Return-path: <firstname.lastname@example.org> Received: from whale.simmons.edu by VMSVAX.SIMMONS.EDU (PMDF V5.0-4 #8767) id <01HXY7UK5B4G8ZHFDN@VMSVAX.SIMMONS.EDU> for whalenet@VMSVAX.SIMMONS.EDU; Wed, 22 Nov 1995 16:24:44 -0400 (EDT) Received: from 126.96.36.199 (dmn1-30.usa1.com) by whale.simmons.edu (4.1/SMI-4.1) id AA29280; Wed, 22 Nov 1995 16:22:08 -0500 (EST) Date: Wed, 22 Nov 1995 20:25:58 +0400 From: Michael Williamson <email@example.com> Subject: Info: Pacific marine mammals To: whalenet@VMSVAX.SIMMONS.EDU Message-id: <9511222122.AA29280@whale.simmons.edu> Organization: WhaleNet MIME-version: 1.0 X-Mailer: Mozilla 1.1N (Macintosh; I; 68K) Content-type: text/plain; charset=iso-8859-1 Content-transfer-encoding: 8bit X-Url: http://kingfish.ssp.nmfs.gov/olo/unit23.html http://kingfish.ssp.nmfs.gov/olo/unit23.html> UNIT 23 PACIFIC MARINE MAMMALS > > INTRODUCTION > > In 1791, New England whalers first rounded Cape Horn, and by 1820 > they had pressed on to Hawaii where they began to take on > provisions and recruit men for their northern summers in > bowhead-whale-rich Alaskan waters. An average bowhead yielded 100 > barrels of oil, making the fishery attractive to whalers, even > though over 100 whaling ships were lost between 1826 and 1900 due > to crude charts and icy Alaskan waters. > California's whaling industry is documented back to the mid 1850's > when shore whaling stations were set up, ranging from the state's > northernmost border at Crescent City south to San Diego. With a > hunting range of about 10 miles, shore fisheries harvested only > whales frequenting the nearshore waters. The northern stations > targeted humpback whales at first, but included gray whales in > short order; southern stations took advantage of the natural > southward migration patterns of the gray whale. > Sea lions, reported to be abundant along the California coast and > offshore islands before 1860, were also exploited for food, oil, > and clothing. From 1860 to 1870, thousands were harvested for oil. > In 1915 and 1916, a bounty of $2.00 each was paid on 4,074 sea > lions. From the late 1920's until passage of the MMPA in 1972, > commercial and sport fishermen were allowed to kill sea lions that > interfered with their fishing operations. > The Hawaiian monk seal is thought to have been abundant when > Europeans discovered the Hawaiian Islands. However, > overexploitation made this seal the endangered species it is today. > Before passage of the Marine Mammal Protection Act and the > Endangered Species Act the only protective measures for marine > mammals were through the International Whaling Commission (IWC), > and those were for only certain depleted large whales. > All marine mammals are now protected by the MMPA and by the ESA. > Other management responsibilities are addressed in the Magnuson > Fisheries Conservation and Management Act, which extends the > jurisdiction of the MMPA throughout the U.S. exclusive economic > zone, and the Whale Conservation Act, which was intended to further > aid the recovery of whales. > > SPECIES AND STATUS > > At least 50 species of marine mammals occur in U.S. Pacific waters > (36 whales, dolphins, and porpoises; 11 seals and sea lions; > walrus; polar bear; and sea otter). Fourteen are commonly seen > along the coast (gray whale, bottlenose dolphin, harbor seal, and > others), whereas the 28 others frequent offshore or remote island > waters (beaked whales, ribbon seal, Hawaiian monk seal, and > others), or are severely reduced in numbers and thus seldom seen > (North Pacific right whale and Guadalupe fur seal, for example). > Table 2<%12>3<%0>-1 summarizes what is known about the status and > trends of several Pacific marine mammals. Brief discussions below > for selected species give additional data on distribution, current > and historical abundance, and population trends. > > Eastern Tropical Pacific (ETP) Dolphins > > Four species spotted, spinner, striped, and common dolphin (12 > stocks) are incidentally taken in the international fishery for > yellowfin tuna in the tropical Pacific waters off Mexico and > Central America. Until the 1980's, the U.S. maintained the largest > fleet in the fishery. Although mortality of dolphins was in the > tens and hundreds of thousands for the first decade of the fishery, > that mortality has been reduced in recent years (less than 20,000 > were killed in 1992). Because these four species also occur in U.S. > waters, and because the U.S. was the major market for the fishery, > NMFS initiated assessments of these populations. > Three stocks of spotted dolphin are currently recognized in the > ETP: the northeastern stock, the west/south stock, and the coastal > stock. Based on analyses of five years of research vessel data, the > population size for the northeastern stock is