OCA: Hot, cold seasons bane to culture of shrimp PDF Print E-mail
Saturday, 14 February 2015 11:56

After months of study and on-site demonstrations, the Office of the City Agriculturist headed by Diosdado Palacat has found out that the culture of shrimps is not feasible during hot and cold seasons, explaining that exposure of shrimps to such weather conditions causes stress to them, thus making them more susceptible to infection.

Palacat said the study dubbed On-Site Demonstration on Polyculture of Shrimp, Milkfish and Shrimp-Tilapia was conducted in April to September 2014 at SPDA, Barangay Vitali, east of this city, where a fishkill incident, primarily crustaceans such as shrimps and crabs, was reported in January of same year.

Palacat further said the fishkill had affected several hectares of fishpond areas, prompting the government and non-government agencies to create and develop the so-called Aquacultural Farmers’ Field School (Aqua FFS).

The Aqua FFS was primarily aimed at carrying out a collective and collaborative inquiry into the fishkill by fishpond operators and caretakers through an intensive training on cultural management, pest and diseases identification and post-harvest technology with the purpose of initiating community action in solving the problems for the entire cropping period.

Series of field activities from soil sampling, pond preparation, natural food growing, sticking to feeds and feeding, routine pond management and harvesting  were conducted throughout the five-month study period.

In spite of all the preventive measures, the study noted, still the two demonstration farms suffered from shrimp disease problem to include finfish disease. To solve the problem, reduce the losses and minimize the impacts on neighboring farms, an emergency harvest was carried out on both farms. The harvests were subjected to further study.

After everything was taken into consideration, the study concluded that the White Spot Disease (WSD) caused by the white spot syndrome virus (WSSV) affects shrimps of all age groups. It can also infect and kill a wide range of aquatic crustaceans, especially decapods including marine, brackish and freshwater prawns/shrimps, crabs, lobster and crayfish. No decapods from marine and brackish or freshwater had been reported as resistant to the virus. All life stages, eggs to adults, are susceptible to WSSV.

The WSD outbreaks are often characterized by high and rapid mortality of infected population, shortly after the first appearance of the clinical signs. But, even if shrimps infected by the virus may not cause an outbreak if environmental factors are in its favorable range of survival. Disease outbreak may be induced by stressors such as rapid changes in salinity and temperature.

It was further found out that both growth and survival of shrimp are also affected by temperature; the rate of growth increase with temperature, but at higher temperature mortality increases. The optimum temperature ranges between 26?C and 30?C are considered best in terms of maximum harvest. — Vic Larato