The roundscad (Decapterus spp.) forms the largest fishery in the Philippines after World II, with catches reaching 100,000 tons a year since 1965.
Two species. D. macrosoma and D. russelli comprise the fishery at all times in all fishing grounds. The fishery consists mainly of one year class (Age Group II of about 14 cm). The fish matures while it is available to the fishery and leaves the fishery to breed at Age Group III, for deeper unknown waters.
Based on the examination of the conditions of the gonads, the fish leaves the fishing grounds to breed after 10-12 months, having grown to about 21 cm total length.
Most fish do not return to the fishing grounds although very large fishes (23 to 27 cm) representing returning fishes (.Age Group IV and V) may be found at times among the coral reefs.
The use of purse seines have made possible the exploitation of younger and older fishes in view of the greater area where the gear operate which is also the path of the inward and outward movement of the fish from the breeding grounds.
It is hoped that with the larger purse seiners, the largest fishes (breeders) may be found, as well as their breeding grounds, so that the fishery may be expanded. The whereabouts of older year classes may also be determined and made available.
Investigation along this line is requested among member nations of CSK.