| Overview:
Help Save the Right Whales |
The North Atlantic
right whale is one of the most endangered species in the world. Two
major causes of death for endangered North Atlantic right whales are
ship collisions and entanglements in fishing gear. To reduce the number
of human-induced injuries to right whales, the Endangered Species
Act requires that an Early Warning System be developed which would
alert mariners to the presence of right whales to diminish the number
of collisions with ships. This act also requires Maine fishermen to
modify their fishing gear in areas where whales are common to help
reduce right whale entanglements.
In this WebQuest, students are
part of a team of specialists trying to devise a method to reduce
whale mortality caused by either entanglement or ship collisions.
The team studies the feeding behavior, migration patterns and geographical
distribution of Northern right whales. One member of the team will
research the sensory biology of whales to determine how they "see"
and "hear" in their environment. Another specialist will
examine current research and technology involving sonar and echolocation.
Specific issues associated with whale entanglements and collisions
will also be explored.
The Gulf
of Maine is one of the world's most diverse and biologically
productive marine habitats. The landward edge of the Gulf of Maine
runs from Nova Scotia, Canada, to Cape Cod, Massachusetts. Over 2,000
species of plants and animals can be found within this marine environment.
Every spring, rivers carry melting snow to the Gulf of Maine. This
makes the water colder, less salty, and more productive than other
parts of the Atlantic Ocean. The strong ocean currents also bring
nutrients and food to the plants and animals that live here.
The Gulf of Maine is home to a variety
of large
whale species including humpback
whales (Megaptera novaeangliae), finback
whales (Balaenoptera physalus), minke
whales (Balaenoptera acutorostrata), sei
whales (Balaenoptera borealis) and right
whales (Eubalaena glacialis). All of these are
baleen whales, which feed on the abundant supply of plankton found
in the Gulf of Maine. Approximately 3,500 of these individuals migrate
into the Gulf of Maine each summer. During the winter months these
baleen whales return to warmer waters where they breed and calve.
 Right
whales have a worldwide distribution but contain three distinct small
populations in the North Atlantic, North Pacific and southern oceans.
Although there are three distinct populations, there are only two species
of right whales: northern right whales, which have populations in the
North Atlantic and North Pacific, and the southern right whale, which
is only found in the southern hemisphere. Both northern right whale
populations are in danger of becoming extinct. The North Atlantic right
whale population, numbering only 300 individuals, is one of the most
endangered species in the world. The southern population of right whales
is approximately ten times larger (3,000 - 4,000) than the population
of the northern species and has only increased in size in the last 15
years.
The North Atlantic right
whale, Eubalaena glacialis, is a slow moving, surface-feeding
animal that was hunted in the early 20th century to near extinction.
This species was targeted by whalers because they were easy to capture
and floated to the surface when killed, thus they were the "right"
whale to be hunted. In addition, right whales yielded a tremendous amount
of oil, meat, and whalebone. Despite a total ban on hunting right whales
since the 1930's, populations of this species have not shown signs of
increasing.
 Current
threats to right whales include collisions with ships, entanglement
with fishing gear, habitat destruction, and changes in food availability
due to climate fluctuations (Fujiwara & Caswell, 2001). Ship collisions
kill more right whales than any other documented cause of mortality.
The right whale is particularly susceptible to ship strikes because
of its habit of resting near the surface, its slow-moving pace as well
as its surface courtship and skim-feeding behavior. Often, the whales
are not killed outright but are fatally injured by propeller blades,
and eventually die because of injury or loss of function. After ship-strikes,
entanglement in fishing gear is the leading cause of known mortality
in the endangered North Atlantic right whale population. More than 60%
of North Atlantic right whales have scars from entanglement in fishing
gear such as lobster pots and sink gillnets (Waring et al., 1999). Obviously
both causes of mortality need to be reduced in order for the population
to recover. If we could prevent only two deaths of female right whales
per year, the population level would increase (Fujiwara & Caswell,
2001).
Strong currents combined
with large tidal fluxes in the Gulf of Maine cause significant challenges
to offshore lobstermen. To avoid large gear losses, lobstermen not only
weigh down their traps with cinder blocks, steel bars and bricks but
they also link several lobster traps together with rope. This allows
them to find their gear more easily, because if they find one buoy it
will lead them to several more. The ropes, called ground lines or tailer
ropes, are often made of polypropylene, which floats. These ropes tend
to arc or loop upwards towards the surface. When large, baleen whales
feed they swim with their mouths open and often accidentally catch the
fishing line in their mouths. As the whales twist and turn, trying to
disentangle themselves they often make matters worse and cause the rope
to cut into their skin; sometimes it goes clear down to the bone.
 In
a world where sight is limited, many marine animals rely on sound to
accomplish many tasks. For cetaceans, such as whales, hearing is arguably
their most important sensory system. Whales and dolphins have three
times more neurons devoted to hearing than any other animal. For these
organisms, sound is a key element for survival and hearing is a key
component of communication, mate selection, and predator avoidance.
Sounds are also produced during feeding and to help navigate underwater.
There are two ways that
sound is used: passively and actively. In passive acoustics, the animal
makes no sound of its own but instead listens and interprets the sounds
made in the environment. In active acoustics when sound is used actively
it is first created by a source and then received by a "listener"
which could be another whale or technology. Some active acoustic systems
have separate sources and receivers (e.g., underwater telephones). Other
active acoustic systems (sonar/echolocation) emit a sound which bounces
off an object and returns to the receiver. By analyzing the return signal,
information about the object such as its size, shape, orientation, direction,
speed and composition can be obtained. The distance that whales can
"hear" in the environment is much greater than the distance
that they can "see".
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