MARINE BIOLOGICAL STATION AT PORT ERIN. 39 



THE PLAICE HATCHING. 



The hatching operations carried on by Mr. T. N. Cregeen 

 afford what I regard as quite remarkable opportunities for 

 biological investigation. In the first place the morphology 

 itself of these embryonic and larval plaice still awaits satis- 

 factory investigation — in spite of the fact that various members 

 of the staffs of the Liverpool and other Zoological laboratories 

 have made collections with that intention. Secondly, 

 large numbers of plaice have been reared in the spawning pond 

 and in the Aquarium tanks without any obvious difficulty. 

 At the present time some of these fish are four years old and 

 an F 2 generation has been spawned and might, with care, be 

 reared if so desired. 



Larger questions than those of morphology may, however, 

 be studied in connection with the habits of these baby plaice. 



The War and the North Sea Plaice Fisheries. 



The general opinion among fishery zoologists, both in this 

 country and in Germany, is that one effect of the war was a 

 marked improvement in the catch of plaice made by North Sea 

 trawlers. This catch, whether expressed as the total quantity 

 of fish landed, or as the catch per day's fishing, decreased from 

 year to year on the whole, during the period 1908-1914. After 

 the outbreak of war there were military restrictions in the 

 form of areas of sea closed to fishing vessels and there was, 

 therefore, a considerable falling off in the quantities of plaice 

 caught and landed. What fractions of the plaice grounds 

 in the North Sea, English Channel and Irish Sea were so 

 protected from exploitation by fishing vessels appears to be 

 a military secret, and so these data have not been discussed 

 though they have obvious importance in the question at issue. 

 There were restrictions in the Channel and Irish Sea as well as 

 in the North Sea, and so one would expect to find that the 

 same increase in the stock of plaice occurred in the South and 

 West as on the East. Looking critically at the data for the 



