Library Index :: Endangered Species: Protecting Biodiversity :: Marine Mammals - The Marine Mammal Protection Act, The Endangered Species Act, Whales, Dolphins And Porpoises, Seals And Sea Lions

Marine Mammals - The Endangered Species Act

As shown in Table 2.1 in Chapter 2, there were only three marine mammal species on the first list of native TABLE 5.1 Endangered and threatened aquatic mammals, February 2006 Adapted from "Listed U.S. Species by Taxonomic Group," in Threatened and Endangered Species System (TESS), U.S. Department of the Interior, U.S. Fish and Wildlife Service, February 10, 2006, http://ecos.fws.gov/tess_public/SpeciesReport.do?kingdom=V&listingType=L (accessed February 10, 2006)endangered species issued in 1967. Over the following decades additional marine mammals were added as information became available on their population status. As of February 2006 there were fourteen species of marine mammals listed as endangered or threatened in the United States. (See Table 5.1.) Another fourteen foreign species were also listed.

TABLE 5.1
Endangered and threatened aquatic mammals, February 2006
U.S. species
Status* Type Common name Scientific name Note
*E=endangered; T=threatened; XN=nonessential experimental population
SOURCE: Adapted from "Listed U.S. Species by Taxonomic Group," in Threatened and Endangered Species System (TESS), U.S. Department of the Interior, U.S. Fish and Wildlife Service, February 10, 2006, http://ecos.fws.gov/tess_public/SpeciesReport.do?kingdom=V&listingType=L (accessed February 10, 2006)
E Whale Blue whale Balaenoptera musculus Baleen plate
E Whale Bowhead whale Balaena mysticetus Baleen plate
E Whale Finback whale Balaenoptera physalus Baleen plate
E Whale Humpback whale Megaptera novaeangliae Baleen plate
E Whale Right whale (northern & southern) Balaena glacialis incl. australis Baleen plate
E Whale Sei whale Balaenoptera borealis Baleen plate
E Whale Sperm whale Physeter catodon=macrocephalus Toothed
E Sea-lion Steller sea-lion Eumetopias jubatus Eared
E Seal Caribbean monk seal Monachus tropicalis Earless, presumed extinct
T Seal Guadalupe fur seal Arctocephalus townsendi Eared
E Seal Hawaiian monk seal Monachus schauinslandi Earless
T Otter Northern sea otter Enhydra lutris kenyoni Southwest Alaska stock
T (XN at San Nicolas Island) Otter Southern sea otter Enhydra lutris nereis California stock
E Manatee West Indian manatee Trichechus manatus Florida stock
Foreign species
E Whale Gray whale Eschrichtius robustus Western north Pacific Ocean
E Dolphin Chinese River dolphin Lipotes vexillifer China
E Dolphin Indus River dolphin Platanista minor Pakistan
E Porpoise Cochito (or vaquita) Phocoena sinus Mexico (Gulf of California)
E Seal Mediterranean monk seal Monachus monachus Mediterranean, northwest African coast and Black Sea
E Seal Saimaa seal Phoca hispida saimensis Finland
E Otter Cameroon clawless otter Aonyx congicus=congica microdon Nigeria
E Otter Giant otter Pteronura brasiliensis South America
E Otter Long-tailed otter Lontra= lutra longicaudis South America
E Otter Marine otter Lontra lutra felina Peru south to Straits of Magellan
E Otter Southern river otter Lontra=lutra provocax Argentina, Chile
E Manatee Amazonian manatee Trichechus inunguis South America
T Manatee West African manatee Trichechus senegalensis West coast of Africa
E Dugong Dugong dugon Palau (western Pacific Ocean)

Table 5.2 shows that $71.2 million was spent by federal and state agencies during fiscal year 2004 on specific marine mammal species listed under the Endangered Species Act (ESA).

In February 2006 the U.S. Fish and Wildlife Service announced its intention to conduct a status review to determine if polar bears should be proposed for listing under the ESA as a threatened species. The decision was driven by what the agency called "substantial scientific TABLE 5.2 The ten listed marine entities with the highest expenditures under the Endangered Species Act, fiscal year 2004 Adapted from "Table 1. Reported FY2004 Expenditures for Endangered and Threatened Species, Not Including Land Acquisition Costs," in Federal and State Endangered and Threatened Species Expenditures: Fiscal Year 2004, U.S. Department of the Interior, U.S. Fish and Wildlife Service, January 2005, http://www.fws.gov/endangered/expenditures/reports/FWS%20Endangered%20Species%202004%20Expenditures%20Report.pdf (accessed February 11, 2006)

TABLE 5.2
The ten listed marine entities with the highest expenditures under the Endangered Species Act, fiscal year 2004
Common name Species total
SOURCE: Adapted from "Table 1. Reported FY2004 Expenditures for Endangered and Threatened Species, Not Including Land Acquisition Costs," in Federal and State Endangered and Threatened Species Expenditures: Fiscal Year 2004, U.S. Department of the Interior, U.S. Fish and Wildlife Service, January 2005, http://www.fws.gov/endangered/expenditures/reports/FWS%20Endangered%20Species%202004%20Expenditures%20Report.pdf (accessed February 11, 2006)
Steller sea-lion (western & eastern) $42,557,321
Right whale (northern & southern) $12,369,623
West Indian manatee $9,861,677
Hawaiian monk seal $2,321,146
Sperm whale $2,270,475
Southern sea otter $734,386
Humpback whale $666,282
Bowhead whale $190,117
Finback whale $72,160
Blue whale $66,594
Sei whale $66,129
Guadalupe fur seal $1,000
    Total $71,176,910

FIGURE 5.1 A humpback whale, seen off the coast of Massachusetts. (AP/Wide World Photos.)and commercial information" indicating that polar bear populations may be imperiled.

