Why can't it be paisley?
Or plaid?
Or herringbone?

And who decided herrings were suspicious in the first place?

Maybe the herring was just swimming by when some hack decided to send his detective down a rabbit hole and—WHAM—misdirection became a thing. Readers, we are told, enjoy being fooled.

Suddenly the poor fish has motive, opportunity and a questionable alibi.

That's the trouble with mysteries.

Everybody looks guilty if you describe them properly.

Especially the fish.

—Don