Right whale recovery in North Atlantic stalls
More offshore fishing, heavier fishing gear, and more whale movement linked with decline
A new study shows the North Atlantic Right Whale population is having fewer calves at the same time as more whales are dying from fishing gear entanglements.
The chronically endangered species is "not yet a conservation success story," concluded the report, published last month in Frontiers of Marine Science.
Researchers found previous increases in the number of right whales have been offset by declining birth rates and more whales getting lethally tangled in fishing gear.
Hunted nearly to extinction
As a result, the North Atlantic right whale neared extinction in the mid-1930s. Killing the whales was made illegal in 1935.
"After we stopped killing them, the recovery "remained steady until 2010," said Kraus.
"They continued to recover right through 2010, [by which time] we saw the population grow to 500 animals," said Kraus.
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Yet the expansion of offshore fishing activities, advent of heavier offshore fishing gear and increased movement of existing whale populations have meant deadlier consequences for whales that get caught in fishing gear.
In fact, says Kraus, "over 83 per cent of all right whales in the North Atlantic have been entangled in fishing gear at one time."
"As they encounter stronger ropes and heavier gear, the damage to the animals is more severe and lasts longer," said Kraus. "It's like if you break a leg, it takes you weeks or months to recover."
"Even if they're able to break free the consequences last for some time in terms of their health and their ability to reproduce."
Fewer baby whales
The shift has been "surprising" to researchers, he says, but could be linked with food supplies moving in response to "very high warming temperatures in the the Gulf of Maine."
"As they're looking for food they start moving into more areas. The more time you spend looking around, the less time you spend eating.
"And when you don't get as fat, you can't have as many babies."
Other theories have to do with long-term damage caused by fishing gear entanglements and generational diseases.
"There's some change in the ecosystem that's not clear to us," says Kraus.
Changes in fishing gear needed
"We don't have control over some of the natural shifts in distribution, but we do have control over the human causes of injury and mortality," says Kraus.
"Fishermen don't want to kill or entangle whales, and the whales certainly don't want to get entangled," Kraus says.
"We're trying to reduce the probability of entanglement, and if a whale does get entangled, [making it so that] it can break free and get out."
with files from Information Morning Saint John