TROUT. 



Althougli in the general account of the family of Salmonidse many observa- 

 tions have been introduced respecting both trout and grayling, it now becomes 

 desirable to offer some remarks restricted to the marine and fresh-water forms of 

 British trout, which have been considered by some ichthyologists and fishermen 

 to be anadromous and non-migratory fresh-water species. Before entering upon 

 each in detail it appean's desirable to explain why it is that I find myself unable to 

 accept the numerous species that have been described, believing those ichthy- 

 ologists* more correct who have considered them modifications of only one, which, 

 as Salmo trutta, includes both the anadromous and non-migi'atory fresh-water 

 forms. 



For it must be evident when looking through the works of systematic 

 zoologists, that the greatest number of false species among fishes are local 

 varieties existing in such genera as are most prolific in forms ; and that local 

 races have been taken for distinct species. If among certain specimens an 

 example is found similar to what exists in another so-called distinct species, 

 residing in a different locality, this individual specimen might be an indication 

 that both were descended from a common origin, in short, how it may be an 

 instance of atavism, or reversion towards an ancestral form. 



In following out such an inquiry, it is, I thmk, possible to prove that marine 

 salmonoids may take on a frcsh-watcr existence ; also that Salmo trutta, 8. camhriciis, 

 and other anadromous so-called species, can be traced into the fresh-water forms 

 of trout. If sea trout which having entered fresh water in order to breed, are 

 prevented returning to the ocean, it may result, as detailed by a correspondent in 

 The Field (January 8th, 1881), that they become, as he found them, big-headed, 

 lank, and black-looking. But there may have been a reason for this, as insuf- 

 ficiency or inappropriateness of the food, or unfavourable conditions of the water 

 in their new home, which precluded their thriving or even continuing in health. 

 Should, on the contrary, the place j)rove appropriate, they may thi-ive even 

 though they are unable to return to the sea. 



If we examine the various reputed species of British trout we find them 

 divided into the migratory anadromous forms and the non-migratory fresh-water 

 races, but no one has been able to clearly define whore one ends and the other 

 begins. The anadromous forms as sea-trout, Salmo trutta, S. eriox or S. 

 camhriciis or the sewin, known in their younger conditions as S. albus, S. phinoc or 

 S. brachypoma, are silvery in colour, with black spots when resident in the sea. 

 But when they enter fresh waters for breeding purposes an orange margin shows 

 itself to the upper and lower edges of the caudal fin, while the adipose dorsal is 

 likewise margined with orange, and some orange spots appear on the body.f The 



* Widegren {Ofi\ Vet. Akad. Fork. 1863) gave au interesting paper in which he asserted that 

 the anadromous sea trout and non-migratory fresh-water forms were all variations of one species, 

 the differences being due to the localities they inhabited. In these conclusions Malmgren 

 generally Jigreed, and they appear to coincide with the results of the experiment I have, or shall, 

 allude to, and the series of examples in our national collection and elsewhere. 



f Similarly no orange colour is seen on the salmon, Salmo sahir, after it has once become a 

 grilse, except when returning to the rivers to breed, then some may be present on the body, but 

 more on the males or red fish which are the most exhausted of the sexes, while on their cheeks 

 are orange stripes which have been aptly likened to those present on marine wrasses. But after 

 the debilitating effects of the breeding season have been overcome, the orange colour leaves the 

 fish : being in fact restricted to the young and breeding forms, but not in salmon when in their 

 highest condition. 



