Either taken to the nearest English port or destroyed to prevent them falling into enemy hands-at a great loss to the crew if that happened. Some of that sort of information is in the Navy List. I assume that unsuitable ( for war) ships were sold.

As an American I know that this taking of merchant or trade ships ended in our War of 1812. America was neutral in the Napoleonic war and English Captains did not always respect that neutrality. It is amusing to me to read in one of her letters Jane Austin's English perspective of that particular war.