226 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



REPORT ON EXPERIMENTS WITH MARKED 

 FISH DURING THE YEAR 1906. 



By Jas. Johnstone 



The experiments with marked fishes begun in 1904 

 were continued during 1906. It was our intention to 

 mark 1,000 fishes during this year, but for various reasons 

 little more than half that number were dealt with. At 

 the beginning of the year it was suggested to me that the 

 plaice caught in the course of the ordinary trawling 

 experiments carried on by the " John Eell " should be 

 marked and liberated — that is, that special cruises for the 

 purpose of catching fish for marking experiments should 

 not be made, but the routine trawling experiments should 

 be utilised for this purpose. This policy was adopted, 

 and with one or two exceptions the fish marked and 

 liberated were caught on the ordinary trawling stations 

 visited as a matter of routine by the " John Fell." From 

 several points of view this method is to be recommended, 

 but the general result has been that smaller lots of fish 

 were liberated than was desirable. In future it would 

 probably be better to concentrate these experiments, and 

 spend more time on each, catching and liberating largei 

 numbers of fish at fewer stations. Experience of the 

 distribution and migration of plaice has convinced me 

 that quarterly marking experiments (roughly speaking) 

 would probably give the best results. The fish should be 

 liberated about the end of October or beginning of 

 November, then in February or March, then in June or 

 July, and possibly also in September. In this way we 

 should make the experiments correspond with the times 

 when the fish are changing their habits. 



