Maturity, spawning and fecundity of the king seer, Scomberomorus commerson (Lacepede), in the seas Around the Indian peninsula

Abstract

Based on tlie modes of ova, 12 progressive stages are identified in the maturation of ovaries of king seer. A line, 3 standard errors above the regression of Gonad Index on total length of fish in resting or immatures stages, L (G.I. = —0.195 + 0.002046 L), is found useful in the separation of spawning flsh from nonspawning fish. Estimation of maturity on the basis of the regression of maximum ova diameter (m.o.d.) on G.t. holds only up to a G.I. of 7.2, beyond which m.o.d. is in the range of 34 to 47 m.d. (1 m.d. = 0.0167 mm) irrespective of G.I. The length at first maturity (701-800 mm or the median 750 mm) shows considerable agreement with the values reported for the Papua New Guinea and East African regions. Spawning season extends from January to September, during which a weak brood results in January-February, a strong brood during the peak spawning in April-May and another weak brood in July-August. The three batches of ova in the spawn-ripe ovaries (stage L) are spawned successively at an interval of a month or even less. The number of ova in the first, second and third batches are in the ratio of 1 : 1 : 0.27. Spawning grounds are located along strictly inshore and protected coves, as those close to Panaikulam on Palk Bay and Pudumadam on the Gulf of Mannar. Males, females and indeterminates are in the ratio 52.3 : 43.2 : 4.5. Males are dominant up to a length of 1300 mm, and females, beyond this length. There is no significant difference in the fecundity between different maturity stages (F to L) or between estimates by different formulae. The relation between absolute fecundity, defined as the total number of ova spawned in one season over the three spawning acts (y in thousands), and total length of fish (x in mm) is found to be, y = -2273 + 3.5793 x. Fecundity-fish weight relation reveals that, for every ton of spawning females, 291.9 million eggs are produced. For most of the maturity stages, egg size-fish length relation exhibits negative correlation.