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The effects of diet (fish bycatch or a mixed diet of 75% brown mussel flesh and 25% cooked cracked corn) and harvesting regimen (bimonthly selective harvesting, or single terminal harvesting) on growth, survival and production of mud crab Scylla olivacea (Herbst) in brackish water ponds were determined in a replicated factorial experiment. The crabs were stocked at 0.6 individuals per m2 for 118 days. There was no significant interaction (P > 0.05) between the diet and harvesting regimen treatments. Regardless of diet, the survival rate and net production of mud crabs were significantly higher (P < 0.05) when crabs were subjected to bimonthly selective harvesting than at single terminal harvest. Comparative cost–return analysis showed that bimonthly selective harvesting and mixed diet treatments attained higher net return and return on investment, and lower cost of production than the other treatments. Partial budgeting analysis showed that bigger profits can be earned by using a bimonthly selective harvesting and a mixed diet of 75% fresh or fresh‐frozen brown mussel flesh and 25% cooked cracked corn.

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Penaeus monodon juveniles (mean weight, 0.006 g) were reared in 330 m earthen ponds for 120 days at a stocking density of 7.5/m 2 under conditions of the modified extensive system of culturing shrimps. The shrimps were fed diets with or without vitamin and/or mineral supplements. The aim of the experiment was to evaluate the growth and survival of P. monodon when fed a diet lacking in vitamin and mineral supplements. The results showed that growth, survival, apparent food conversion ratio (FCR), net production, and cost of production per kg of P. monodon were not significantly different between treatments. The cost of production per kg of diet was lower in the shrimps fed a diet without vitamin and mineral supplements, but not significantly different from the rest of the treatments. The favorable cost difference of P8.00 per kg of shrimp produced would make it more profitable to use a diet that contained no vitamin and mineral supplements in a modified extensive culture system.

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