estimated to be > 731,000 individuals, for the west/south stock, 1,298,000 indi- > viduals, and for the coastal stock, 36,000 individuals. Eastern > spinner dolphins number 632,000, whereas the whitebelly spinner > dolphins number about 1,019,000. Stock specific estimates of common > dolphin abundance were based on too few sightings and are > considered unreliable; therefore in 1992, NMFS initiated research > vessel surveys designed specifically to obtain estimates of > abundance for common dolphin stocks. A pooled estimate of 3,093,300 > encom- passes the northern, central, and southern stocks of common > dolphin. Striped dolphin are currently considered to consist of a > single stock in the ETP with an estimated abundance of 1,918,000 > individuals. > Relative abundance estimates have also been generated from dolphin > sightings obtained using tuna vessel observer data (TVOD). Trends > in these estimates suggest that most dolphin stocks declined in the > 1970's, but have been relatively stable since the 1980's. The > northern stock of common dolphin is an exception. A significant > decrease in sightings has been observed in the ETP. The cause(s) of > the decrease in this region is not clear, but it has been suggested > that if the decline cannot be attributed to fishery mortality, then > it may have been caused by a shift in distribution in response to > environmental fluctuations. > > Harbor Porpoise > > Harbor porpoise appear to have more restricted movements along the > western U.S. coast than along the eastern coast. Studies have shown > some indication that harbor porpoise do not mix freely between > California, Oregon, and Washington. Regional differences have also > been seen within California; therefore, it has been recommended > that animals inhabiting central California be treated as a separate > stock for management purposes. > The current estimate for the central California stock is 3,806. The > combined estimate for northern California, Oregon, and Washington > outer coast is 45,713, and for the waters of Puget Sound is 3,352. > The species was once abundant in Wash-ington's inland waters, > especially southern Puget Sound, but its abundance is very low > there now. Harbor porpoise tend to concentrate at the mouth of the > Columbia River and at many other bays. The kill of harbor porpoise > is largely limited to set gillnet fisheries for halibut and > rockfish in central California (coastal setnets are not allowed in > northern California, and harbor porpoise do not inhabit southern > California). In recent years, the kill has decreased primarily as > a result of decreased fishing effort in areas of high harbor > porpoise concentrations. > > Bowhead Whale > > The endangered bowhead whale has ranged as far as the polar ice > fields of the Northern Hemisphere. Total pre-whaling abundance is > believed to be 12,000-18,000, but by 1900 it was probably in the > low thousands. In the U.S. western Arctic, 18,650 bowheads were > killed by Yankee whalers between 1848 and 1914 from a population > estimated at less than 20,000. The take by Alaska Eskimos has > averaged 20-40 whales per year since 1914. The present population, > 7,500, is about 41% of its 1848 carrying capacity. The stock has > been increasing since commercial whaling ended and has grown by > 3.1%/year since 1978 (Fig. 2<%8>3<%0>-1). > > Gray Whale > > Still listed under ESA as endangered is the western stock of North > Pacific gray whales. The eastern North Pacific or California > stock was heavily exploited by Yankee whalers in the last half of > the 19th century. The 1987/88 stock size, 20,869, is believed to be > equal to or larger than the estimated size of the 1846 population > of 15,000-20,000, but below estimates for a carrying capacity of > 24,000. Population growth rate was 3.3%/year between 1967 and 1988, > despite a subsistence catch of 167 whales per year by the former > Soviet Union (Fig. 2<%8>3<%0>-2). In light of this recovery, the > Secretary of Commerce has determined that the eastern Pacific stock > should be removed from the ESA's list of endangered and threatened > wildlife. > > Humpback Whale > > The endangered humpbacks in the eastern North Pacific Ocean migrate > between the subtropical waters of Hawaii and coastal Mexico during > the calving season and the temperate and subarctic waters of > northern California and Alaska where they feed. Previously, > humpback whales were estimated to be at 13% of their pre-whaling > population size estimate of 15,000 (ca. 1850). More recent > preliminary analysis of photographic identification of individual > whales in the North Pacific suggests that the total population may > exceed the current estimate of 1,398-2,040 individuals. Detailed > analyses of the available data may provide a better understanding > of the status