I had a student do her thesis on circle vs. j-hook, along with different
baits and other gear modifications. Strictly done for longline and
northeast distant water fleet. The data were NOAA (NMFS) data collected
from experiments funded and supervised by NOAA; the student had nothing to
do with data collection or the experiments. She applied data envelopment
analysis, using directional distance functions which penalize technical
efficiency when there are undesirable outputs (in this study, sea turtles
were viewed as undesirable outputs), to assess technical efficiency. She
also did an extensive amount of tobit analysis to tease out influences of
gear modifications and other concerns.
The bottom line was that, overall, there was no difference in technical
efficiency when evaluating circle hook vs. j-hook, without regard to size
of hook and bait. There were, however, differences when considering the
different size hooks and baits. Also of importance was the loss in catch
of requiring circle hooks rather than j-hooks--the losse equaled about
6,570 pounds per trip and about $16,287 (2004 US dollars). Also, the cost
of replacing all j-hooks with circle hooks was up to $1,650 for 18/00 hooks
and $1,241 for 16/0 hooks.
Bottom line from study: (again note that limited to area and U.S. longline
vessels)--circle hooks reduced mortality and catch of sea turtles but also
reduced catch of target of marketable species. Given us regulations on sea
turtles, the circle hook may be the only viable hook to allow continuation
of the longline fishery.
Baseline or reference studies, which I believe have been recommended,
include Watson et al. (2002). Experiments in the Western Atlantic
northeast distance waters toe valuate sea turtle mitigation measures in the
pelagic longline fishery: report on experiments conducted in 2001. Draft
(at time of student's thesis) available at
www.mslabs.noaa.gov/mslabs/docs/watson1.pdf, and Watson et al.
(2002). Experiments in the Western Atlantic northeast distance waters toe
valuate sea turtle mitigation measures in the pelagic longline fishery:
report on experiments conducted in 2001-2003. Draft (at time of student's
thesis) available at www.mslabs.noaa.gov/mslabs/docs/watson4.pdf.
James (Jim) E. Kirkley
Department of Fisheries Science
College of William and Mary
Virginia Institute of Marine Science
School of Marine Science
Gloucester Point, VA 23062
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