Acoustic Sensors are Helping to Save Fuel and Increase Fishing Efficiency

With the current resource problems facing the fishing industry, fishermen are often seeking way to improve their efficiency.  One method that is gaining popularity among trawl fishermen is the use of acoustic gear sensors.  Typically, fishermen rely on their knowledge of how their boat works and feels to know how their net is behaving under water.  With the use of acoustic sensors placed on the trawl gear fishermen can have a much better understanding of what is happening under water to maximize their productivity and increase overall efficiency.

Captain Jim Ford is a fisherman out of Newburyport, MA and has been using sensors on his trawl gears for the past four years.  He has sensors on the doors of his trawl gear, which are used to spread the net.  While fishermen generally know by feel how much they are spreading their net, Ford’s sensors provide him with real time information, displayed on a computer screen, of how his doors are passing through the water column.  Ford also has a catch sensor, sometimes two, in the codend of his net, the section of the net that holds the fish that are caught.  The idea behind the catch sensor is to notify Ford when his codend is filled with fish so that he can haul in the net, empty out the fish, and start a new tow.  Depending on what species of fish Ford is fishing for, he sets the catch sensor to a maximum weight, say 2,000 lbs.  When the codend is filled with 2,000 lbs of fish, a light goes off on his computer screen notifying Ford that his net is full and that he can haul it in. 

Sensors provide fishermen with a better viewpoint of what is happening under water.  Without a sensor a fishermen will pick a tow time, say two hours, and only deviate from that time if they feel a large change in the feel of their boat.  Besides feel, they have no way of knowing how full their net truly is.  They may catch all of their fish in the first thirty minutes of their tow yet they will keep going for another hour and a half to complete the two hours.  During this time they are decreasing fuel efficiency, reducing the amount of fish they can catch, and decreasing their fishing efficiency.  By having a sensor that notifies the fishermen that their net is full they can know exactly where they caught the fish so they can stay in that area and reach their desired total catch in a shorter period of time.  Fishermen already know the ocean; sensors just give them a little added information that improves the way they fish.       

Finding solutions in trout aquaculture

The NHSG Fisheries and Aquaculture team is always seeking ways to improve fishing operations while maintaining a healthy marine environment and sustainable fish stocks for the future. One of their recent endeavors is to develop a methodology for rainbow trout aquaculture. Trout grow much more quickly than cod or haddock in offshore pens--the trout can grow to market size of 3 or 4 lbs. within six months, while cod and haddock take up to two years to reach market size. However, trout need to gulp air occasionally to regulate their air bladder for buoyancy and swimming ability. This limits how long the offshore pens can remain fully underwater, so Michael is conducting experiments to determine the optimum length of time to keep the pens submerged while preventing the trout from being negatively impacted by it.

Dick Prunier, owner/operator for the Sumner Brook Trout farm in Ossipee, N.H., delivered 800 rainbow trout to the Judd Gregg Marine Research Complex in New Castle. With help from NHSG Doyle Fellow James Quadrino, Dick transferred the trout into buckets at the top of the pier.

NHSG marine aquaculture specialist Michael Chambers lowered the trout to technician Jess Cranney below. The trout were divided up into a few different pens beneath the pier. 

These trout will be used in short-term experiments to determine the impacts of salinity and fish density on the species.

After transferring the trout to the pens beneath the pier, James and Michael headed out by boat to the fish pens moored just south of the Portsmouth Harbor Lighthouse. There are 140 additional trout in these offshore pens that need to be fed. Later in the summer, Michael will transfer the feeding and pen maintenance duties to a handful of local fishermen who will be in charge of growing the trout until they are ready for market. The fishermen will be able to keep the profits. The goal is to teach local fishermen about aquaculture as a way to supplement their income and provide another local, healthy and sustainable seafood choice to consumers.

The mooring lines for this pen also act as a suitable spot for mussels to grow and filter the water near the fish. The mussels that grow in these offshore waters are delicious and tender, too.

Michael checked out the various seaweed species and mussels growing alongside the wooden platform surrounding the pens. Although he hasn't yet run the calculations, he said it would be possible to estimate how much nitrogen and other nutrients the seaweeds remove from the water.