Yep, I'm sure they are all initially temp positions, as I heard it directly from the mouth of the Recruitment Manager, sorry.
If you knock their socks off they may offer you perm after the summer, but I believe they are more likely to offer a return for the following summer season, as they don't need as many crew over the winter season. I have heard of crew getting full time perm after two summer seasons, but I don't work for them so I can't really confirm that.