As of February 2006 ESA-listed endangered and threatened marine mammals fell into five main categories: whales, dolphins and porpoises, seals and sea lions, sea otters, and manatees and dugongs.

WHALES

Whales are cetaceans, or marine mammals that live in the water all the time and have torpedo-shaped, nearly hairless bodies. (See Figure 5.1.) There are approximately seventy known whale species. The so-called "great" whales are the largest animals on Earth. In general, the great whale species range in size from thirty to 100 feet in length. There are thirteen whale species normally considered to be "great" whales. The blue whale is the largest of these species.

Whales are found throughout the world's oceans; however, many species are concentrated in cold northern FIGURE 5.2 Baleen plates "What Are Baleen Whales Like?" in Groups of Cetaceans, U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Marine Mammal Laboratory, March 3, 2004, http://nmml.afsc.noaa.gov/education/cetaceans/groupsofcetaceans.htm (accessed January 18, 2006)waters. Although they are warm-blooded and do not have fur, whales can survive in very cold waters because they have a thick layer of dense fat and tissue known as blubber lying just beneath the skin. This blubber layer can be up to a foot thick in larger species.

Most whales have teeth. A handful of species filter their food through strong flexible plates called baleen. (See Figure 5.2.) Baleen is informally known as "whalebone." It is composed of a substance similar to human fingernails. Baleen whales strain large amounts of water to obtain their food, mostly zooplankton and tiny fish and crustaceans. Nearly all of the "great" whales are baleen whales.

Many marine mammals can vocalize (make sound). Whales, in particular, use sound to communicate with each other and for navigational purposes. Some whale vocalizations are audible to human ears. These sounds are known as "whalesong."

Whales are believed to be highly intelligent. Scientists use a measure called the Encephalization Quotient (EQ) to compare the relative intelligence of different species. EQ is a number based on the ratio of brain mass to body mass. For example, the average human brain is much larger than needed just to operate an organism the size of a human. This extra capacity indicates higher intelligence. Likewise, the brains of cetaceans, such as whales, are larger than expected, indicating that they probably are very intelligent animals.

Imperiled Whale Populations

As of February 2006 seven whale species had been listed for protection under the ESA in U.S. waters: humpback whales, sperm whales, bowhead whales, northern right whales, sei whales, fin whales, and blue whales. In addition, the ESA covers southern right whales in the southern hemisphere and gray whales, a species that inhabits the northwest Pacific Ocean. All of these whales are considered "great" whales. All but the sperm whale have baleen plates.

The National Marine Fisheries Service publishes annual Stock Assessment Reports (http://www.nmfs.noaa.gov/pr/sars/) that provide population estimates for endangered whale species in U.S. waters. Surveys of all species are not conducted every year. As of February 2006 final reports were available for the Pacific Coast (2004), Atlantic and Gulf Coasts (2003), and Alaskan Coast (2003). Summing survey results from each report provides a rough estimate of the minimum population of each species:

  • Blue whale—1,692
  • Bowhead whale—8,886
  • Fin whale—5,004
  • Humpback whale—5,655
  • Northern right whale—291
  • Sei whale—72 (based on incomplete data)
  • Sperm whale—10,956

The NMFS notes that sei whale populations are extremely difficult to estimate. The whales prefer the open sea and rarely enter U.S. waters. Also, they tend to travel alone or in small groups, making them difficult to count.

The northern right whale is also known as the North Atlantic right whale because it is primarily found along the eastern coast of the United States. Although a few sightings have been confirmed in the North Pacific Ocean, there is no official estimate of that population. The National Marine Fisheries Service considers both populations to be of the same species. However, this opinion is disputed by some scientists. As of 2006 the World Wildlife Fund estimated that there were only 350 northern right whales in existence worldwide (http://www.worldwildlife.org/cetaceans/pubs/whales_current_status.pdf).

The northern right whale is the most endangered of the great whales. It was once the "right" whale to hunt because it swims slowly, prefers shallow coastal waters, and floats upon death. The species was nearly driven to extinction by whaling, which was banned in 1937 when the population had been reduced to an estimated 100. Despite decades of protection, the northern right whale population has not recovered, and as of 2006 the WWF estimated no population increase at all since the 1980s. Some scientists believe the animal is in grave danger of becoming extinct within only a few decades.

Threats to Whales

Whale populations are imperiled due to a long history of hunting by humans. As early as the eighth century, humans hunted whales for meat and whalebone (baleen). Whales were relatively easy for fishermen to catch because the animals spend a great deal of time at the surface of the water and provide a large target for harpoons. Advances in shipbuilding and the invention of the steam engine allowed fishermen greater access to whale populations, even those in Arctic areas that had previously been out of reach. By the nineteenth century, large numbers of whales were being killed for blubber and baleen. Blubber was rendered to extract whale oil, which was used to light lamps. Baleen was valued for making fans, corsets, and other consumer goods.

On December 2, 1946, the representatives of fourteen nations signed the International Convention for the Regulation of Whaling to form the International Whaling Commission (IWC). The signatory nations were Argentina, Australia, Brazil, Canada, Chile, Denmark, France, the Netherlands, New Zealand, Peru, South Africa, United Kingdom, United States, and the Union of Soviet Socialist Republics. The IWC was formed as a means to regulate the industry and limit the number and type of whales that could be killed. The Marine Mammal Protection Act of 1972 banned commercial whaling in U.S. waters. As of February 2006 there were sixty-six member nations in the IWC.

Centuries of whaling severely depleted whale populations. Low birth rates and high mortality rates due to a variety of factors have prevented many species from recovering. Like other marine animals, whales are endangered by water pollution and loss or degradation of habitat. However, the biggest threats to the northern right whale are believed to be entanglement in fishing gear and ship strikes.

