Northeast Trawl Advisory Panel Trawl Door Testing

Researchers fitted a trawl net used in research surveys with different door types to better understand net spread.

New England/Mid-Atlantic

Overview

Consistent performance of research survey gear is critical to maintaining a time series of data. By testing different types of doors—the part of the gear most involved in keeping the net open when it is being towed—researchers can learn more about what influences net spread when the gear is in use.

Research Question

What type of trawl door can provide the most consistent and optimal net spread of 13 meters over a range of depths?

Project Goal

The goal is to find a trawl door that achieves a target net spread of 13 meters and provides consistent wingspread performance over the range of depths sampled in the Northeast Fisheries Science Center bottom trawl survey. Further work on door testing has been delayed by COVID-19 and the lack of sea days currently available.

Project Description

The Ecosystem Survey Branch is working with Northeast Trawl Advisory Panel members to test the performance of different types of doors on the NEFSC bottom trawl survey aboard the NOAA Ship Henry B. Bigelow. The trawl doors currently used have variable wingspread performance. Optimal wingspread is 13 meters, but the net fishes at wingspreads from 9 to 16 meters (narrower in shallow sites and wider in deeper sites). The goal is to find a door that achieves the optimal target net spread of 13 meters and provides consistent wingspread performance over the range of depths sampled in the survey.

Study Methods

In August 2019, we evaluated the performance of three door types:

1.5 square meter Thyboron Type 21 flipper
66 inch Thyboron Type IV (used in the NEAMAP survey)
Bison 9

The doors were evaluated on NOAA Ship Henry B. Bigelow during two legs. The first leg focused on deep water and the second leg focused on shallow water. A fourth door type, Bison 8, has been rigged and is ready for testing when sea days are available.

Preliminary Results

Both the Bison 9 and Thyboron Type IV doors achieved stable target spread in shallow water, but overspread in deep water
Thyboron Type 21 flipper doors were generally unstable at all depths and were underspread in shallow water and overspread in deep water
No door tested consistently achieved the target spread in deep water

Collaborators/Partners

Northeast Trawl Advisory Panel

The panel includes New England and Mid-Atlantic Fishery Management Council members, commercial trawl fishermen, academic and industry gear experts, leaders of other regional surveys, state scientists, and the Center staff assigned to work with this important panel.