Josh Cutler Lowell Fritz Katie Luxa
Here is the blog from AFSC’s Dispatches from the Field written by this year’s aerial survey team—and featured Steller Watch bloggers—during the 2017 Steller sea lion aerial survey they conducted from June 27th to July 6th.
How Many Steller sea lions are there?
June 21, 2017—It is impossible to know exactly how many Steller sea lions are in the ocean. Luckily, the sea lions converge every summer on shore to give birth, mate, and rear newborn pups. For us researchers, this is a fantastic opportunity to count how many are on shore every year.
However, we must conduct our survey within a three week window. The timing has to be just right to ensure females have given birth. Wait too long and the animals (including newborn pups) will begin to disperse.
On top of the time constraint, we have 2,500 miles of coast to survey, from southeast Alaska through the Aleutian Island chain.
Collecting Information from the air
With the help of NOAA’s Aircraft Operations Center, we fly over the Steller sea lion rookery (where most of the pups are born) and haul-out sites in a Twin Otter plane.
This year we are going to fly over southeast Alaska, Prince William Sound, the Kenai Peninsula, and Kodiak Island. We will start our survey in Sika on June 26 and end near Kodiak on July 10.
Cameras mounted to the belly of the plane take high-resolution images of the sites below. Because it would take more than three weeks to survey all of the beaches, islands, and offshore rocks of Alaska, we alternate between the eastern (southeast Alaska through Kodiak) and western (the western Gulf of Alaska and Aleutian Islands) halves each year.
Technology helps us cover more ground
Our group also uses unmanned aircraft to survey Steller sea lions, primarily in hard-to-reach sites of the Aleutian Islands. This survey is done off the U.S. Fish and Wildlife research vessel M/V Tiĝlâx when we are surveying from the Twin Otter. See this link for more information.
Analyzing collected data
At the end of the survey, two scientists will independently count every sea lion in the 1000’s of high-resolution images that we took.
Counts of Steller sea lions during the breeding season are a consistent proportion of the total population (since some are at-sea when our images are taken). However, when compared across years, these counts allow us to track population trends.
A lot of ground covered in under two weeks
July 14, 2017—The 2017 Steller sea lion aerial survey went by so fast that we did not have a chance to send out an update until it was over! We had nearly perfect weather for flying and aerial photography: low winds, little precipitation, and high clouds. In 2015, this survey took 17 days to complete. We completed the 2017 survey in 10 days. There were only 3 “down days” – days we could not fly due to weather – during the survey period. Over the course of the 7 days in the air, we surveyed 196 sites , took 22,184 photographs, and traveled almost 6000 miles in approximately 40 hours of flight time. This includes 23 bonus sites in the Shumagin Islands, an area we did not plan to survey until the 2018 Aleutian Islands survey. The weather in the Shumagins is often poor and dangerous, so we took advantage of our extra time and unusually good weather to survey the islands this year.
What we saw
We saw sites with 1 or 2 lonely males, and sites with thousands of sea lions packed on a beach. We will know how many sea lions were actually at those sites in the next couple of months after two scientists independently count every sea lion in the images we took.
We even saw some of our marked sea lions from our survey altitude of 750 feet. You can read about the valuable information we learn from marked sea lions, and you can even help us find marks in the western Aleutian Islands at Steller Watch.