REARING OF PLAICE {PLEURONECTES PLATESSA) LARVAE 

 TO METAMORPHOSIS USING AN ARTIFICIAL DIET 



J. W. Adron, a. Blair, and C. B. Cowey» 



ABSTRACT 



Newly hatched larval plaice were grown to metamorphosis using an artificial diet. The overall survival 

 rate to metamorphosis was of the order of 20%. This compares with a survival rate of 38% in control 

 larvae fed Artemia in a similar tank system. 



The preparation of the artificial diet is described. The main protein component was freeze-dried cod 

 muscle and the diet contained 70.7% crude protein, 9.7% lipid, 7.9% ash, and 5% digestible carbohy- 

 drate. 



This food in particle sizes ranging from 180 to 355 m was introduced automatically into the inflowing 

 water of a cylindrical tank containing 200 yolk sac larvae. Water temperature was 10± 2'C. After about 

 13-14 days a relatively high larval mortality occurred, leaving approximately 70 established feeding 

 larvae. Unfed larvae in an identical control tank did not survive beyond this time. 



Once feeding had been established larval mortalities were occasional and sporadic. Thirty-five days 

 after commencement of the experiment some larvae began to metamorphose, and 56 days from the 

 start some 35 metamorphosed fish were transferred to a separate tank. These fish have since continued 

 to feed and grow on the same diet. 



The rearing of marine flatfish from egg to 

 metamorphosis and subsequently to more adult 

 stages was achieved under laboratory or hatchery 

 conditions using live food {Artemia salina) about 

 10 yr ago ((Shelbourne, 1964). The experimental 

 animal was plaice, Pleuronectes platessa. Since 

 then other flatfish (lemon sole, Microstomus kitt; 

 Dover sole, Solea solea; and tuvhot, Scop h thai mus 

 maximus) have been similarly reared to 

 metamorphosis, using either the same food or- 

 ganism for sole or a combination of organisms 

 such as rotifers followed hy Artemia for turbot. 



While such methods have been applied success-' 

 fully on a pilot scale the ability to rear these fish on 

 an artificial diet may confer certain advantages 

 such as: ( 1 ) the ability to change the composition of 

 the food and so. ultimately arrive at a composite 

 ration approaching the optimal requirement of 

 the larva; (2) continuity of a food supply of stand- 

 ard quality (the large scale production of live food 

 other than Artemia involves cultivation of several 

 organisms, e.g. rotifers, and food for rotifers. Thus 

 the whole cultivation program must be carefully 

 synchronized and there must be certainty that 

 production of food will keep pace with the increas- 

 ing demands of the growing larval fish. Moreover, 



Artemia themselves may vary in nutritional qual- 

 ity and may contain variable amounts of pesticide 

 residues (Bookhout and Costlow, 1970)); (3) elimi- 

 nation of the need to wean metamorphosed larvae 

 from a natural to an artificial food. There can be 

 little doubt that the availability of compounded 

 foods has contributed greatly to the growth offish 

 farming procedures for freshwater fish such as 

 trout, salmon, and channel catfish in several coun- 

 tries. All these species of fish have large eggs 

 which give rise to large fry so that, compared with 

 the early rearing of marine fish larvae, few techni- 

 cal problems arise. 



The present paper describes a partially success- 

 ful attempt to rear plaice from egg to metamor- 

 phosis using artificial food under small scale 

 laboratory conditions. 



EXPERIMENTAL 



The apparatus used is shown in Figure 1 and 

 Figure 2. The larval rearing tank was cylindrical 

 and measured 26 cm in diameter with a depth of 23 

 cm. It was contained in an outer vessel which was 

 normally full of sea water. The bottom of the tank 

 was formed from a circular piece of rigid polyvinyl 

 chloride pipe (Durapipe^) which fitted closely 



'Institute of Marine Biochemistry, St. Fittick's Road, Aber- 

 deen ABl 3RA Scotland. 



^Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



Manuscript accepted September 1973. 

 FISHFRV BULLETIN: VOL. 72. NO. 2. 1974. 



353 



