For Dr. Shannon Bayse, testing and evaluating experimental fishing gear starts at the Marine Institute’s (MI) flume tank.
It’s a critical first step in testing ideas and underwater technology.
Dr. Bayse is a research scientist with MI’s Centre for Sustainable Aquatic Research (CSAR) at Memorial University.
His research focuses on fishing gear, fish behaviour, conservation engineering, fish physiology and bycatch reduction.
World’s largest flume tank
He and a team of graduate students, trawl designers and technologists are working on experimental codends – the end part of the net where fish are collected – to improve size selectivity in redfish trawls and reduce fish mortality.
“The flume tank plays an important role in this because it educates both scientists and fishers as to what the gear is actually doing,” said Dr. Bayse. “Without the tank, you can’t see what needs fixing or tweaking before you put this experimental gear in the ocean.”
The world’s largest flume tank is the aquatic equivalent of an aerospace wind tunnel: circulating 450,000 gallons of water at up to six feet per second to mimic towing objects through the ocean.
Academic and industry researchers use the flume tank for performance evaluations, tests and observations of new technology, including fishing gear, marine turbines and underwater robotics.
“In the tank we can measure how the different water flows affect openings of the mesh, which affects selectivity,” Dr. Bayse said.
Improving size selectivity
This research is part of a larger project led by Dr. Paul Winger, director of CSAR and one of three principal MI researchers working on Ocean Frontier Institute projects on sustainable capture fisheries and their ecosystems.
One goal is to develop fishing gear that enables undersized redfish – those less than 22 centimetres – to escape the codend. To do that, the researchers are testing a net mesh known as T90 used in Europe.
In July, the team published the results of T90 sea trials in the Canadian Journal of Fisheries and Aquatic Sciences.
Those field tests were conducted in the Gulf of St. Lawrence, where there has been no redfish fishery since the early 1990s.
Researchers compared the size selectivity of one traditional codend with three experimental ones with different T90 mesh sizes.
Smaller fish escape
Overall, the researchers found that a greater percentage of undersized redfish were able to escape the T90 codends.
As the nets were towed through the water, the T90 mesh remained open, providing small redfish a greater opportunity for escape.
“When they escape is a really important piece of the puzzle.”
The same was not true of the traditional net mesh.
“Very few fish escaped the traditional codend,” said Dr. Bayse. “When you’re towing the net, the mesh opening will shrink under load and not a lot of fish are escaping.”
The next step?
Figuring out if redfish survive their release from the T90 codend.
“When they escape is a really important piece of the puzzle,” Dr. Bayse said. “If they’re getting out of the mesh when the codend is sitting near the top of the water, that fish isn’t going to live. That’s something we need to quantify and that will help us know how effective the T90 approach is at lowering fishing mortality.”
