PARR AND SMOLTS 107 



the turn of the year, then, and, if the winter has been mild and open, 

 all the sooner, the various shoals up-stream begin to pack in earnest 

 and work down towards estuary or sea. By April of this year the 

 youngest of these fish will have had two full years of life since ceasing 

 to be alevins. In hatchery parlance they are " two year olds," and it is 

 at this age the earliest true descent is made. In any event, it is only 

 on the fish assuming the sea-going silvery scales prior to its descent, 

 whensoever that descent may take place, that the young fish should 

 properly be designated a " sea-trout smolt." That the period when 

 the young sea-trout thus becomes a smolt varies considerably I shall 

 now proceed to show. 



I mav make first this general observation that, with the Salmonidcs, 

 size has very little co-relationship with age. One is apt unthinkingly 

 to take it very much for granted that a large salmon, for instance, is an 

 old salmon and that a small trout is a young trout. How far this is 

 erroneous may be seen when we consider that a Tay salmon weighing 

 over 50 lb. may be only six years old, while an Add fish of 10 lb. may 

 quite well be two years older. Even more strikingly, a young salmon 

 may be larger than an older salmon taken from the same river owing to 

 the latter having been handicapped in its growth by having visited fresh 

 water more frequently for the purpose of spawning. Similarly with 

 regard to trout, the stunted little occupant of the moorland burn or hill 

 loch weighing but a few ounces may very well be an older fish than the 

 pampered occupant of some rich reservoir weighing as many pounds. 

 One has therefore no real warrant for supposing that the sea-trout 

 smolt which is seen descending a river at any time is only as old as it 

 looks. On the contrary there are reasonable grounds for the belief 

 that it may very well be much older. Even allowing that sea-trout 

 parr, as has been noted, grow propordonately quicker than salmon parr, 

 I had often puzzled myself to account for the remarkable size attained 

 by some of the Loch Lomond and Leven sea-trout parr, specimens of 