of these whales. > > Northern (Steller) Sea Lion > > The northern or Steller sea lion, classified as threatened under > the ESA, ranges in coastal waters of the North Pacific Ocean from > California to Japan. The species has declined sharply throughout > its range in just the last 20 years, and it is now well below its > optimum level. The number of adults and juveniles in U.S. waters > crashed from 154,000 in 1960 to 40,000 in 1992. Most of this 73% > decline occurred in Alaska waters between Kenai and Kiska, where > sea lion trend site counts declined from 105,289 in 1959 to about > 21,000 in 1992 (Fig. 2<%6>3<%0>-3). The decline in Alaska is > believed to be due to a combination of incidental kills in > fisheries, illegal shooting, changes in the numbers and/or quality > of prey, and possibly unidentified factors. The Steller sea lion > population off Washington and Oregon is low but stable at about > 3,000. In California, they have slowly declined since the 1950's to > about 2,000. The 1992 range-wide estimate for this species is > 116,000. > > Northern Fur Seal > > The northern fur seal of the North Pacific Ocean, considered > depleted under the MMPA, ranges across subarctic Pacific Rim waters > from California to Japan. It numbers 982,000 in U.S. waters. The > major U.S. breeding population is on Alaska's Pribilof Islands of > St. Paul and St. George. Production on the Pribilof Islands dropped > more than 60% between 1955 and 1980, but has since been stable. On > St. George Island, production has continued to decline about > 6%/year since 1970 (Fig. 2<%12>3-<%0>4). Small U.S. breeding > populations are also found on Alaska's Bogoslof Island (1,500), and > California's San Miguel Island (6,000). > > California Sea Lion > > There are three subspecies of California sea lion found on the U.S. > west coast and British Columbia, in the Galapagos Islands, and in > Japan (probably extinct). The breeding range of California sea > lions extends from the Channel Islands off the coast of southern > California, U.S., to Isla Santa Margarita, on the Pacific coast of > Baja California, Mexico, and at various islands located in the Gulf > of California, Mexico. Annual U.S. pup production during 1990 > exceeded 26,700 pups. The U.S. population is currently increasing > at a rate of 10.2% annually (since 1983). In 1990, the U.S. stock > had a population size of 111,000. The total population size of the > western Baja California stock was estimated at 74,500. > A number of human-related interactions, such as incidental take > during fishing operations, entanglement, illegal killing, and > pollutants, result in deaths of sea lions. Estimates of California > sea lions killed incidentally by commercial setnet and driftnet > fishing vessels operating off California were obtained from data > collected by scientific observers on fishing vessels, fishing log > books, and fish landing receipts. Those estimates ranged from 1,865 > sea lions killed in 1991 to 4,288 killed in the fishing year > 1986-87. Sea lions have also been observed entangled with > monofilament line, gillnet and trawlnet fragments, packing bands, > rubber bands, polyfilament rope and line, and other manufactured > items. Studies of entanglement rates indicate that entangled > animals make up a small proportion of the population. There is also > evidence of sea lion mortality resulting from gunshot wounds. These > interactions appear to be a result of fishermen shooting the > animals when either their gear or their catch was in danger. > Studies have been initiated to look at rates of premature births in > relation to the level of environmental contaminants and disease > agents. > > Harbor Seal > > The Pacific harbor seal ranges along the west coast of North > America from Cedros Island, Baja California, Mexico, northward to > western Alaska. In a recent count of harbor seals during their > molting period (which is considered to be the time of peak > abundance on shore), approximately 23,000 harbor seals were > estimated to reside in the Channel Islands and along the California > mainland (Fig. 23-6). The population sizes of harbor seals in > Oregon and Washington have been estimated at 45,700 seals. Harbor > seals in the Gulf of Alaska have declined significantly during the > past two decades. > > Hawaiian Monk Seal > > The Hawaiian monk seal is limited to the small islands and atolls > of the 1,100-mile northwest portion of the Hawaiian Archipelago. > This species is listed as endangered under the ESA, due to a > decline of approximately 50-60% between the late 1950's and the > late 1970's. The largest population is located at French Frigate > Shoals, and since 1989 this population has declined by 25-40%. At > present, the total population is approximately 1,550. Since 1985, > average counts (including