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Subject: Re: circle hooks
From: James Kirkley <[log in to unmask]>
Reply-To:Scientific forum on fish and fisheries <[log in to unmask]>
Date:Tue, 9 Dec 2008 10:53:22 -0500
Content-Type:text/plain
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Juan:

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.

Jim Kirkley

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
For Express mail: 1208 Greate Road
FAX:804-684-7989
WORK:804-684-7160
e-mail:[log in to unmask]

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