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Commercial Fishing


Collaboration between fishers and scientists in USA brings benefits

Collaboration between fishers and scientists in USA brings benefits

A collaborative study conducted aboard a Rhode Island-based commercial trawler from 2015 to 2017 is bearing fruit. It was led by the Northeast Fisheries Science Center in the USA and commercial fishermen interested in how catches of the same species varied depending on the type of trawl net used.

Since 2019, stock assessment scientists have used the results from this Northeast Trawl Advisory Panel study in multiple stock assessments to ensure sustainable fisheries for several flounder species as well as monkfish and red hake. Specifically, the results help produce more accurate estimates of abundance which can increase the confidence in catch advice for some species.

“Cooperative research is essential to obtain accurate assessments and catch advice in our nation’s fisheries,” said Chris Roebuck, former Northeast Trawl Advisory Panel member, commercial fisherman and participant in the experiment.

“This research is an excellent example of collaboration between scientists and fishermen. It provided solid efficiency numbers for each targeted species,” he said. “The information produced was clearly the best available science and has the potential to ultimately influence catch advice for every species evaluated.”

“Any piece of data from a new study used by a stock assessment helps create a more accurate tool,” agreed Terry Alexander, a commercial fisherman and panel member, “This data is especially important for assessments using an index-based model.”

The Northeast Trawl Advisory Panel was instrumental in planning this collaborative study.

There are a range of stock assessment models. Catch indices, a measure of catch per net tow, are used in almost all of them. The indices have more influence on the models when there is little other data on a species.

In the Northeast, we develop indices for species captured in our long-running bottom trawl survey. Over time, the indices provide information on trends in a fish stock’s population. The trawl gear we use is more efficient at catching some species than others because it rolls over the bottom, disturbing less habitat and snagging less often. For example, it is less efficient at catching species that live near the ocean bottom such as flounders.

The results of this study measured how much the catch differed when the research net stayed closer to the bottom to better capture flounders and some groundfish. Stock assessment scientists were then able to adjust the data they obtained using our standard research trawl to account for that difference. This produced more accurate indices for some species.

In the study, two of our research survey trawl nets were fished side by side. Each net had a different sweep—the part of the gear that contacts the bottom while fishing. One net was rigged with our standard rockhopper sweep used in the Bottom Trawl Survey, and the other with a chain sweep commonly used by the fishing industry.

Both the monkfish and Gulf of Maine winter flounder assessments use index-based models and have benefitted from this study.

The monkfish population appeared to be trending downward in the last assessment based on Bottom Trawl Survey data. “When the catch efficiency estimates from the collaborative study were used in the assessment, we were able to show that relative exploitation rates were quite low, suggesting that fishing may not have been the primary driver of the declining survey trends,” said assessment scientist Jon Deroba. Fishery managers were able to consider this information when deciding on allowable catch alternatives.

Paul Nitschke is an assessment scientist and member of the New England Fishery Management Council’s Groundfish Plan Development Team. “Using these data in the Gulf of Maine winter flounder assessment gave the science team more confidence in the model’s catch efficiency and a much better estimate of catch,” he said.


Main Image: The twin trawl was rigged with two nets with different sweeps; rockhopper on the left and chain on the right. Photo: NOAA Fisheries