July 25, 2014
Blue Whales Face Many Challenges, Including Fishing Traffic
April Flowers for redOrbit.com - Your Universe Online
Whales have been endangered by human activity for hundreds of years mainly due to commercial hunting and fishing concerns. A new study from Oregon State University, published in PLOS ONE, reveals that these are not the only human-derived challenges whales face. Blue whales, in particular, are also at an increased risk of injury and death from shipping traffic.The research team, led by OSU Marine Mammal Institute researcher Ladd Irvine, performed a 15-year comprehensive analysis of satellite-tagged blue whales off the West Coast of the US, finding that the animals' favorite fishing grounds were bisected by heavily used shipping lanes.
Shifting the shipping lanes off the coast of Los Angeles and San Francisco during the summer and fall, when blue whales are most abundant, could significantly lower the risk of whale/ship collisions. An estimated 80 percent decrease in collision risk was observed in the Bay of Fundy off eastern Canada when the shipping lanes there were shifted.
This study, led by OSU's Marine Mammal Institute, is the most comprehensive analysis of blue whale movement to date and allowed the researchers to identify important habitat areas and environmental correlates. This led to an understanding of why the whales were present near major ports and shipping traffic.
"The main areas that attract blue whales are highly productive, strong upwelling zones that produce large amounts of krill – which is pretty much all that they eat," Irvine said in a recent university statement. "The whales have to maximize their food intake during the summer before they migrate south for the winter, typically starting in mid-October to mid-November."
"It appears that two of their main foraging areas are coincidentally crossed by shipping lanes," Irvine added.
Between 1993 and 2008, 171 blue whales were tagged with transmitters that tracked their movements via satellite. The researchers focused on seasonal and individual differences in whale distribution. They found a high degree of variability, as well as a strong affinity for the upwelling zones. Unfortunately, these upwelling zones coincide with ship traffic moving in an out of the ports of Los Angeles and San Francisco.
Blue whales are enormous creatures with mouths that could hold 100 people, and bodies as long as basketball courts. They weigh as much as 25 elephants combined, somehow achieving this massive stature on a primary diet of krill. Krill are tiny, shrimp-like animals less than two inches in length. Despite being one of the largest animals to ever roam the planet, our knowledge of the range and breeding habits of the blue whales was nearly non-existent until OSU's Bruce Mate led a series of tracking studies that became the basis of the 2009 National Geographic documentary, "Kingdom of the Blue Whale."
Ranging from the Gulf of Alaska to the Costa Rica Dome, an estimated 2,500 of the 10,000 blue whales in the world prefer the US West Coast, and are known as the North Pacific population. The researchers found that the tagged whales leave US waters, for the most part, from mid-October to mid-November. They also tend to head to the northern edge of their home range during the end of the feeding season.
Most of this sub-group spends the summer and fall along the West Coast. The group of tagged whales, for the most part, congregated off the coast of Santa Barbara and San Francisco, putting them in constant danger from ship strikes.
"During one year, while we were filming the documentary, five blue whales were hit off of southern California during a seven-week period," said Mate, who directs the Marine Mammal Institute at OSU's Hatfield Marine Science Center. "Blue whales may not be as acoustically aware as species that rely on echolocation to find prey and there is some evidence that the location of the engines in the rear of the ship creates something of an acoustic shadow in front of them, making it hard for whales to hear the ship coming."
"Putting some kind of noise deterrent on the ships isn't really an option, however," Mate added. "You don't really want to drive endangered whales out of their prime habitat and best feeding locations."
The proposed shift in shipping lanes is not without precedent. When researchers brought concerns about the right whale / ship collisions in the Bay of Fundy to the International Maritime Organization more than a decade ago, the industry led the push to modify those lanes. The shipping lanes around Santa Barbara and Los Angeles have been moved before, as well. They were shifted south to accommodate the California Clean Air Act, and returned after gaining an exemption to the law.
"It is not often that research results are so applicable to a policy decision." said Daniel Palacios, a principal investigator with OSU's Marine Mammal Institute, "It's not really our place to make management decisions, but we can inform policy-makers and in this case it is pretty straightforward. You will eliminate many of the ship strikes on blue whales by moving the shipping lanes south of the northern Channel Islands."
The changes for San Francisco are possible, but more challenging to enact. Three separate shipping lanes bisect the feeding grounds and home range of the tagged whales.
"We did find that the northernmost shipping lanes crossed the area that was most heavily used by tagged whales," Irvine noted. "Restricting use of the northern lane during the summer and fall when more whales are present is one option; another would be to extend one lane further offshore before separating it into different trajectories, minimizing the overlap of the shipping lanes with the areas used by blue whales."
A review of the California shipping lanes, informed by these findings, is in the planning stages at the National Oceanic and Atmospheric Administration. Before any changes can be made, however, a wide variety of stakeholders must be consulted.