2008 Annual Report
Gulf of Maine Research Institute

Spotlight on Science

Catch Sensors

Fishermen make many decisions every day about where to fish and when to haul their nets. For many years, they have used sonar devices to indicate where fish are schooling but must guess as to which species swims beneath them. Once they lower the net, fishermen have no way of knowing how many fish they have caught. They decide when to haul based on local conditions and their years of experience. To address this challenge, Gulf of Maine Research Institute (GMRI) scientists worked with fishermen to study new codend sensors that can remove much of the guesswork in fishing, allowing fishermen to work more efficiently and effectively.

The sensors are attached to trawl gear and send signals back to the boat. As fish enter the codend (the rear part of the net) the trawl mesh stretches. The captain programs the sensor to trigger when the mesh is stretched to a predetermined limit, indicating that a certain amount of fish has been caught. Once triggered, the captain knows that it is time to haul the net.

GMRI scientists Steve Eayrs and Adam Baukus partnered with fishermen to test three different types of codend sensors. The sensors were deployed on the trawls of commercial fishing vessels and adjusted over the course of several hauls to attain the desired catch weight. When the sensors were triggered, the trawl was hauled and total catch weight recorded for each species in the net.

Fishermen using the nets found that the sensors gave them better control over catch weight, which is critical under the new sector management system in the groundfish fishery. Fishermen are now limited by the amount of fish they catch rather than the number of days they spend at sea and can be penalized for going over their limit of fish. Using the sensors allowed captains to avoid unexpectedly large catches that may put them over those limits. They reduced towing times as well because the sensors alert the captain when the net is full, allowing him to pull the net immediately instead of towing longer than needed. Shorter tow times also mean that the fishermen are using less fuel, sometimes by 50% or more. The sensors performed particularly well when cod or haddock dominated the catch and also prevented huge bycatches of dogfish and skate.

Several fishermen are already investing in sensors thanks to promising early results. GMRI scientists plan to survey participating fishermen to formally gauge their perspectives on the different sensors tested. The sensors seem to offer a tremendous opportunity to give captains greater control over their catches while reducing fuel consumption and environmental impact.

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