Wednesday, April 8, 2009

Right Whale Records Set in Whale of a Season

A record-breaking season is drawing to a close as North Atlantic right whales head north for the summer. Research survey results indicate that the number of right whales spending the winter in the South again increased this year, a hopeful sign for these endangered marine giants.

Each winter, pregnant right whales travel to waters offshore of Georgia and Florida to give birth. Many other right whales also make the trip to the Southeast. In spring, the whales make their way back north to waters off New England and Canada, where they spend the summer months feeding on plankton. Research done by conservation partners including the Georgia Department of Natural Resources, Wildlife Trust and the National Oceanic and Atmospheric Administration, or NOAA, is helping wildlife biologists determine the status of the species.

Decimated by commercial whaling in the 19th century, approximately 400 North Atlantic right whales remain. This winter, almost 200 were sighted off the Georgia coast, up from 150 in 2008. The total includes 39 sets of mother and calf pairs, breaking the previous record of 31 calves set in 2001. The rest of the whales were juveniles and non-breeding adults. Whales are counted using aerial surveys and on-the-water monitoring.

Unfortunately, this season also set another record: five right whales were documented entangled in commercial fishing gear. The Georgia DNR, NOAA and other partners managed to free four of the five young whales. At least one was entangled in Canadian lobster gear. Gear removed from other whales also appeared to be lobster gear. In some instances, more than 500 feet of line had been dragged more than a thousand miles, resulting in potentially life-threatening injuries to the whales.

“Whales have shown up in the Southeast entangled in U.S. and Canadian lobster gear during previous years, also,” said Clay George, a natural resources biologist with the DNR’s Nongame Conservation Section. “While we are glad we were able to disentangle four of the whales this year, we need to find a way to keep whales from becoming entangled in the first place.”

Entanglement in commercial fishing rope is a leading cause of right whale mortality. More than 70 percent of the population has scars from entanglements.

From 2005-2007, researchers documented at least one adult whale mortality each year. This winter, however, marks the second in a row during which none were reported. There were two reported cases of calf mortalities, both from unknown causes. Ship strikes are another leading cause of right whale deaths.

Although positive about the increases in sightings, biologists stress that the road to recovery for North Atlantic right whales remains long. While the number of calves has risen, the number of breeding females has not. Right whale conservationists consider the latter number the most important statistic in determining the species’ recovery.

“Only one in four calves on average will live to become a mature breeding female. What that means is that each female right whale must have four calves within her lifetime to ‘replace’ herself within the population,” George said. “Given that it takes about 10 years for each female to reach breeding age, the whales will need many more calving seasons like this one before we see substantial growth in the population.”

Right whales are baleen whales with a bow-shaped lower jaw and a head that is up to one-quarter of the body length. Calves weigh approximately 1 ton at birth and adults can reach 60 tons and almost 50 feet in length. They have no dorsal fin and breathe through two blowholes on the top of their heads. These unique blowholes create a V-shaped blow, which also helps researchers identify the whales from a distance. Right whales can live for up to 70 years.

Protected from whaling since the 1930s, the whales are listed as a priority species in Georgia’s State Wildlife Action Plan, the blueprint for conservation in Georgia.

Although not hunted, right whales face continued conservation problems including ship strikes and entanglement in commercial fishing gear.

Researchers identify the whales by the unique pattern of callosities, or rough patches of skin, found on the whales’ heads and around their mouths. These patches are usually covered with whale lice, a type of crustacean, making the patches appear white. Photographs are used to tell which whale is being observed.


North Atlantic right whale estimates for winter 2008-09:

** Whales spotted: almost 200

** Mother-calf sets: 39

** Entanglements: 5 (four whales disentangled)

** Adult mortalities documented: 0

** Calf mortalities: 2 (causes unknown)

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