Mysterious Mobula mass mortality

From the Italian news site La Repubblica comes this disturbing story (with 15 graphic pictures) of a mass stranding of “manta” rays on a beach in the Palestinian territories.  According to Google Translate, the caption reads something like “For now only remains a mystery. Difficult to determine the cause, but the scenario that occurred on the beach was really disconcerting. And here that some Palestinian fishermen have discovered at dawn hundreds of manta rays beached on the sands of Gaza Beach (afp)“.  Looking more closely, these are not manta rays but actually devil rays or Mobula sp..  You can tell because the mouth is under the head and not right on the front end (taxonomists would say subterminal rather than terminal).  There are dozens and dozens of them and they are the biggest Mobula I have seen; I have to think they were aggregating for mating purposes when the event took place.  Mobula form larger groups than do Manta, but at this size and this many, mating is the most likely explanation.

How could something like this happen?  I can think of two feasible explanations:

  • A toxic spill.  In that case you might expect other species to be affected as few toxins are so species specific in their action.  More likely:
  • An algal toxin.  Mobula are filter feeders that ingest food pretty low on the food chain, but lots and lots of it.  For that reason, they are susceptible to algal toxins such as brevetoxin (from the red tide organism Karenia).  I have no evidence for this, but it seems the most likely explanation.

Any way you look at  it, it’s kind of sad.  I wish I could have been there to whip the gills and guts out of each one; that’s a PhD worth of parasitology right there on the beach!

Dozens of large dead mobulid rays on a beach in Palestine. Click to go to Repubblica.it

Dozens of large dead mobulid rays on a beach in Palestine. Click to go to Repubblica.it

H/T to Chris Coco for the tip about this remarkable story

 

para_sight (138 Posts)

Dr. Alistair Dove is a systematic and ecological parasitologist by training, with broader research interests in the natural history and health of marine animals, especially whale sharks. He is currently Director of Research and Conservation at Georgia Aquarium in Atlanta USA. His comments here do not necessarily reflect the opinions of Georgia Aquarium





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20 comments on “Mysterious Mobula mass mortality
  1. Have a look on the Palestinian news website ‘Ma’an’ this is how they report the above:
    GAZA CITY (Ma’an) — Fishermen say the locally rare batfish stingray is making a comeback in the waters off the coast of Gaza. For the first time in five years, fishermen say they are catching the rays by the hundreds.

    That may explain why so many of the fish beached themselves in straight lines and just happened to have rope tied to them.

  2. I’m situated in Israel, studying biology at Tel Aviv Universtiy.
    If you’d like I can provide you with contact details of one or two researchers who may be the proper academic address to look into this.

    Feel free to email me.

  3. Israel poisons the waters off of gaza to punish the palestinians. Israel is one of the largest polluters of the Mediterranean. They put underwater fences and mines and disturb the natural environment of the sea.

    • Um, being quite active in the marine biology area of interest in Israel, this is news to me. Would you mind providing sources for these claims?

  4. A quick question to the experts out there. Are these Giant Devil Ray?? If so, are they endangered? (There are more photos on the Repubblica website)

    • The Giant Devil ray (Mobula mobular) is native to the shores of Israel and Gaza, and they are classified as endangered, so I believe the answer is “yes” on both counts.

  5. In the early morning shot, they all look like they are on their backs. Does anyone know how their navigation works? There has been some minor quakes in the area and I’m curious how most could end up in the same position.

    • They also look pretty well organized in that shot, my guess is that the Gazan authorities flipped them over when organizing them.

  6. Pingback: Mystery of the massacred mobula rays: Just why DID dozens of these bloodied sea creatures wash up on the beach in Gaza? | we must know

  7. i thought cartilaginous fishes will sink to the bottom if they are freshly killed. Judge from the video, those fish are really fresh. There are also unheard of that those cartilaginous fishes will beach themselves like dolphin and whale. To me, it looks very unlikely they were killed by natural causes… it looks like someone drag them up to the beach…

  8. Hell Deep Sea News

    My observation is thus. Having had some experience in commercial fishing operations, my seeing those images reminded me of maybe a netting operation and the mobula lined up on the beach for the fishermen to choose amongst them and then collect what was their allocation. Maybe not a stranding at all??

    Guy

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