There is also in Northumberland a Trout called a Bull-trout, of a much
greater length and bigness than any in these southern parts; and there
are, in many rivers that relate to the sea, Salmon-trouts, as much
different from others, both in shape and in their spots, as we see sheep
in some countries differ one from another in their shape and bigness,
and in the fineness of the wool: and, certainly, as some pastures breed
larger sheep; so do some rivers, by reason of the ground over which
they run, breed larger Trouts.

Now the next thing that I will commend to your consideration is, that
the Trout is of a more sudden growth than other fish. Concerning
which, you are also to take notice, that he lives not so long as the
Pearch, and divers other fishes do, as Sir Francis Bacon hath observed
in his History of Life and Death.

And next you are to take notice, that he is not like the Crocodile, which
if he lives never so long, vet always thrives till his death: but 'tis not so
with the Trout; for after he is come to his full growth, he declines in his
body, and keeps his bigness, or thrives only in his head till his death.
And you are to know, that he will, about, especially before, the time of
his spawning, get, almost miraculously, through weirs and flood-gates,
against the stream; even through such high and swift places as is almost
incredible. Next, that the Trout usually spawns about October or
November, but in some rivers a little sooner or later; which is the more
observable, because most other fish spawn in the spring or summer,
when the sun hath warmed both the earth and water, and made it fit for
generation. And you are to note, that he continues many months out of
season; for it may be observed of the Trout, that he is like the Buck or
the Ox, that will not be fat in many months, though he go in the very
same pastures that horses do, which will be fat in one month: and so
you may observe, That most other fishes recover strength, and grow
sooner fat and in season than the Trout doth.