Royal Netherlands Institute for Sea Research
Royal Netherlands
Institute for Sea Research

Valve gape monitor

Valve gape monitor (VGM) for eight bivalves. A NIOZ-NMF development.


Bivalve shellfish filter water to obtain food and oxygen by keeping their valves open and generate a water current over their gills. They response to disturbance or a change in environmental conditions by changing the degree to which the valves are opened. Briefly stated: if a shellfish (e.g. a mussel) is happy, it’s valves are more often and wider open. Monitoring the mutual valve position of a clam over a prolonged time provides insight in the environment the shellfish is in.

The request of the biologists was to develop a valve gape monitor for eight bivalves which can run and store data autonomously for months on only a few alkaline batteries. A further request was that the method was minimally intrusive. The solution chosen for the measurement is to measure the electric field between to micro coils. This meant that two small coils with wires need to be glued to the valves. Experiments showed that these wires didn’t disturb the normal behaviour of different shellfish species which were tested (jack-knife clam, blue mussel, cockle).

The Valve Gape Monitor (VGM) design functions already perfect for several years. The only real wear of the system concerns the wires. The system now uses 16 wires (2 per shellfish). A new system that only uses 8 wires is now under development while at the same time a researchers’ wish to be able to extract the collected data wireless is taken into account. This new design is planned to be fully tested operational before the end of this year.

For technical specifications or other information, contact Rob Witbaard by email (preferred). You will get a response as soon as possible. In very urgent matters, you can contact him directly.

T+31 (0)113 577 462 / +31 (0)222 369 537