Definition of "bonetta"

On the morning of this day we caught five bonettas, being the only fish taken since leaving England, excepting several flying fish, which at times flew aboard during the night, in their endeavours to escape from their pursuers, the bonettas and dolphins, whose principial food they constitute.

1819, A Voyage To South-America And The Cape Of Good Hope: In His Majesty's Gun Brig The Protector: