Brand_Name_Justification_Thyboron_Trawl_Doors.docx

Brand Name Only Justification

Thyboron Trawl Doors

1333MF18QNFFM0045

The materials and construction methods used in the NEFSC survey bottom trawl gear are standardized in order to minimize variability in indices of fish abundance calculated from data collected by the survey gear. The survey trawl doors are a critical component of the survey gear, which are essential to ensure consistent performance and area swept by the survey gear to maintain comparability between survey tows and survey years.

NEFSC’s Ecosystems Surveys Branch maintains an inventory of multiple trawls and trawl rigging to facilitate the completion of the biannual NEFSC bottom trawl survey. All survey trawls are inspected prior to usage to insure each trawl meets standard construction specifications. Small differences in materials, summed over a fully constructed trawl, may alter lengths, weights or buoyancy of key trawl components, potentially altering performance characteristics between individual trawls and between survey years.

Since listed manufacturer specifications are not always accurate, the NEFSC requires specific brand name items for some trawl materials to insure a fully constructed trawl adheres to specifications. The NEFSC’s plan to improve the consistency of the NEFSC survey trawl performance over the full depth range of the NEFSC bottom trawl survey requires trawl doors capable of being adjusted to minimize and maximize spreading force. The Thyboron Type 21 “flipper” Trawl Door, 1.5m², 550kg each, with Scanmar SS4 door holders installed has adjustable louvers that can be opened or closed to achieve the desired spreading force over the full depth range of the NEFSC bottom trawl survey. This style, size and brand trawl doors are essential to ensure consistent performance and area swept by the survey gear to maintain comparability between survey tows and survey years.