March 7, 2007

 

Drought in Colombia reveals pitfalls of caged-fish aquaculture

 

 

An estimated 3 million fish have suffocated in a reservoir in southern Colombia, where a four-month drought has drastically drained water levels, leaving too little oxygen to sustain dozens of hatcheries.

 

The Associated Press has reported that more than 1,320 tonnes of tilapia raised inside giant metal cages behind a hydroelectric damn have died as soaring temperatures lowered water levels by as much as 82 feet in the dam.

 

The local fish industry, which exports the tilapia to the US and Europe, could lose more than US $2 million, said Eliseo Motta, government secretary in Huila state, where the farm is located.

 

Colombia's government has temporarily banned the sale of fish produced in Betania's hatcheries to protect consumers from possible contamination.

 

The government also promised US$700,000 in federal subsidies and tax credits to help the hatcheries recover.

 

Colombia has asked the power company to gradually restore the reservoir's water levels by reducing production of electricity at the dam.

 

Norbert Sporns, CEO of HQ Sustainable Maritime Industries, Inc. said the incident highlighted the advantages of pond-raised aquaculture over cage-based aquaculture.

 

Sporns said advocates of cage-raised practices assume that fish in cages are raised in a constantly flowing water supply which reduces the effects of algae cultures and leads to better-tasting, healthier fish.

 

However, this reliance on an uncontrolled water environment can lead to many problems.

 

Dr. Claude E. Boyd, Professor of Agriculture and Environment at Auburn University, Alabama, said conflicts in management of water resources can result in such a kill-off.

 

Dr. Boyd said pond culture is generally more environmentally friendly than cage culture as it enables greater control of the water environment and effluents that affect fish health.

 

Pond stability provides favorable feed conversion rates over cage-raised tilapia, he added.

 

Seattle-based HQ Sustainable's seafood is located in the province of Hainan, China..

 

The water in the company's pond environment is controlled, avoiding the need for any prophylactic use of antibiotics. Moreover, the company also grows algae that provides an excellent feed supplement and dissolved oxygen to the fishes. Tilapia are herbivorous fish and thus no fishmeal need to be added to tilapia feed.

 

The company even introduces bottom-feeder fish and predator fish to maintain the pond eco-system.

 

Moreover, these ponds are located away from mangrove swamp areas to limit environmental damage. Used pond water, which contains valuable nutrients, are provided to neighbouring farmers' fields.