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For information on the Harriman Retraced Expedition e-mail: harriman2001@science.smith.edu |
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One of the most striking things
about the original Harriman Alaska Expedition reports is the
absence of an organized report on either terrestrial or
marine mammals. There is only brief mention of marine
mammals in Expedition narratives. There is a description of
the Native sealing camp at Yakutat and a mention of harbor
seals, and other brief references to the over hunting of sea
otters and fur seals, but no mention is made of harbor seal
and sea lion haulouts as the George W. Elder steamed
along the coast, nor of the large and small whales they must
have seen as they spent many hours at sea without making
landfall. As they passed north into the Bering Sea, there
were no descriptions of sea otters or walruses at the
Pribilof Islands. By the time The Harriman Expedition
transited the Bering Sea, the Steller sea cow had been
hunted to extinction. Perhaps part of the reason these
animals weren't much mentioned is that already by the turn
of the century, many species had already been over hunted
and were no longer easy to see. Grey whales were depleted by
the 1880s. Bowheads were depleted in the Bering Sea by the
mid 1800s, only 10 years after their discovery there. Sea
otters and walruses were gone from the Pribilofs by the time
the Harriman Expedition arrived there, and sea lions were
greatly reduced in number. By 1900, fur seals were close to
an all time low. And so -- where are we today?
Grey whales and walruses have recovered. Grey whales are
probably as numerous as they ever were … more than
20,000 ply the waters between Baja California and Alaska
each year. Walruses -- at least when we last counted them in
the mid 1980s -- were thought to be at or near carrying
capacity. Sea otters are numerous throughout much of their
former range… although recently a large and unexplained
decline has been noted in the Aleutian Islands. The thing
these species -- grey whales, walruses, sea otters - have in
common is a link to benthic food webs. They get their food
from the bottom of the sea. They don't feed within the
pelagic food web of the Bering Sea -- the world of plankton
and forage fish. And what about the others? The
fur seals, sea lions and seals? The species that DO eat
pelagic forage fishes. Have they recovered? Are they
healthy? A cursory look at the Pribilofs today -- like the
one afforded members of the Harriman Expedition Revisited as
they visited St. Paul and St. George Islands on their way
north through the Bering Sea - initially suggests "yes." The
beaches are alive with the bleats of fur seal pups looking
for their mothers, and with the jostling of males protecting
their harems along the boulder beaches. There is no
unregulated commercial hunt for these seals as there was at
the turn of the century when the Harriman Expedition
visited. Visits to the rookeries -- even by scientists --
are highly controlled. And yet, although almost 800,000 fur
seals now come there to have their pups and breed -- up from
a few hundred thousand when Harriman was here -- this is a
far cry from the 3-4 million that biologists estimate were
present 200 years ago -- or the 2 million that were here as
recently at the 1950s. And why? Is it entanglement in human
debris so common in our oceans today? Competition with
commercial fisheries for food? A change in ocean conditions
that has altered the availability of the right kind of food
for fur seals? As hard as we try, scientists still don't
know the answers. Likely there is no one cause … making
it even more difficult to determine what might reverse such
a decline. And what of Steller sea lions --
also once so abundant in the western Gulf of Alaska and the
Bering Sea? The story there is even more confusing. Until
the 1970s, sea lion numbers were high throughout Alaska.
Since then, however, there has been a startling decline in
sea lion numbers in western Alaska. Counts of pups -- an
index of overall abundance and population health -- have
dropped along the Alaska Peninsula and the Aleutian Islands,
at the Pribilof Islands in the Bering Sea, and in the Kuril
Islands of Russia. At Walrus Island in the Pribilofs, only
50 pups were born in 1991 -- a vivid contrast to the 2,800
pups that were once born here each year. In fact, sea lions
in western Alaska have declined to such a degree that they
are now classified as an endangered species. As for fur seals, the reasons
for the sea lion decline are unclear and may not necessarily
be the same now as they were 20 years ago when the decline
began. Could it be a change in the ocean? In the late 1970s,
ocean temperatures warmed by several degrees, causing quite
dramatic changes in the abundance of some of these fishes.
Some species, such as pollock, became much more abundant and
others such as capelin, a high-fat schooling forage fish,
became far less abundant. It may be that the replacement of
such high-fat forage species with lower fat pollock may have
made it more difficult for sea lions -- especially juveniles
-- to get enough calories to make a living. And yet, that is certainly not
the whole story. Killer whales eat sea lions. As the seals
and sea lions on which they dine have become less abundant,
predation pressure on the remaining marine mammal
populations has increased. Sea lions and commercial
fisheries compete for the same fish. Commercial fisheries in
the Steller sea lion range remove millions of pounds of fish
each year. While the fishery itself is considered
sustainable, its side effects on other species are unknown.
