Marine Fish Culture in Britain: VII. Plaice (Pleuronectes platessa L.) Post-larval Feeding on Artemia salina L. Nauplii and the Effects of Varying Feeding Levels

Abstract

Plaice produced by hatcheries have an unusually large size range and exhibit pigmentation peculiarities. Small size is known to be correlated with pigment and certain structural abnormalities. The experiments demonstrated the quantities of food eaten in the larval and post-larval stages and the role of food availability in determining the percentage survival, overall size and normality of pigmentation of survivors. The number of Artemia nauplii consumed per fish per day varied from ten during stage I and early stage II to 240 in late stage III. Midway through metamorphosis stages IV and V food consumption fell to fifty-eight nauplii per day but recovered to 200–250 on the completion of metamorphosis. Peak mortalities per day during stage I to II ranged from 6·4% in excess feeding conditions to 18·5% in tanks receiving one-eighth of the food the fish would normally take. Similarly, modal total lengths of survivors were reduced from 15 mm to 11 mm. Increased pigmentation deficiency within millimetre size groups was also found in the poorly fed fish although fish in surplus feeding conditions still showed appreciable abnormality. The fundamental cause was probably physiological disturbance induced by other features of the hatchery environment. Metamorphosis was delayed by only an average of sixty-three hours by low rations or 6·4% of the time since first feeding. The experiments were part of a series of rearing experiments during which production of Artemia nauplii as food reached up to seven million per day. This was made possible by a multiple hatching unit and by the use of electronic counting methods.