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Subject: Re: circle hooks
From: David Kerstetter <[log in to unmask]>
Reply-To:Scientific forum on fish and fisheries <[log in to unmask]>
Date:Mon, 8 Dec 2008 09:42:36 -0500
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Greetings from Florida, J.P.

As with Mike Pol, I'm curious how you reached 
your conclusions about the use of circle hooks 
with regards to bycatch.  There's actually quite 
a bit of literature available on the use and 
results of circle hooks, ranging from original 
research (for examples, see such papers as Watson 
et al., 2005 or Kerstetter and Graves, 2006) to 
reviews (including Cooke and Suski, 2004).  This 
body of work with circle hooks now covers several 
commercial and recreational fisheries, examining 
aspects such as catch rates and hooking 
location.  A free "Google Scholar" 
(http://scholar.google.com/) search shows many of 
these papers even have free .pdf versions available online.

I would also suggest differentiating between 
catch rates of bycatch species and bycatch 
mortality -- they are very different ideas, and 
the use of circle hooks may affect these two 
factors differently.  For example, circle hooks 
in multiple studies have shown a decrease in the 
catch of pelagic stingrays, a bycatch species in 
the pelagic longline fishery.  Circle hook 
studies with catch rates of sharks have shown 
conflicting results, in part I believe because of 
the difficulty in correctly ascribing catch rates 
with lost hooks, events that can occur when 
sharks are hooked deeply or at least in such a 
way that they can bite through the monofilament 
leader and thus release themselves from the 
gear.  Catch rates of istiophorid billfishes have 
shown conflicting results in studies with circle 
hooks in the pelagic longline fishery, although 
their mortality rates are generally lower with 
these hooks at haulback than with J-style 
hooks.  Assessments of the post-release mortality 
associated with capture by different hook types 
is yet another field of work, one generally 
involving the use of electronic tags (e.g., 
Horodysky and Graves, 2006) or acoustic 
tracking.  Please note that I've cited some 
pelagic fisheries work only because it's most 
familiar to me, but much more literature exists 
on the use of circle hooks with other marine 
fisheries, such as serranid groupers (e.g., Bacheler and Buckel, 2004).

Circle hooks are not the "silver bullet" answer 
to bycatch interaction and bycatch mortality 
issues, but then again, there are very rarely 
such solutions for any fisheries problems.  In a 
grossly oversimplying sense, circle hooks appear 
to show a good deal of promise in many fisheries 
for reducing bycatch mortality, especially for 
such species as the istiophorid billfishes, while 
remaining neutral to the catch rates of target 
species.  Not all fishes (or marine organisms, 
for that matter) feed using the same techniques 
however, which would be just one of many factors 
explaining the variations in results between species and fisheries.

Best regards,

Dave Kerstetter




Bacheler, N.M. and J.A. Buckel.  2004.  Does hook 
type influence the catch rate, size, and injury 
of grouper in a North Carolina commercial 
fishery?  Fisheries Research 69: 303-311.

Cooke and Suski.  2004.  Are circle hooks an 
effective tool for conserving marine and 
freshwater recreational catch-and-release 
fisheries?  Aquatic Conservation: Marine and 
Freshwater Ecosystems 14(3): 299-326.

Horodysky, A.Z., and J.E. 
Graves.  2005. 
<http://web.vims.edu/fish/faculty/pdfs/jeg_Horodysky_and_Graves_2005.pdf>Application 
of pop-up satellite archival tag technology to 
estimate postrelease survival of white marlin 
(Tetrapturus albidus) caught on circle and 
straight-shank ("J") hooks in the western North 
Atlantic recreational 
fishery<http://web.vims.edu/fish/faculty/pdfs/jeg_Horodysky_and_Graves_2005.pdf>. 
Fishery Bulletin, 103:84-96.

Kerstetter, D.W. and J.E. 
Graves.  2006. 
<http://web.vims.edu/fish/faculty/pdfs/jeg_Kerstetter_and_Graves_2006_FO.pdf>Effects 
of size 16/0 circle versus size 9/0 J-style hooks 
on target and non-target species in a pelagic 
longline 
fishery<http://web.vims.edu/fish/faculty/pdfs/jeg_Kerstetter_and_Graves_2006_FO.pdf>. 
Fisheries Research 80: 239-250.

Watson, J.W. et al.  2005.

Fishing methods to reduce sea turtle mortality 
associated with pelagic longlines.

Canadian Journal of Fisheries and Aquatic Sciences 62(5): 965-981.




At 01:48 AM 12/8/2008, Juan Pedro Monteagudo wrote:
>Hi everyone, im looking for some literature on 
>implementation of circle hooks and estimates on 
>mitigation of bycatch, as it seems they might 
>not be such a good alternative or even being worst at the end.
>
>Thanks in advance.
>
>JP Monteagudo
>
>--
>Juan Pedro Monteagudo González
>Asesoria Técnica en Pesquerías y Ciencias del Mar
>Fisheries and Marine Sciences Consultant
>[log in to unmask]
>[log in to unmask]
>+(34) 647844645
>Skype:Dubduap


David W. Kerstetter, Ph.D.
Research Scientist and Adjunct Faculty
Nova Southeastern University Oceanographic Center
8000 North Ocean Drive
Dania Beach, FL 33004
http://www.nova.edu/ocean/profiles/kerstetter/kerstetter.html

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