Pictured Puzzles and Word Play / A Companion to the Twentieth Century Standard Puzzle Book - A. Cyril Pearson

The doublet by missing words, in which a grilse is turned into a salmon, is solved thus—

To silver Tweed, or broader Spey,
The grilse of silver, sailer gay,
Guides on; the sailor morals draws
When salmon follows Nature’s laws.

One letter is changed in each link.

The enigma—

I never move, and yet I run
From place to place all day;
Some loving swain, hot foot for fun,
Sees Dora in my way—

is solved by Road, which spells also Dora.