ENTANGLEMENT IN FISHING GEAR

Entanglement of whales in fishing gear is a major problem, as noted by the National Marine Fisheries Service in "What Kinds of Fishing Gear Most Often Entangle Right Whales?" (Right Whale News, November 2005). The article describes recently published research related to whale entanglement. According to studies conducted in 2003 by the New England Aquarium, 71.9% of all known northern right whales have been entangled at least once in fishing gear. In 2005 researchers from Duke University investigated thirty-one cases of right whale entanglements and tried to identify the type of fishing gear involved in each case. They found that nearly a third of the whales had become entangled in lobster pot gear, mostly buoy lines. It was concluded that any type of fishing line that rises vertically in the water column poses a "significant entanglement risk" to northern right whales.

SHIP STRIKES

As shown in Figure 5.3 the National Marine Fisheries Service documented nearly 300 ship strikes on large whales off the U.S. East Coast between 1975 and 2002. Strikes on northern right whales are particularly troublesome because so few of the animals remain in existence. According to the NMFS fourteen northern right whales were confirmed killed by ship strikes between 1991 and 2002.

Figure 5.4 shows the locations of ship strikes on northern right whales that occurred between 1990 and 2000 along the North American coastline. Most strikes in U.S. waters occurred along the Massachusetts coast near Cape Cod and along the Georgia and northern Florida coastline. These areas are near or within critical habitats designated by the National Marine Fisheries Service for the whales. The southern critical habitat is the only known calving area of the northern right whale and is used from mid-November to mid-April. During calving season the NMFS performs aerial surveys and alerts ships about whales in their vicinity. In addition, federal law requires that ships remain 500 yards from right whales. Any sightings of dead, injured, or entangled whales must be reported to authorities.

In January 2006 the NMFS announced that a dead right whale calf had been reported by a fishing crew near the Florida shore. The animal was towed to shore and found to have large propeller marks and other wounds on its body, indicating it had been struck by a ship. The whale was male and only one month old.

In 2004 the National Marine Fisheries Service announced plans to propose rules requiring routing changes and speed limits for large vessels traveling in U.S. coastal waters frequented by northern right whales. The agency was still developing the rules in May 2005 when several environmental and animal groups petitioned the NMFS requesting that a temporary emergency regulation be imposed until the permanent rules could be issued. The petitioners asked for a speed limit of 12 knots (13.8 miles per hour) for all ships entering and leaving major East Coast ports during time periods of high use by right whales. In September 2005 the NMFS formally denied the petition. Two months later, three of the petitioners—the Defenders of Wildlife, the Humane Society of the United States, and the Ocean Conservancy—filed a lawsuit against the NMFS accusing the agency of "failing to protect" northern right whales as required by law. The lawsuit had not been resolved as of early 2006, when the petitioners filed papers that added the U.S. Coast Guard as defendants in the suit for their failure to adequately protect the whales in U.S. waters.

Whale Recovery Plans

Table 5.3 is a table published by the National Marine Fisheries Service in 2004 showing the status of recovery FIGURE 5.3 Confirmed ship strikes on large whales, by species, 1975–2002 "Ship Strikes by Species," in North Atlantic Right Whales and Ship Strikes off the U.S. East Coast, U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Northeast Fisheries Science Center, June 2, 2004, http://nefsc.noaa.gov/press_release/2004/advisory04.02.pdf (accessed February 11, 2006) FIGURE 5.4 Locations of confirmed ship strikes on North Atlantic right whales, 1990–2000 Donna Wieting and Aleria Jensen, "Ship Strikes During 1990–2000: North Atlantic Right Whales," in NOAA Fisheries' Proposed Strategy to Reduce Ship Strikes of North Atlantic Right Whales, U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Office of Protected Resources, 2004, http://www.nmfs.noaa.gov/pr/pdfs/shipstrike/ss_meetings.pdf (accessed March 28, 2006)plans for endangered whale species. As of February 2006 no recovery plans had been developed for bowhead or sperm whales. A draft recovery plan was published in 1998 for fin and sei whales and is undergoing revision. A recovery plan for the Pacific population of the northern right whale is under development. Final plans have been published for the blue whale (1998), humpback whale (1991), and the Atlantic population of the northern right whale (2005).

Table 5.3 also shows the recovery priority numbers assigned by the NMFS to each endangered whale species. Priority numbers can range from a value of 1 (highest priority) to 12 (lowest priority). The northern right whale has a priority level of 1, indicating strong concern about its abundance and chances for survival as a species.

The recovery plan for the North Atlantic right whale lists five goals for recovering the species. In order of importance, the goals are:

  • Significantly reduce sources of human-caused death, injury and disturbance
  • Develop recovery criteria based on demographic criteria
  • Identify, characterize, protect, and monitor important habitats

TABLE 5.3 Endangered and threatened whale species in the United States, 2004 Adapted from "Table 1. ESA-Listed Species under NMFS' Jurisdiction Including Listing Status, Trends, Priority Numbers, and Recovery Plan Status," in Biennial Report to Congress on the Recovery Program for Threatened and Endangered Species (October 1, 2002–September 30, 2004), U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Office of Protected Resources, 2004, http://www.nmfs.noaa.gov/pr/readingrm/ESABiennial/bien04.pdf (accessed February 14, 2006)

