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Predicting seal behavior

Posted: August 29, 2014 - 12:03am
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A tour boat pauses in front of Tracy Arm's South Sawyer glacier to watch the glacier calve in late July of this year. ADF&G's study may result in the National Marine Fisheries Service recommending hours for boat activity in the fjord.  Mary Catharine Martin | Juneau Empire
Mary Catharine Martin | Juneau Empire
A tour boat pauses in front of Tracy Arm's South Sawyer glacier to watch the glacier calve in late July of this year. ADF&G's study may result in the National Marine Fisheries Service recommending hours for boat activity in the fjord.

The Alaska Department of Fish and Game knows environmental factors like tide, temperature, and boat activity affect harbor seals, says Gail Blundell, ADF&G’s principle investigator for the statewide research program on harbor seals. But the department doesn’t always know to what extent.

So this summer, Blundell and a team of researchers conducted an in-depth study of seals at Tracy Arm’s South Sawyer Glacier. Depending on the results, the study may recommend hours of operation for the cruise ships and tour operators that travel the fjord in the summer.

Seals develop a liking for particular areas and sometimes travel hundreds of miles to pup, Blundell said. It takes a substantial amount of energy for them to travel to and pup at tidewater glaciers, but the icebergs apparently provide the sort of protection and benefits that make it worthwhile.

They haul out on icebergs in order to conserve energy; they especially prefer to do so at solar noon, and in weather that’s not too windy or rainy, so it’s easier for them to regulate their body temperature.

Studies in Disenchantment Bay and other locations have shown that depending on the kind of boat, its speed, and its direction, seals do leave their haul-out for the water when vessels near, but researchers don’t know how often that traffic may affect an individual seal, Blundell said. So researchers tagged 30 female seals in Tracy Arm this summer in order to study how those environmental factors affect seals individually. Quite a few studies have observed seal behavior as a result of those factors as a whole, but what’s still unknown is how often one seal hauls in and out of the water depending on different factors.

Adventure Bound boat captain Steve Weber said he was concerned the study may result in Tracy Arm being closed or extremely limited to tour traffic, but Blundell said it was more likely to result in recommended hours. She also pointed out that ADF&G doesn’t manage the species; it is only collecting data that will advise management decisions the National Marine Fisheries Service, a division of the National Oceanic and Atmospheric Administration, would make. Any management decision, like recommended hours, would also involve plenty of time for public comment, she said.

“We still don’t know why they travel great distances to pup in glacial habitat … (but) we know it’s important habitat for pupping,” she said. “It’s a concern what effects vessels might have, but it’s also quite possible seals are habituated to the presence of vessels.”

• Contact Outdoors reporter Mary Catharine Martin at maryc.martin@juneauempire.com.

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