pups) at the five main breeding sites > peaked at 656 in 1986, but have generally declined since then to a > low of 480 in 1991. Pup production during the same period has been > highly variable, increasing from 1985 to 1988, declining 35% in > 1990, and increasing again in 1991 and 1992 (Fig. 23-7). > > ISSUES > > Studies of marine mammal populations have focused on four primary > questions: 1) Have fisheries interactions and other human-related > activities directly harmed marine mammals or significantly altered > the carrying capacity of the marine ecosystem for them; 2) Are the > depleted marine mammals recovering, and have the best steps been > taken to speed their recovery; 3) What actions are necessary to > minimize potential conflicts between the ESA, MMPA, MFCMA, and > other Federal laws on marine resources and fisheries management; > and 4) How can marine mammal populations be monitored in the face > of environmental variability? > Specific concerns in light of these research issues are discussed > below. > > Bycatch and Multispecies Interactions > > El Ni¤o events in California are often associated with increased > interactions between California sea lions and fisheries. This seems > to be related to a change in forage conditions for sea lions during > El Ni¤o events, where sea lions tend to feed more heavily on fish > caught by commercial and recreational fishermen. Given the > increased number of California sea lions at this time, the most > recent El Ni¤o could result in major problems for west coast > fishermen unless methods for minimizing this interaction are > developed in the near future. > Another issue involves competition for food. U.S. and foreign > commercial fisheries have been operating in the eastern North > Pacific for more than 100 years, and fish catches have been > sustained there for many decades. Some fish populations, however, > have collapsed and are no longer commercially viable, such as the > California sardine. The impact of removing millions of fish and > shellfish from the marine ecosystem each year on the marine mammals > that also depend on them is unknown. > Marine mammals are also incidentally killed in many fisheries. In > recent years, the fishery-caused mortality of spotted, spinner, and > common dolphins has been reduced dramatically relative to mortality > levels in 1986. In 1991, the kill of dolphins in the ETP, expressed > as a percentage of population size, was less than 2% for all the > stocks. The current population is thought to be able to withstand > this level of mortality. Still, incidental mortality in 1991 likely > exceeded 20,000 animals. An in- ternational regime is currently > being developed by nations that purse seine for tunas in the ETP > with the goal of eliminating dolphin mortality entirely over the > next few years. > The harbor porpoise kill in California's fisheries declined from > 200-300/year in the mid-1980's to less than 100/year after gillnet > fishing ceased. The harbor porpoise kill by the Makah Indian tribal > setnet salmon fishery off the north coast of Washington declined > from over 100 in 1987-88 to 13 in 1990 when the fishing effort was > reduced. > The known kill of Steller sea lions in Alaska fisheries has > declined from over 1,400 in 1982 to 23 in 1990. The numbers killed > in other fisheries is believed to be even smaller. > > Recovery of Protected Species > > Eleven U.S. west coast marine mammal species are listed as > endangered or threatened under the ESA. Though the data are > limited, right whales in the eastern North Pacific Ocean are > believed to be near extinction: only <%8>5<%0>-7 sightings have > been made in the past 25 years. There are far too few data on other > species, such as blue and humpback whales, to judge whether any > recovery is taking place. Gray whales have recovered to levels near > those estimated for the mid-1800's. California sea lions, northern > elephant seals, and harbor seal populations along the west coast > are also increasing. Some human activities may, however, be > affecting the recovery of some species. For example, adult female > humpback whales with calves have apparently been abandoning > traditional nearshore calving and calf rearing habitat near Maui, > Hawaii, possibly in response to repeated human interference or > contact. > In the case of the Hawaiian monk seal, progress in managing the > recovery of this species varies among the main breeding > populations. At Kure Atoll, with a high level of management > intervention, excellent progress is apparent in the increase in > number of births from one in 1986 to 14 in 1992. In addition, the > management programs have bolstered the immature size classes, and > recruitment of females into reproductive age classes is expected to > further enhance recovery at this