Kyne & Simpfendorfer.. - Shark Specialist Group

Leucoraja circularis, blonde skate Raja brachyura, thornback skate R. clavata, clearnose
skate R. eglanteria, brown skate R. miraletus and rough skate R. radula.
Some particular species which require justification as to their absence from this report are the
broadnose sevengill shark Notorynchus cepedianus, which although recorded to 570m is
primarily a coastal inshore shark of temperate waters; the spiny or piked dogfish Squalus
acanthias, primarily a shelf species, but which occurs occasionally on the slope and
exceptionally to 1446m; the Sparsetooth dogfish Scymnodalatias oligodon and the Largetooth
cookiecutter shark Isistius plutodus, although both occur over very deep water (to 4000m),
they have both only ever been recorded in the epipelagic zone (0-200m depth in the water
column) (it should be noted though that these species are potential vertical migrators and may
also occur in the mesopelagic and bathypelagic zones); the megamouth shark Megachasma
pelagios, a coastal, shelf and epipelagic species recorded from the pelagic zone to depths of
166m over water to 4600m depth, but never recorded from deep water. One last notable
species is the great white shark Carcharodon carcharias, a coastal, inshore, shelf and
epipelagic offshore species known to undertake considerable migrations. Great whites have
rarely been recorded from the continental slope (Compagno 2001), and thus in deepwater, and
a reported capture at 1280m (Bigelow and Schroeder 1948a, Compagno 2001) is doubtful
(Bonfil et al. 2005). However, more recent research of a shark tagged off South Africa has
shown that during transoceanic migration great whites undertake periodic deep dives to
depths of up to 980m (Bonfil et al. 2005). It should be noted that this depth is the sensor limit
for the tag employed and so it is possible that the tagged shark dived to depths in excess of
980m. While deep dives were regular in occurrence during its migration, with the shark
spending 18% of the time at depths of 500-750m, a far greater amount of time (61%) was
spent at the surface in water 0-0.5m deep (Bonfil et al. 2005). Thus, given the species'
primarily coastal and epipelagic occurrence, it is not further discussed here.
AIMS OF THE PROJECT
The overall aim of the present study is to provide a collation and summarization of the
available information and data on the biodiversity, life history and fisheries of deepwater
chondrichthyan fishes at the global level.
By examining the present status of knowledge, the project will also address the specific data
needs required to provide a global understanding of the vulnerability of deepwater
chondrichthyans to fisheries, and to provide a baseline from which to prioritize research,
conservation and management. To address the central aim, the report is divided into three
Sections. Section I reviews the global biodiversity of deepwater chondrichthyans and
provides a checklist of all known living, described and undescribed deepwater species. This
annotated checklist incorporates a summary of the known distribution, habitat and depth
occurrence of each species, as well as any taxonomic notes where relevant. Section II collates
available (published and unpublished) information on life history and provides relevant
summaries of biological data including a demographic assessment of the productivity of
deepwater chondrichthyans. Section III summarizes global and regional catch data for
deepwater chondrichthyans. Regional and fisheries case-studies are presented to illustrate
specific examples of catch trends, management or monitoring information.
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