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Dispatches from the field

Investigating Steller sea lion declines on remote Aleutian Islands


Steller sea lions
Aerial view of a Steller sea lion breeding site from a previous Aleutian survey  Photo: NOAA Fisheries

 
Steller sea lions
Steller sea lion
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Settling into our first week

June 28, 2016- Our team flew to Adak Island, Alaska on Thursday, June 23 and we were welcomed with clear skies and beaming sunshine—a rare sight in the Aleutian Islands since this area can be plagued by fog during the summer. We loaded our gear onto the Tiglax, a 120-ft research vessel operated by the Alaska Maritime National Wildlife Refuge. The ship is quite comfortable, especially given our moderately-sized crew of eight people.

We have four Steller sea lion, National Marine Fisheries Service (NMFS) biologists on board, they are: Tom Gelatt (the Alaska Ecosystem Program Leader), Brian Fadely, Van Helker and me. Killer whale biologist, Paul Wade, his volunteer Kristen Campbell, and NMFS fish biologists Susanne McDermott and Mike Levine also joined us.

Since sailing on Thursday evening, we have been lucky with calm seas and relatively low winds. Unfortunately, this is the perfect formula for fog, a marine mammal biologist's nemesis because fog obstructs our view. Despite the fog, we have been able to survey all of the sea lion sites along the 300 miles of the Island chain we have passed so far. Most of the sites are quite small and we have surveyed them from the ship or a skiff offshore.

 


Hexacopter or drone
Hexacopter (or drone) researchers use to survey Steller sea lions  Photo: NOAA Fisheries

 

Fortunately, the weather cooperated enough to allow Van Helker and me to fly the hexacopter (unoccupied aircraft vehicle, or drone) and survey two of our larger sites. These sites are rookeries, which are breeding and pupping areas. Aerial images offer an incredible perspective to easily collect accurate and complete sea lion counts.

We had low fog at another rookery site which meant we could not fly above that location due to safety restrictions. We had to resort to more tedious measures for collecting counts--hiding in the grass and counting with binoculars. Luckily, the site is at the base of a 40-foot bank giving us a favorable, vertical perspective and allowing us to obtain accurate counts of adults, juveniles, and newborn sea lions or pups.

 


Killer whale
Killer whale spotted swimming along the Aleutian Island chain during first week of survey  Photo: Kristen Campbell

 

The whale survey team has been getting some observation time in between the fog banks, which can limit visibility to only a few hundred feet. So far, they have documented three groups of killer whales. On June 24, we encountered a group of four resident (fish-eating) whales. Over the weekend, we saw a group of four transient (marine-mammal eating) whales in the Rat Islands. The Rat Islands are a killer whale hot spot.

Transient killer whales prey on marine mammals, including Steller sea lions. Resident killer whales are fish-eating and may have a diet that is similar to Steller sea lions, including the Stellers’ main prey in the western Aleutians, Atka mackerel. Paul and Kristen are attempting to attach satellite-linked transmitters to either type of killer whale to collect information on the animal's movements and dive patterns. They made two attempts at tagging but were unsuccessful.

Aside from killer whales, they also spotted six Dahl’s porpoise, three adult male sperm whales, and one minke whale.
 


Scientist holding underwater camera
Fish biologist Mike Levine shows underwater camera  Photo: NOAA Fisheries

 

The fish biologists have been using every spare moment to lower their prototype underwater camera system to capture video at varying depth zones from 25, 50, 75, and 100 meters. They have almost completed three survey efforts and towed the camera ten times. This is valuable footage that will provide information about Steller sea lions’ feeding grounds.

This unique surveying method allows scientists to sample areas that cannot be reached with traditional methods, like trawling, due to the rugged seafloor. In just a few days, they’ve already explored different types of bottom substrate, like sand and rocky bottom, and have seen numerous fish species.

There is much more to come so please stay tuned! We are now going to finish up surveying around the Rat Islands and continue west to Buldir and the Near Islands in the coming week. Wish us luck, low winds, little fog, and dry skies!


Post by: Katie Sweeney, NOAA Fisheries Biologist


 
 
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