Whales Counted Off US Pacific Coast

Scientists have published results of the most comprehensive survey to date of whales, dolphins and porpoises off the United States' west coast. Based on their sightings, researchers at the US National Ocean and Atmospheric Administration estimate 556,000 of the marine mammals live within 345 miles (556 km) of shore.

Altogether the survey tallied 21 species off the coast of California, Oregon and Washington. The counts do not include three kinds of cetaceans that live close to shore: harbour porpoises, gray whales and coastal populations of bottlenose dolphins.

The whales spotted include the elusive dwarf and pygmy sperm whales, open-ocean animals that are seldom seen. Some species were found mainly in warmer waters off central and southern California, including blue whales, long-beaked common dolphins and striped dolphins. Others, such as Dall's porpoise, primarily keep to cooler waters near Oregon and Washington.

The most prevalent species off the California coast is short-beaked common dolphin, totalling 352,000 individuals. Dall's porpoise is the most numerous species off Oregon and Washington, numbering around 86,000. Together, these two species comprise about 80 percent of all the cetaceans in western US offshore waters.

The most common whale is Cuvier's beaked whale, with 4300 living along the California coast. Among the rarest of the marine mammals surveyed are sei whales. They used to be harvested by the west coast whaling industry. But in recent years, sei whales have remained scarce. Only about one hundred sei whales are believed to survive in the area.

The cetacean population counts are based on five years of ocean surveys conducted from research ships between 1990 and 2005. Altogether, surveyors spotted 1913 whales, dolphins and porpoises in the 440,000 square miles (1.14 million km²) studied.

Whale numbers varied from year to year due to factors such as ocean temperature fluctuations and movements of food supply. Nevertheless, some trends are discernible from among the surveys. For one, fin whales show a steady increase in number.

A bleaker revelation is that Baird's beaked whale and small beaked whales of the Mesoplodon genus haven't been seen along the California coast since 1996. Beaked whales are particularly sensitive to loud noise. The commotion in the ocean caused by people may have driven the whales away.