site. The Pearl and Hermes Reef > population also appears to be growing and is expected to continue > its recovery in the near future. > The largest monk seal population, at French Frigate Shoals, may be > near its environmental carrying capacity, in which case further > growth would not be expected. Indeed, in the past three years, this > population has declined, due to poor juvenile survival and low > birth rates triggered by reduced prey availability. Management > efforts have been directed toward rehabilitation of juvenile > females to enhance their survival and reproductive potential. In > addition, the foraging ecology of seals at French Frigate Shoals is > being assessed through studies of relative prey abundance over > time, as well as seal movement and diving patterns using > satellite-linked telemetry. > Populations at Laysan and Lisianski Islands have not grown as > expected, and appear to be limited by high mortality of females due > to male mobbing behavior, where multiple males simultaneously > attempt to mate with a single female. Management has focused on > monitoring the occurrence of such behavior and conducting research > into mitigation methods. Currently, efforts aim to disassociate > offending males from the breeding process by chemically suppressing > their testosterone level and aggressive reproductive behavior. > The status of the species as a whole is indicated by the annual > mean beach counts of seals and the number of pups born. The total > number of births has been highly variable, but without trend since > the early 1980's. However, mean counts have fallen since 1985, > largely as a result of declines at French Frigate Shoals. Efforts > to reverse this trend will continue, through rehabilitation of > seals at French Frigate Shoals and elimination of mobbing-related > mortality at Laysan and Lisianski Islands. > Recovery plan action will provide a way to gauge progress in the > restoration of endangered and threatened resources. > > Scientific Advice and Adequacy of Assessments > > Some northern pinniped populations, such as Steller sea lion, > northern fur seal, and harbor seal, have declined in the last 20 > years. During the same period, other pinniped populations farther > south along the west coast have increased, such as harbor seal, > California sea lion, northern fur seal, and northern elephant seal. > Growing marine mammal populations will raise different fishery > management concerns. The biological information needed to assess > and manage these problems is generally lacking. > Marine mammal populations need to be monitored on a regular basis. > However, annual changes in environmental conditions make accurate > monitoring difficult. For example, large-scale > oceanographic changes associated with El Ni¤o conditions > affect the distributions of whales. Because of the expense > involved, many of the marine mammal populations are moni-tored only > once every 2-5 years. Generally, precision of marine mammal > population estimates are such that changes in population size must > be on the order of 20-50% to be detectable, but management advice > is often needed before such large changes occur. > > Progress > > International Dolphin Conservation Act of 1992: Bill H.R. 5419 > amended the MMPA to establish a global moratorium to prohibit > harvesting of tuna through the use of purse seine nets deployed on > or to encircle dolphins or other marine mammals. Proposed > Management Regime for Marine Mammals: The Marine Mammal Protection > Act governs the management of marine mammals in the United States. > Prior to the 1988 amendments to the MMPA, fisheries could only be > granted permits to take marine mammals incidentally if there was > scientific evidence to prove that all stocks of marine mammals > involved in the fisheries were at or above their optimum > sustainable population (OSP) level. However, sufficient evidence > regarding the status relative to OSP only exists for a few stocks. > Due to problems and economic losses associated with this system of > management, the Act was amended in 1988 to allow a 5-year interim > exemption period, during which time the incidental taking of marine > mammals was permitted in commercial fishing operations. During > this time, it was expected that additional information would be > gathered on the species involved and on the nature and extent of > their interactions with different fisheries. This period ended on > 1 October 1993 and a decision will have to be made between the old > system or development of a new management scheme for all marine > mammals. NMFS is currently collaborating with a number of > scientists, conservation organizations, and fisheries experts in > order to formulate this new regime which will require the best > available information on marine mammal stocks.