Skomal, John Chisholm
As the coastal and open ocean waters of New England warm
in May and June, many species of fish migrate north from their
southern wintering grounds - among them the sharks. While
most people don't think of Massachusetts when they think of
sharks, that doesn't stop the migration of no fewer than a
dozen shark species in and out of New England waters annually.
Oceanic sharks like the blue, mako, thresher, and basking
shark swim onto the continental shelf from offshore capitalizing
on the productive northeast waters rich in food and reproductive
opportunity. Coastal species like the sandbar shark, spiny
and smooth dogfish, dusky, and sand tiger invade nearshore
waters. Tropical species, like the tiger and the hammerhead,
make an occasional appearance during our warmest months. The
porbeagle shark is the only species found year-round in Massachusetts
waters because of its preference for colder temperate waters.
Although rare, the most notorious of all sharks, the great
white shark, is known to visit New England waters, keeping
to itself despite its heinous reputation. In fact, Massachusetts
represents the northernmost range for several species of sharks.
Therefore, it is an important area for monitoring the health
and distribution of shark populations.
Science currently recognizes over 360 species of sharks occurring
throughout the world, ranging in size from the eight-inch
dwarf dogshark to the 60-foot whale shark. Their habitat ranges
from coastal areas to the open ocean, from Arctic waters to
tropical seas, from surface waters to abyssal depths, and
from estuaries to freshwater rivers. Sharks are uniquely distinguished
from other fishes by their cartilaginous skeleton, five to
seven gill slits, and sandpaper-like scales called denticles.
They have evolved over 400 million years and the modern species
have changed little since the dinosaurs. The evolutionary
success of these animals can be attributed to their unique
adaptations. They possess at least six senses finely tuned
to navigate, communicate, and detect prey. Their multiple
rows of sharp teeth are replaced continually to insure efficiency.
Despite popular belief that sharks will eat anything (including
humans), many species are highly selective in their food habits.
In general, fishes, mollusks, and crustaceans comprise the
bulk of a sharks diet. Most species reproduce as mammals do.
Fertilization is internal and gestation ranges from nine months
to two years, resulting in the birth of a relatively low number
of fully developed baby sharks or 'pups'. Growth rates of
sharks are generally very slow compared to other types of
fishes with some species growing only inches a year and taking
up to 20 years to sexually mature. Sharks are long-lived,
with some species reaching ages in excess of 50 years.
Each species of shark is unique and no single life history
characteristic (i.e. growth rate, food habits, distribution)
can be applied to all shark species. Unfortunately, much of
the basic life history research remains to be done. However,
those general characteristics, which have allowed shark populations
to flourish such as, slow growth, low numbers of young, and
late ages of sexual maturity, have rendered them extremely
sensitive to fishing pressure. Historically, shark populations
have plummeted in the face of intense fishing activities because
they cannot replace themselves fast enough to sustain the
In Massachusetts, there are no directed commercial fisheries
for sharks except trawl and gillnet fisheries for spiny dogfish,
a small schooling fish weighing less than 10 pounds. Of the
5.7 million pounds of shark landed in the Commonwealth in
2000, 99% were spiny dogfish with a commercial value of $1.3
million. The remaining 1% was primarily makos, threshers,
and porbeagles taken incidental to offshore trawl, longline,
and gillnet fisheries based in this state.
A substantial recreational fishery for sharks occurs in Massachusetts
from June through September each year. Although many Massachusetts
recreational fishermen target sharks, most of those caught
are released. Not only is the shark an important component
of the Massachusetts recreational fishery, but it is currently
fished as a sustainable resource.
The National Marine Fisheries Service Fishery Management Plan
for sharks of the Atlantic Ocean recommends that states, "actively
participate in acquiring pertinent information and data"
on sharks. The Massachusetts Shark Research Program (MSRP)
was established in 1990 to study the ecology, distribution,
and relative abundance of sharks that are subject to recreational
fisheries in the Commonwealth. A thorough understanding of
these parameters is crucial to the management process and
wise utilization of these resources. In addition to fieldwork,
the project also provides public education and technical information
on the biology, management, and use of sharks. DMF biologists
conduct cooperative research with other world-renowned shark
researchers to provide local expertise and biological samples
for these cosmopolitan, highly migratory predators.
Inshore: From late June through August of each year,
MarineFisheries personnel set longlines to sample those
species of sharks that enter coastal waters. The inshore areas
east and south of Martha's Vineyard are consistently sampled.
Sharks are taken on longlines and either tagged with standard
NMFS tags and released or sacrificed for life history research.
Biologists examine biological parameters including age structure,
feeding ecology, local movements, and reproductive status
through dissection and tagging of shark specimens. They generate
annual catch indices from longline data to monitor trends
in the relative abundance of coastal shark species. During
this period, surf fishermen that routinely target sharks on
the Cape and Islands are surveyed for important information
on the species, size, sex, and other details for each shark
they land. When compiled, these data help elucidate the ecology
of these species in our waters.
Offshore: Anglers participating in offshore fishing
tournaments make large pelagic sharks including the blue,
mako, and thresher available to the program. In addition,
biologists make offshore trips with cooperative fishing vessels
and our own research vessel to sample offshore sharks. The
collective information that is gathered contributes to our
understanding of these elusive predators.
One of the most important aspects of the program is the educational
component. Throughout the year, biologists present extensive
slide shows to schools, clubs, and conservation groups throughout
the Commonwealth on New England sharks, their biology, fisheries,
and study. Also, information about sharks is provided to a
variety of media interests that include magazines, television,
and documentary producers. These efforts educate the public
about these remarkable animals that are an integral component
of the marine ecosystem.
MarineFisheries biologists routinely sample sharks
for other researchers during field activities. Academic scientists,
students, public aquariums, conservation groups, and other
state and federal agencies are among the groups that have
been assisted. Some of the more recent examples include:
National Marine Fisheries Service (http://nmfs.noaa.gov/):
A number of studies have been conducted with the NMFS Apex
Predator Program (Narragansett, RI). These include an updated
study on the age and growth rate of the blue shark, the tracking
of porbeagle sharks in the Gulf of Maine, and post-release
survivorship studies on the sandbar shark in Delaware Bay.
Moreover, MSRP personnel routinely participate in NMFS shark
surveys along the eastern seaboard.
Tennessee Aquarium (http://www.tennis.org/):
Working with George Benz of the Tennessee aquarium, MSRP researchers
were the first to study the behavior of the Greenland shark
under the Arctic ice.
University of Hartford (http://www.hartford.edu/):
MSRP biologists have collaborated with UH researcher Joanna
Borucinska to study the pathological effects of retained fishing
hooks in the blue shark.
Louisiana State University (http://lsu.edu/index2.html):
Program personnel have teamed up with LSU's Shark Researcher
Group to investigate the physiological effects of capture
stress on the bull shark in the Gulf of Mexico.
Boston University Marine Program (http://www.bu.edu/bump/):
MSRP has fostered a relationship with BUMP in Woods Hole,
Mass. to study shark species in a number of areas.