Ecosystems Surveys Branch Gear Efficiency Study

Metadata Updated: February 27, 2019

An experiment aimed at quantifying the herding efficiency of flatfish for the Northeast Fisheries Science Center (NEFSC) survey trawl bridles was conducted during autumn 2014 aboard the F/V Karen Elizabeth. Using a blocked design, the standard survey bridle length, 36.6m, was compared to two longer bridle lengths, 58.5m and 80.5m. One tow of each bridle length was conducted per block at equal towing speed and duration. Bridle angle and net width were held constant at approximately 12° and 13m, respectively, at each bridle length in an effort to maintain equal bridle efficiency, equal area swept by the net width and equal net efficiency for each length configuration. Restrictor ropes made of positively buoyant, 9/16” tenex rope, were connected between the trawl doors to define and maintain proper door spread at each bridle configuration for the duration of the study. A total of 77 blocks were sampled during 19 sea days on eastern Georges Bank and south of Martha’s Vineyard, producing data for 5 species of flatfish: yellowtail flounder, winter flounder, summer flounder, windowpane flounder and fourspot flounder. Aggregate weights were recorded at 45 of the sampled blocks for skates, monkfish, American lobster and sea scallops. The total number of each flatfish species captured were 4062 yellowtail flounder, 2834 winter flounder, 2933 summer flounder, 2148 windowpane flounder and 3892 fourspot flounder. Catch rates were significantly higher during nighttime tows for each of the flatfish species other than yellowtail flounder. Preliminary results suggest that herding efficiency of the NEFSC survey trawl bridles is relatively low for these species of flatfish. Mean bridle angles for the standard, medium and long bridle lengths were 12.6°, 12.3° and 12.0° respectively. Mean net widths for the standard, medium and long bridles were 12.7m, 13.2m and 13.3m respectively. Underwater video observations were recorded from 20 tows at various positions on the trawl net, doors and bridles.

Access & Use Information

Downloads & Resources


Metadata Date September 4, 2018
Metadata Created Date March 28, 2016
Metadata Updated Date February 27, 2019
Reference Date(s) (publication)
Frequency Of Update asNeeded

Metadata Source

Harvested from NOAA CSW Harvest Source

Additional Metadata

Resource Type Dataset
Metadata Date September 4, 2018
Metadata Created Date March 28, 2016
Metadata Updated Date February 27, 2019
Reference Date(s) (publication)
Responsible Party Northeast Fisheries Science Center (Point of Contact, Custodian)
Contact Email
Access Constraints Access Constraints: User must read and fully comprehend the metadata prior to use. Applications or inferences derived from the data should be carefully considered for accuracy. NEFSC Data Access Constraint: If data is stored on an internal NEFSC network, the requester may not have direct access to query the data unless they are also authorized for network access. | Use Constraints: Acknowledgement of NOAA/NMFS/NEFSC, as the source from which these data were obtained in any publications and/or other representations of these, data is suggested.
Coupled Resource
Frequency Of Update asNeeded
Guid gov.noaa.nmfs.inport:27386
Harvest Object Id d0c24a3c-fe62-494d-81f2-55a29210927d
Harvest Source Id 2aed8e29-fc5b-4cde-aa66-fb1118fd705e
Harvest Source Title NOAA CSW Harvest Source
Licence NOAA provides no warranty, nor accepts any liability occurring from any incomplete, incorrect, or misleading data, or from any incorrect, incomplete, or misleading use of the data. It is the responsibility of the user to determine whether or not the data is suitable for the intended purpose.
Metadata Language eng
Metadata Type geospatial
Progress completed
Spatial Data Service Type
Spatial Reference System
Spatial Harvester True
Temporal Extent Begin 2014-09-15
Temporal Extent End 2014-10-08

Didn't find what you're looking for? Suggest a dataset here.