Wreckfish on the Mid-Atlantic Ridge - Habitat Query

InterRidge Office mac at ext.jussieu.fr
Thu Feb 6 10:50:53 EST 1997


Wreckfish on the Mid-Atlantic Ridge - Habitat Query

REPLY TO:   sedberryg at mrd.dnr.state.sc.us

Dear Mid-Atlantic Ridge investigators:

For several years I have been investigating the biology of the wreckfish,
Polyprion americanus.  This species is globally distributed and is locally
important in the fisheries of many regions, including the US, the Atlantic
and Mediterranean waters of Europe and Africa, in Australia and New
Zealand, in South America and around many islands such as Bermuda, the
Azores and Madeira.  It is known as wreckfish in South Africa, cherne in
Portugal and Brazil, cherna in Spain and the Canaries, bass groper in
Australia and bass or hapuku in New Zealand.  Wreckfish also occur,
apparently in high numbers, on the Mid-Atlantic Ridge.

Wreckfish are found in waters from 40 - 1000 m, although Atlantic fisheries
mostly operate in depths from 200 - 600 m, presumably because that is the
preferred range and fish are most abundant there.  The adults (fish from 85
- 150 cm total length) occupy high-relief rocky-bottom habitat, and off the
US they are confined (as far as we know) to the Charleston Bump on the
Blake Plateau, coral mound and hard-bottom areas of the Blake, and a few
areas in the Florida Straits between Florida and the Bahamas.  The
juveniles (those less than about 60 cm in length) live at the surface, and
associate with floating weed, debris and wreckage, and drift around the
North Atlantic gyre.

A fishery has become established since 1987 off the coast here; fisheries
have existed for decades in a few other parts of the range, but are
expanding to other parts of the range.  We have genetic and circumstantial
evidence for migration of this species in the North Atlantic (see J. Fish.
Bio. 49(A)), and we think recruitment to US waters may depend in part on
migration from the wreckfish populations on the Mid-Atlantic Ridge and
North Atlantic islands (or, possibly, vice-versa).  At the least, we have
good evidence that fished concentrations of wreckfish on both sides of the
Atlantic are genetically linked.  If so, the success of management and
conservation plans for the US wreckfish stock (currently regulated with a
quota, limited entry and spawning season closure) may depend on
availability of fish from other parts of the range.

I have been able to make submersible observations of wreckfish on the
Charleston Bump, and there are some other limited underwater observations.
So, we have a feel for the density of these fish in their preferred habitat
(high-relief rocky bottom).  If I knew extent of this habitat in the North
Atlantic, we could (crudely) estimate potential population size.  So, I was
wondering if any of you ridge investigators know the extent of available
ridge habitat that exists between depths of 200 - 600 m.  Are there any
charts, satellite or other images, etc., that I could go to and maybe
estimate this?  Any data available on the web?  Any suggestions at all?

Our evidence for migration in this species is the occurrence of fish hooks
in American wreckfish of a type that are not used by American fishermen.
These include small eyed hooks, and small to large eyeless hooks, with
flattened shank and snelled monofilament leaders.  Our fishermen use 16/0
eyed circle hooks.  If you have any information on the origin of the
unusual hooks in American fish, or if you ever see American hooks in fish
from outside US waters, I would appreciate any information you may have on
that.

Thanks, and if you need anything from this part of the world, drop me a line.

George


George R. Sedberry
Marine Resources Research Institute, SCDNR
P.O. Box 12559
217 Ft. Johnson Rd.
Charleston SC  29412  USA
803-762-5045
FAX 803-762-5110
sedberryg at mrd.dnr.state.sc.us





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