For their part Ulster Rugby have also signed new players from Scotland in internationals centre Rob Dewey and wing Simon Danielli with former Bourgoin and 21-times capped Italy lock Carlo Del Fava boosting their front five resources.
Former Wales lock Chris Wyatt has replaced Del Fava at Bourgoin and his knowledge of the Welsh game may help his new club when they travel to face the Ospreys in Round 1.
The Ospreys have been active in the transfer market with the capture of All Blacks flanker Marty Holah joining fellow Kiwi Justin Marshall at The Liberty Stadium.
Thirty-year-old Holah has won 36 All Blacks caps, the latest against South Africa last September, and joins the Ospreys from the Waikato Chiefs in late October. Those making shorter trips to the Liberty are Wales internationals scrum half Mike Phillips and lock Ian Gough.