MARINE PISCICULTURE 



311 



speaking, a week to a fortnight, and they are then 

 transferred to rearing-tanks or ponds. During 

 this period the little fish is feeding on the supply 

 of food contained in its own yolk-sac. When this 

 food-yolk is exhausted, then the troubles of the fish- 

 culturist begin. 



It has been suggested that a kind of inherited 

 anaemia afflicts the embryo hatched in artificial 

 conditions, and probably also in the sea in a state 

 of nature. It is extremely difficult to induce a 

 considerable proportion of the larvae to feed on any 

 kind of food-material supplied to them. All kinds 

 of food have been tried, both natural and artificial ; 

 but it has always been found that by far the 

 greater number of the larvse hatched out from the 

 eggs die in the hatching-boxes, or in the rearing- 

 tanks or ponds. It is true that considerable success 

 has been achieved by various investigators in rear- 

 ing sea-fishes hatched artificially — H. Dannevig 

 did this, with regard to plaice, on at least two 

 occasions. In 1896^ he reared a number through 

 the metamorphosis. No figures are given, how- 

 ever, showing what proportion of those started 

 with were successfully reared. In 1900 Dannevig 

 again reared " a few specimens " for about nine 

 months, by which time they were about 3^ inches 

 long.^ These results are very interesting, and are 

 of very considerable theoretical importance. The 



1 Report, Fishery Board for Scotland for 1896, pt. iii. p. 175. 



2 Ibid., 1900, pt. iii. p. 229. 



