B. Menu, J.H. Robin, M.F. Gouillou-Coustans-1998
Bulletin Francais de la Peche et de la Pisciculture, (350-51) : 279-289 (from Current Contents)
Abstract:
Larvae from a natural spawn of sea bass were distributed into 3 larval rearing lines in 2 distant sites, after simulated or true transportation. The specific rearing methods in the specific rearing environment of each laboratory were used: starvation under darkness for 160 degrees days and first feeding on Artemia (PP) in the Mediterranean laboratory of Palavas; first feeding on rotifers at 75 degrees days in the laboratory of Brest (Brittany) in 250 liters (BB) tanks or 35 liters tanks (Bb) of a separate rearing line. In the 250 liters tanks in Brest, 2 additional treatments before first feeding on Artemia were tested: starvation up to 160 degrees days under darkness with no bubbling (BP); starvation up to 160 degrees days under continuous illumination with bubbling (BI). Vertebral, maxillary, opercular (short or swollen) abnormalities as well as uninflation of the swimbladder and urinary calculi were recorded on 3 months old juveniles in all batches. Some abnormalities appeared to be closely related to a specific site or treatment such as urinary calculi in Palavas, uninflated swimbladder in Brest (maxillary abnormalities in 35 liters tanks). Swollen operculum deformities occurred in two rearing lines subjected to different rearing methods (PP and Db) but were absent in the rearing line where environmental and nutritional factors were compared. Significant differences in survival rates were observed between treatments. The frequency pattern of lordosis seemed to be the result of selective mortality. Lordosis was often associated with uninflation of swimbladder. Short operculum occurred ten times more often when fish had an abnormal swimbladder. A separate investigation of juvenile populations with or without a normal swimbladder shows that the frequency distribution of the short operculum is independent of treatment and rearing site. The high frequency of short operculum recorded in some treatments cannot be dissociated from the high occurrence of uninflated swimbladder.
(Stn IFREMER, Chemin Maguelone, F-34250 Palavas Les Flots, France)