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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

Content-Type:

text/plain

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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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