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Each October, as the northern ice pushes southward, small groups of gray whales in the eastern Pacific start a two to three-month, Template:Convert/-Template:Convert/test/A trip south. Beginning in the Bering and Chukchi seas and ending in the warm-water lagoons of Mexico's Baja peninsula and the southern Gulf of California, they travel along the west coast of Canada, the United States and Mexico.
Traveling night and day, the gray whale averages approximately Template:Convert/kmTemplate:Convert/test/A per day at an average speed of Template:Convert/km/hTemplate:Convert/test/A. This round trip of Template:Convert/-Template:Convert/test/A is believed to be the longest annual migration of any mammal. By mid-December to early January, the majority are usually found between Monterey and San Diego, California, often visible from shore. The whale watching industry provides ecotourists and marine mammal enthusiasts the opportunity to see groups of gray whales as they migrate.
By late December to early January, they begin to arrive in the calving lagoons of Baja. The three most popular lagoons are Laguna Ojo de Liebre (formerly known in English as Scammon's Lagoon after whaleman Charles Melville Scammon who discovered the lagoons in the 1850s and hunted the grays,), San Ignacio, and Magdalena.
These first whales to arrive are usually pregnant mothers that look for the protection of the lagoons to bear their calves, along with single females seeking mates. By mid-February to mid-March, the bulk of the population has arrived in the lagoons, filling them with nursing, calving and mating gray whales.
Throughout February and March, the first to leave the lagoons are males and females without new calves. Pregnant females and nursing mothers with their newborns are the last to depart, leaving only when their calves are ready for the journey, which is usually from late March to mid-April. Often a few mothers linger with their young calves well into May.
By late March or early April, the returning animals can be seen from Everett, Washington to Puget Sound to Canada.
A population of about 200 gray whales stay along the eastern Pacific coast from Canada to California throughout the summer, not making the farther trip to Alaska waters. This summer resident group is known as the Pacific Coast Feeding Group (PCFG).
Humpback whales inhabit all major oceans, in a wide band running from the Antarctic ice edge to 77° N latitude, though not in the eastern Mediterranean or the Baltic Sea.
Humpbacks are migratory, spending summers in cooler, high-latitude waters and mating and calving in tropical and subtropical waters. An exception to this rule is a population in the Arabian Sea, which remains in these tropical waters year-round. Annual migrations of up to Template:Convert/kmTemplate:Convert/test/A are typical, making it one of the mammal's best-traveled species.
A large population spreads across the [Hawaiian islands every winter, ranging from the island of Hawaii in the south to Kure Atoll in the north. A 2007 study identified seven individuals wintering off the Pacific coast of Costa Rica as having traveled from the Antarctic—around Template:Convert/kmTemplate:Convert/test/A. Identified by their unique tail patterns, these animals made the longest documented mammalian migration.
In Australia, two main migratory populations have been identified, off the west and east coast respectively. These two populations are distinct, with only a few females in each generation crossing between the two groups.
Range and migrationEdit
Sei whales live in all oceans, although rarely in polar or tropical waters. The difficulty of distinguishing them at sea from their close relatives, Bryde's whales and in some cases from fin whales, creates confusion about their range and population, especially in warmer waters where Bryde's whales are most common.
In the North Atlantic, its range extends from southern Europe or northwestern Africa to Norway, and from the southern United States to Greenland. The southernmost confirmed records are strandings along the northern Gulf of Mexico and in the Greater Antilles. Throughout its range, the whale tends to avoid semi-enclosed bodies of water, such as the Gulf of Mexico, the Gulf of Saint Lawrence, Hudson Bay, the North Sea, and the Mediterranean Sea. It occurs predominantly in deep water, occurring most commonly over the continental slope, in basins situated between banks, or submarine canyon areas.
In the North Pacific, it ranges from 20°N–23°N latitude in the winter, and from 35°N–50°N latitude in the summer. Approximately 75% of the North Pacific population lives east of the International Date Line, but there is little information regarding the North Pacific distribution. Two whales tagged in deep waters off California were later recaptured off Washington and British Columbia, revealing a possible link between these areas, but the lack of other tag recovery data makes these two cases inconclusive. In the Southern Hemisphere, summer distribution based upon historic catch data is between 40 and 50°S latitude, while winter distribution is unknown.
In general, the sei whale migrates annually from cool and subpolar waters in summer to temperate and subtropical waters for winter, where food is more abundant. In the northwest Atlantic, sightings and catch records suggest the whales move north along the shelf edge to arrive in the areas of Georges Bank, Northeast Channel, and Browns Bank by mid to late June. They are present off the south coast of Newfoundland in August and September, and a southbound migration begins moving west and south along the Nova Scotian shelf from mid-September to mid-November. Whales in the Labrador Sea as early as the first week of June may move farther northward to waters southwest of Greenland later in the summer. In the northeast Atlantic, the sei whale winters as far south as West Africa, and follows the continental slope northward in spring. Large females lead the northward migration and reach the Denmark Strait earlier and more reliably than other sexes and classes, arriving in mid-July and remaining through mid-September. In some years, males and younger females remain at lower latitudes during the summer months.
