Hatchery cultivation of king scallop (Pecten maximus) spat with cultured and bloomed algal diets

Growth rates of small (2-15 mm shell length) hatchery-reared king scallop ( Pecten maximus L.) spat were estimated by computer analysis of video images taken of the scallops held in petri dishes containing seawater. This techn ique reduced the amount of handling and minimised any effect stress due to handling might have had on growth. Experimental diets consisting of algae f rom both intensive hatchery cultures and from outdoor bloom tanks were fed to the scallop spat. For all diets, growth rate (as increase in shell lengt h) increased linearly with a logarithmic increase in initial shell length. Scallops thus characteristically showed a growth pattern whereby dry weight -specific growth rate increased rapidly with increasing shell size to a max imum at 4-5 mm shell length (2.6-5.0 mg dry weight). This weight-specific g rowth rate then showed a gradual decrease with a further increase in shell size. For the algal diets consisting of single species that had been cultur ed intensively, nutritional value was in the order Pavlova lutheri (Droop) Green > Chaetoceros calcitrans (Paulsen) Takano > Rhinomonas reticulata var . reticulata Novarino > T-ISO (Isochrysis sp.)> Tetraselmis suecica (Kylin) Butcher. A mixture of the first two of these species gave significantly fa ster growth rates than any other combination of species tested. Growth rate s of scallop spat fed bloomed seawater at rations of 0.33-1.0 g (organic we ight of algae) g(-1) (live weight of spat) week(-1) were similar to those f ed an intensively cultured algal diet of high nutritional value. There was some evidence that the spat were less efficient at filtering smaller (2-5 m u m) algae cells. Crown Copyright (C) 1998 Published by Elsevier Science B. V.