PARR AND SMOLTS 115 



young turbot, sand eels, pipe fish, and various marine shore forms. In 

 this we repeated the experience of Mr. Dahl in his attempts to follow 

 salmon smolts from the rivers of Norway down the fjords." Then in 

 course of renewed operations with a boom-net in the following year, 

 Mr. Calderwood made further discoveries of which one in particular 

 is relevant to the present subject, namely : "All salmon smolts captured 

 were taken when the net was set so as to fish the ebbing tide. When 

 the net was set so as to fish the flood tide or incoming current sea- trout 

 were alone taken, and many of these were nearly twice the size of the 

 salmon smolts. Sea-trout were also taken during ebb tide." 



The relatively larger size of the sea-trout was illustrated in my 

 description of a Leven smolt given on a previous page. But the main 

 point which Mr. Calderwood's investigation brings out is that the sea- 

 trout is essentially an estuary fish. It may be presumed, therefore, 

 that in such great estuaries as those of the Tay and the Clyde there is 

 no occasion for the sea-trout to leave even the narrower waters of the 

 estuary in its transitional stage between the smolt and the whitling, nor 

 in such environment does the whitling do so before it again ascends to 

 fresh water, as one finds them there in all stages of the transition. 



But there are few estuaries so extensive and so rich in feeding 

 grounds as those of Tay and Clyde. Many sea-trout streams have 

 practically no estuary at all, and between both types the variety of 

 river formation in Scotland is endless. On the type of estuary, then, 

 and the feeding grounds afforded by it, and where there is barely an 

 estuary or none, then on the available feeding grounds in the sea in the 

 vicinity, will, I think, depend in great measure the habits of the local 

 sea-trout. For this reason alone I think it would be unwarrantable to 

 lay down any scheme of definite uniformity in the habits of the fish 

 although most of these habits, I imagine, will be found to be not 

 inconsistent with certain broad general principles. 



