FISHING AT HOME AND ABROAD 

 using vulcanite tubes in which the fish were held during the process of 

 marking. None of these fish was seen again during 1905, which was 

 negative evidence against the belief entertained by many fishermen 

 that smolts descending in April and May reascend the rivers as grilse 

 during the ensuing summer. But during the summer of 1906 forty grilse 

 bearing the tell-tale silver wire were taken in the nets above Perth. Their 

 aggregate weight was 266 J lb. — an average of about 6§ lb., the two 

 heaviest grilse, taken in August, weighing 10 J lb. each.* From this the 

 inference is fair that the smolt requires not less than a year's marine 

 diet to fit it for revisiting fresh water. Even so, the rapidity of growth 

 is very remarkable; a smolt weighing, say, 1| oz. is proved to increase 

 to fifty or sixty times that weight in twelve months, and in the case of 

 the August grilse abovementioned, to one hundred times its weight in 

 fifteen months. 



There was nothing, so far, to cast doubt upon the accepted belief that all 

 salmon first reappear in the rivers as grilse during the summer and 

 autumn months; but this doctrine was conclusively dispelled during the 

 season of 1907, when thirty -seven fish marked with silver wire were taken 

 as spring salmon between February 18 and June 14, of weights ranging 

 from 7 lb. to 13 lb. Further surprises were in store for the observers. 

 Between July 18 and August 20 twenty-five marked fish were taken as 

 summer salmon, and two more after the nets were off — ^thirty salmon in 

 all, averaging 16|^ lb., the heaviest being 27 lb. in weight. Again, in 

 February and March, 1908, four salmon were taken in the Tay that had 

 been marked with silver wire nearly three years before. Their weights were 

 13 lb., 15 lb., 15 lb., and 35 lb. 



Now, all these fish— the grilse of 1906 and the salmon of 1907 and 1908— 

 were pronounced to be maidens — ^that is, fish which had never spawned — 

 returning to the fresh water for the first time; whence the conclusion 

 is that the period of a salmon's sojourn in the sea after he goes there 

 as a smolt, is of uncertain duration, and that all salmon do not, as has 

 hitherto been assumed, make regular annual migration. The influence 

 of the knowledge thus acquired ought to modify considerably all legis- 

 lation affecting such an important source of food supply as our salmon 

 fisheries. 



But all smolts do not grow at an equal rate. Some are probably less 



*Thii U far in excess of the weight attained by grilse in smaller rivers, the Tay and the Tweed being exceptional 

 among Scottish waters in that respect. 



10 



