|This paper was written as part of the 1999 Alaska Ocean Sciences Bowl high school competition. The conclusions in this report are solely those of the student authors.|
in part by each of the following:
Chugiak High School
IntroductionThe Steller sea lion, Eumetopias jubatus, is a pinniped whose primary locations include the coastal areas along the rim of the North Pacific Ocean, from Hokkaido, in northern Japan, northwards as far as 66 degrees N in the Bering Sea and thence along the coast of Alaska southwards as far as the Santa Barbara Channel Islands, off of California (Bonner, 1994). Seventy percent of Stellers live in Alaska. The Steller is the largest member of the family Otariidae. When born, a Steller sea lion is chocolate brown with a frosty appearance. This is because the tips of their hair are colorless. The color, however, eventually fades to a tan or golden brown, often becoming chocolate brown on the flippers and the underside of the body. Adult females average about 260 kilograms, whereas the males weigh in excess of 800 kilograms. An average male Steller is about 282 centimeters in length, while an average female measures roughly 228 centimeters (Hoover, 1988).
The female Steller begins to breed between the age of three and six. Males are also capable of breeding at this age, but tend not to mate until the age of about ten because of territorial competition. The gestation period for a Steller is approximately one year; they mate in July and give birth at roughly the same time the following year.
Steller sea lions most often live in rookeries. Rookeries are usually on relatively remote islands where access by predators is limited. Important breeding colonies are located on the Kuril Islands, Kamchatka; on islands in the Sea of Okhotsk; the Aleutian Islands; on the Pribilof Islands (their northernmost breeding station); on the Alaskan-British Columbian coast; and in Oregon (Bonner, 1994).
The main sources of food for Steller sea lions include pollock, flounder, herring, capelin, Pacific cod, salmon, rockfish, sculpins, and other invertebrates such as squid and octopus (Grolier's Multimedia Encyclopedia, 1992).
In recent decades, the population of Steller sea lions in the Gulf of Alaska and the Bering Sea has been greatly declining. Overall, the population has been estimated to have decreased from about 250,000 in the late 50's, to around 65,000 in 1989, and to less than 40,000 animals today (See Table 1, Table 2, Table 3). The decline in some areas has been estimated to be over 90% (Bonner, 1994). In 1990, the National Marine Fisheries Service described the species as being threatened under the Endangered Species Act (Spiess, 1998). In 1997, the Steller population in their Western Range (from the Gulf of Alaska to Russia) was designated endangered. Numerous theories have been presented as to why Steller populations are plummeting so rapidly, but the complete answer still remains a mystery. Some scientists blame the Greenhouse Effect, a phenomena in which gases such as water vapor, carbon dioxide, and methane, found in the Earth's lower atmosphere, are slowly but steadily increasing the surface temperature of the planet (Grolier's Multimedia Encyclopedia, 1995). Others are saying that a reduced birthrate and a decline in infant survival are the reasons for the decline (Perlov, 1991). While we agree that these are all contributing factors in the population decline of Steller sea lions, we believe that since there is still no definite explanation as to why this species is disappearing, the reasoning for this trend is open to debate and interpretation.
This lack of definitive explanation leads us to our theory on the decline of Steller sea lions. We believe that the reduced numbers of Steller sea lions can be linked to two main causes; the fisheries of Alaska that dominate the Alaskan economy, and the whaling industry which took the world by storm beginning in the 1750's. Before going further into the latter subject, a little whaling history is needed.
