May 27, 2013 — Researchers already know that heavy-duty commercial fishing lines and lobster and crab traps, connected to the surface by long ropes, pose a formidable threat to whales in the North Atlantic, by inflicting deep wounds and sapping their energy reserves. Accidental entrapment is the leading cause of death for Atlantic whales in records going back to 1970. The National Marine Fisheries Service reported 25 sightings of entangled whales in 2010. Five did not survive the encounter. Many of the surviving whales were described as thin and weak.
The whale spotted on Christmas, a 2-year-old female right whale cataloged as Eg 3911 (Eg for the species' scientific name, Eubalaena glacialis), tangled with a fishing trap line sometime between February and December 2010. By the time researchers rescued her on January 15, 2011, she was 20 percent thinner than other right whales her age. The team suspects she wasn't able to dive deep enough to reach the plankton and crustaceans she'd normally feed on.
Once liberated, Eg 3911 began swimming faster and diving deeper, but she had no way to bulk back up. Right whales normally feed in cool northern waters during the summer, and Florida's winter waters offered no food sources. "You're tired, you're hungry, you're really skinny, and there's nothing for you to eat," says Julie van der Hoop, a marine mammal biologist at the Woods Hole Oceanographic Institution in Massachusetts and lead author of a new paper documenting the incident. Eg 3911 was found dead in the water on February 1, sporting lethal shark attack wounds. Van der Hoop suspects that the whale was lethargically bobbing at the surface when she was bitten.
Following Eg 3911's death, van der Hoop and colleagues wondered how much the gear taxed the emaciated whale's energy reserves. Scientists lowered some of the very fishing gear removed from Eg 3911 into the water behind a moving skiff to estimate how much drag the lines and buoys generated, and how much energy the whale would have to expend to compensate. They estimated that Eg 3911 was burning up to twice as much energy while entangled. Their results appear online this week in Marine Mammal Science.
Read the full story at the New Bedford Standard-Times