Bay of Marennes - Oléron, France

We worked in Marennes Oléron, France, from june 20 to september 4, 2008 and from june 9 to october 29, 2009. The goal was to record oyster spawning in the field, to understand when they spawn and to learn if they spawn with a precise timing. It was a success.

The site was only emersed during a couple of hours at low tide. No way to have a telegraph pole! Consequently, we set a fully waterproof HFNI valvometer, programmed to give us a ring at low tide. The left picture below shows the in-situ set up on a bench. In the bottom, an oyster farm. The electronic was in the grey tube. It was composed of our home made mini µPC, equipped with the core of a mobile phone and an antennae. Everything was developped, build and programmed by our laboratory (UMR 5805 EPOC) and the EUKREA Télématique company, Pessac, Gironde. Two batteries are on the left.

One half of the oysters was in a traditional oyster bag (covered by algae) on the right of the grey tube. The other half was set on the floor, lightly attached to a piece of oyster bag, independently of the recording cables. All records were published dailly on our website, the MolluSCAN Eye.

This site is an IFREMER La Tremblade site. The experiments were performed in collaboration with Stéphane Pouvreau (researcher in IFREMER Argenton) and one of his PhD student, Ismaël Bernard. The aim was to precisely characterize the timing of spawning events in Crassostrea gigas. We also intended to correlate spawning with environmental changes, looking for key drivers.  To record spawning was a success. A full report is in preparation. Photos I. Bernard et JC Massabuau.

    Spawning in female oysters is very typical. It is characterized by a series of contraction occurring first every 20 seconds. A series last from 20-30 minutes. Male behaviour is quite different.
    Fundamental: fecondation occurs in water, all partners must be perfectly synchronized !
    Amazing: Oysters are alternatively male and female.
This record was caught on july 23th, 2009, at 5:35 a.m., in a female oyster freely living in the Bay of Marennes



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