Despite knowing some general migration patterns, exact routes are not known and scientists cannot readily predict exactly where groups will appear from one year to the next. F.O. Kapel noted a correlation between appearances west of Greenland and the incursion of relatively warm waters from the Irminger Current into that area. Some evidence from tagging data indicates individuals return off the coast of Iceland on an annual basis.
- ↑ Davis, T.N.. Recovery of the Gray Whale. Alaska Science Forum. URL accessed on 2009-01-25.
- ↑ Niemann, G. (2002). Baja Legends, 171–173, Sunbelt Publications.
- ↑ Lang, A.. Demographic distinctness of the Pacific Coast Feeding Group of Gray Whales (Eschrictius robustus). NOAA Fisheries Service, Protected Resource Division, Southwest Fisheries Science Center. URL accessed on 2011-02-25.
- ↑ 4.0 4.1 American Cetacean Society Fact Sheet. American Cetacean Society. URL accessed on 2007-04-17.
- ↑ (February 1, 2011) Humpback whale Megaptera novaeangliae song reveals wintering activity in the Northwestern Hawaiian Islands. Marine Ecology Progress Series 423: 261–268.
- ↑ Rasmussen K, Palacios DM, Calambokidis J, Saborío MT, Dalla Rosa L, Secchi ER, Steiger GH, Allen JM, & Stone GS (2007). Southern Hemisphere humpback whales wintering off Central America: insights from water temperature into the longest mammalian migration. Biology Letters 3 (10.1098/rsbl.2007.0067).
- ↑ (2007). Megaptera novaeangliae in Species Profile and Threats Database. Australian Government: Department of the Environment and Water Resources. URL accessed on 2007-04-17.
- ↑ <includeonly>[[Category:Pages with broken references]]</includeonly><span class="citeerror">Cite error: Invalid <code><ref></code> tag; no text was provided for refs named <code>nmfs</code></span>
- ↑ <includeonly>[[Category:Pages with broken references]]</includeonly><span class="citeerror">Cite error: Invalid <code><ref></code> tag; no text was provided for refs named <code>Gambell85a</code></span>
- ↑ <includeonly>[[Category:Pages with broken references]]</includeonly><span class="citeerror">Cite error: Invalid <code><ref></code> tag; no text was provided for refs named <code>mead</code></span>
- ↑ CETAP (1982). Final Report of the Cetacean and Turtle Assessment Program, University of Rhode Island, to Bureau of Land Management.
- ↑ Sutcliffe, W.H., Jr.; P.F. Brodie (1977). "Whale distributions in Nova Scotia waters" Fisheries & Marine Service Technical Report No. 722.
- ↑ Kenney, R.D., H.E. Winn (1987). Cetacean biomass densities near submarine canyons compared to adjacent shelf/slope areas. Cont. Shelf Res. 7: 107–114.
- ↑ Masaki, Y. (1976). Biological studies on the North Pacific sei whale. Bull. Far Seas Fish. Res. Lab. 14: 1–104.
- ↑ <includeonly>[[Category:Pages with broken references]]</includeonly><span class="citeerror">Cite error: Invalid <code><ref></code> tag; no text was provided for refs named <code>horwood87</code></span>
- ↑ Rice, D.W. (1974). "Whales and whale research in the North Pacific" Schervill, W.E. (ed.) The Whale Problem: a status report, 170–195, Cambridge, MA: Harvard University Press.
- ↑ <includeonly>[[Category:Pages with broken references]]</includeonly><span class="citeerror">Cite error: Invalid <code><ref></code> tag; no text was provided for refs named <code>mizroch84</code></span>
- ↑ Mitchell, E., D.G. Chapman (1977). Preliminary assessment of stocks of northwest Atlantic sei whales (Balaenoptera borealis). Rep. Int. Whal. Commn Spec. Iss. 1: 117–120.
- ↑ <includeonly>[[Category:Pages with broken references]]</includeonly><span class="citeerror">Cite error: Invalid <code><ref></code> tag; no text was provided for refs named <code>martin83</code></span>
- ↑ Jonsgård, Å., K. Darling (1977). On the biology of the eastern North Atlantic sei whale, Balaenoptera borealis Lesson. Rep. Int. Whal. Commn Spec. Iss. 1: 124–129.
- ↑ Kapel, F.O. (1985). On the occurrence of sei whales (Balenoptera borealis) in West Greenland waters. Rep. Int. Whal. Commn 35: 349–352.
- ↑ Sigurjónsson, J. (1983). The cruise of the Ljósfari in the Denmark Strait (June–July 1981) and recent marking and sightings off Iceland. Rep. Int. Whal. Commn 33: 667–682.