A first-of-its-kind rescue operation resumed today off the coast of Southern California as crews attempt to disentangle a 24 metre blue whale (Balaenoptera musculus) from crab trap lines.
The entangled whale was spotted on Monday afternoon about three to four miles (four to six and a half kilometers) off the coast of Orange County, California. Initially reported by a whale watching vessel operated by Captain Dave's Dolphin and Whale Watching Safari, the whale appeared to have 100 to 200 feet (30 to 60 meters) of crabbing lines and buoys wound around it.
According to Michael Milstein, a spokesperson for the National Oceanic and Atmospheric Administration, the crabbing lines appear to run along the length of the whale's body, possibly passing through its mouth, and they are clearly wrapped around one of its pectoral flippers. The whale also appears to be dragging the crab trap.
The crew got close to the whale yesterday, but was unable to cut away the lines wrapped around the large cetacean. The rescue operation was suspended after the animal grew increasingly distressed.
As of this morning, rescuers were on standby as they awaited another sighting of the whale. The rescue team had initially affixed a telemetry buoy to the whale, but it was removed over concerns that the system would become twisted in the crab lines and lost when the lines were severed.
NOAA is leading the rescue effort, assisted by an disentanglement team composed of volunteers trained to assist in whale rescues. The operation is also supported by a small fleet of fishing and whale watching vessels that are helping to relocate the whale.
The coastal waters of Southern California are primary foraging grounds for blue whales, and they are common at this time of year; however, blue whale entanglements are rare.
"Blue whales are typically thought to be more offshore animals, and crabbing gear is thought be more inshore, but obviously the spatial overlap between those two is coming into conflict more and more," explained Leigh Torres, a marine ecologist at Oregon State University who has studied blue whales. "The fact that we see this entanglement isn't terribly surprising, though it is unique."
The uniqueness of this event was reiterated by NOAA's Milstein, who noted that this is the first attempt at disentanglement of a blue whale off the coast of California. Milstein also emphasized that the size of the whale, and its thorough entanglement, have made this rescue especially challenging. The entanglement around the animal's head further complicates disentanglement because the rescuers are unable to approach undetected.
"It is a quite tricky operation," agreed Torres. "These whales, no matter what species it is, can be quite powerful...the animal has to be fairly calm and ok with the vessel approaching closely. You have to get the cutting implement just in the right place...it's no easy task."
Line entanglements can be dangerous for whales, though the degree of danger will depend on the situation. Whales may drag gear around for a long time, but the line may have a ball-and-chain effect on the individual and eventually compromise its health.
For blue whales, entanglement may be especially detrimental to their feeding habits because they rely on high mobility. They often employ a late burst of speed to overtake a patch of krill—a practice known as lunge feeding—which may be compromised if they are snarled in fishing or crabbing lines.
Blue whales are thought to be the largest animal in the world, growing to lengths of 100 feet (30 meters) and weights up to 150 tons. Decimated by whaling in the early 1900s, the blue whale has recovered over recent decades, partly as a result of protection under the Endangered Species Act of 1973.
Today, the blue whale is primarily threatened by human activities including ship strikes, noise in the environment (sonar, vessel traffic, and seismic surveys), and entanglements from fishing and crabbing gear.