146 THE SEA-TROUT 



not glen-lakes — are so nearly beyond tidal influence that their waters 

 are barely more than brackish. And, lastly, of others near sea-level, 

 many of our great lakes, like Loch Shiel, Loch Maree, Loch Morar, 

 Loch Lomond and Loch Eck, are now wholly beyond tidal influence, 

 although the fact that sea-shells may be gathered in the clay of certain 

 beaches in a state of almost perfect preservation in some of them proves 

 that their fresh-water environment is of no great antiquity. 



Now, whether we attribute to trout a marine or a fresh-water origin, 

 it is quite easy to imagine that the trout of any fresh-water loch to which 

 the sea gradually obtained access would adapt themselves to the 

 changing conditions of their environment and become in time, to all 

 intents and purposes, sea-trout. They would still, as such, continue 

 to migrate to their accustomed spawning streams. Similarly the sea- 

 trout of any sea-loch which gradually became elevated above tidal 

 influence would not for that reason necessarily abandon their habits of 

 frequenting it, though these habits might possibly change to some 

 extent. For instance, the tentative run to certain lochs in spring may 

 be the survival of some ancient habit which existed when the loch still 

 retained its marine character. At all events the habit of seeking the 

 loch for the purpose of spawning in its streams would almost certainly 

 persist unchanged. It would, one may suppose, be the last habit to be 

 definitely abandoned. My belief is, that it is practically immaterial to 

 the trout of those districts, where such conditions as I have indicated 

 prevail, whether they inhabit at one time or another the fresh-water, 

 brackish, or salt-water loch, whichever it may be, which gives character 

 to the river channel, and that the runs of fish differ locally just because 

 of the variety of local conditions. 



But particularly I would suggest that such tidal, semi-tidal, and 

 almost tidal lochs serve as convenient gathering grounds for the sea- 

 trout shoals preparatory to their periodical migrations. For example, 

 it is quite plain that Loch Lomond is the natural gathering ground for 



