Maybe you could try visible implant elastomers. Success probably depends on the type of sea cucumber, but it might be worth a shot. http://www.nmt.us/products/vie/vie.shtml

I wonder if a piece of dental floss type material (or fish line) could be attached to a sharp curved surgical needle.  You could then poke the needle into the back of the cucumber and back out and pull the floss through and tie in a loose loop.  This would give you a place to attach a tag.  I'd assume you'd not want to poke the needle too deep.  Sound like an interesting project Dr. Brennan!  

Thanks Joacim, as you mentioned the sea cucumber species probably influences this.  Many of these are very dark and so pigmentation may reduce the elastomers visibility.  Perhaps a white fluorescent VIE could be visible.  I'm not even sure if the material would be retained by the body however...

Hey Dr. Brennan.  Ah yes, dental floss is a great research material and I have used this to tie net holes and as seam for sea cages, PNG style :)  Often an internally lodged external tag creates health issues with the animal, and are prone to result in poor tag retention.  Sea cucumbers continue to amaze me and they have this incredible ability to heal from traumatic evisceration quite quickly, but maybe they would also expel the tag and quickly heal.

I think white is still non-fluorescent, but several of the colours are really strong under UV light (yellow, orange, red). Similar to the floss-method, you might be able to stick a piece of fishing-line through the skin, and then melt the ends into small balls, which can be painted with nail-polish (described e.g. in this paper: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0023565)

Hi Nathan. We met in Seattle some years back (at a SESR symposium) - you were still working on snook then, and doing some nice release experiments. I did some trials on a number of different tagging/marking methods for sea cucumbers, mainly for a tropical species Holothuria scabra, and then later tried a couple tag methods on a few other species. We did try the VIE tags, and the problem was the opacity of the body wall of the animals, which obscured the elastomer. That could be worth another try if you're working with a species with a relatively transleucent body wall (but that is not so for most of the commercial species). We reported that in our 2006 paper in JEMBE, which I think you can download from my publications on ResearchGate. We ended up using a couple fluorochrome markers, which we reported in the 2009 Aquaculture paper and also the field application in the 2008 Rev Fish Sci paper - I think those you can also download from my ResearchGate page. The only downside is that the fluorochromes are batch markers. But very cheap and reliable to at least 1 year post release. We later tried PIT tags on two species, with little success - also published that in 2009 in SPC BDM Bulletin. Very recently, I developed a photographic marking technique on a couple species and that study is in review in MEPS. The applicability will depend on the species you are interested in. What species do you want to work with??

Awesome, thanks Steve.  I will certainly read up on these.  Sorry for my late response.  My use of this site is somewhat erratic.  I am interested in species local to Florida.  As with most stocks, the Florida species are also over-harvested.  The more I learn about sea cucumbers, the more impressed I am with them.  My interest is with integrated aquaculture as a system stabilizer, bioturbator, but also a valuable aquaculture product.  Also, as you know, these animals are needed for stock enhancement- especially for their "ecosystem enhancement" attributes.  The local stocks are likely way below historical levels (shifting baseline problem though) and the fishery is tightly managed. Florida could certainly use more proactive aquaculture management with these species.  

As an update Steve, we are working with Isostichopus badionotus (see photo) and they would probably be an ideal candidate for photographic identification because they are distinctly spotted with unique patterns.  Tapping into software that identifies patterns would be a helpful tool with this but I have not looked into it yet.  

I would refer to the comment from Steven Purcell I think he has done most of the tagging work for sea cucumbers. I just finished my PhD with sea cucumber, seaweed and fish IMTA at Cinvestav, with Dr. Miguel Olvera. Based on my experience, badionotus is a very hard candidate for tagging, they are one of the most delicate sea cucumbers in the Caribbean and Gulf (if not the most), ive worked with I. badionotus, H. floridana and H. sanctori in the Canary Islands, Mexico, Belize and Panama and badionotus is by far the most prone to lysis

I would suggest what several others have done - image analysis for individual identification. Our experience from trying several tagging methods on Parastichopus tremulus (and failing...) is that morphological variation is large enough to easily identify each cucumber. I would be very careful to pierce the body wall, since this might lead to infections down the road. It of course depends on whether you intend to use this id method in a lab environment or for observations in the wild.

Thanks Jan, image analysis is a great suggestion. Do you have any recommended software that might help with this type of analysis? Thanks much!

Nathan,

If you are thinking FREE like me, then I think ImageJ should be possible to use, otherwise there are several quite advanced Python libraries available for image analysis, if you are fluent (I am not...). I have no knowledge of commercial solutions. We have not yet attempted automating this through software, but have plans to do it old-fashioned style by comparing our individuals in a "Usual Suspects"-style line up with pictures in a "yearbook". We are, however, working in a lab environment which makes it a lot easier.