TABLE 5.3
Endangered and threatened whale species in the United States, 2004
Species/ESU/DPSa Date listed reclassified Endangered Species Act status Population/ESUa trend Recovery priority numberb Status of recovery plan
aESU=evolutionarily significant unit; DPS=distinct population segment.
bRecovery priority numbers are designated according to guidelines published by the National Marine Fisheries Service (NMFS) on June 15, 1990 (55 FR 24296). Priorities are designated from 1 (high) to 12 (low) based on the following factors: degree of threat, recovery potential, and conflict with development projects or other economic activity.
cDuring the timeframe for this report (2002–2004), two separate endangered species of right whale in the Northern Hemisphere were listed: the North Atlantic right whale (Eubalaena glacialis) and the North Pacific right whale (Eubalaena japonica). In January 2005, NMFS published a final rule to remove this distinction, thereby reverting to the previously used taxonomy of one endangered species—the northern right whale (Eubalaena glacialis)—for both North Pacific and North Atlantic populations. This report, therefore, uses the taxonomy at time of publication (northern right whale), noting that the taxonomic split may be reinstated in the future pending an upcoming status review and following ESA listing procedures.
SOURCE: Adapted from "Table 1. ESA-Listed Species under NMFS' Jurisdiction Including Listing Status, Trends, Priority Numbers, and Recovery Plan Status," in Biennial Report to Congress on the Recovery Program for Threatened and Endangered Species (October 1, 2002–September 30, 2004), U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Office of Protected Resources, 2004, http://www.nmfs.noaa.gov/pr/readingrm/ESABiennial/bien04.pdf (accessed February 14, 2006)
Whales
Blue whale 6/2/1970 Endangered Increasing 7 Completed 07/1998
Bowhead whale 6/2/1970 Endangered Increasing 9 None
Fin whale 6/2/1970 Endangered Unknown 7 Draft completed 07/1998—under revision
Humpback whale 6/2/1970 Endangered Increasing 3 Completed 11/1991
Northern right whalec 6/2/1970 Endangered Unknown 1 Completed 12/1991 (Atlantic), draft revision completed 2004; under development (Pacific)
Sei whale 6/2/1970 Endangered Unknown 3 Draft completed 07/1998—under revision
Sperm whale 6/2/1970 Endangered Unknown 7 None
  • Monitor the status and trends of abundance and distribution of the whale population
  • Coordinate federal, state, local, international and private efforts to implement the recovery plan

DOLPHINS AND PORPOISES

Dolphins and porpoises are toothed cetaceans. They are similar in shape; however, dolphins are generally larger than porpoises and prefer shallower, warmer waters. Dolphins tend to have long bottlenoses and cone-shaped teeth, as opposed to the flatter noses and teeth found in porpoises. Porpoises are members of the Phocoenidae family, which includes only six existing species. Dolphins are members of the Delphinidae family, a large family containing at least thirty known species. Most dolphin and porpoise populations around the world are hardy and not in danger of extinction. However, there are several species that are in trouble due to limited geographical distribution.

There are no U.S. species of dolphin or porpoises listed under the ESA. There are three foreign species listed as endangered as shown in Table 5.1: the Chinese River dolphin, the Indus River dolphin, and the cochito. The Chinese River and Indus River dolphins live in freshwater rivers in China and Pakistan, respectively. Their numbers are considered to be extremely small. In both cases extensive river damming, water drawdown due to human consumption, fishing, and pollution are blamed for the declines.

The cochito (or vaquita) is a kind of porpoise found only in the Gulf of California, a narrow body of water that separates the western Mexican mainland from the Baja California peninsula. This stretch of water is known in the United States as the Sea of Cortez and contains a great diversity of sea life. Cochitos are among the rarest of all marine mammals. According to the NMFS the cochito species has been nearly eliminated because so many of the animals have become entangled in fishing lines and drowned.

Protection of Prevalent Dolphins

Although they are not considered endangered or threatened, dolphins receive special consideration under U.S. law because of public concern about them. Dolphins are believed to be highly intelligent. They have a high encephalization quotient, perhaps the highest of any animal, besides humans. In addition, many people have been exposed to dolphins through marine entertainment parks, movies, television shows, and even personal encounters and sightings at tourist beaches. As a result, there is widespread public fondness for the animals.

Dolphins are protected by the Marine Mammal Protection Act and laws designed to limit their capture during tuna fishing. In 1990 large U.S. tuna canning companies announced they would no longer purchase tuna caught in a manner that endangered dolphins. The companies began labeling their products "Dolphin Safe" if their practices met specific standards established by the U.S. government. The International Dolphin Conservation Program Act, passed in 1992, reduced the number of legally permitted dolphin deaths. This act also made the United States a dolphin-safe zone in 1994, when it became illegal to sell, buy, or ship tuna products obtained using methods that kill dolphins.

SEALS AND SEA LIONS

Seals, sea lions, and walruses are considered pinnipeds. This designation comes from the Latin word pinnipedia, which means "feather or fin foot." Pinnipeds have fin-like flippers. Although they spend most of their time in the ocean, pinnipeds come on shore to rest, breed, give birth, and nurse their young. Areas preferred for breeding, birthing, and nursing are called rookeries. Pinnipeds not yet of reproductive age congregate at shore areas known as "haul-outs."

Seals and sea lions were hunted extensively during the 1800s and early 1900s for their blubber, fur, and meat. They continue to be imperiled by human encroachment of haul-out beaches, entanglement in marine debris and fishing nets, incidental catches, disease, and lack of food due to competition from humans for prey species.

Imperiled Seal and Sea Lion Populations

As of February 2006 there were four U.S. species and two foreign species of seals and sea lions listed under the ESA as shown in Table 5.1. The species are Caribbean monk seal, Guadalupe fur seal, Hawaiian monk seal, Mediterranean monk seal, Saimaa seal, and Steller sea lion. However, the Caribbean monk seal has not been sighted since 1952 and is presumed by the NMFS to be extinct.

