Preliminary biological evaluation of some formulated feeds for P. monodon

Rice bran is widely used by fish farmers as supplementary feed while soybean cake is used both as feed and as fertilizer in fishponds. Both fish meal and shrimp head have been found acceptable as feed ingredients. However, not much is known of the acceptability and efficiency of a mixture of these ingredients as feed for Penaeus monodon larvae. Ninety 127-day old P. monodon were measured for length and weight and were randomly divided into nine aquaria each containing 20 liters of water. These were fed 'lampirong' for two months previous to the study. There were three replications for each treatment. Length, weight, and survival rates were used to compare the efficiency of the diets. Weighed amounts of pellets equivalent to 100% of the body weight were fed during the first three days and reduced to 50% thereafter. A stopwatch was used to determine the length of time that elapsed before the shrimps would approach the pellet. Ten shrimps approximately 4 months in age were placed in 10 liters of water in a 25-liter aquarium. Two grams of each pellet type were placed simultaneously on opposite sides of the aquarium. The time that elapsed from the moment the pellets sunk to the bottom up to the time that any one shrimp approached the pellets was recorded. The group fed the imported pellets gained the most. Those fed FP-2s-77 elongated faster than those fed FP-1s-77. Survival rate of those fed FP-2s-77 was 37% while those fed imported pellets was 73%. Both 1s and 2s pellets disintegrated in water easily but the imported pellets were stable even after six hours in water. The attractability test for the pellets showed that the prawns were more readily attracted to the pellets 1s and 2s than to the imported pellets.

Mass culture of marine diatom Skeletonema costatum (Greville) Cleve collected from the Bay of Bengal

The growth of Skeletonema costatum in two artificial nutrient media was studied using various culture vessels. Skeletonema costatum was collected from the Cox's Bazar coast around the Bay of Bengal. Different growths stages i.e. lag phase, exponential phase, prestationary phase, stationary and death phase were observed during the culture period. The number of cells increased during the active division period and decreased after the beginning of the prestationary phase. The average densities of S. costatum in primary and secondary cultures were 0.55 x 10 super(6) cells mlˉ¹ and 0.93x10 super(6) cells mlˉ¹, respectively. In mass culture of S. costatum two, types of media were used. Highest cells densities of S. costatum cement tank culture were recorded 1.23x10 super(6) cell mlˉ¹ and 0.78x10 super(6) cells mlˉ¹ in their respective f/4 medium and commercial fertilizer medium. In the cement tanks culture fertilizer medium was found to be the best medium for mass culture of S. costatum in respect of production efficiency and culture stability.

Modifications in bangus culture

The article presents the milkfish aquaculture techniques in the Philippines modified from the traditional method. These are modular method and silo method, methods on eliminating snails, fertilizer-water replenishment scheme, supplemental feeding and the stunting of fingerlings are also presented.

AQD recommends semi-intensive milkfish culture

Details are given of a system for semi-intensive milkfish (Chanos chanos) vulture recommended by the SEAFDEC Aquaculture Department, under the following headings: 1) Pond preparation; 2) Pest (snails) control; 3) Pest (tilapia and other fish) control; 4) Fertilizer application; 5) Stocking density in nursery ponds; 6) Stocking density in grow-out ponds; and, 7) Water management.