In the not-so-distant past, sea lions have been killed
intentionally -- as well as accidentally -- in conjunction
with fisheries. Is the problem more deep seated
than all of these? People and commercial fisheries change
not only the abundance of the species they target, but also
ecosystem dynamics of who eats who and how much. Within the
past 200 years, people and their fisheries have vastly
altered the Bering Sea ecosystem. Species like Pacific ocean
perch and yellow fin sole were overfished, the great whales
seriously depleted. Removal of these and other species,
which were significant consumers of both fish and plankton,
has undoubtedly greatly altered the way creatures of the sea
interact -- and the aftermath of such changes may also be
part of the unexplained and continuing declines we see.
Whatever the cause, it is clear
that people must do whatever they can to prevent further
human-caused problems. Because there is nothing we can do
about cyclic climate change or killer whale predation, we
must do what we can -- protect habitat, prevent intentional
and accidental killing, minimize competition with commercial
fisheries, and minimize emissions that may cause global
warming and exacerbate other environmental
change. And what else has changed in the
Bering Sea since Harriman's time? What is the status of
OTHER marine mammals in this region? One of the
unanticipated consequences of the sea lion decline in
particular -- which has impacted how a multi-million dollar
fishery for pollock is conducted -- is that vast monetary as
well as human resources are now directed at solving the
"Steller sea lion problem." Because so much attention is
being focused here, research on other species is not
receiving the attention it deserves. Spotted seals, the ice-breeding
form of harbor seals, eat many of the same small forage
fishes that have been implicated in declines of harbor
seals, sea lions, and some seabirds. And yet, there is not
adequate information on population status or health and
condition to know whether this species, too, has been
declining. What is the impact of almost two decades of
reduced abundance of high-fat forage fish? How do extreme
oscillations in the annual extent of sea ice, and
particularly years of very light ice coverage, affect
feeding and survival of pups which are born and weaned in
the ice front? What of ribbon seals? These
seals also inhabit the Bering Sea ice front in spring, where
they feed and have their pups. Where do the go in winter?
How many are there? Are they abundant and healthy? No one
knows. The last studies of ribbon seals were conducted more
than 25 years ago. It's hard to believe that we could know
so little about a population that probably numbers more than
100,000 seals. Bearded seals are also largely a
mystery. As is the case for ribbon and spotted seals, little
research has been conducted since the 1970s and there is no
current population estimate. Yet these seals are one of the
preferred foods of local Native people throughout western
and northern Alaska. They are hunted along the coast in
spring when the sea ice first begins to break up -- and
again in fall as the ice returns. Bearded seals eat clams
and crabs and other benthic creatures. Have they been
impacted by snow crab fisheries which harvest that same
kinds of crabs that bearded seals eat? What are the
interactions between bearded seals and walruses? Are there
enough clams and snails to feed them both? Do bearded seals
migrate? And if so, to where? There is no ongoing research
in Alaska to address these questions. Scientists are in a little
better shape for ringed seals -- the most northern on the
ice associated seals. These "polar bear popsicles" inhabit
the stable land fast ice along Alaska's northern shorelines.
They make and maintain breathing holes through ice that may
be 6 ft thick, and the pups are born in snow caves or lairs
excavated in snow drifts on the ice. These seals are the
major prey of polar bears throughout the Arctic, and are
also a source of food for coastal residents. There have been
recent surveys of this species, indicating that densities on
fast ice are similar to densities in the 1980s. But we still
have no current information on reproductive rates, the age
at which they mature, and how they use different geographic
regions and habitats throughout the year. How will a
thinning ice pack across the arctic affect these seals which
depend on a stable ice platform on which to bear and nurture
their pups? And walruses? The last usable
aerial census of walruses in Alaska was conducted more than
15 years ago. At that time, the population was quite high --
more than 250,000 -- but since then Native hunters and some
biologists have noticed changes in walrus condition and age
composition. Does this indicate a change in population
status? Is the diet the same now as it was the last time
walrus food habits were studied more than 15 years ago? Do
changes in sediment transport through the Bering Strait
affect the clam populations upon which walruses
feed? So where does this lead us? When
I first came to Alaska and began to study its many marine
mammals, there was a burst of funding -- part of an
environmental assessment program associated with leasing of
the outer continental shelf - to provide baseline
information about Alaska's marine ecosystems. Since then,
however, such funding has disappeared - there were "no
significant issues" and populations were "healthy, high, and
stable." There wasn't enough money to go around, and healthy
species with no problems didn't come out on top in funding
allocations. Twenty-six years later at least two of these
species -- Steller sea lions and harbor seals -- have
declined so significantly that we are now spending millions
of dollars a year to try to retroactively determine the
causes for these declines and determine what, if anything,
people can do to improve the situation. What of the other
seals for which we have no recent information? There must be a better way for
the next 26 years … to look as we go, to make sure the
bases are covered for even those healthy, "non-problematic"
species. There must be a way to put our heads together and
design research and monitoring programs that will help us to
detect changes as they are occurring - not so far down the
line that we are trying to figure out how to solve a problem
before we even know its cause.
For information on the Harriman Retraced Expedition e-mail: harriman2001@science.smith.edu
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