March 23, 1883.] 



♦ KNOWLEDGE ♦ 



A NATURALIST'S YEAR. 



By Grant Allen. 



I X . — C H A R R JUMP. 



YONDER little spreaduig circle of concentric wavelets 

 on the still surface of the mere is caused by the 

 flapping struggles of a poor, fallen fly ; and the flash that 

 succeeds is clearly due to his sudden engulfment \>y a leap- 

 ing charr. Yes, there they are, basking among tho smooth 

 pebbles on the clear bottom, for charr love a clean basin to 

 lie upon ; and it takes a sharp eye to make out their 

 contour against the indistinguishable mottled grey of their 

 bed, as they lie motionless, without even a tin moving, in 

 the broad sunliglit River trout, which have to pass the 

 best part of their lives heading up against stream, acquire an 

 almost ceaseless trick of gently f;uining their tins in rhyth- 

 mical motion ; but charr, which ai'e rather lake lish than 

 river fish, lie perfectly motionless at the bottom, unless they 

 see anything on the surface that induces them to rise placidly 

 from their lazy attitude. They seem, in fact, like the 

 lizards among tish — creatures that love best to bask in the 

 sunshine, and never bestir themselves except for the sake 

 of replenishing the empty larder. Moving about so seldom, 

 they require very little food indeed ; for, the less work the 

 body does, the less fuel it requires to supply it with energy; 

 and indeed, when the charr do happen to get a good stock 

 of flies or worms, brought down by the mountain 

 streams that empty into their clear tarns, they do 

 not generally use up the material so aftbrded them 

 in their own persons, but store it away as fat 

 in their pylorics, thus forming a reserve against the heavy 

 demands made upon them in the breeding season. When 

 the young fry have to be provided for, this fat is expended 

 in producing eggs or milt, as the case may be, the hard or 

 soft roe of our domestic anatomical phraseology. If you 

 catch a charr some time before the breeding season, you 

 will tind the p3'lorics completely enveloped in bags of fat, 

 like the kidneys of a Southdown mutton, while the milt> 

 bags are long and thin ; but if (in defiance of law) you 

 catch one during the spawning time you will tind the 

 pylorics shrunken and naked, while the milt-bags have 

 swollen enormously, by the transference of fatty matter to 

 them from the provisional reserve. 



Charr, as a group, cannot be distinguished from trout by 

 any very well-marked line of division ; they form a sub- 

 genus of tho salmon tribe, noticeable mainly as having a 

 slightly different arrangement of the palatal teeth from that 

 of the true trouts and salmons. The fact is, there is no 

 group of animals in which it is harder to draw lines lietween 

 the species than in this royal family of fishes. Though an 

 immense number of species have l^een described, many of 

 which are a good deal dilierent from one another in their ex- 

 treme forms, it is almost always possible to bridge over the 

 gap by an equally immense number of intermediate types. 

 Besides, most of the species breed readily with one another, 

 and natural hybrids are very common; so that the old- 

 fashioned systematic biologists had hard work to divide 

 them all out into neatly-labelled batches, each consigned 

 to its own particular cut-and-dried pigeon-hole. The 

 evolutionist, however, flnds the family much less difti- 

 colt to deal with. He sees at once that it is a very 

 wide-spread and variable one, descended at no very remote 

 period (as we count geological time) from a single ancestor, 

 and greatly moditied by the extraordinary variety of cir- 

 cumstances to which it has been exposed, but still clearly 

 traceable to a single source. Indeed, there is one little 

 peculiarity common to all the salmonoids — the graylings 

 and gwyniads, as well as the trout and charr — which im- 



mediately shows the closeness of their subsisting relation- 

 ship ; and that is the fact that the young of almost all the 

 species are barred with bluish stripes, known to tishermin 

 as finger-marks. In this stage, they are all still practically 

 indistinguishable from one another, and are all called alike 

 by the onr name of parr. 



On the other hand, as the young salmon-kind attain to 

 years of discretion they begin to display their various 

 acquired specific peculiarities. Some of them, like the 

 true salmon and the sea-trout, have taken to invading the 

 salt water ; and these have, therefore, developed cei-tain 

 special points of structure which fit them for their migra- 

 tory mode of life and altered habits of feeding. Others, 

 again, like the common trout, stick to the basins of their 

 native rivers, and vary among themselves in colour or size 

 according to the nature of the bottom or the quality of the 

 food they i.an obtain. Yet others, like the great lake 

 trout of Scotland, or the namaycush of North America, 

 confining themselves to large sheets of fresh inland 

 waters with little or no current, grow much bigger in 

 size, and acquire other distinctive peculiarities in adapta- 

 tion to their chosen habitat. Of course, these varieties or 

 species have only been produced by long selecticn of tl»e 

 liest adapted individuals, and they have, doubtless, been 

 largely aflected by many minor points in the environment, 

 less ob\'ious than food or climate. For example, the com- 

 petition of other types, and tho nature of the local enemies, 

 such as kingfishers, grebe, or divers, must have a great deal 

 to do in producing the diflereutiatiou of the various lake or 

 river salmonoids. 



The species-making among the charr and trout, however, 

 has gone a great deal further than that Wherever a little 

 body of either group got isolated in asinglc disconnected tarn 

 or sheet of water, away from the main watercourses of the 

 country, it has generally been acted upon by special selec- 

 tive causes, which have at last succeeded in producing a 

 new and distinct type. Thus, among the true trouts, we 

 have in the British Isles alone several of these isolated 

 forms, such as the gillaroo, from the Irish lakes ; the Loch 

 Leven trout, confined to one Scotch sheet of water ; and 

 the Loch Stennis trout, found only in a single mountain 

 tarn of the Orkneys. Much tho same thing has also 

 happened among the charr, for besides the common 

 northern charr, which is found in Scotland, we have 

 three or four local s|)ecies, each confined to a solitary 

 locality. Even our Scotch northern charr itself, though 

 almost identical with that of Lapland, has three less joints 

 in its backbone, and never grows to the same size, thus 

 showing the first steps towards the production of a dif- 

 ferent species. But in Loch Killin there lives another peculiar 

 charr, much more distinct, and not migratory ; while in 

 the Llanberis lakes wo get yet another kind, the torgoch ; 

 and in Windermere we meet only with a restricted local 

 form, known as Willughby's charr. Again, Dr. Giinther, 

 of the British Museum, who is the great authority on the 

 salmon-kind, has shown that the Irish charr, long separated 

 from all the rest of their kindred elsewhere, form a 

 distinct little group by themselves, with teeth much more 

 feebly developed than in other charr ; and this, which is 

 probably a mark of an early form, may be accounted for by 

 the fact that Ireland was comparatively early separated 

 from Great Britain and the continent after the glacial 

 epoch, so that no recent improvements in charr economy 

 can ever have been imported thither. Furthermore, even 

 these local Irish charr themselves have split up into at 

 least two distinct forms, one of which, known as the fresh- 

 water herring, haunts the bottom of Lough Melvin only, 

 while the other is entirely confined to Lough Eske and 

 Lough Dan. Equally confusing types arc found on the 