WhalingThe whaling industry actually first began in 1100 with the Basques. The Basque whalers, considered to be the first large-scale whalers, quickly moved their range out into the North Atlantic and then to the New World, in waters just off of Labrador. In 1650, due to a demand for whale oil and baleen, used for "whalebone" corset stays and skirt hoops, shore whaling began off the coast of Long Island, New York (Bockstoce, 1986). This represented the beginning of the American whaling industry. In 1789, after the end of the American Revolution, which had hindered the American whaling industry for a little over a decade, the British ship, Emilia, became the first vessel to enter the Pacific Ocean. In 1819, whale ships reached Hawaii, and in 1848, the Superior became the first whale ship to sail through the Bering Strait. Due to large quantities of bowhead whales in this area, by 1852, there were more than 220 whale ships stationed in the Bering Strait (Francis, 1990). At the end of the nineteenth century, the machinery of industrialism was applied to whaling, with devastating results. Armed with exploding harpoons, rapid catcher boats, and large factory ships, whalers ransacked the world's waters for prey. Modern-style whaling annihilated the whales. Between the 1920's and the 1970's, more than two million were killed, and several species were reduced to the verge of extinction (Francis, 1990). By this time, the populations of whales had been diminished to the extent of rendering the practice of whaling much less profitable. The United States and the European nations--with the exception of Norway and Iceland--gradually ended their whaling industries. By the 1960's, only the Soviet Union and Japan maintained factory-ship fleets (Grolier Encyclopedia, 1995). In 1982, members of the International Whaling Commission, created in 1946, agreed to a moratorium on commercial whaling, a breathing space to assess the condition of the world's whales (Francis, 1990). However, the damage had already been done.
This great harvest of whales inevitably led to an immense decrease in whale populations, considering that an estimated 19,142 bowhead whales alone were killed between 1848 and 1915 (Bockstoce, 1980). This enormous decrease in whale population had a great impact on the ecosystems around them.
Whales are extremely large creatures with large diets. Depending on the suborder of the whale, the diet can consist of anything from minuscule plankton to large salmon. Mysticetes, or baleen whales, such as gray whales and bowhead whales, have diets primarily composed of plankton and krill. Because of the huge demand for baleen, used in corsets, baleen whales were the primary targets for whalers, excluding the main odontocete, or toothed whale, the prized sperm whale, which was severely hunted for its large deposits of high quality oil and spermaceti, a waxy substance used to make candles (Francis, 1990). We believe that the vast reduction of whales in Alaskan waters led to a considerable growth increase in the numbers of planktonic creatures. This in turn, led to a more abundant food source for fish, such as salmon and pollock. Because of this enriched food supply, and because of reduced fatality rates due to lowered numbers of predators such as odontocetes, the fish population experienced a considerable increase. Due to the increased numbers of fish (the primary food source of Stellers), the Steller sea lion community in Alaska experienced the same boom in population as pollock and salmon. This population rise in Stellers was due mainly to a more plentiful diet. More pups were born, and due to a large supply of food, more pups survived. The species continued to thrive well into the 1970's, when all of a sudden, the populations started to drop. We believe that this complete turnaround was due to the rapidly evolving fishing industry.
Fishing IndustryToday, human intervention is most probably accentuating the natural downward cycle forcing the Steller population to extremely low numbers, well outside the optimum sustainable population range (See Table 7). Probably the single most important factor leading to the Steller's decline is their interaction with commercial fisheries. Hoover notes that the "Steller sea lions have been ranked among the top three of 26 species of Bering Sea marine mammals likely to interact with fisheries, on the basis of the sea lions' heavy reliance on species of fish of similar size classes to those sought by fisheries, their moderately diverse diet, and their tendency to use regular feeding without other regular or optional feeding grounds" (Hoover, 1988). In the Gulf of Alaska, the Steller sea lions interact with the fisheries in much of the same ways. Generally, the Stellers compete with the fisheries for groundfish such as pollock, cods, flatfishes, and rockfishes, as well as herring and salmon (Hoover, 1988). While interaction with the fisheries also includes direct (i.e. shooting by frustrated fishermen) and incidental (i.e. lions caught in nets) killings, decreased population is probably due primarily to the competition for the above named fish because increased numbers of carcasses are not being found (Hoover, 1988).
