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Part III. — Thirteenth Annual Report 



bed as a catchment area, but the foreshore of the lower reaches of the 

 river, as was noticed in the 1889 Report, cannot afford a resting-place for 

 the spat owing to the great quantity of silt thrown Upon it. fortunately, 

 however, dredging is not permanent. During the spatting season there 

 are years when the increase in the rainfall is not appreciable, and so the 

 spat is not lost from this cause. In such years the spat can collect on the 

 large stretch of foreshore, below Ferryden as well as on the Scalp, Rossie 

 Island, and the Briggs of Binny. After dredging operations have been 

 concluded the river bottom is hard and presents the best condition 

 possible for a catchment area for spat. Gravel, shingle, and rocks are the 

 natural resting-places of such young molluscs as the common musselj and 

 when the surfaces of these are clean, they form the best kind of collectors 

 for the free-swimming embryos. 



Whilst the two great drawbacks to a plentiful supply of mussel-spat 

 are the silting of mud depriving them of a solid foundation on which to 

 rest, and the increased volume of rivef-water brought about by great 

 rainfalls carrying the free-swimming embryos to sea, there are other 

 conditions which are favourable. Where the bed of a stream is uneven, 

 and where the river banks are winding, eddy currents are formed which 

 carry the young mussels into quiet spots where they obtain time to affix 

 themselves. Oysters are helped in a similar manner, and by the arrange- 

 ment of sluices and collectors eddy currents are promoted in order that 

 as large a brood as possible may be captured. The chief places at 

 Montrose, where such eddy currents exist, are on the north side, at the 

 Briggs of Binny and Binny Bank, and on the south side in the neigh- 

 bourhood of the Scalp. The tongue of land, which is seen at low 

 water running from the north side eastward into the stream of the 

 South Esk, causes an eddy to be formed at this part ; hence these banks 

 become natural collecting-ground for spat. The current of the South 

 Esk impinges against the shore of Rossie Island at the Trout Shot, and 

 sometimes a coating of seed is obtained at that point where the current is 

 divided, part flowing down the Inch Burn, but the chief stream running 

 to the north of Rossie Island and forming an eddy. The best and most 

 constant eddy, however, is found where the bank known as the Scalp 

 narrows the breadth of the channel of the river. Consequently, this is 

 the best seeding area at Montrose. Along the shores of the lower 

 reaches of the river there are always currents running in a direction 

 opposite to the direction of the current in the channel. While these side- 

 currents are generally too swift to allow much seed to settle on the 

 foreshore, yet, In some years, a large quantity is obtained from the shingle 

 and gravel of the Ferryden foreshore below the village and above Johnny 

 Mearns' Harbour. In addition to the eddies there are other agencies con- 

 tributing to a successful deposit and ingathering of mussel spat. The 

 number of mussels present in Montrose Basin bears a direct relation to 

 the quantity of spat obtainable in any year. If all the spat, extruded 

 from say a dozen mussels, were to fix, settle, and grow, probably these 

 might stock as large an area of foreshore as is seen in an average year 

 below Ferryden. But as only a very minute proportion of the free- 

 swimming embryos — possibly not a millionth of a millionth of a millionth 

 — ever finds a resting-place and grows, the larger the stock of adult mussels 

 in Montrose Basin, the better the crop of seed that may be looked for. 

 When the stocks were low at Montrose the quantity of mussels obtain- 

 able was not so great as when the whole basin in the upper reaches was 

 completely stocked. The French recognise the direct relation of the 

 quantity of adults to the yield of spat and so maintain large hatics reserves 

 of oysters in order to supply a sufficient number of young oysters for 

 stocking the growing-beds id future years, tu mussel culture similar 



