2. Namibia: Oyster farmers fight red tide (The Namibian, New Era)

| April 28, 2008

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Every so often, conditions are right for a red tide. In Walvis Bay Lagoon on the Namibian coast, a warm ocean current can bring about the phenomenon. The heat causes algae to multiply rapidly, blooming in such abundance that the water appears red. It’s a sight that no fisher wants to see.

Too much algae sucks the oxygen out of water. When the plants die, they leave behind natural toxins. Lack of oxygen and high levels of toxins can devastate fish populations. This March, a red tide killed some 70 per cent of the oysters in Walvis Bay Lagoon. Oyster farmers were unable to save their stock, which they grow in underwater cages.

This year’s red tide was the third since 2005. Previous red tides occurred in June 2006 and December 2005, but oyster farmers say this year’s was the worst they’ve ever seen. The farmers say they will be better prepared next time.

In wake of the most recent red tide, farmers and other stakeholders in the oyster industry met to discuss ways to reduce losses. They called upon two oyster ecology researchers from the United States to help prepare a strategy.

They learned that their oysters died because they were very fragile, and that they could “toughen up” the oysters by exposing them to conditions that mimic the red tide. For example, since the red tide reduces oxygen levels in the water, farmers can condition oysters by pulling them out of the water for a couple of hours each day. Some oyster farmers speculated that a device to rotate the caged oysters in and out of the water could do the trick.

Farmers also learned that they should note which kinds of oysters withstood the harsh red tide conditions this year, and breed more of these kind. When the next red tide comes, both the oysters and the farmers should be better able to cope. Farmers now know to anticipate blooming algae when water temperatures rise. They also know the depth of water in which they should house oysters at during a red tide.

An oyster farmer quoted in a Namibian newspaper said that while they can’t control nature, farmers want to be able to control their losses. In case their efforts fail, the oyster farmers also talked about securing insurance.

Oyster farming is a small but growing industry in Namibia. Several hundred farmers produce oysters in Walvis Bay Lagoon. Last year, 35 million Namibian dollars (about 4.6 million American dollars or 2.9 million Euros) worth of oysters were exported to markets such as South Africa and Singapore.