ABSTRACT
An attempt was made to find out the impact of shrimp farm discharges on benthic diversity in the discharge point of a shrimp farm. The duration of the study was one culture period right from stocking to harvest. The results revealed that the values of environmental entities were in the safe levels. As regards nutrients, maximum value of TOC and phosphorus were recorded in the sample collected after harvest and minimum in the sample collected during culture. BIO-ENV method revealed that nitrogen, sediment salinity and TOC were manifested as best variable combination explaining faunal distribution. Polychaetes are the dominant group (50%) with 13 species followed by crustaceans (32%) with 10 species, gastropods (10%) with 2 species and bivalves (8%) with 3 species. The faunal density was found to vary in relation to months as observed in the samples which were collected during various seasons in the other areas of estuary. In line with this, diversity values were also paralleled to the faunal density. In a nut shell, the study revealed no negative impact of shrimp farming to the estuarine benthic biota.
ABSTRACT
Insecticidal effects of Agnique MMF were investigated in the coastal brackish water shrimp farms in the Tan Thuan commune, Dam Doi district of Ca Mau province in 2000. The investigations were made in terracotta jars and shrimp ponds with the surface area 30m2 and 1000m2 each. Agnique MMF was found to have a high and fast killing effect on larvae of An.sundaicus at all three testing doses of 0.3ml/m2, 0.4ml/m2 and 0.5ml/m2. Especially larvae at instars of III, IV and pupae. However, the insecticide produced a low effect on Culex sitiens killing larvae of IV ins tar and only retarding larvae of I, II, III instar. The residual effect of Agnique MMF was found to be 14 days in the terracotta jars and 6 days in the ponds. In the direct observations, Agnique MMF was found to have no negative effects on rearing shrimps