Ixiv 



Thirtieth Annual Heport 



eggs and larval fishes from the localities where spawning takes place. 

 Thus many of the adult plaice which had been marked and liberated 

 in the Firth of Forth, or eastwards of the Isle of May, were recaptured 

 off the coast of Aberdeenshire, or in the Moray Firth ; many of those 

 liberated off the coast of Aberdeenshire were again taken in the Moray 

 Firth, or on the North or West Coast, having in such cases traversed 

 the Fentland Firth. In like manner many of the adult plaice liberated 

 in the Moray Firth, or in the vicinity of Fair Isle, were recaptured at 

 the Orkney Isles, or on the North Coast and the West Coast, one of them 

 as far as the Gairloch. It is interesting to have determined that the 

 plaice in the Moray Firth are recruited to such an extent from the 

 grounds off the East Coast, and even from the Firth of Forth, by the 

 migration thither of the adult fish. It is also fairly certain, though 

 direct experimental proof is lacking, and indeed could hardly be 

 obtained, that the grounds to the south are recruited by supplies of 

 floating eggs and larval plaice carried from the Moray Firth by the 

 prevailing current. 



Another point on which the marking experiments throw light is the 

 intensity of fishing operations. There is no reason to suppose that 

 the marked plaice are either more liable or less liable to capture than 

 those which exist beside them in their natural condition on the 

 grounds. The proportion of the marked fish recaptured thus offers an 

 indication of the proportion of the natural stock which is within a 

 given time removed by fishing operations, and that proportion is 

 larger than might be expected. Thus of 622 plaice liberated in 1910 

 on Aberdeen Bank, about thirty-four miles to the south-east of Aber- 

 deen, 353, or 567 per cent., have been recaptured; of 572 liberated 

 eastwards and south-eastwards of Fair Isle, 264, or 46*2 percent., were 

 recaptured; of 197 set free in the Firth of Forth or eastwards of the 

 Isle of May, 109, or 55*3 per cent., have again been caught. It is, 

 however, desirable, before accepting these results as showing the 

 intensity of fishing along the East Coast, to await the outcome of the 

 further experiments. 



The Sea Currents and Fishery Problems. 



As above indicated, the part taken by marine currents in distri- 

 buting the floating eggs and larvae of the food-fishes is of importance, 

 as is also their relatfon to the migrations of the fishes themselves, and 

 to the movements of the floating organisms upon which young fishes 

 of most species, and certain fishes at all stages, as the herring, chiefly 

 subsist. An investigation was therefore undertaken, and is now 

 proceeding, to ascertain as completely as possible the course, direction, 

 and rate of the currents along the East Coast and throughout the 

 North Sea, the results of which will be afterwards considered in 

 connection with the hydrographic observations. For this purpose a 

 large number of sealed bottles, suitably weighted and containing 

 numbered cards for identification, have been thrown into the sea from 

 the " Goldseeker " at various places along the coast. Of 2150 thus 

 used, 528, or over 24 per cent., have been returned, partly from our 

 own coast, and largely from the Continent, more especially from 

 Norway, some of them having been found as far as the North Cape, 

 and even farther east in Barents Sea and the Murman coast. 



