BAKENTS SEA IN AUGUST, 1907. 85 



length have survived, considering that each year the growth becomes 

 less and less ! 



Although the material in Table III cannot be regarded as satis- 

 factory, it shows plainly how slow the rate of growth must be, and 

 would seem indicative of the direction future plaice investigations 

 should take in this inhospitable region. 



In connection with the majority of these specimens (Table III), the 

 possibility presents itself that they may be actually amongst the best 

 grown fishes of their respective year groups. That plaice in the North 

 Sea are larger for their age the further they are caught from the 

 coastal grounds has been very clearly shown by Wallace in a recent 

 paper {op. cit), so it seems possible, if not probable, that a similar state 

 of things obtains in the off-shore grounds of the Barents Sea. 



The youngest plaice of either sex amongst those examined had 

 apparently already completed five years, but this would seem quite 

 exceptional. In addition to the slow rate of growth, the evident late 

 age at which maturity is attained is striking. 



Amongst these few fish examined for age, no male less than eight 

 years (32 cm.), and no female less than twelve years old (41 cm.) was 

 found to be mature, though younger mature specimens must have 

 occasionally been present in the catch (see Table I). In the North Sea 

 few males are found to survive to eight years. 



If the plaice in the Barents Sea have really to live through some 

 eight or nine years before they attain the size at which they reproduce 

 their species, the question occurs to us, " How long will the present 

 stock, accumulated through many years, hold out in sufficient abund- 

 ance to make this long, expensive voyage of three to four thousand 

 miles down to the Arctic Ocean profitable to our trawlers ? " 



Migrations. 



Speaking in a general way, the migrations of mature fish seem to be 

 determined by the search for food, or to be in connection with the re- 

 production of the species. Currents, temperature, and such local factors 

 as a general exodus from shoal to deeper water in stormy weather, are 

 amongst other causes of fish movements, but all have more or less 

 direct bearing on one of the main stimuli. 



Although conclusions as to migrations in the Barents Sea would be 

 impossible from the material collected on the voyage of the Roman, 

 nevertheless every fact in my possession points to a general movement 

 of this mature plaice population from deeper and here probably 

 warmer water, after spawning has taken place, on to the banks to the 

 eastward, apparently in search of food. 



