IMPROVED RATE OF INITIAL SWIM BLADDER INFLATION IN INTENSIVELY REARED SPARUS-AURATUS

Initial swimbladder inflation in Sparus auratus was artificially inhibited by covering the surface of the rearing tanks with a layer of liquid paraffin. The results showed that the larvae must gulp air to achieve inflation. They also suggested that the low rates of inflation (< 30%) obtained when the species is intensively reared could be due to the oily surface film that arises from the feed. Three systems for eliminating this film were tested. The only system that significantly improved the inflation rate (up to 80%) without disturbing growth consisted of a blower and a floating trap. The other two systems had either little (sprinkler) or no effect (hydrojets) on the inflation rate. Although they effectively removed the surface film, they created strong water turbulence, preventing the larvae from reaching the surface in the required time. © 1990.