Nutritional condition of larval milkfish,Chanos chanos,occurring in the surf zone

In order to clarify the nutritional conditions of larval milkfish in the surf zone, the following parameters were examined: 1) DNA and RNA content and RNA/DNA ratio of fed and unfed larvae collected from the surf zone and reared in the laboratory; 2) survival rate of the unfed larvae; and 3) total length, otolith increment counts and RNA/DNA ratio of wild larvae collected daily from the surf zone. The DNA and RNA content of the unfed larvae decreased, but increased in fed larvae. The RNA/DNA ratio decreased in unfed larvae, whereas in the fed larvae it decreased for the first three days after capture and increased thereafter. These results indicated that the values of DNA and RNA content and RNA/DNA ratio could be used as an indicator of nutritional condition of milkfish larvae after 6 days of starvation. Although total length of the wild-larvae did not show serial changes, their otolith increment counts showed continuous increases, indicating that the larvae sojourned in the surf zone for several days. In the same period, RNA/DNA ratios of the wild larvae decreased continuously, the ratios of larvae with fewer otolith increment counts being relatively higher than those of larvae with greater increment counts. Based on these results, the milkfish larvae remaining in the surf zone were concluded as being under insufficient nutritional conditions.