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Wednesday, May 28, 2008

ANIMAL TRACKER

Four-eyed perch


Japanese name: Oyanirami

Scientific name: Coreoperca kawamebari

Description: This fish could be called the tiger perch, for the striped pattern on its body that helps it merge in with the background. But the English name comes from the fake eye on each flank near the gills. These two extra "eyes" give the fish another Japanese name, yotsume (four eyes). Four-eyed perch grow to about 11 cm long and have rough scales. They have soft and hard sets of dorsal fins and a large fleshy lower jaw.

Where to find them: Western Japan, on the Japan Sea side of Honshu and northern Kyushu. Four-eyed perch prefer clear, slow-flowing rivers and streams; anglers know to try and catch them from the middle sections of rivers.

Food: Aquatic insects, small fish and worms. Worms are popular items to feed perch kept in aquariums. This fish is also highly prized for its taste and can be eaten as sashimi. It has white flesh, and as sashimi, it is often served thinly sliced.

Special features: Biologists have tested the function of the fake eyes using model fish presented with and without the fake eye painted on. The fake eye, it turns out, is a fight-stimulus: Males will become aggressive and even attack a model with a fake eye, but not one without. The species is highly territorial, and the males help the females build and defend a nest. The female spawns in May and June, and the male guards the vulnerable — and tasty — eggs and fry from being eaten by other fish. Males swim sideways when another male approaches, displaying the fight-provoking fake eye. Interestingly, their nests are often parasitized by other fish, just like a cuckoo takes advantage of another bird's nest. In this case, minnows sneak in and lay their own eggs in the perch's nest. While they are laying their eggs, they eat some of the perch's own eggs. The perch are none the wiser, and they guard the minnow eggs as if they were their own.

PHOTO COURTESY OF BIO-IMAGE NET



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