"The Steller sea lion began an alarming slide toward extinction in the late 1970's. Since then, the Alaska population has fallen more than 70 percent to less than 40,000 animals today. While the population is slipping across the Alaska coast, the western stock--from Prince William Sound out to the Aleutian Chain--has fallen most dramatically. In the same waters where trawlers pull 2.5 billion pounds of pollock from the sea each year, biologists believe sea lion pups are dying for lack of food. Adults appear to be undernourished" (Spiess, 1998). "Since the 1970's, pollock has evolved from a small-scale fishery to a massive annual take of 2.5 billion pounds of fish worth about $650 million. As more boats headed into the waters and critical areas were being overfished, the harvest concentrated on the rich waters in the eastern Bering Sea. Biologists believe 70 percent of the pollock catch comes from critical Steller habitat" (Spiess, 1998). When a population grows, more food is necessary to ensure the continued health of the species. However, when that food source is depleted, the species is no longer capable of feeding all of its numbers, and so the species experiences a rapid decline in population. This is what we believed happened to the Steller sea lion population in Alaska. After the whaling epidemic of the 1800's and early 1900's, pollock populations rose and in turn, Steller populations rose. Until the 1970's, the Steller sea lions had a vast quantity of food available to them because pollock wasn't in very high demand. Nevertheless, when pollock became a major commodity for the fishing industry in the 1970's, pollock was severely overfished, and pollock numbers drastically decreased (See Table 4). With a depleted food supply, Stellers were no longer able to feed themselves adequately, and so more and more sea lions died due to undernourishment. Another clue that Stellers are literally starving their population away is that Stellers observed in the Central Gulf of Alaska tend to grow more slowly and reach sexual maturity later than in the past, suggesting decreased food availability (Bonner, 1994). Decreased food amounts may also lead to decreased fetal survival rates, weak pups being born, and less opportunity for mating (Bonner, 1994, See Table 5, Table 6).
SolutionsAlthough it would be easy to say that a solution to this dilemma is no problem, that would not be the case. The obvious conclusion would be to completely stop fishing pollock, so that the populations of pollock could increase, and in turn, the populations of Steller sea lions could increase as well. But things aren't that easy. The fishing industry is one of the staples of the Alaskan economy. Thousands of families depend on the fishing season for their year's keep. It would be unjust to tell them that they can no longer do their jobs, and feed their families. But something must be done. It would be truly sad to just sit back and let two beautiful creatures be exploited to the point of extinction. However, the way in which we must proceed is a delicate matter. We believe that a compromise could be reached between the biologists and the fishermen. Maybe sanctuaries could be established in certain areas, where no pollock fishing would be allowed, so as to protect the Stellers and pollock, and to ensure that pollock is not overfished. Maybe the fishing guidelines could be redrawn so that the numbers of pollock allowed to be caught would be reduced. Whatever way we go about solving the problem will not be easy. There will be opposition on both sides. But hopefully, an agreement will be reached so that we can start to think about helping bring back the numbers of Steller sea lions to where they once were.
References1. Bockstoce, John R. Whales, Ice and Men: The History of Whaling in the Western Arctic. University of Washington Press, Seattle and London, 1986.
2. Bonner, Nigel. Seals and Sea Lions of the World. NY, NY: Facts on File Inc., 1994.
3. Ferrero, R.C. and L. W. Fritz. Comparisons of Walleye pollock. National Oceanic and Atmospheric Administration. September, 1994.
4. Fritz, Lowell W. AFSC Processed Report 93-13: Estimated Catches of Walleye Pollock, Atka Mackerel and Pacific Cod Within Critical Habitat of the Steller Sea Lion. October, 1993, National Marine Fisheries Service.
5. Hastings, Kelly. Population Status of Steller Sea Lions on the Furallones. http://www.isc.apc.org/prbo/observer112/Pinniped.html.
6. Lentfer, Jack W., ed., Selected Marine Mammals of Alaska: Species Accounts with Research and Management Recommendations. Article by Anne A. Hoover, "Steller Sea Lion", 1988, Marine Mammal Commission, Washington, D.C.
7. Miller, R. V. AFSC Processed Report 91-14: Present Abundance of Steller Sea Lions in the USSR. Alaska Fisheries Science Center; National Marine Fisheries Service; US Department of Commerce, April 1991.