How Is The Population Of Killer Whales In The Puget Sound Changing? The Killer Whale Population Is

Resident and Transient Orcas

Pacific Northwest Orcas: distinct populations

Killer whales,(Orcinus orca) normally called orcas, are found in all the earth'south oceans, simply the all-time known and most studied populations are those of the Pacific Northwest.

All orcas are peak predators, with complex social structures. Every bit a species, killer whales feed on a variety of fish and marine mammals, but private populations have become specialized to feed on particular casualty species.

In the Pacific Northwest one group of killer whales feeds exclusively on salmon. These are referred to equally "residents" considering they remain in inland or nearby littoral waters.

A second group, known as "transients," feeds simply on marine mammals. Transient orcas move n and south along the coast from Southeast Alaska and British Columbia as far south as Southern California, but they frequently make forays into the Salish Sea. CA189, the orca that stranded near Dungeness Spit in 2002, was a transient killer whale.

A 3rd population, known every bit "offshore orcas" inhabits the water well beyond the coast. Far less is known about offshore orcas, only recent observations testify that sharks are an important part of their diet. More data on offshore orcas tin be institute at Orca Network.

Killer whales are highly intelligent predators with complex social interactions. Each population has its own "culture," closely tied to its food source, hunting manner and advice. Although residents, transients, and offshore orcas are all members of the same species, they take not been observed to interbreed.

Resident (fish-eating) Orcas

Resident killer whales inhabit the inland waters of Washington and British Columbia.

There are ii subgroups. Northern residents range from Vancouver Island north to SE Alaska while Southern residents occupy greater Puget Sound.

Resident orcas consume only salmon -- primarily Chinook salmon -- a large, calorie-rich nutrient source. They travel and hunt in large sociable groups of closely related individuals.

Since the salmon they feed on are not very sensitive to the sounds they brand, resident orcas vocalize underwater, communicating with each other frequently as they hunt.

Residents accept a large repertoire of unique, identifiable calls, none of which are used by transients. Their clear vocalizations and easily identifiable dorsal fins and saddle patches accept made them piece of cake for scientists to study.

Resident orcas are probably the most well-researched grouping of orcas in the world.

Transient (mammal-eating) Orcas

Transient killer whales are only occasional visitors to inland waters of Puget Audio, where they are unremarkably seen hunting for harbor seals. In other parts of their range transients prey on Dall's porpoises, Steller sea lions, minke whales or grey whales.

Unlike resident orcas, transients travel and hunt in small groups of 2-half dozen individuals. These small groups are usually based on a female person and her offspring, but often change as animals mature and disperse.

While searching for prey, transient killer whales almost never breach or splash. They swim silently underwater for long periods, surfacing briefly to look around. They exercise take recognizable calls simply they apply them rarely, and never when hunting. Since the mammals they feed are able to hear their vocalizations, transients rely on stealth and surprise to sneak upward on their prey.

These features, and the fact that they are continuously on the move, make transients much harder to study than resident orcas.

THREATS AND CONSERVATION

Orcas are a familiar sight to people living around the Salish Sea and a visual symbol of the Pacific Northwest, but orcas in United states of america waters are facing serious threats. In 2011 the Southern resident population was estimated at just 88 individuals, down from around 200 individuals in the belatedly 1800's. Between 1967 and 1971, when orcas were captured for large aquarium shows, this population was diminished by some other 30%, and their numbers have never recovered. In 2005 southern residents were listed as endangered under the Endangered Species Act. Northern resident and transient populations were non every bit seriously depleted past live capture and their numbers are non as low, however they face other serious threats.

Declining Nutrient Resource

Resident orcas depend on salmon returning to rivers flowing into the Salish Sea to spawn. After years of habitat degradation, contamination and poor fisheries direction, these salmon populations are also severely depleted. In 1999, Puget Audio Chinook salmon were listed as threatened nether the Endangered Species Act. Some resident orcas are now traveling much farther in search of food than in the by and others are becoming malnourished when runs of Chinook salmon are poor. These signs indicate that shortage of nutrient resources is a significant factor in declining resident orca populations.

Different residents, transients feed on a broad range of marine mammals and are not dependent on a single food source. They also forage over much wider areas and are less vulnerable to local food shortages. Although their exact numbers are non known, most sources agree that transient populations have increased.

Vessel Noise

Resident orcas spend substantial periods of time in the heavily traveled waters of Puget Audio, the Straits of Juan de Fuca and the northern Salish Sea. In addition to disturbance and occasional injuries from boat strikes, they face up ever-increasing dissonance from boat traffic: small motorboats, regular ferry crossings, large freighters and cruise ships. Excessive vessel noise may affect their ability to echo-locate, find nutrient and communicate with one another. Recent hydrophone research shows that orcas often have to expend more energy to communicate in noisy environments, energy that might otherwise be used for hunting and traveling.

Contaminants

Both transient and resident orcas are impacted as they larn and retain persistent organic pollutants through the foods they eat. These chemicals, which include PCBs, Dichloro-diphenyl-trichloroethane and other pesticides, accept been released into the surround where they accrue in the tissues of marine life. Even compounds that have been banned for decades are turning upwards in very high concentrations in orcas, making them some of the most contaminated of all marine organisms. The scientists investigating the death of CA189 (Hope) were surprised to discover that her PCB levels were among the highest always recorded. To learn more about contaminant loads in transient orcas and how this orca might take acquired these chemicals go to Contaminants in Orcas.

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