44 



Fortieth Annual Report 



tigate conditions in the North Sea with special reference to the herring 

 problem. 



At the end of October the " Goldseeker " proceeded to Lowestoft 

 with the object of trawling for black soles (Solea vulgaris) for trans- 

 plantation to Scottish waters in order to ascertain whether it would 

 be possible to establish this valuable fish in those waters. After 

 considerable delay owing to stormy weather, 762 of these soles were 

 captured, but during the passage north very rough weather was again 

 encountered and the fish were badly damaged by the heavy motion, 

 and also by the accumulation of mud, slime, etc. in the tanks on 

 board. By the time the Firth of Forth was reached only 39 soles 

 survived, and these were marked and liberated to the westward of May 

 Island. The severity of the conditions of transport can be judged by 

 the fact that in the control experiments with plaice and dabs none 

 of the fish survived, although the transplantation of these species 

 is comparatively easy under normal conditions. It is hoped to make 

 a further trial under more favourable circumstances. 



The remainder of the cruises were occupied in working on the fixed 

 stations in the Moray Firth and off the Aberdeenshire coast, com- 

 prising trawling, the collection of plankton, and taking of water 

 samples and temperatures, the results of which are dealt with more 

 specifically under the various sections below. 



During the year 1450 fish, chiefly lemon soles, plaice and dabs, 

 were marked and liberated. 



3. Herring. 



About one-third of the total value of fish landed in Scotland is 

 attributable to the herring, and this fish is, therefore, of the utmost 

 importance to the Scottish fisheries, and as such is one of the chief 

 subjects of the Board's investigations. 



Being a pelagic fish, i.e., a fish that swims freely about the open 

 sea at all depths from the surface to the bottom, and being dependent 

 for its food on the minute floating or plankton organisms which 

 drift with the tides and currents, the herring presents a problem 

 which is quite distinct from that of the demersal or bottom-living 

 and feeding species. After maturity, the herring frequents the 

 bottom in order to deposit its spawn, but except during the period 

 of spawning and perhaps in the earlier stages of growth, it would 

 appear that dependence on the nature of the bottom or the depth 

 of water is not a factor in its life history. Its habits are reflected 

 in the methods used for its capture, of which by far the most 

 important is the drift-net ; and in order that large catches may be 

 made the nets must be shot in a position where large shoals are 

 swimming at just the right depth to strike the nets; and it cannot 

 be insisted upon too strongly that when a " scarcity " of herring is 

 spoken of it may only mean that these conditions were not fulfilled. 



Scientists have evolved various methods of approaching this 

 problem. If the scale of a herring be examined, it will be seen that 

 it is marked by a series of more or less concentric hoops or rings. It 

 is held that these marks are due to the slower growth of the fish 

 during the winter, and that the clearer space between the rings is 

 consequent upon the rapid growth during the summer months. By 



