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Part III.— Fifteenth Annual Report 



The experiments with eod and haddock were not so successful. No 

 marked haddock was recovered, but about 5 per cent, of the cod 

 were re-caught ; the total number is too small for generalisation. 

 One liberated in the Firth of Forth was got off Stonehaven, 52 

 miles to the north, in sixty nine days. But it is clear that if the plaice, 

 a comparatively slow moving flat-fish, travels so far northwards, there is 

 no difficulty in assuming that the more rapid round-fish may do like- 

 wise. The experiments with the dabs show that they may move 

 considerable distances (as far at leist as 39 miles), and that their 

 movement is irregular, and may be to the south as well as to the north. 

 As previously explained, this fish spawns within the territorial waters as 

 well as offshore, and has a small egg, which hatches rapidly. 



While the normal movement of the surface water off the East Coast, 

 and therefore the normal movement of the eggs and larva? floating in it, 

 is towards the south, it must be borne in mind that it is subjected to 

 temporary deviations from the prevalence of continuous strong winds or 

 gales blowing over a period. Instances of this will be found in the first 

 part of the paper. A northerly gale drives the south-going water with 

 greater rapidity in the same direction ; a gale from the south-east will 

 retard it or temporarily reverse it according to its force and duration. 

 Strong easterly gales tend to drive the surface water in to the coast ; 

 westerly gales drive the offshore water further away towards the east. 

 There is therefore what may be termed a disturbing factor frequently in 

 operation, the effect of which may be to disperse the floating eggs and 

 larvse more or less temporarily in various directions. Sometimes this 

 factor will bring towards the inshore grounds large supplies of eggs and 

 larva? from spawning areas, ex adverse-, possibly even from the southward 

 (as in January of this year). At other times it will carry them rapidly 

 seawards, when large numbers of certain kinds will perish. The liability 

 to loss in this way must be regarded as the principal reason why the 

 fecundity of species producing floating pelagic eggs is so much greater 

 than the fecundity of those producing demersal, attached, eggs ; the 

 mean number of eggs shed by each female of twenty-three species pro- 

 ducing pelagic eggs is 2,388,000, while the mean number shed by each 

 female of twelve species producing demersal eggs is only 24,700, or very 

 nearly a hundred times less. 



But notwithstanding such temporary deviations, due to gales, the 

 normal movement is to the south. 



It is evident that the circulation of the surface waters of the North 

 Sea, as shown by the experiments described in this paper, may be of 

 importance in other directions, and opens up other aspects of fishery 

 inquiry. It is not improbable that it is associated with the succession 

 in time of the summer and autumn herring fishing along the East Coast, 

 which begins in Shetland in June, and ends off the Norfolk coast in 

 November. It explains also the frequent appearance of Atlantic forms 

 in the waters off the East Coast ; and perhaps also the occasional 

 anomalous distribution of certain fishes, as the anchovy, which appeared 

 a few years ago on the west, north, and then on the north-east coast of 

 Scotland. But these points require further consideration before definite 

 statements can be made. 