GUADALUPE FUR SEALS

The Guadalupe fur seal breeds along the eastern coast of Isla de Guadalupe, Mexico. The island is approximately 400 miles west of Baja California. Although populations once included as many as 20,000 to 100,000 individuals, decline and endangerment resulted from extensive fur hunting in the 1700s and 1800s. The species was believed extinct in the early twentieth century, but a small population was discovered in 1954. NMFS scientists believe that the population is now on the increase.

HAWAIIAN MONK SEALS

Hawaiian monk seals are the only pinnipeds found on Hawaii and are endemic to those islands—that is, they occur nowhere else on Earth. Hunting was the primary cause of population decline. Hawaiian monk seals are also extremely sensitive to human activity and disturbance and now breed exclusively on the remote northwestern Hawaiian Islands, which are not inhabited by humans. Most females give birth to a single pup every two years, a reproductive rate lower than other pinniped species. The seals also fall prey to shark attacks and mobbing, violent mating acts perpetuated by adult male seals on females and pups of both sexes. Mobbing can result in fatal wounds or drowning. Scientists monitoring seal populations have relocated males guilty of repeated mobbing. The National Marine Fisheries Service Web site (http://www.nmfs.noaa.gov/) estimates the species population at around 1,400 animals.

MEDITERRANEAN MONK SEALS

Mediterranean monk seals inhabit remote areas around the Mediterranean Sea and northwest African coast. Most are found off the coasts of Mauritania/Western Sahara, Greece, and Turkey. According to the Seal Conservation Society there are only about 300 of the seals believed to be in existence. Mediterranean monk seals are very sensitive to disturbance. As humans have encroached on beaches and coastal areas, the seals have retreated to isolated caves.

In 1997 there was a massive die-off in a colony of the seals near Mauritania. The exact cause is not known; however, a virus or "red tide" event is generally blamed. This was a severe blow to the seal population. The animals are also purposely killed by fishermen, who consider them a nuisance and competition for limited fish stocks. Scientists fear that Mediterranean monk seals could become extinct with a few decades.

SAIMAA SEALS

Saimaa seals are found only in the cold waters of the Saimaa Lake system in eastern Finland. Their numbers were decimated by hunting over the centuries to the point of extinction. However, protection measures and fishing restrictions allowed some measure of recovery. In 2005 the World Wildlife Fund estimated that there were approximately 250 Saimaa seals remaining, making them one of the most endangered species in the world. Although the number of seals has been slowly increasing, they are still imperiled by entanglement in fishing nets when they leave protected areas of the lake.

STELLER SEA LIONS

Steller sea lions are large animals, with males reaching a length of about eleven feet and weight of 2,500 pounds. Females are significantly smaller. Steller sea lions are found in Pacific waters from Japan to central California, but most populations breed near Alaska and the Aleutian Islands. The breeding season is from May through July. The species was named after George Wilhelm Steller, a German scientist who studied the animals when he accompanied Russian explorer Vitus Bering on an expedition to Alaska in 1741.

The Steller sea lion population is divided into two stocks as shown in Figure 5.5. The eastern stock inhabits the area east of Cape Suckling, Alaska, and extends down the west coast of Canada and the U.S. mainland. The western stock is found west of Cape Suckling and extends across the Aleutian Islands to Russia and Japan.

According to the National Marine Fisheries Service, the western stock declined by 75% between 1976 and 1990. In April 1990 the Steller sea lion was listed under FIGURE 5.5 Distribution of the Steller sea lion, 2004 "Steller Sea Lion Distribution," in Steller Sea Lion Research, U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Marine Mammal Laboratory, March 8, 2004, http://nmml.afsc.noaa.gov/AlaskaEcosystems/sslhome/distrib.htm (accessed February 9, 2006)the ESA as threatened. Over the following decade the western stock continued to decline. This stock was declared endangered in 1997. The eastern stock increased at a rate of approximately 3% per year from the 1980s to the 1990s as shown in Figure 5.6. This stock remains classified as threatened.

Steller sea lion populations have declined for a variety of reasons including bycatch, illegal and legal hunting, predation, and disease. In addition, scientists believe that the animal has experienced reduced productivity due to the indirect effects of climate change and competition from humans for prey species (food fish).

In February 2004 the North Pacific Universities Marine Mammal Consortium reported that population declines may be explained by the fact that Steller sea lions had switched from eating fatty fish to fish with low fat content. In particular, their diet now consists primarily of pollock and flatfish, rather than herring. The low fat content of the new diet prevents Steller sea lions from building up enough blubber to survive and reproduce in their cold aquatic habitat.

The NMFS has conducted surveys of Steller sea lion populations since 1985. These surveys are primarily aerial. The most popular rookeries and haul-outs are photographed from the air, and the animals are counted from examination of detailed photographs. During the summer of 2005 the first Alaska-wide aerial pup count was conducted. The results are shown in Figure 5.7 for target rookeries in the Gulf of Alaska and the Aleutian Islands. Pup populations have declined dramatically since the 1980s. However, the numbers appeared to level off during the early 2000s.

As shown in Table 5.2 species-specific expenditures under the ESA for Steller sea lions totaled $42.6 million in fiscal year 2004, accounting for 60% of expenditures on all marine mammals. The Steller sea lion ranked third in spending among all species covered by the ESA. (See Table 2.8 in Chapter 2.)

FIGURE 5.6 Trends in Steller sea lion populations, through 2005 "Steller Sea Lion Decline," in Steller Sea Lion Research, U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Marine Mammal Laboratory, August 1, 2005, http://nmml.afsc.noaa.gov/AlaskaEcosystems/sslhome/DECLINE.htm (accessed February 9, 2006)

Recovery Plans for Seals and Sea Lions

Table 5.4 shows the status of recovery plans for endangered seal and sea lion species as of February 2006. No plans have been developed for Caribbean monk seals (which are believed to be extinct) or Guadalupe fur seals. A recovery plan published in 1983 for the Hawaiian monk seal is currently being revised. Likewise, a plan published in 1992 for the eastern and western stocks of the Steller sea lion is also being revised.

