We have three different Bongo nets in operation. The most advanced one is our motion compensated Bongo net. A standard Bongo net will be deployed over the side of the ship collecting plankton on its way up vertically from depth up to 300m. While the ship is pitching and rolling in the seas means that in one moment the drag and the speed of the net is dramatically increasing whereas in the next moment the wire will slack of and the speed of the net is slowing down.
To compensate the ships movements the Bongo net has a spring mechanism. When the ship heaves upward the inertia and increased drag of the net cause yet more wire to come off the drum, thus maintaining the net’s upward velocity somewhere close to the steady state. As the ship moves down the spring takes in wire and maintains the upward motion of the net. Our motion compensation unit not only maintains a more or less steady speed of the net and taking out lots of stress on the wire but also catches plankton in much better conditions as without such a unit.
The same sized Bongo net can be configured to be used as a towed Bongo, where it is towed behind the ship. This method is mainly used to get samples from the certain water depth or strata. It opens the opportunity to get more samples as you can tow it at a certain depth for a longer time, compare with the vertical Bongo, where the net is passing through the water column constantly.
Additionally we have a much smaller Bongo net, the so called Mini-Bongo. It is small and light and can be deployed from smaller boats with small winches. It is mainly used to catch small Zooplankton in good condition in depth up to about 100m.