198 ANIMAL LIFE AND HUMAN PROGRESS 



seven and a half millions of pounds, valued at over 75,000 

 dollars. 



The Fishery Board for Scotland carried on for some yea 

 an interesting experiment in adding artificially hatched plaice 

 larvae to a circumscribed sea-area (Upper Loch Fyne), with the 

 view of determining whether an increase was noticeable in 

 the number of young fish present. Positive results seem to 

 have been obtained. During a period of six years millions of 

 larvae were hatched at Aberdeen and deposited in Loch Fyne, 

 and during the next six years none were added ; while during 

 the whole period of twelve years experimental hauls of the 

 net were made on certain selected beaches where the young 

 metamorphosed plaice congregate. The statistical results 

 show that during the years when larvae were added the 

 number of young fish caught, per hour of fishing, was more 

 than double the number caught in the succeeding period of 

 six years. Or, to put it another way, the figures given in the 

 Report show that the addition of about twenty millions of 

 plaice larvae a year doubled the number of young meta- 

 morphosed fish on the shallow beaches of Loch Fyne. 



It has sometimes been said that the young fish turned out 

 from hatcheries may possibly be weaklings, which on account 

 of having been reared under artificial conditions may die in 

 their early youth, perhaps even before undergoing meta- 

 morphosis. Experience shows that all such fears are ground- 

 less. In the hatchery at the Port Erin Biological Station 

 young plaice have been reared up to their fourth year, when 

 they had become sexually mature, and had, a year before, in 

 their turn produced spawn for the hatchery. Last year (1917) 

 there were three generations of plaice living together in the 

 institution the grandparent spawners which had been 

 originally wild fish, the parents which were hatched in the 

 spring of 1914 and were then spawning (in March 1917), and 

 the young of the third generation which were developing as 

 normal larvae. This year again (March 1918) some of the 

 fish hatched in 1914 have produced fertile spawn there can 

 be no doubt that they are perfectly normal, healthy fish. 