Table 5.4 also shows the recovery priority numbers assigned by the NMFS to each endangered seal and sea lion species. Priority numbers can range from a value of 1 (highest priority) to 12 (lowest priority). The Hawaiian monk seal has a priority level of 1, indicating strong concern about its abundance and chances for survival as a species.

SEA OTTERS

Sea otters are the smallest marine mammals in North America. They are furry creatures that grow to be about four feet in length and weigh up to sixty-five pounds. Otters are related to weasels and mink and are members of the Mustelidae family. Sea otters are almost entirely aquatic and inhabit relativly shallow waters along rocky coasts of the North Pacific Ocean. They eat a wide variety of marine invertebrate. Sea otters are the only animals, besides primates, known to use tools. They use rocks and other objects to smash open the hard shells of clams and crabs to get the meat inside.

FIGURE 5.7 Counts of Stellar sea lion pups at rookeries in Alaska and the Aleutian Islands, 1987–2005 Lowell Fritz, Tom Gelatt, Charles Stinchcomb, and Wayne Perryman, "Figure 3. Steller Sea Lion Pup Counts at Trend Rookeries in the Range of the Western Stock in Alaska by Region from the Late 1980s to 2005 in the Gulf of Alaska (A) and Aleutian Islands (B)," in Memorandum: Steller Sea Lion Pup Counts, June-July 2005, U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Northeast Fisheries Science Center, October 20, 2005, http://nmml.afsc.noaa.gov/AlaskaEcosystems/sslhome/sslpdf/SSLPupCount2005Memo.pdf (accessed February 11, 2006)

Although they inhabit cold waters, sea otters do not have a blubber layer to keep them warm. Instead, they have extremely dense fur coats and high metabolism rates. Their fur coats are waterproof, but only if kept clean. This makes sea otters very susceptible to water contaminants, such as oil.

Imperiled Otter Populations

At one time sea otters were very populous along the entire U.S. West Coast from Southern California to Alaska. Their thick and lustrous fur made them a target of intesive hunting for many centuries. By the dawn of the twentieth century sea otters were on the brink of TABLE 5.4 Endangered and threatened seal and sea lion species in the United States, February 2006 Adapted from "Table 1. ESA-Listed Species under NMFS' Jurisdiction Including Listing Status, Trends, Priority Numbers, and Recovery Plan Status," in Biennial Report to Congress on the Recovery Program for Threatened and Endangered Species (October 1, 2002–September 30, 2004), U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Office of Protected Resources, 2004, http://www.nmfs.noaa.gov/pr/readingrm/ESABiennial/bien04.pdf (accessed February 14, 2006)

TABLE 5.4
Endangered and threatened seal and sea lion species in the United States, February 2006
Species/ESU/DPSa Date listed reclassified Endangered Species Act status Population/ESUa trend Recovery priority numberb Status of recovery plan
aESU=evolutionarily significant unit; DPS=distinct population segment.
bRecovery priority numbers are designated according to guidelines published by the National Marine Fisheries Service (NMFS) on June 15, 1990 (55 FR 24296). Priorities are designated from 1 (high) to 12 (low) based on the following factors: degree of threat, recovery potential, and conflict with development projects or other economic activity.
cThis species was first listed as threatened via a 240-day emergency rule on 4/10/1990, then officially listed as threatened in a final rule on 11/26/1990. NMFS separated the species into western and eastern DPSs via a final rule on 5/5/1997, which maintained the eastern DPS as threatened and reclassified the western DPS as endangered.
SOURCE: Adapted from "Table 1. ESA-Listed Species under NMFS' Jurisdiction Including Listing Status, Trends, Priority Numbers, and Recovery Plan Status," in Biennial Report to Congress on the Recovery Program for Threatened and Endangered Species (October 1, 2002–September 30, 2004), U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Office of Protected Resources, 2004, http://www.nmfs.noaa.gov/pr/readingrm/ESABiennial/bien04.pdf (accessed February 14, 2006)
Seals and sea lions
Caribbean monk seal 3/11/1967 Endangered Presumed extinct 12 None
Guadalupe fur seal 12/16/1985 Threatened Increasing 10 None
Hawaiian monk seal 11/23/1976 Endangered Declining 1 Completed 03/1983; under revision
Stellar sea lion—eastern distinct population segment (DPS) 4/10/1990; 11/26/1990; 5/5/97c Threatened Increasing 10 Completed 12/1992; under revision
Stellar sea lion—western distinct population segment (DPS) 4/10/1990; 11/26/1990; 5/5/97c Endangered Declining 7 Completed 12/1992; under revision

extinction. In 1911 they became protected under the International Fur Seal Treaty and their numbers began to increase. By the mid-1980s there were approximately 110,000 to 148,000 sea otters around the world. Nearly half lived in the Aleutian Islands off the coast of Alaska. A much smaller population survived off the California coast.

Figure 5.8 shows the distribution of sea otters in 1995. Biologists recognize two distinct populations. The northern sea otter extends from Russia across the Aleutian Islands and the coast of Alaska south to the state of Washington. The southern sea otter is found only off the California coast.

Beginning in the 1960s the U.S. Fish and Wildlife Service began translocating (moving) limited numbers of sea otters from established locations to new locations within their traditional range of distribution. Attempted translocations to Oregon failed; however, translocated colonies were established at four locations: southeast Alaska, Washington, and San Nicolas Island, California, in the United States, and Vancouver, British Columbia, in Canada. (See Figure 5.8.)

