Research to track otters' response to seismic surveys

How sea otters will be affected by sonic ocean testing is only the latest effort to protect their recovery

dsneed@thetribunenews.comOctober 20, 2012 

For decades, wildlife biologists have been concerned about the fate of the southern sea otter.

After being hunted to near extinction in the 1800s, the furry ocean carnivore is staging a slow but faltering recovery. Starting as early as next month, the otters will face a new challenge — high-energy seismic surveys conducted offshore of Diablo Canyon nuclear power plant.

For most of this month, a team of 20 veterinarians, biologists, technicians and research experts has been capturing and tagging sea otters along the San Luis Obispo County coastline from Port San Luis to San Simeon in an attempt to learn how the otters will react to the planned earthquake fault mapping that calls for 250-decibel blasts of sound to be emitted into the ocean every 15 seconds. “How they are going to react is the million-dollar question,” said Tim Tinker, lead researcher for the tagging project with the U.S. Geological Survey.

What is not in question is the fact that California’s sea otters are struggling. Biologists had expected the otters, a fully protected species, to be recovering much more quickly.

The population is 2,800 animals. However, nearly 12 percent of the population died last year, victims of harmful algal toxins, parasites and infectious diseases, mating trauma, emaciation, bacterial infections, heart disease and boat strikes.

“It’s a complex combination of issues that are affecting sea otter health, including natural and man-made factors,” Tinker said.

“The research we are doing into the effects of the seismic surveys on otters is a continuation of research we have been doing on the overall health of the otter population for decades.”

Intent, impact of seismic testing

PG&E, the owner of the Diablo Canyon plant, is in the process of getting 10 regulatory permits it will need to conduct the high-energy seismic surveys. One of the most important is a permit from the California Coastal Commission, which will consider the matter when it meets in Santa Monica starting Nov. 14.

The testing is intended to give PG&E and regulators a better understanding of the earthquake faults off Diablo Canyon. Such information became more critical following the Fukushima tsunami and nuclear disaster in Japan last year.

Studying the effects the seismic surveys will have on a variety of marine species, including sea otters, is one of the mitigation measures already imposed on PG&E by state officials.

The seismic testing has garnered intense opposition, mostly because of the damage it could do to marine life. Previous research indicates that the otters’ behavior initially changes in reaction to the sonic blasting, but they become habituated to it and return to more normal behavior.

“The chance of seeing an otter killed or injured by this type of seismic surveying is very remote,” said Jim Curland, advocacy program director for Friends of the Sea Otter in Monterey. “Sea otters spend much of their time on the surface and deal with sound differently than other marine mammals like whales, which use sound to echolocate.”

However, it is unknown if the surveys will cause more subtle or long-term behavioral changes in the otters. For this reason, Friends of the Sea Otter is opposed to the seismic surveys, but supports capture-and-tag research in order to learn more about the animals.

“If these surveys are going to get green-lighted, it’s important to have in place something that will measure the effects,” Curland said. “I have faith in the scientists doing the monitoring.”

The researchers are capturing as many as 60 otters, two-thirds of them from within the seismic survey area and a third outside it. The otters tagged outside the seismic survey area will be used as a baseline against which the behavior of the otters from within the survey area can be compared.

Each captured otter has a time-depth recorder and a VHF radio transmitter implanted within its abdominal cavity. The time-depth recorder logs how frequently and deeply the otter dives and how long it stays submerged. It also records the animal’s body temperature, said Michelle Staedler, sea otter research coordinator with the Monterey Bay Aquarium.

The data will paint a detailed picture of the otter’s behavior over a year and a half. After that time, the otter must be recaptured and the device removed to download the data. The radio transmitter allows researchers to track the movements of the otter and pinpoint its location for recovery of the time-depth recorder, Staedler said.

Tagging sea otters is complex

Capturing and tagging a sea otter is a complicated effort. Spotters locate groups of the animals resting atop kelp beds. They wait until one of the animals falls asleep.

Divers sneak up underneath the sleeping otter and scoop it up in a closable net called a Wilson trap. A boat ferries the otter to a mobile surgical laboratory on shore.

There, veterinarians implant the tracking devices and take a myriad of blood and tissue samples before the otter is taken back to its capture site and released. The blood and tissue samples contain as many as 14 chemical markers that will tell biologists what kind of stressors the otter is experiencing and what type of prey it is eating.

The surgery is tricky because the incision must be sutured closed without shaving the area around it. To shave the incision area would expose the otter to hypothermia, said Dr. Mike Murray, a wildlife veterinarian with the Monterey Bay Aquarium.

Biologists have been tagging sea otters since the 1980s, starting in Alaska; no otters have died during the tagging process. This is because they are robust animals and veterinarians follow well-established procedures, Murray said.

“When you are handling wildlife, it’s a tricky proposition, especially with carnivores and endangered species,” he said. “You don’t want to take any shortcuts. The otters deserve better.”

The U.S. Fish and Wildlife Service is considering issuing PG&E an incidental harassment agreement as part of seismic testing. If issued, it will allow limited harassment of otters, but no lethal take.

How officials will monitor surveys

In order to enforce this agreement, monitors will be keeping close track of the otters and their behavior while the seismic surveys are taking place. Federal wildlife officials could consider shutting down the seismic surveys if any of the following scenarios occur, Tinker said.

• An inordinate number of sick or dead otters wash up on local beaches.

• A dead otter is found with damage to its brain or eardrums as a result of the sonic blasts.

• A significant number of female otters are displaced from the survey area.

Female otters are potentially more vulnerable to the seismic surveys, Tinker said. They tend to remain in one relatively small geographic area where they are familiar with food sources.

Any sea otter must consume a quarter of its body weight a day in order to maintain the high metabolic rates needed to stay warm in the chilly waters of the Pacific Ocean. Nursing females need even more food because a third of their diet goes to their pups, Staedler said.

Even under optimal conditions, most females are emaciated and in poor physical shape by the time they wean their pups, a condition biologists call end-lactation syndrome. The stress of being displaced by the seismic testing to areas the females are unfamiliar with could cause lower weaning rates and other problems that may not be immediately evident, Tinker said.

The public is encouraged to report any sick sea otters to the local Marine Mammal Center office in Morro Bay at 771-8300.

As of Wednesday, 42 otters had been tagged, with eight of them coming from outside the seismic survey area. The researchers hoped to tag 50 otters by Friday, when the operation was to conclude.

More otters could be tagged next year to bring the total to the desired 60 animals. PG&E plans to begin the seismic surveys this year and complete them next year.

The researchers encountered several unexpected problems that reduced the number of otters they were able to catch and tag. These included a great white shark scare and poor sea conditions.

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