and spawning takes place only once during the season. 5. The size of the femaleSillago at first maturity has been approximately fixed at 235 mm. in total length. The females were found to attain a maximum size of 354 mm. in total length. 6. The smallest male specimen with 'mature' testes measured 224 mm. The males attain a relatively smaller size, the maximum size noted being 273 mm. 7. The number of mature eggs liberated in a single spawning has been found to vary from 16,682 to 166,130 in sizes of fish ranging between 184 mm. and 340 mm. in total length.