The Welsh centre made his name playing for the Celtic Warriors and Ospreys before being hampered by a succession of knee injuries.
After fighting back to save his career, Bishop spent a season at Edgeley Park with Sale Sharks before enjoying short-term stints with Newport Gwent Dragons and Edinburgh.
Bishop made two appearances for Rob Moffat's men against Leinster and the Ospreys.
"David is a good professional and gave a good account of himself during his time at the club," said Moffat.
"He hasn't had much luck with injuries in the last few years, but he's a talented player who is willing to work hard. I'd like to wish him all the best for the future."
Guinness PRO12
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