of the Fishery Board for Scotland, 



153 



VI, — THE RELATION OF MARINE CURRENTS TO OFF- 

 SHORE SPAWNING AREAS AND INSHORE NURSERIES. 

 By Dr T. Wemyss Fulton, F.R.S.E., Superintendent of Scientific 

 Investigations. (Plate II.) 



Of late years the physical conditions of the sea in relation to fishery 

 problems have received a considerable amount of attention in various 

 countries, more particularly with regard to the range and variations of 

 temperature and density. On Continental coasts, as well as on our own, 

 periodical observations have been made, both at fixed stations and by 

 means of vessels, into the changes which take place in these two impor- 

 tant physical factors ; but practically nothing has been hitherto attempted 

 to ascertain the influence of another factor which has an important 

 bearing upon several fishery questions, namely, marine currents. Tt is 

 now well known that the eggs of almost all edible sea-fishes float at or 

 near the surface of the sea, and that they, as well as the newly-hatched 

 larval fishes which emerge from them, are borne helplessly by the 

 currents. It has also been shown that nearly all the food fishes with 

 floating eggs spawn on the East Coast outside the three-mile limit, and 

 that their spawning areas may extend for very considerable distances 

 from shore ; and, further, that certain grounds, such as Smith Bank, in 

 the Moray Firth, are frequented at the spawning period by immense 

 shoals of the food fishes, which in succession shed their eggs in myriads 

 into the waters. Before the experiments described in this paper were 

 begun no attempt had been made to determine the relation between such 

 spawning areas and the inshore grounds along the coast. From the 

 absence of spawning fish in the territorial waters and the presence there 

 of their floating eggs and larvae it was known that the latter were derived 

 from the offshore areas, and had been borne shoreward by the currents ; 

 and it was generally assumed that the spawning areas from which they 

 came were in the neighbourhood of the territorial waters in which the 

 eggs and larvae were found. The experiments which have been made 

 show, however, that such is not the case. The floating eggs and the 

 larval fishes derived from a particular spawning area may be carried 

 considerable distances in a definite direction in a comparatively short 

 space of time and may hence form the source of supply not to the 

 adjacent parts of the coast but to parts situated at a considersble distance. 

 The chief aim of the experiments was to determine this relationship — 

 to show the course traversed by the currents bearing the floating 

 spawn and larvae and the portions of the coast on which they impinge. 

 Knowledge of this kind is obviously of importance in relation to pro- 

 posals to control fishing operations on the spawning grounds. For 

 instance, the experiment, so far as they have gone, tend to show that 

 the inshore waters of the Firth of Forth and St Andrews Bay derive 

 their main supplies not from the waters lying contiguous to them to 

 the eastward, but from northern areas. When these experiments are 

 sufficiently complete it will be pussible to assign the offshore spawning 

 area which is in natural connection with any portion of the territorial 

 waters, and which forms its chief source of supplies. The experiments 

 also show the direction in which the pelagic fish-food is carried. 



Similar experiments have been made previously for hydrographic 

 purposes, and on several occasions in connection with oceanic circulation 

 especially in the Atlantic ; but I am not aware of any having been made 

 in the North sea. The most extensive and elaborate were those carried on 

 by the Prince of Monaco and Professor Pouchet in the North Atlantic, and 



