Mon, Apr 13, 2009 - Page 2 News List

COA offers rainbow trout farmers new fish-feed options

SENSITIVE Although the two species of crustacean require some extra care while they mature, a researcher said the work would be worth the effort

By Meggie Lu  /  STAFF REPORTER

The Council of Agriculture (COA) on Friday unveiled two types of copepods that it has bred as fish feed for farmed rainbow trout, a type of fish that is widely popular in Taiwan.

Copepods are small crustaceans that are found both in fresh water habitats and in the sea. The little creatures are an important link in the food chain as they are major food organisms for fish or other crustaceans.

“To successfully raise rainbow trout, nutritious feed is crucial,” said Chen Tsi-ying, chief of research at the COA’s Fisheries Research Institute (FRI).

SUITABLE

Recently, the FRI successfully bred two types of copepods that are highly suitable for this purpose — the Pseudodiaptomus annandalei and Apocyclops royi — Chen said.

“Copepods undergo two transformation stages before maturing — first they appear as one-section larva called nauplii, then they become copepodids and lastly more mature copepods,” Chen said.

Since copepod nauplii contain high amounts of poly-­unsaturated fatty acids, docosahexaenoic acid and eicosapentaenoic acid, they are prime food for rainbow trout, she said.

SPECIAL CONDITIONS

However, Chen advised fish farmers to raise the creatures in controlled, indoor tanks before feeding them to fish.

She said that the number of days it takes for the tiny crustaceans to mature greatly depends on a number of environmental factors such as temperature and nutrients, adding that it only takes 5 days for copepods to mature in water that is 30°C, while it takes 11 days when the water is 20°C.

But the extra work would pay off, Chen said, “as when bred appropriately, copepod larva can increase rainbow trout growth very efficiently and are good for the quality and health of the fish.”

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