Many shrimp breeders in the Mekong Delta Province of Bac Lieu, Vietnam recently made losses due to breeding giant freshwater prawns imported from China. These shrimp died quickly or grew too slowly.

A breeder in Phuoc Long District said that he bought 10,000 Chinese breed shrimps. After 20 days he found that all of them had died.

Some households bred such prawns for five to six months but ended up harvesting small prawns and had to sell them at a low price.

Hepatopancreatic Parvovirus (HPV) is a small icosahedral, non-enveloped virus containing a single-stranded linear DNA genome that is placed as a member of Parvorividae. There is no specific gross sign for HPV-infected shrimp, but histology revels the presence of intra-nuclear inclusion bodies in hepatopancreatic tubule epithelial cells.

Discovered in cultured Penaeus merguiensis in Singapore in 1982, the virus has been associated with poor growth and mortalities up to 100% in larval and postlarval penaeids. It has since been detected in P. chinensis, P. semisulcatus, P. monodon, P. stylirostris and P. vannamei. HPV has been found in both cultured and wild stocks in Southeast Asia, the Middle East, the Americas, Oceania and Africa.

HPV Variation

The authors' laboratory at the University of Arizona maintains an archive of samples of shrimp infected with HPV received from around the world. This has afforded the opportunity to study genetic variation among isolates collected over a wide geographic area.

Thai Union Frozen Products Plc (TUF) yesterday teamed up with 185 shrimp farmers across the country in a contract farming arrangement on an unprecedented scale of 10,000 tonnes, worth about 1.2 billion baht.

Under the deal, Thailand's major producer and exporter of canned and frozen seafood will buy from farmers at specified prices based on production costs plus a level of profit agreed between the farmers and the company.

The contract should help farmers plan what size of shrimp to produce and should cut their market risks from price fluctuations - especially between May and December, when shrimp is normally in abundant supply - said Rittirong Boonmechote, managing director of TUF's shrimp business unit.

"We believe contract farming will help reduce risks for all parties involved, especially for farmers, who will not have to worry about how to sell their shrimp during periods of surplus," he said.

Thai

Tiger shrimp breeders in the Mekong Delta are facing huge losses due to unseasonal rains, which brought a sudden change to salt concentration and the death of large numbers of shrimp.

According to the latest reports from the Department of Fishery Cultivation and Breeding of the Mekong Delta, out of 540,000 hectares of land used for trigger shrimp in late 2008, all shrimp in 148,000 hectares in Ca Mau, Kien Giang and Soc Trang provinces were killed by unseasonal rains. Only 45 percent of farmers made a profit, leaving the others to break even, at best. Many incurred losses.

The situation has led to many local farmers not having enough capital to reinvest in the coming crops.

Farmers in Lai Hoa Commune of Soc Trang Province had previously used all the land for breeding tiger shrimps, but now only 30 percent of the land has been used. Truong Thai Binh, a farmer in Lai Hoa said, “We don’t have much capital and have to buy feed on credit, but feed sellers are no longer ready to offer us this method of payment.”