Hi Ramon,

I once used a smaller plastic dart head to tag a white shark with a smaller Vemco V13 acoustic tag, it was lent to us by Oceans Research while we were out of V16 tags that used the same plastic umbrella dart as the PATs. It wasn't from Wildlife Computers, but was probably a similar (if not smaller) size and attached pretty well. We were actively tracking the shark, so only followed it for a month or two, but the tag held in place for at least that long. If you can get a hold of either Enrico Gennari or Dylan Irons they should be able to tell you more about the overall performance of the heads and link you to the site they ordered from. 

Hope this helps!

Oli

Hi Oliver

Thanks a lot for sharing. It's not clear from your answer if the dart you used was the one I am talking about, the 20mm umbrella Domeier dart (not the 31mm version...). Either way, thanks for the interest. I do not have trouble finding the darts, I have both sizes; I only need information from people who have used the 20mm version of the umbrella dart. 

Cheers,

Ramón

Hi Ramon,

I have used a few of the exact 20mm umbrella anchors you intend to use on Dasyatis sp.. with Vemco V13 tags. Tag retention times ranged from 34 - 96 days. Interestingly, the shortest tag retention times were on the largest individuals tagged, with smaller individuals retaining the tags for much longer. The rays I tagged were sighted by myself and other divers quite regularly. If the rays were disturbed and swam away fast, it was pretty clear that the larger ones put a lot of stress on the anchor (as evidenced by a lump appearing where the anchor was pulling beneath the skin). I had wished I had some larger anchors to use on larger rays - maybe you could try this? I think rays of > 2 m disc width could take them.

Hope this is of help.

Aleks

Hi Ramon,

Yeah I've only used the 31mm in the Domeier version and the smaller one was from a different brand. Sorry about that, but good to know there's a few different options! 

Oli

Rather than umbrella dart heads -- or any dart heads at all -- we used the method of LePort et al. (Journal of Experimental Marine Biology and Ecology 359 (2008) 110–117) on our pelagic stingray tagging, which threaded a tether through the base of the tail.  We didn't want to impose an imbalance on our rays, and the dorsal muscle is relatively thin on that species anyway.  Let me know if you can't get a copy of their article -- ours is still in review right now.  Good luck!

Thanks Aleksandra, Thanks David.

Very good point Aleksandra. Nice to learn that you managed to visually assess what happends during flight response in larger rays. Will take your advice into account and will probably use the larger dart for rays over 1 m DW.  

David. I couldn't get the paper, not enough info. Would be great if you can plase email it to [email protected]  The method sounds similar to other systems I have seen around. However, all those require capture of the fish and our problem is we do not intend nor will we try to capture the devil rays. Too much stress (for both parties), effort and higher costs. But thanks anyway.

Ramón

No worries, Ramón.  If I could, one more suggestion: get a dead specimen (preferably not fixed in formalin/ethanol) and evaluate both the placement of the tag on the animal as well as a couple of dart heads before going to sea.  Doing a little practice on land will help your tagging (and confidence thereof!) while working on a fishing vessel.  Best of luck!

HI David. Good point. That was precisely what I did over 10 years ago before going out to PAT tag great whites. It is an incredibly useful excercise. I used a mako I bought in Boston as a proxy. Problem will be to find a dead Mobula or Manta that is not preserved. They are protected in Mexico (where I am now) and I would definitely not one to get one killed. Cheers,

Hello,

I will have to used the 'standard' umbrella plastic anchor (model: Domier anchors) using the miniPAT tag for Carcharhinus galapagensis in Chile (Easter Island and Sala y Gomez) and I am wondering whether the medium size will be good enough to retain the tags in this species.

We are trying to tag large individuals (200-300 cm TL) in order to test the connectivity between Easter Island and Sala y Gomez. Both island are separated between 400 km and are connected through seamounts. However, we will deal with juveniles individual as well (>200 cm TL).

Any suggestion about the umbrella plastic anchor size will be appreciate.

Saludos, Sebastian

Hi Sebastían. I am afraid there is little evidence of the pros and cons of the size of the umbrella dart. I used the larger size with white sharks for many years with retention ranging from 2 to 11 months. I recently started using the smaller umbrella darts in Mobula tarapacana and my retention of the miniPAT goes from 8 days (due to poor tagging techinque, dart did not enter deep enough) to 4.5 months.

I think the safer option would be to use the larger umbrella darts, just in case, but that depends on the size of your sharks... If they are larger than 1.5 m TL I would definitely use the larger umbrella dart, but if smaller than 1.5 m TL I would use the smaller umbrella darts.

Hope this helps, and good luck.

Ramón

Hi Ramon,

What did you decided to use at the end? How was retention?

We have 2 mini-pat and a few V13 for M. thurstoni but as of now they are equipped with the large TI anchor. Happy to change it though.

HI Alessandro

I decided to go with the smaller darts because of the size of Mobula hypostoma. However, I have not been able to deploy any minPATs on them yet. They are very elusive and since I live in Mexico City I have few opportunities to go to the Mexican Caribbean where they occur. Where are you working with M. thurstoni? I am considering changing species and M. thurstoni was my next candidate.

Cheers,

Ramón

Hi Ramon,

Thanks a million for the information.

We have thurstoni, japanica and tarapacana here in the Philippines.

We have 2 minipat and a few V13 acoustic to try.

I just ordered a mix of 31mm and 20mm from WC.

Do you think the 31mm are too big for a 1.5 m animal?

I've never had them in my hand to compare.

Cheers

Ale

Hi Alessandro

Similar mix of species to what we have in the Mexican Pacific... We tagged a few M. tarapacana in Brazil and we are writing a paper about that. For those (up to 3 m DW) I see no issue with the 31 mm darts. But for the 1.5 m animals and smaller I would go with the 20 mm darts.

Good luck

Ramón