puffin home

Harriman Expedition Retraced


expedition log



Kathryn Frost

Marine Mammals in the Gulf of Alaska: Conservation Issues and More

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.

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.

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

Home | 2001 Expedition | 1899 Expedition | Maps | Log | Educators and Students | Film | Century of Change | After Expedition | About This Site