150 NORTHERN ZOOLOGY. 



the back and sides are effaced, the salmon-louse shrivels and drops off, and the tape- 

 worms die and are discharged. As the spawn augments in volume, the flesh of the 

 salmon deteriorates, growing lean, flabby and insipid, and the bright silvery tints of 

 the scales are replaced by brownish stains, giving rise to the epithet of " red-fish," 

 in contradistinction to that of " clean," which the fish had on its first arrival from 

 sea in high marketable condition. The gravelly shoals selected as spawning places 

 are generally as high up the river as the fish can ascend. Furrows about eighteen 

 inches deep being formed in the gravel by the male, according to some observers, 

 or by both male and female as others report, the latter deposits in them her roe, 

 and the former his milt, and carefully covers them up. The fish has been said to 

 plough up the gravel with its fins, but it is more probable that it uses the nose for 

 this purpose. Mr. Potts (quoted by Pennant) thinks that the tail is the instru- 

 ment by which the gravel is filled in over the spawn, as he had observed the skin 

 rubbed off that part ; this abrasion, however, may be the result of friction against 

 stones, in the efforts the fish makes to ascend the shallow streams. After securing 

 the spawn, the salmon commences its return to the sea, being now named, in the 

 language of the fishermen, a " foul fish," ligger, kipper, or kelt ; its gills are in- 

 fested by the gisler, or brachlella salmonia, and it continues to have a dark colour, 

 lank form, and to be unfit for food during the remainder of its stay in fresh water. 

 The period of a salmon's stay in a river is determined by various causes. The 

 ascent of most streams is facilitated by the land-floods of wet seasons, or rendered 

 impracticable for a time by droughts ; and Dr. Fleming thinks it probable that 

 circumstances which favour the upward passage of the fish tend also to accelerate 

 the ripening of the spawn *. In returning to the sea the fish keep the middle of 

 the stream, and seek the deepest and saltest water of the estuary. 



The following observations on the spawning of the salmon, and subsequent 

 evolution of the young fry, in one of the tributary streams of the Tweed, are re- 

 corded by Dr. Knox in the paper we have already cited. " In November the 

 river Whitadder, which has its source in a mountainous country nine hundred feet 

 above the level of the sea, abounded in all the different kinds of salmon usually 

 taken in the Tweed, with which this stream communicates at a short distance from 

 Berwick. They were engaged every where in spawning, this being the usual 

 time in which the act is carried on. A pair, seemingly f of the ordinary Tweed 



* Ed. Phil. Journ., x„ p. 375, in a paper which gives a detailed account of the movements of the Salmon in the river 

 Tay. The facts therein stated coincide generally with Mr. Potts's history of the Tweed salmon in Pennant's British 

 Zoology. 



f The Tweed Bull-trout, or Salmo hamatus, might be readily mistaken for the Salmo salar. 