SOUTHERN SEA OTTERS

Southern (or California) sea otters were designated a threatened species in 1977. At that time the animals inhabited a small stretch of coastline in central California. Scientists feared that this isolated population was in grave danger of being wiped out by a single catastrophe, such as an oil spill. In 1987 the U.S. Fish and Wildlife Service decided to establish an FIGURE 5.8 Distribution of sea otters, including locations of successful translocations, 1995 James L. Bodkin, Ronald J. Jameson, and James A. Estes, "Fig.1b. Current Distribution of Sea Otters Including Locations of Successful Translocations," in "Alaska," Our Living Resources: A Report to the Nation on the Distribution, Abundance, and Health of U.S. Plants, Animals, and Ecosystems, U.S. Department of the Interior, U.S. Geological Survey, National Biological Service, 1995, http://biology.usgs.gov/s+t/pdf/Alaska.pdf (accessed March 1, 2006) "experimental population" of sea otters at another location. Over the next few years 140 sea otters were moved, a few at a time, to San Nicolas Island. It was hoped that these translocated animals would thrive and develop an independent growing colony. Unfortunately, the venture achieved only limited success. Many of the otters swam back to their original habitat; others died, apparently from the stress of moving. During the early 1990s the transport effort was abandoned. The FWS spent $3.8 million on the program between 1987 and 1995.

In October 2005 the U.S. Fish and Wildlife Service proposed officially ending the translocation program and removing the designation of "experimental population" for the thirty or so sea otters remaining at San Nicolas Island. These animals would be considered threatened under the ESA, just like their fellow southern sea otters. The FWS collected comments on this proposal and expected to make a final decision in 2006.

Figure 5.9 shows annual survey results for southern sea otter populations from 1983 through 2005. These surveys were conducted during the springtime and count both independent otters and pups. As indicated in Figure 5.9 the populations have been gradually increasing. In FIGURE 5.9 Spring population counts of southern sea others, 1983–2005 "Spring Counts of Southern Sea Otters, 1983–2005," in California Sea Otter Surveys U.S. Department of the Interior, U.S. Geological Survey, western Ecological Research Center, 2005, http://www.werc.usgs,gov/otters/ca-surveydata.html (accessed February 2, 2006)spring 2005 just over 2,700 otters were counted (2,417 independent otters and 318 pups).

In 2005 the U.S. Geological Survey (USGS) reported that the California otter population declined during the late 1990s for a surprising reason. The USGS National Wildlife Health Center found that more than 40% of otter deaths occurring between 1992 and 2002 were the result of parasitic, fungal, or bacterial infections. (See Figure 5.10.) Toxicological analyses indicated that the immune systems of the animals had been damaged by water pollutants, particularly butyltins and organochlorine compounds, such as polychlorinated biphenyls (PCBs). Butyltins are tin compounds widely used as wood preservatives and as a component of ship paints.

A revised recovery plan was issued for threatened southern sea otters in 2003. The primary recovery objective is management of human acitivities that could damage or destroy habitat (for example, oil spills). The plan notes that southern sea otters can be considered for delisting under the ESA when the average population level over a three-year period exceeds 3,090 animals. As shown in Figure 5.9 population trends through 2005 are encouraging. Absent of any catastrophic events, the FIGURE 5.10 Causes of mortality in southern sea otterws, 1992–2002 Nancy Thomas. "Causes of Mortality in Southern Sea Otters," in Sea Otter Mortality, U.S. Department of the Interior, U.S. Geological Survey, National Wildlife Health Center, May 2005, http://www.nwhc.usgs.gov/publications/fact_sheets/pdfs/Seaoter2005.pdf (accessed March 9, 2006)

southern sea otter could achieve delisting within the next decade.

SOUTHWEST ALASKA DISTINCT POPULATION SEGMENT (DPS)

Translocations of northern sea otters to southeast Alaska, British Columbia, and Washington established thriving colonies in those areas. Likewise, populations in south central Alaska are believed to be stable or increasing. However, the stock of sea otters in southwest Alaska has experienced severe decline. In August 2005 the U.S. Fish and Wildlife Service listed the southwest Alaska distinct population segment (DPS) of the northern sea otter as "threatened" under the ESA.

The southwest Alaska DPS extends from the tip of the Aleutian Islands to a point roughly beneath the letter "A" in the word "Alaska" in Figure 5.8. Populations in this area have decreased dramatically since the mid-1980s, when more than 70,000 sea otters inhabitated southwest Alaska. Table 5.5 shows the decline in sea otter populations across the region since the 1980s and early 1990s. According to Douglas Burn in "Alaska Sea Otters: The Southwest Decline Continues" (February 2004, http://alaska.fws.gov/media/seaotter2004/fact-sheet.pdf), surveys conducted in 2003 in the Aleutian Islands found that sea otter counts were down by 63% from the year 2000. Scientists are not sure of the reasons for the decline; however, there is suspicion that orca whales are preying on the otters.

