As variables, the headrope
length (HL) of the nets and the drag speed (5) were used.
Model Rope Length Diameter (inch) Japanese headrope
12.8m + 1m from each end 1/2" to the wire rope thimble footrope 14.8m + 1m from each end 1/2" to the wire rope thimble Korean headrope
11.27m + 1m from each end 1/2" to the wire rope thimble footrope 13.75m + 1m from each end 1/2" to the wire rope thimble Model Rope Material Japanese headrope
combined rope ("tralla") footrope combined rope ("tralla") Korean headrope
combined rope ("tralla") footrope combined rope ("tralla") Table 2.
Gulf Item mandatory penaeid Net type (%) Flat 22.6 Unknown 15.5 Main net headrope
length (ft) n=17,735 Mean 50.5 Range 14.0-74.5 s.d.
The current sampling gear consists of a 2-seam otter trawl with a 3.2-m headrope
, 6.4-mm bar mesh with body netting of 210/6-size twine, and a tailbag made of 3.2-mm Delta-style knotless nylon and with a 150-mesh circumference and 450-mesh length.
Attached to each outrigger are one or two nets typically 30-50 ft in headrope
On August 6, 1998, an unusual flatfish, 80 mm standard length (SL), was collected north of La Jolla Submarine Canyon, California (latitude 32[degrees]53.32' N and longitude 117[degrees]16.66' W) at a depth of 63 m in a 7.6-m wide (headrope
) semiballoon otter trawl with 1.2-cm cod-end mesh.
In 2011, a Yankee 36 otter trawl with an 18.3-m headrope
, a codend that had a 1-cm mesh liner, and deepwater headrope
floats ("rock hoppers") was deployed from the stern trawl A-frame by using both trawl winches and 2.5-cm trawl wires.
Each turtle was released into the trawl at the headrope
by one member of a three-person NMFS dive team.
Following the 1997--1998 El Nino, two specimens of the blacklip dragonet were collected in the Southern California Bight (SCB) by semiballoon (7.6-m wide headrope
) otter trawls with 1.2-cm cod-end mesh.
Additionally, large Pacific cod do not routinely swim above the trawl because analysis of acoustic backscatter collected concurrently with trawl hauls indicated that only 4% of the acoustic backscatter attributed to Pacific cod occurred at heights above the headrope
. We found no evidence that survey-gear efficiency decreased with increasing fish length either because large fish outswam the trawl or because they tend to occur further from the bottom.