Jack, your remark made me smile!

Here's what I can find:
Johnny Handle, with Chris Hendry, recorded The Mackerel Song on an album called Here Dwells My Heart.
David Kidman wrote an online review at Living Tradition Magazine's website. In it he says,

A Mackerel Song, penned by Aaron Watson, probably in the 1890's and forecasting the eventual demise of the inshore fishing industry.

Clearly Aaron Watson and Johnny Handle are two different people
in two different time periods.