Cite references. The same blue tailed fly? No evidence in North American or British print about the minstrel song before the 1846 printing.
There is another, unrelated English song, "The Blue Tail'd Fly," which is earlier, prob. c. 1830.

Lyr. Add: THE BLUE TAIL'D FLY

A hungry fish chanced to spy,
Fal de ral, etc.
A little wicked blue tail'd fly,
Fal de ral. etc.
This fly unto the fish did say,
As in the flood he saw him play,
If you can bite my tail you may,
Fal de ral, etc.

This hungry fish then made a spring,
Fal de ral, etc.
But he could not catch this blue tail'd thing,
Fal de ral, etc.
So like the fox he lost a treat,
For the fish the fly could not eat,
So says he your nasty tail's not sweet,
Fal de ral, etc.

Now a little man by chance came by,
Fal de ral, etc.
And he caught with his hand this blue tail'd fly
Fal de ral, etc.
Then on a hook this fly he hung,
And in this river this blue tail flung,
Where death soon stopt his wicked tongue,
Fal de ral, etc.

This hungry fish saw the blue tail'd fly fall,
Fal de ral, etc.
I'll eat says he his body and all
Fal de ral, etc.
My hungry belly you shall fill,
The fly I'fll eat against his will,
He bit- but the hook stuck in his gill,
Fal de ral, etc.

The little man drew him on land,
Fal de ral, etc.
And took this hungry fish in hand,
Fal de ral, etc.
Then on a twig did him suspend,
For to eat this fish he did intend,
So my song good folks is at an end.
Fal de ral, etc.

Bodleian Ballads, Harding B 11(2226), Catnach, c. 1813-1838; also Firth b.26(36), c. 1819-1844.

No, probably not by Izaak Walton. Could be an English minstrel or music hall song.