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Extension Associate Dana
Morse is working with Boothbay Harbor fishermen
Kelo Pinkham and Stanley Coffin, in their efforts
to reduce bycatch, improve energy efficiency,
and improve mesh size enforceability in trawl
nets. The study, entitled "Sea Trials to Assess
Knotless Mesh Codend Selectivity," is enabled
through a $46,180 grant from the Northeast
Consortium.
The size, shape and materials
used in mesh netting of trawls has much to do
with escapement of fish during trawling, and
on the species and sizes of fish that come up
in the net. Traditionally, twine is knotted,
which decreases the space available for fish
to escape, and uses more energy to tow than
knotless netting. This study will help to evaluate
escapement by undersized fish, and any energy
savings that might occur by using the newer
mesh. Captains Pinkham and Coffin are running
at-sea operations aboard Capt. Coffin's 54-foot
vessel, the F/V Bad Penny, with Morse as the
scientific partner and PI.
Eight days at sea are
planned for these trials, using an alternate
tow strategy to evaluate the control codend
(knotted) against the experimental (knotless).
A standard-type groundfish net is used for the
trials, with the codend being switched between
tows. Sea trials began in late March 2003, and
will run through May 2003.
Update
The selectivity of knotless twine used in the
codend of a groundfish trawl was tested, relative
to a standard codend constructed of knotted
twine. Between April and July of 2003, 13 tow
pairs (26 tows) tests were conducted aboard
the F/V Bad Penny, berthed in Boothbay Harbor,
Maine. Analysis of catch per unit effort (CPUE)
and length frequency by species detected a small
difference between catches from the knotless
and knotted codends. Larger sample sizes and
covered codend experiments would help to more
fully describe the selectivity of knotless twine
in the Northeast groundfish fishery. Evaluations
were somewhat hampered by a low catches in both
control and experimental tows.
Video footage suggests
a general tendency for the knotless twine to
remain more fully open during trawling, and
escapees from knotless codends may suffer less
scale loss and other damage during the escape
process. The knotless twine is lighter, easier
to handle, and more supple. Future work should
focus on the health of escapees, and on continued
field trials, including square mesh arrangements.
For
more information, contact Dana
Morse.
"Selectivity Tests with Knotless Mesh in Trawl Codends in the Northeast Ground Fishery" Fact Sheet -  PDF 129 KB
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