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For information on the Harriman Retraced Expedition e-mail: harriman2001@science.smith.edu |
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When the Harriman Alaska
Expedition traveled to Alaska in 1899, it included an
unprecedented assemblage of some of the nation's finest
scholars -- painters, poets, naturalists, geologists,
glaciologists, and a variety of other specialists. A
fundamental difference between the original Harriman Alaska
Expedition and this 2001 venture is there was no one
specializing in marine mammals on board. Not only that, but
expedition leader C. Hart Merriam, who was also the mammals
expert on that original expedition, didn't complete his
final report! There were two volumes each on insects and sea
stars, but no chapter on either mammals or marine
mammals. As a result we have no succinct account of the
status of marine mammals at that time. Giving a lecture on "Marine
Mammals" is a rather imposing task. Because we lump them
under those two simple words, we sometimes forget that
"marine mammal" in Alaska encompasses 25 different species.
Talking about seals, sea lions, killer whales and sea otters
-- not to mention beluga whales -- all in the same talk is a
little like covering mink, wolves, bears -- and oh,
by-the-way -- deer in the same short period of time. Add to
the complexity three declining species, an oil spill, an
endangered species, and an understanding of the importance
of these animals to subsistence hunters and it's a tall
order. So -- here goes. It's not possible to
cover all of the different species that are out there in one
lecture, so my focus will be on the animals we've heard the
most about and the ones with real conservation issues today
-- sea otters, sea lions, killer whales, harbor seals and a
little bit about belugas. The only two of these that I have
direct research experience with are harbor seals and
belugas. Sea Otters - When the
Harriman Expedition traveled through this part of Alaska 100
years ago, M. L. Washburn wrote, "The beautiful sea otter is
practically extinct." Thanks to legal protection, efforts to
translocate otters to other locations to accelerate their
recovery, and a little plain good luck, otters have
recovered and are present today throughout most of their
original range. At the time Vitus Bering sailed
to Alaska, biologists estimate that there were probably
300,000 sea otters in the North Pacific. That number was
reduced to a few hundred by the time the Harriman Alaska
Expedition visited. An estimated one million sea otters were
killed between 1742 and the early 1900s. In 1911, sea otters
were protected under the North Pacific Fur Seal Convention.
That began the long road to recovery. Some areas grew faster
than others, but populations in Prince William Sound and
Amchitka did particularly well. Starting in the 1960s and
1970s, efforts were begun to translocate otters from Prince
William Sound and Amchitka and to reestablish them
throughout their former range. Some of the translocations
were really successful, for example southeast Alaska where
the 150 sea otters moved there in 1969 may now exceed
20,000. Sea otters play an extremely
important ecological role in their environment. They are
known as a "keystone species." That means they have a
particularly important role in structuring the biological
communities around them. Sea urchins are a favorite food of
sea otters. When there are many urchins in an area, they
graze heavily on kelp and prevent large kelp beds from
forming, sometimes creating what are referred to as "urchin
deserts." When sea otters are present or move into an area,
they eat the urchins, allowing kelp beds to become
established. These kelp beds in turn provide food and
shelter for many small fishes and invertebrates. When sea
otter populations were so drastically reduced in the 1700s
and 1800s, many of the extensive kelp forests along Alaska's
coasts vanished with them. As sea otters have returned, so
have the kelp beds. In more recent times, sea otters
have faced other problems. In 1989, the Exxon Valdez
oil spill occurred. Perhaps 1000 sea otters were killed as a
result of the spill. Today, 12 years later, sea otters in
many areas have recovered to pre-spill abundance. However,
in some of the hardest hit areas their numbers have not
increased, mortality -- particularly of young animals -- is
higher than expected, and there is evidence of ongoing
exposure to oil. It is clear that sea otters have been more
sensitive to long-lasting effects of the spill than some of
the other animals that were also impacted by the
spill. More recently, substantial
declines of sea otters have been noted in the Aleutian
Islands. In some areas declines are greater than 50% in just
a few years. The cause for the decline is uncertain, making
it even more worrisome. Unusually high predation by killer
whales -- thought to occur because other resources such as
harbor seals and sea lions are less abundant -- is likely
the cause in some areas. However, it is not at all certain
that this is the cause throughout the area of
decline. Sea Lions -- Steller sea
lions are larger cousins of the California sea lion so often
seen in zoos and circuses and of the fur seals found in the
Pribilof Islands and harvested extensively for their fur.
