How about using a non-toxic paint mark on the carapace. Individuals could be marked with different symbols or numbers. An alternative to this would be to use small coloured beads which can be glued on to the carapace with each individual having a unique colour code. I know that such techniques work for marking marine turtles.

I like the idea of using epoxy to affix colored beads to the carapace. If you expect some aggregations of individuals in which the markings would be obstructed, you could affix several redundant markings at multiple points on the edge of the carapace.

There is a paper about to come out in Journal of Fish Biology that uses small plastic discs with binary codes.

Contact Tanja for details:

http://staff.lincoln.ac.uk/tkleinhappel

Thanks for reply.

We used the colored lobster rubber bands in different color combinations to wrap around the joint behind the cheliped to identify individuals.

For spiny lobsters, colleagues of mine have used colored cable ties attached around the base of the antennae. They're easy to apply, come in multiple colors, relatively easy to identify underwater or in aquaria/mesocosms. You might be able to buy or make them fluorescent but the fluorescence signal would likely be lost underwater. The cable ties typically don't get fouled or wear off which can be a problem for some carapace marking systems.

If you're worried about loss through molting, there are a few papers that report use of sphyrion tags in lobsters. My recollection is that another paper used streamer tags to track tagged lobsters that had been released in an attempt to gauge tag loss (double tagging with streamer and sphyrion), but I haven't read these papers in a couple of years and I likely forgot some details. Try google scholar on sphyrion tag and homarus. The sphyrion tags are invasive and there is some tag loss. Moriyasu's paper indicates that mortality to tag loss isn't too high if you tag at intermolt as opposed to premolt. I think Lander's work indicates good tag retention through several molts.

Thanks for answers. I have the opportunity to tag one lobster in captivity first, to see what will work best. I find the colored cable ties attached around the base of the antennae very interesting.

You can find cable ties (you may call them zip ties?) come in different sizes, particularly small sizes which can be used on 20-30 mm CW juveniles. Behringer published a short duration mark-recapture study using small cable ties on Panulirus argus.

While this is a late response I wanted to offer an opinion/recommendation. Make sure you have a way for someone to contact you if they caught your lobster...