TABLE 5.5 Survey results for sea otter populations in southwest Alaska, 1986–2001 "Table 1. Southwest Alaska Sea Otter Survey Results, 1986–2001," in Sea Otter Declines in Southwest Alaska: A Growing Concern, U.S. Department of the Interior, U.S. Fish and Wildlife Service, October 2001, http://alaska.fws.gov/media/sotter/declineotter.pdf (accessed February 13, 2006)
TABLE 5.5
Survey results for sea otter populations in southwest Alaska, 1986–2001
Location Year Count or estimate Decline
SOURCE: "Table 1. Southwest Alaska Sea Otter Survey Results, 1986–2001," in Sea Otter Declines in Southwest Alaska: A Growing Concern, U.S. Department of the Interior, U.S. Fish and Wildlife Service, October 2001, http://alaska.fws.gov/media/sotter/declineotter.pdf (accessed February 13, 2006)
Aleutian Islands 1992 8,044
2000 2,442 70%
North Alaska peninsula 1986 9,061-13,091
2000 5,756 36-56%
South Alaska peninsula 1986 15,346-17,835
2001 1,344 91-92%
Kodiak Archipelago 1989 13,526
1994 9,817
2001 5,893 56%

Foreign Species of Sea Otters

As shown in Table 5.1 there were five foreign otter species listed as endangered under the ESA as of February 2006. They populate areas of Africa and South America. All species are imperiled by illegal hunting for meat and fur. Loss of habitat and water pollution are also threats to their survival. The southern river otter of South America is in dire danger of extinction. According to the International Union for Conservation of Nature and Natural Resources' IUCN Red List of Threatened Species, the species is found in only a handful of isolated areas, all of which are threatened by massive deforestation and expanding fishing operations.

MANATEES AND DUGONGS

Manatees are large stout mammals that inhabit fresh waters and coastal waterways. They are from the Sirenian order, along with dugongs. There are only five Sirenian species, and all are endangered or extinct. Scientists believe that Steller's sea cow, the only species of cold-water manatee, was hunted to extinction during the 1700s.

The West Indian manatee, also known as the Florida manatee, primarily swims in the rivers, bays, and estuaries of Florida and surrounding states. (See Figure 5.11.) As shown in Table 5.1 this species is listed as endangered under the ESA.

Manatees are often called "sea cows" and can reach weights of up to 2,000 pounds. They swim just below the surface of the water and feed on vegetation. West Indian manatees migrate north in the summer, though generally no farther than the North Carolina coast. In 1995 a manatee nicknamed "Chessie" made headlines by swimming all the way to Chesapeake Bay. Eventually biologists, concerned about his health in cooler waters, had him airlifted back to Florida. During the winter many manatees huddle around warm water discharges from FIGURE 5.11 A Florida manatee nurses its calves. (© Douglas Faulkner/Corbis. Reproduced by permission.)power plants and other industrial facilities. Although this can keep them warm, scientists worry that overcrowding in small areas makes the animals more susceptible to sickness.

Imperiled Manatee Populations

Each year during cold weather biologists conduct surveys to determine the number of Florida manatees remaining in the wild. The numbers are estimates based on surveys conducted at known wintering habitats. The latest survey was performed in January 2005 and found 3,143 manatees living along the Florida coast. This number is up from 1,267 reported in 1991. Many manatees have scars on their backs from motorboat propellers—these allow individual manatees to be recognized. In a press release entitled "FWC Biologists Release Preliminary 2005 Manatee Mortality Data" (January 6, 2006, http://www.floridamarine.org/news/view_article. asp?id=26330), the Florida Fish and Wildlife Conservation Commission noted that "the manatee population appears to be doing fairly well" throughout much of the state. Populations in the northern and central parts of Florida are increasing or remaining stable. However, manatees in southwest Florida face extra threats due to their exposure to red tide incidents (proliferation of harmful algae in the water). Scientists warn that these populations "could decline significantly."

Threats to Manatees

Manatees are imperiled for a variety of reasons. Although they can live for fifty or sixty years, their birth rate is low. Mature females bear a single offspring only every three to five years. Many baby manatees die in the womb or soon after birth for unknown reasons. These are called perinatal fatalities. Disease, natural pathogens, and cold water temperatures are also deadly. However, motorboat strikes are the major documented cause of manatee mortalities. Manatees are large and swim slowly at the surface of the water. They often cannot move away from boats quickly enough to avoid being hit. Environmentalists have tried to protect manatees from boat collisions, and have successfully had several Florida waterways declared boat-free zones. There are also areas where boaters are required to lower their speeds.

During 1995 and 1996 a pneumonia-like virus killed more than 100 manatees in southern Florida. The disease, according to marine microbiologist John H. Paul and his colleagues, was caused by a red tide that occurred when toxin-producing aquatic organisms called dinoflagellates bloomed in large quantities ("A Filterable Lytic Agent Obtained from a Red Tide Bloom That Caused Lysis of Karenia Brevis [Gymnodinum breve] Cultures," Aquatic Microbial Ecology, 2002). The Florida Marine Research Institute reported in 2006 that human-related activity accounted for 30% of all manatee deaths between April 1974 and June 2005, most from watercraft collisions. (See Figure 5.12.) The cause of death could not be determined in 28% of the cases. Nonhuman causes were blamed for 42% of the deaths.

A lawsuit by the Save the Manatee Club and other environmental and conservation organizations in 2000 successfully required the state to implement new low-speed zones for boats and establish safe-haven areas for manatees. The rules were immediately challenged by individual boaters and boating organizations; however, the restrictions were upheld by Florida courts in 2002.

Foreign Manatee and Dugong Species

There are two surviving foreign species of manatees found in western Africa and in and around the Amazon River in South America. Both species are designated under the ESA as endangered and are in grave danger of extinction due to illegal hunting, deforestation, habitat destruction, and water pollution. The only remaining dugongs live in the coastal waters of the Indian Ocean FIGURE 5.12 Causes of mortality in Florida manatees, April 1974–June 2005 Adapted from "Summary Report by County, Month, Year and Probable Cause of Death," in Manatee Mortality Database, Florida Fish and Wildlife Conservation Commission, Fish and Wildlife Research Institute, 2005, http://research.myfew.com/manatees/ (accessed January 20, 2006)and Pacific Ocean. Their populations are also considered imperiled. Dugongs around the tiny island of Palau in the western Pacific Ocean are considered endangered under the ESA.

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