Unlike sea otters and fur seals, coarse-furred Steller sea
lions were not the focus of commercial hunting for the fur
market during Harriman's time. To the best of our knowledge,
sea lions were quite abundant throughout their range in
Alaska until sometime in the 1970s. However, since then sea
lion numbers in western Alaska have dropped dramatically --
by more than 70% in some areas. Where once there were
thought to be more than 300,000 sea lions there may now be
fewer than 100,000. For example, counts of pups -- an index
of overall abundance and population health -- have dropped
from about 6,700 to only 800 at Marmot Island in the
northern Gulf of Alaska. Similar declines have been recorded
at the Pribilof Islands in the Bering Sea and in the Kuril
Islands of Russia. In fact, sea lions in the western Gulf of
Alaska have declined to such a degree that they are now
classified as an endangered species. The reasons for the original
decline -- and particularly the continuation of the decline
at this time -- are far from clear. Sea lions eat a diet
primarily of fish. 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. In fact, there is evidence
that the size and weight of same-age sea lions have declined
over the last 20 years, reinforcing the idea that food is
somehow limiting. However, that is almost certainly not the
whole story. In recent years environmental conditions have
changed again, and many of the forage fish species are once
again becoming abundant. None-the-less, the sea lion decline
continues. Other factors have been
suggested as possible contributors. Sea lions may be killed
both incidentally and intentionally in conjunction with
fisheries. Under certain conditions sea lions may be caught
in trawls. Because sea lions eat fish such as salmon, and
may damage not only fishing nets but also the fish caught in
nets, fishermen have sometimes shot them. Furthermore, some
of the kinds of fishes that sea lions eat are the same
fishes that people harvest in commercial fisheries in
Alaska. As commercial fisheries for species such as pollock
(which goes into fish sticks and surimi) have grown
dramatically during the last two decades, it is likely that
these fisheries have affected sea lions. However, scientists
are not sure exactly what the effect would be. On the one
hand, the fisheries compete with sea lions for the same
fish. On the other, the removal of large pollock -- which
are cannibalistic -- by the fishery may in some cases
actually result in more young pollock for the juvenile sea
lions to eat. 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 - protecting habitat, prevent
intentional and accidental killing, and minimize competition
with commercial fisheries. Killer whales --
Descriptions from the original Harriman Expedition reports
provide no descriptions of killer whales in Alaska. In fact,
information about killer whales in Alaska has not been
available until quite recently. In Alaska -- as elsewhere --
killer whales occur as two types: resident and transient
whales. Resident whales eat primarily fish -- such as salmon
and herring -- and transient killer whales eat marine
mammals such as seals, whales and porpoises. For many years
the separation of killer whales into these two types was
based on photo identification of individuals coupled with
observations of feeding, but it was not until the 1990s that
these observations were confirmed by genetics and other
chemical analyses. Some people suggest that killer
whales may be part of the explanation for ongoing declines
in marine mammals such as harbor seals and sea lions. While
it is unlikely that killer whales had anything to do with
the original declines that began more than 20 years ago, it
is entirely possible that predation may have a much greater
impact on the greatly reduced populations of
today. While many human activities do
not directly affect killer whales, some do. For example,
killer whales sometimes interact with long line fisheries by
taking commercially valuable fish such as halibut directly
off the fisherman's hooks. In the past this has resulted in
fishermen taking matters into their own hands and deterring
killer whales by shooting at them. More recently, changes in
the way fisheries are conducted have reduced this type of
interaction. In 1989, the Exxon Valdez oil spill
impacted killer whales in Prince William Sound.
Approximately a third of one of the most commonly seen
resident pods (known as AB pod) turned up missing in the two
years after the spill. This was compounded by the fact that
no new calves were born into the pod for several years
following the spill. Findings like this reinforce the need
to have good baseline data to use in evaluating the impacts
of human activities and mistakes, and to do our best to
avoid them. Harbor Seals - In the
original Harriman Expedition report, Grinnell wrote about
the Expedition's visit to a sealing camp in Yakutat Bay as
follows: "From the poles which support the roof of the
shelter hang delicacies of all sorts from the hair seals
body.… All of these things are eaten….." One
hundred years later, much the same can be said about harbor
seals in Yakutat Bay and other coastal communities along the
Gulf of Alaska. Harbor seals today are still food for many
coastal Native people. We don't have any direct information
from the original Expedition about the status of harbor
seals at that time. Clearly they were abundant enough to
bring several hundred people from the Yakutat region
together for the annual seal hunt. Today, the status of harbor
seals in the Gulf of Alaska region is mixed. In southeast
Alaska, these seals are stable or increasing. In contrast,
in the northern Gulf, harbor seal populations have declined
by as much as 60 to 80 percent in the last 25 years. Much
like sea lions, the causes for this decline are not clear.
It is likely that environmental changes in the late 1970s
made some species of shrimps and forage fish less available.
