Settlement of released artificial seedlings of the red sea bream around two types of net artificial habitat

Abstract

Swarming behavior toward two types of artificial habitats made of nets for the settlement for released seedlings of artificially reared red sea bream Pagrus major was studied. Field research was conducted in a nursery ground at Morode Cove, Ehime Prefecture, using scuba from 21st July to 18th August, 1998. One type of aritificial habitat consisted of three, black colored 2 mm-mesh nets (each 50 cm wide and 15 cm high) set vertically in parallel, facing offshore just above the bottom (A type). The other type consisted of the above-mentioned net set in the same way but with two sheets of green 2.5 cm-mesh-net (each 50 cm × 50 cm) set in piles covering the bottom just inshore of the vertical net (B type). About 3000 fish (mean: 25.6 mm TL) were released on 21st July as the first release, and about 1700 fish (mean: 69.7 mm TL) were released on 28th July as the second one. Released fish swarmed around the artificial habitats just after the releases. In the first release, no fish was found in the areas without artificial habitats. B type was more attractive than A type. This trend was clear in smaller fish, which were released in the first trial.