Where are the Tahitian seashells hiding ?

Author : David Touitou, 2004

 

I decided to write this article, due to my anger over the disappearance of our seashells…
A strange phenomenon must have happened here, but which one ? Of course, everywhere around the world, in any place, shells are less abundant than before.
When I first came here in August 2002, I could find regular species, even if the locals and the local collectors said that shells were now not so easy to find. It seems that 2003 was fine too, then 2004, was the year of the real disparition of our seashells…

We are now in January 2005. When I snorkle along the different reefs of the island of Moorea (next to Tahiti, where I live) I do not find seashells anymore. The dominent missing family is for sure the cowries' one. I find nothing else than C. obvelata… and this one is not as commom as before. In 2002, while searching for coneshells, I regularly encountered classic species like Cypraea isabella (=controversa), Cypraea carneola, Cypraea moneta, Cypraea caputserpentis, Cypraea maculifera, Cypraea fimbriata and some other commom species. In 2005, I rarely find anything else except Cypraea obvelata. I saw one Cypraea poraria and one very small Cypraea isabella during many hours of shell hunting.

It sounds incredible, but if you ask me to collect a Cypraea caputserpentis, I cannot promise to bring one back to you.

Well, the Cypraeidae family is not the only one in that case. It seems that all reef species have been touched by this strange phenomenon. The only cone shells that I have seen recently are the very common ones like C. Lividus, C. Flavidus, C. Sanguinolentus, C. Frigidus and a few Conus textile. When I look under dead coral plates, now I do no not see any shells underneath, even common ones such as the Mitra Cucumerina, for example.

There are some exceptions though. First of all, this disaster does not seem to affect the Tuamotu and Marquesas Islands. Shells are still abundant there. Also, the shells living in the sand are not really touched by this problem. Maybe by the fact that they usually feed on small sand worms. The chain is not destroyed until the worms disappear (chain : Molluscs eating worms which are eaten by other molluscs etc…). So it seems that only the reef's chain is broken.

Now you know the facts.

But this disappearance was quite fast ! Only a huge disaster can cause such a phenomenon, like local pollution, huge temperature variation, or whatever else. But if shells really died all at the same time, we should have seen them during 2004, thousands of empty shells would lie along the reef and in the lagoons…
This did not happened. This case happened in Martinique though, some years ago, where divers found hundreds of dead Conus ermineus while diving, especially around the Diamond Rock diving spot. Since then, this specie has become extremely rare there. But this touched only one specie, we can imagine if it had touched all families…

That's why I choose the word "hiding" for my title… Where in the blazes are our seashells ?
Of course, I have no answer to this problem. Maybe seashells will come back as fast as they disappeared. If some of you have any idea or heared some similar stories mail me and I'll publish your text below this one. One thing is actually true, keep your shells from Tahiti (like Cypraea cumingii), you might not see so many fresh specimens on the market in the upcoming years…

Thanks to Mrs Carlie White for her help (English correction)

 

 

Comment from M. Caro Olivier (France) February 18th 2005 :

 

In this strange article, you mention the abscence of thousands of dead shells, a phenomenon which might occur when all a class or a phylum went to die. For example, beside the Martinique Conidae dooming, european fishermen experienced a similar case with Haliotis tuberculata which, at the end of the millenium, failed to completely disappear of the NW. french
shores. This, due to a viral attack, led to zillions of empty shells found by divers and beachcombers across the Channel islands and in other parts of the northern and southern brittany (St Brieuc 1998, Groix 1997).
An other incident was a new antifouling paint for boats which caused the sterilization of many shell species, like Nucella lapillus in the Channel and the northern shores of continental west Europa. I believe that this last species was about to be protected (CITES). Dunno if it finally was or not. Such a thing apparently did not occured in Moorea, so what ?

I submit a comment which could open a new path to solve this curious
mystery : Each average year, the number of seashells which die is relatively constant, and then does not reach to any noticeable level. This seems to be the case here: the number of dead shells did not drammatically increase. Thus, they have not been killed. The only thing is that no living shell can be found: then, I imagine
that all the living species had a reproductive problem, which led to extinction. That's the only remaining solution: they did'nt mate any more, or, if they did, this was unsuccessful.

Such a sexual apathy can be caused by many factors, of course: religious fever, love strike, or, more probably, two things:

1- something they ate: The diet chain begins with herbivorous, then carnivorous species and so
on… right to frater Nassarius and other necrophagous fellows. Maybe herbivorous ate something they had not to eat, something fixed in the microalgae, fixed again in their body, mantle etc… which could finally kill the reproductive programs (gamete production, gamete quality etc.)

2- something (the gremlin from the outer space) which penetrates the egg's mantle and destroys something inside: what ? bacteria, tons of new hungry fishes, chemical product ?

What happened on the islands in 2003-2004 ? New airport, new harbours, paper industry, shrimp farming, chicken factory, something else ? Any idea ?

Cheers, Olivier Caro