It is a low-rise, 2-seam flatfish trawl characterized by a headrope
that is 25.
The corkline, floatline, or headrope
is attached to the top of the net and is fixed with varying numbers of floats.
Water temperature and depth profiles were collected at each station by using bathythermographs attached to the headrope
of the bottom trawl net (expendable models before 1993 and microbathythermographs in later years).
A two-seam commercial bottom trawl (54 m headrope
, 60 m footrope) was fished from the 37.
The depth of the thermocline was estimated algorithmically from data collected with the microbathy-thermograph (MBT) attached to the trawl headrope
A SCANMAR acoustic sensor was used to measure net height; that is, the distance from the center of the headrope
to the bottom.
was rigged with floats for towing at the surface at a speed of nominally 3.
Floats on the headrope
and bridles helped maintain the net near the surface (usually within 1.
Most observed vessels utilized a transducer, or net sounder, placed on either the headrope
or footrope to determine the depth and opening of the net.
The survey was conducted with a three-to-one two-seam trawl (25-m headrope
1 they are initially high up in the water column and do not "dive" to lie below the oncoming headrope
of the trawl;
Presently, an acoustic trawl monitoring system allows trawl mounted transducers to send information back to the ship on headrope
height, wing spread and bottom temperature.