MARINE PISCICULTURE 313 



The great mortality which occurs when the mode 

 of nutrition of the larva is changing is thus avoided 

 in the hatchery simply because the fry are liberated 

 before this mortality begins. Now, with regard 

 to the part of the sea in which the fry are set 

 free, two considerations have to be borne in mind. 

 The reader will remember that the pelagic eggs 

 of most fishes are spawned well out at sea, and 

 that those which come within the influence 

 of a favourable drift of the surface water ulti- 

 mately find themselves in shallow waters near 

 the land, on those sandy bottoms which seem 

 to be necessary for their further development. 

 Further, this drift inshore must be completed 

 about the time when the little fish is abandoning its 

 pelagic mode of life, and is assuming the bottom- 

 living habit characteristic of its after-existence. If 

 the larvae drift on to a rocky, deep-water coast, then, 

 from what we do know of the life-histories of such 

 fish as the plaice, it is probable that they do not 

 meet with the conditions favourable to the develop- 

 ment of further stages. Again, if they drift into 

 shallow water some time before the metamorphosis 

 begins, there is a probability that they may be 

 stranded by the receding tides and destroyed. And 

 if they do not accomplish this drift in the proper 

 time, it may also happen that the metamorphosis 

 may take place in relatively deep water, and that 

 the larvae may go to the sea-bottom in too great 

 a depth and on unsuitable ground. Therefore, 



