OUR FOOD FROM THE SEA 197 



and by adding some millions from his hatchery do something 

 to repair the damage and avert or delay the destruction of a 

 local fishery. 



It may be pointed out further that even though the young 

 fish, such as plaice, are turned out to sea soon after being 

 hatched, say about the time of the absorption of the food-yolk, 

 they have been protected from their natural enemies during 

 some three or four weeks at least about half the time from 

 the egg to the metamorphosis and that moreover is the 

 period when, as eggs, embryos and young larvae, they are 

 most feeble and defenceless, and most in need of artificial 

 protection. 



We find at the Port Erin hatchery that, although the 

 periods of embryonic and larval life vary to some extent 

 probably with the temperature of the sea- water the average 

 times are as follows, in the case of the plaice : 



Embryo, from fertilisation of egg to hatching, in February, 24 days. 

 Embryo, from fertilisation of egg to hatching, in March, 22 days. 

 Embryo, from fertilisation of egg to hatching, in April, 20 days. 

 Larva, from hatching to absorption of yolk, about 7 or 8 days. 

 Post-larval, abs. of yolk to metamorphosis, 28 to 40, say 34 days. 



The most significant work, and most interesting experiments 

 in connection with artificial operations, have been carried out 

 by the United States Bureau of Fisheries and by the Fishery 

 Board for Scotland. One example may be given from the 

 work of each of these organisations. It has been long recog- 

 nised that if a species of fish could be introduced into an area 

 where it was previously unknown, that would be satisfactory 

 evidence of the success of artificial operations, and the United 

 States Bureau has shown in its successive Annual Reports of 

 the Commissioner of Fisheries that by collecting and hatching 

 the eggs of the shad (Clupea sapidissima) on the Atlantic 

 coast, and setting the larvae free in the Pacific, in the neighbour- 

 hood of the Sacramento River, a profitable shad fishery has 

 been established on the Californian coast. The last report 

 published shows that in 1915, the latest year for which 

 statistics are completed, the Pacific shad fishery yielded over 



