Report by Shark Info
Commercial shark catches rose in the western North Atlantic and the Gulf of Mexico between
1979 and 1989 from 135 tons to 7,122 tons. During the same period sharks caught by anglers
declined from 11,512 tons to barely 1,665 tons, as indicated by a 1993 study conducted in U.S.
territorial waters by the National Oceanic and Atmospheric Administration (NOAA) of the U.S.
Government. How can such a contradictory development be explained? The rise in commercial
catches was undoubtedly caused by a rising demand for shark products, which means they
were caught more intensively using more efficient fishing methods. The simultaneous decline of
catches made by anglers was, however, a clear warning signal that shark populations were
being decimated by unregulated regional commercial fishing.
To protect the remaining shark populations, the National Marine Fisheries Service (NMFS, a
division of the NOAA) developed a fishing management plan in 1993. To implement the plan it was
important to develop a method of determining actual shark populations independent of any
statistics prepared by commercial fishing interests in order to monitor the effectiveness of the
management plans. One of the first measures was to assign scientific observers to the
commercial fishing fleets. At the same time, NOAA developed a pilot project with the purpose of
gathering shark population statistics in the impacted regions. Mississippi Labs, a branch of
NOAA, was entrusted with the field work, supported by a division of the NMFS, specializing on
frequently migrating sharks. Project leader was Mark Grace*, who was kind enough to supply us
with information on the project.
Field work for the Pilot Project was performed from 1995 to 1996, usually from mid to end
summer, since a suitable research ship, the Oregon II, was only available during that time period.
Unfortunately, this restriction meant that known seasonal fluctuations of shark catches could not
be considered in the research work.
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Normally, the 52 m long NOAA research ship, the Oregon II,
was used as a catch ship. In addition to 18 crew members it has room
for 13 scientists and their equipment.
© Mark Grace / Shark Foundation
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The areas to be reviewed regularly were the western portion of the North Atlantic, stretching
from Maine to the Florida keys and the Gulf of Mexico, Cuba and the catch areas around the
island of Navassa (see map). For this purpose, special cooperative agreements were signed
with Cuba and Mexico.
To obtain the data, sharks had be caught and tagged. Commercial catch methods could not be
applied since the sharks had to be caught very carefully and freed again after the procedure. For
this purpose long-lines measuring 1.85 km long were used on the ocean ground. As a rule these
had about 100 hooks baited with native Atlantic mackerels (Scomber scomber). However, in
contrast to commercial practices the lines were only deployed for about an hour and then hauled
in. Radar-reflective buoys were used to locate the long-lines as quickly as possible. The fishing
depth measured between 9 and 73 meters in U.S. territorial waters and Mexico, and between 9
and 413 meters around Cuba and Navassa. Fishing took place in 24-hour shifts. In each arbitrarily
selected fishing ground, physical and chemical profiles were made of the water columns and
atmospheric data was collected.
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An Atlantic brown shark (Carcharhinus plumbeus) is tagged on board the
Oregon II and will be freed later on.
© Mark Grace / Shark Foundation
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To investigate animal populations it is important to catch, tag, release and later to recatch as many
animals as possible. Population sizes can be estimated by statistically analyzing tagged and
untagged animals. However, markings are also important aids to gain information on migrations
and to find out which populations may move out of territorial boundaries. The markers deployed
by the Mississippi Laboratories are engraved with a request addressed to fishermen to report to
the NMFS the identification number, catch location, date and if possible the length and weight of
the animals caught.
The voyages of the Oregon II offer many scientists a genuine opportunity to come into direct
contact with and investigate various shark species. Students, teachers and reputed scientists
are regularly invited on board the Oregon II. Researchers from Mexico, Cuba, Canada, Germany,
France, England, New Zealand and Switzerland have already had the opportunity to participate in
such excursions.
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Marked in green are fishing zones in the North Atlantic, the Gulf of Mexico and the Caribbean which were regularly inspected by the
crew of the the Oregon II during the project.
© Mark Grace / Shark Info
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During the pilot project - which lasted from 1995 to 1996 - 875 sharks, consisting of 22 different
species, were caught. Most could be tagged and released alive back into their natural watery
element. The careful handling made possible by this catch method proved to be successful. The
most frequently caught species were the Atlantic sharp-nosed shark (Rhizoprionodon
terranovae) (about 62%) and the tiger shark (Galeocerdo cuvier) (about 9%). Less than 5% of
those caught were hammerhead sharks (Sphyrna sp.), while silky sharks (C. falciformis) and
bull sharks (C. leucas) and some other species amounted to less than 1% (see detailed list in
table below). The different types of species caught and the various sizes of species members
corresponded to commercial fishing data. This was encouraging for two reasons: First, a single
ship like the Oregon II could not cover the same territory as an entire commercial fishing fleet.
Samples had to suffice. Still, the statistical arbitrary selection of catch locations within a region
supplied quite reliable data. Second, the reliability of the methods used suggested the feasibility of
also reviewing areas which do not normally belong to the fishing grounds used by larger fleets in
order to permit a comparison of death rates of fished and nonfished populations.
The encouraging results motivated NOAA to continue with the project. Until the end of the
summer 1999 about 2,600 sharks were caught and examined, with most of them released after
being tagged. The knowledge level on shark populations in the reviewed areas has grown with
each voyage of the Oregon II. By comparing statistics of different years it may soon be possible
to calculate development trends for regional shark populations and hence to establish meaningful
catch quotas. Hopefully this will lead to a future for both fishermen and sharks, preventing
unemployment on the one hand, while ensuring that sharks are not overfished and decimated on
the other hand.
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Species |
Scientific Name |
Percentage |
Atlantic sharp-nosed shark |
Rhizoprionodon terranovae |
62% |
Tiger shark |
Galeocerdo cuvier |
9% |
Black-nosed shark |
Carcharhinus acronotus |
7% |
Atlantic brown shark |
C. plumbeus |
5% |
Large blacktip shark |
C. limbatus |
5% |
Hammerhead sharks |
Sphyrna sp. |
< 5% |
Spinner shark |
C. brevipinna |
< 5% |
Spiny dogfish shark |
Squalus acanthias |
< 5% |
Silky shark |
C. falciformis |
< 1% |
Bull shark |
C. leucas |
< 1% |
Lemon shark |
Negaprion brevirostris |
< 1% |
Nurse shark |
Ginglymostoma cirratum |
< 1% |
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* Mark Grace is a fish biologist and has been Project
Leader of the NMFS Mississippi Laboratories
Shark Study since its founding in 1995. He began his career at NMFS as a scientific observer on
Japanese long-line tuna catchers who fished in U.S. territorial waters.
May be published only by indicating the source: Shark Info
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