抄録
In recent years, discharged nutrient from the fish culture farms has
been causing the problem of self-pollution in the farming area, and we
have been recommended integrated culture with various alga for fish
farming. In order to execute integrated culture of Ulva ohnoi
and red sea bream Pagrus major, we set conditions for
culturing U. ohnoi in a farm of red sea bream in
Tanabe Bay, Japan. Then, nitrogen (N) and phosphorus (P) budgets in
the fish-alga integrated culture system were studied. The culture cage
of U. ohnoi was placed in a block adjacent to a fish
culture cage (3×3×3 m) to reduce the loads of nutrient discharge from
the fish cage. From July to September 2003, 260 young fish (mean
weight of 38.4 ± 5.4 g) of red sea bream were cultured in the cage by
feeding 26.8 kg of artificial compound feed (EP-pellet) containing
1,951 g of nitrogen and 281 g of phosphorus. At the end, 19.8 kg of
fish growth was obtained and 565 g (29.0 % of the given feed) of N and
164 g (58.4 %) of P were stored in the fish bodies. U. ohnoi
absorbed N and P at estimated rates of 3.18-10.56 μmol
wet-g-1 hr-1 and 0.09-0.31 μmol wet-g-1
hr-1, respectively, and the daily growth rate
of U. ohnoi was 11.0-24.2 %, which varied with
the initial input weight of thalli. At the most effective design, the
total amounts of N and P absorbed by U. ohnoi corresponded
to 7.0 % and 3.2 % of those in given food, respectively.
