The Kinsale fishery was fairly late - see http://www.ee.surrey.ac.uk/Contrib/manx/fulltext/worthies/p195a.htm for a comment on Robert Corrin - my guess is that only a few boats in 1861 went.
Why he was important was that previously the fishing was for Herring (from June to Sept) but this opened up a new season and thus moved men from a combined fishing/farming to all fishing job.

Many manx men would be abroad esecially in England or at sea in the Navy etc - however it would be good to do some research on these