164 Part L17.—Twenty-third Annwal Report 
the height of spring tides the currents in the neigh bourhood 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 
i¢vel 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 coid 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, 4} 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. 
