Innovative New Trawl Net Developed for U.S. West Coast Fish Research Surveys

NOAA Fisheries' surveys off the U.S. West Coast have begun deploying a new trawl net specifically designed to catch multiple fish species at different depths. Scientists are looking at integrating two fisheries surveys into one. Such a net would save time and money in the long term, and improve data collection for managing West Coast fisheries.

NOAA Fisheries' scientists collaborated with fishing industry experts from Ocean Gold Seafoods and Seattle-based net manufacturer Swan Nets. They designed a net that improves trawling efficiency and flexibility, called the Multi-Function Trawl net. It allows for trawling species at or near the surface-such as sardines and anchovies-at night. It also allows for trawling in midwater depths, such as for Pacific hake, during the day. NOAA Fisheries previously dedicated two surveys on separate vessels to assess these species, each using a different style of trawl net configuration at different depths.

In late 2023, and continuing this past summer, NOAA Fisheries' scientists, crew, and fishing industry experts conducted sea trials using the net. They observed the net's performance and fine-tuned the various deployment configurations.

Since then, the scientists and crew have become more familiar with how to handle and operate the net, said Josiah Renfree, a research scientist at NOAA Fisheries' Southwest Fisheries Science Center. He is the chief scientist of the inaugural survey using the net to catch sardines and anchovies, among other coastal pelagic species. "We pretty quickly came up to speed, and the operations thus far have been impressively smooth. But we'll only continue to improve, and the data is coming in, which will help us to further evaluate the net's performance."

"The collaborative learning with industry partners was vital for the success of our initial testing, which brings us much closer to upgrading our survey equipment to use the latest technologies," said Annie Yau, director of the Fisheries Resources Division at the Southwest Fisheries Science Center, and one of the co-leads responsible for integrating the two surveys.

The new nets were funded through NOAA Fisheries' Inflation Reduction Act essential data acquisition efforts. The research funding promotes climate-ready fisheries by helping develop information and tools to adjust fisheries management in response to climate-driven shifts.

Sensors Track Performance

The net's adaptability is its strength. Its shape, size, rigging, and modern materials contribute to its versatility. The trawl doors, a mechanism that helps keep the net open while fishing, also have a unique design. For example, they contain more attachment points, allowing fishing at both the surface and midwater. This feature eliminates the need to change doors depending on the trawling depth, improving efficiency and increasing the deck crew's safety.

The net is designed with gradual changes in mesh sizes to promote water flow down the center of the net. It herds fish in and then funnels them down to the codend, the part of the net where the fish caught are collected. The mesh sizes were chosen to retain a wide range of the target species. It will also capture other small organisms important to the ecosystem, such as deep-water lanternfish and invertebrates like squid.

Numerous sensors measure the depth, temperature, water flow, and distances between the trawl doors and the top and bottom of the net. This allows scientists to monitor the net's performance in real-time. Additionally, underwater cameras collect images inside the net, which researchers can review after each deployment to monitor animal behavior and further assess net performance.

Underway with NOAA Fisheries: Fishing with the Multi-Function Trawl Net

During this summer's Pacific hake research survey, scientists compared the function of the Multi-Function Trawl net to the trawl net previously used to catch hake. Both these species are fished during the day in midwater. "We dedicated research time this summer on the NOAA Ship Bell M. Shimada to conduct paired trawling operations with treaty partners from Fisheries and Oceans Canada, who were aboard the Canadian Coast Guard Ship Sir John Franklin, to learn how the new net fishes relative to our existing net," said Julia Clemons, who leads the Northwest Fisheries Science Center's Joint U.S.-Canada Pacific Hake and Ecosystem Survey. "This will help us better understand how a switch in trawl gear might influence our estimates of Pacific hake biomass."

This year's Coastal Pelagic Species Survey on NOAA Ship Reuben Lasker collected data on the distribution and abundance of sardine, anchovy, and mackerels from Mexico to Canada. "The new net appears to be successful at catching the target species, and the crew demonstrate expert skill in using it," said Renfree. "Working side by side with industry on the project has led to innovations that enhance operations and are exciting to see in action."

Now that we've concluded the summer and fall fisheries surveys, scientists will assess their experience with the new net to ensure it will collect the necessary data. "We can start to analyze the data to get a clearer picture of the net performance and accuracy," Renfree said. "This will build our expertise and help us prepare for the integrated survey in 2025."

Science in Support of Sustainable Fisheries

These innovations and the data they produce support the agency's mission of sustainable fisheries management.

These surveys maintain NOAA Fisheries' long time-series of fish species abundance and ocean conditions. Over many years, such records may reveal cycles and trends that could otherwise be missed. Long-term records will help understand how climate change affects West Coast waters and their inhabitants.

Greg Shaughnessy, Chief Operations Officer of Ocean Gold Seafoods, was one of the industry members who helped design the net system in partnership with Seamus Melly of Swan Net USA. Both were aboard the Lasker and the Shimada to train the crew and test the net. Shaughnessy noted the real-world impacts of these data on fisheries science, resource management, and beyond:

"These continued improvements benefit the scientists, the stock assessors and managers, and the fishing communities that all depend on accurate information to ensure our fisheries are sustainable and contribute to both the economy and the ecosystem," says Shaughnessy.

Public link

Please use the above public link if you want to share this noodl on another website.