Natural History. — Zoology, 375 
they retire again to the sea, and evidently to great depths, re- 
mote from cod and haddock ground, to recruit their exhausted 
strength, and prepare for future efforts of the same kind. Before 
beginning their journey, they are in good condition, the body 
being loaded with fat, as a magazine for supplying the wants of 
the fish during migration, and for furnishing the great quantity 
of matter requisite for the evolution of the spawn. When the 
fish enter the Frith at the commencement of their upward mi- 
gration, and are thus in good condition, they are termed, in 
the language of fishermen, clean fish. At this period they 
are infested with the Salmon louse, C aligns productus of 
naturalists, and which chiefly adhere to the more insensible parts. 
But when arrived at the place of spawning, the fish is lean, as the 
whole fat of the body has passed into the melt and the roe. In 
this state, in which they are termed red Jish^ they are worth- 
less as an article of food. After the fish have spawned, they 
are termed helts or Jhul fish^ and are equally despised as the red 
fish. The gills are now more or less covered with the Entomoda 
salmonea. The motion of the fish upwards from the sea to 
the river and place of spawning, is influenced by several causes. 
When there is abundance of fresh water in the Frith, the 
fish seem to proceed regularly and rapidly up the middle of the 
stream, enter the rivers, and hasten on to their destination. Un- 
der these circumstances, it is probable that the ripening of the 
spawn is accelerated by the influence of favourable external cir- 
cumstances. When the rivers are but scantily supplied with 
water, the fish, which have entered the Frith, roam about in it 
in an irregular manner, influenced by the state of the tide ; 
while those which have been surprised in the rivers by a drought, 
betake themselves to the deepest pools. In returning to the 
sea after spawning, the fish seem to keep the middle of the 
stream in the river, and the deepest and saltest water in the Frith. 
Salmon enter the river and frith at all seasons of the year, but 
they approach in greatest numbers during the summer months. 
Fish taken in May, June, and July, are much fatter than fish 
in the same condition as to spawning, taken in February, March, 
or April. They fall off in fatness very rapidly from August to 
January, when they are leanest. The principal spawning sea- 
son is in November, December, and January. The roe becomes 
