Efforts to save whales on the West Coast often focus on individual stressors—things like entanglements in fishing gear or vessel strikes. But since humans pose multiple threats to whales, researchers say a collaborative, multifaceted approach may work better.
“We live in this world where there’s not just one or two things that threaten whales,” said Helen Killeen, a PhD candidate at the University of California-Davis. Moratoriums on whale hunting and mitigation measures to stop boat strikes can all help, she said, but “now, we have lots of activity going on in the ocean all the time,” she said.
Killeen and a group of colleagues diverse fields—from economics to ecology—wanted to see what threats whales face in California and come up with some measures to protect them. Looking at humpback (Megaptera novaeangliae), gray (Eschrichtius robustus), blue (Balaenoptera musculus), fin (Balaenoptera physalus), minke (Balaenoptera acutorostrata), sei (Balaenoptera borealis), sperm (Physeter microcephalus), North Pacific right (Eubalaena japonica) and killer whales (Orcinus orca) in the California Current Ecosystem, they published their findings in Marine Policy.
To see what was killing whales, they conducted a literature review. “We ended up reviewing hundreds of papers,” said Killeen, who co-led the study with her colleague, and fellow PhD candidate at UD Davis, Eliza Oldach. They expanded their search to also include indirect, or sublethal, factors that cause whales to become more stressed. “Many sublethal effects can add up to something that is quite lethal,” Killeen said.
Then, they broke down the key drivers of whale mortality. Some, like entanglements, were obvious. But others included things like noise pollution and water quality issues. Those rarely directly led to mortality by themselves, but the accumulated stress from them could cause something like an entanglement or vessel strike to more likely be fatal.
Other threats derived from climate change. For example, warmer waters can cause changes in prey distribution. “[Whales] have to move around to search for food and use more energy than they otherwise would have,” she said. That also could cause them to move to areas where they’re more likely to come across vessels and fishing gear, yet whale protection measures don’t address them.
The next step was looking at what different levels of government—even down to individual ports—are doing to address these issues. They found that policy actions were in place to target specific issues, like entanglement and vessel strike, but they missed other issues, such as nutritional stress, disease and predation.
“I think the biggest takeaway that we had is that there are all these different threats out there, and we’re only addressing some of them,” Killeen said. “For any given individual whale, all of these threats are happening at the same time.” They’re also happening over wide jurisdictions, with different levels of policy restrictions.
Killeen stresses the need for a more holistic approach to address whale mortality. Some efforts are already doing this. For example, the statewide Risk Assessment Entanglement Program in California uses environmental models to predict water temperature changes and blue and humpback whale foraging patterns. When whale foraging is likely to overlap with fishing effort, the state stops Dungeness crab (Metacarcinus magister) fishing to avoid entanglements.
“That kind of approach is what we see more fruitful moving forward,” Killeen said.
|Dana Kobilinsky is associate editor at The Wildlife Society. Contact her at email@example.com with any questions or comments about her article. You can follow her on Twitter at @DanaKobi.|
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