While there was probably plenty of food around for adults,
it may have been much more difficult for young,
inexperienced seals to get enough to eat in the absence of
abundant shrimps and small schooling high-fat fishes like
capelin, sand lance and eulachon. They were behind the
energetic eight ball. The question we face today is
why has that decline continued? It appears that
environmental conditions in the 1990s have become more
favorable for many of the forage fishes. Large schools of
capelin, eulachon and sand lance are once again seen along
the coast. In some parts of the northern Gulf -- near Kodiak
Island for example - it appears that harbor seals have begun
to increase. And yet harbor seals in Prince William Sound
are not increasing and in fact may still be declining
although at a much slower rate. Factors other than food
availability may also affect harbor seal abundance. In 1989,
the Exxon Valdez oil spill killed an estimated 300
harbor seals in Prince William Sound. In addition, fewer
pups may have been born in the year of the spill. Seals are
an important food of killer whales. As marine mammals have
declined, the food available to killer whales has decreased
substantially and there is more predation pressure on the
seals that remain. Harbor seals compete with fishermen for
salmon and are sometimes accidentally or intentionally
killed during fishing activities. Could disease be a
problem? Within the last decade, disease outbreaks in other
parts of the world have substantially reduced seal
populations. Harbor seals are food for humans and are hunted
throughout their range in Alaska. While it is certain that
hunting did not cause the original decline, could it be
contributing to the lack of recovery? My research since 1989 in Prince
William Sound has focused on trying to understand harbor
seal biology -- what they eat, where they go, how they dive,
how many there are -- and to tease apart possible causes,
not for the original decline, but for the ongoing decline
which continues today in Prince William Sound as well as to
understand how they were impacted by and recovered from the
Exxon Valdez oil spill. These studies -- conducted
not only by me but many other friends and colleagues -- have
included disease assays, reviews of contaminants, genetic
studies of how seals in Prince William Sound are related to
others in Alaska, health and body condition, diet, abundance
and trends, and satellite tagging of more than 100 seals of
all ages. What have we learned? We now
know that disease is not likely involved in the ongoing
decline. Although contaminants data are scarce, there is no
indication that they are unusually high and there is no
reason to implicate them in the decline. Prince William
Sound harbor seals are genetically distinct from others in
Alaska, suggesting they should be managed as a separate
stock. Harbor seal pups and yearlings are remarkably fat -
among the fattest in the world -- suggesting that food
availability is no longer responsible for ongoing declines.
We've learned that most harbor seals stay close to home,
never moving more than about 10 miles from their regular
haulouts. Some however -- especially young ones -- may move
hundreds of miles. Some return to their "home" haulouts and
others appear to stay in these remote areas. So where does this leave us
relative to answering our question? We've made a lot of
progress in determining what is important to a harbor seal,
how and where they live. We have a much better idea about
what is not the cause of the decline. But we still don't
know what is the cause -- and must continue looking for new
research tools and new ideas until we do. Recap of Issues - So,
perhaps it is useful to recap marine mammals issues that
face us today. Unlike circumstances at the time of the
original Harriman Alaska Expedition, overhunting is
not a problem for seals, sea lions and sea otters
today. However, the problems we do face are in some ways far
more complex and much less easily remedied. 2) Marine mammals and people
use many of the same species for food. This creates
direct interactions when marine mammals damage gear or
fishermen entangle marine mammals in their nets -- but it
also creates indirect interactions such as competition
for the same resource. It's not possible to have the
maximum number of marine mammals possible and also the
largest possible fisheries. People must develop policies
that balance the need to accommodate both marine mammals
and our need for fish to eat. 3) Marine mammals have
certain basic habitat requirements so that they can make
a living. People also need to make a living. As the
number of people increases and people increasingly impact
the world around them, it is important to incorporate the
needs of both people and marine mammals -- as well as
other wildlife -- in the way we manage and care for the
world we live in. It may be glib, but the marine
mammal problems we face today are more complex than the
wildlife issues apparent when Harriman and his expedition
visited Alaska. It is no longer a matter of simply stopping
the commercial overexploitation of these animals. Many of
the problems we face today have no clear-cut causes -- and
similarly the solutions to these problems are complex and
not at all clear. It will be necessary for all of us, no
matter how different our value systems or our philosophies,
to work together to find these solutions. The world will be
a better place if we do.
For information on the Harriman Retraced Expedition e-mail: harriman2001@science.smith.edu
Expedition
Log
1) In today's world, we
live with a variety of value systems. Marine mammals are
not only food for coastal Native peoples, but they are
also "watchable wildlife." We must find a way for both of
these value systems to exist in a western world that
hunts less and less and is critical of those who
do.
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