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Part III. — Twenty-third Annual Report 



the height of spring tides the currents in the neighbourhood of Craighead 

 and Newcome Spit are too strong, and occasionally damage or carry the 

 nets away altogether. 



Fishing is also entirely stopped for a short time, extending from half - 

 an-hour to three-quarters of an hour, during the slack water between 

 tides. 



Many of the fishermen are of opinion that most of the fish enter the 

 river during spring tides and make their way to the sea again as the 

 tides slacken ; this, however, was not borne out by the daily returns of 

 the fishing during the past season. 



The main mass of the flood tidal current, after sweeping through 

 between Broughty-Ferry and Tayport, flows in the direction of West- 

 Ferry Bay and the Stannergate, then south-west between the Chequer 

 Buoy and the Newcome Spit. It next flows west between the Middle 

 Bank and the Fife shore, then north again in the vicinity of the Tay 

 Bridge to Ninewells and Invergowrie Bay. The returning ebb tide flow- 

 ing in the opposite direction passes over much the same course. 



All the important sprat and herring fishing-grounds lie in the above 

 course, and the fish when not very plentiful in the estuary appear to 

 always follow more or less these main tidal currents on their way from 

 and to the sea. When the fish are very plentiful, on the other hand, 

 they are caught in all parts of the estuary. 



The presence of the flood tide is perceived on the north side of the 

 estuary in several ways. First, the saltness of the water at spring tides 

 upon the north shore is between 10 and 25 per cent, greater than that 

 upon the south shore till the ebb tide has fairly commenced. Secondly, 

 the current of the flood tide is so strong in the vicinity of Dundee as to 

 give an inclination to the surface of the water, so that at half flood the 

 level is 2 to 3 inches higher than it is on the opposite side of the 

 estuary. 



The deeper parts of both tidal currents are much Salter and, during 

 the cold months, warmer, than the surface waters ; but there is generally 

 a greater difference in salinity and temperature between the surface and 

 bottom layers of water upon the flood than upon the ebb, these layers 

 tending to intermix somewhat less upon the flood-tide than upon the ebb. 



At the Abertay Lightship stationed at the mouth of the Tay, the salt- 

 ness of the surface water, near low water and during heavy land floods, 

 is sometimes as low as two-fifths of that of sea-water. 



The normal ratio, however, of sea- water to land-water in the estuary 

 is such that at the middle of its length — at Dundee — there is just as 

 much fresh water as salt, and at the Pile Lighthouse, \ of a mile below 

 Tayport, the quantities of sea-water and land-water are, on the average, 

 as 2 to 1. The ratio of the land- water to sea- water at Dundee usually 

 fluctuates between one-fifth and four-fifths. 



So far as I can make out meanwhile, the movements of the sprats and 

 herring in the river are not influenced to any marked extent by variations 

 in temperature, although both kinds of fish appear not to wander very far 

 from the slightly warmer water of the main flood tidal currents. 



Some Notes on the Natural History of the Sprat and Winter Herring. 



Sprats and winter herring frequent bays, inshore waters, and estuaries. 

 They usually ascend the estuaries of rivers in large numbers during the 

 months of October, November, December, January, and February. The 

 main shoals appear to remain in the Tay estuary for short periods, 

 extending from two to five or more days at a time, and then gradually 

 make their way to the sea again. 



