We use drones to survey Steller sea lions but what about northern fur seals?
January 16, 2018
Here is something you may not know: the Steller Watch team also studies northern fur seals! We have a blog post about an interesting research project on northern fur seals but I would like to share another project with you all that I’m working on with this incredible species.
But, before I dive in, I’d like to share a little bit of background information about northern fur seals. This species ranges throughout the North Pacific Ocean and similar to Steller sea lions, they gather during the summer breeding season however, unlike Stellers, they only gather at a handful of locations in California, Alaska, and Russia.
In Alaska, where our program primarily studies northern fur seals, they gather on the Pribilof Island Archipelago and Bogoslof Island. We’ve mentioned Bogoslof Island in our last two blog posts (here and here) as this island erupted over 50 times in a 9-month period in 2017. Fortunately, the eruptions seem to have caused little, if any, displacement of the wildlife and there is a lot more real estate for these northern fur seals to spread out as the population on this island has been increasing since the mid-1990s. Contrary to the increasing trend of northern fur seals on Bogoslof, we are seeing continued declines in the populations that inhabit St. Paul and St. George Island (in the Pribilof Islands).
The northern fur seal drone project was featured on the UAS Program website and we wanted to share it with you, here!
Advanced UAS Sensor Development for Marine Mammal Monitoring
In 1963, NOAA Fisheries’ Marine Mammal Laboratory (MML) began to use the mark-recapture method of shear-sampling northern fur seal pups to estimate pup abundance. Presently, these surveys are conducted every two years on St. Paul and St. George Island (Pribilof Islands, Alaska). These trips require up to 22 people to be stationed on the islands for up to three weeks and the presence of scientists on the rookery creates disturbance (authorized by a Federal permits: NMFS/MMPA 14327 and IACUC ANW2013-3).
With the help of the UAS Program Office, MML has been collaborating with NOAA’s Aircraft Operations Center (AOC), National Environmental Satellite Data and Information Service (NESDIS), Mystic Aquarium, Aerial Imaging Solutions, and GeoThinkTank (Figure 1) to work on developing a UAS-based approach for conducting northern fur seal abundance surveys.
MML has successfully implemented unoccupied aircraft systems (UAS; i.e., drones) to supplement annual Steller sea lion abundance surveys since 2014. Given the size and relatively more distinct coloration from their background, using a high-resolution mirrorless camera has worked well for capturing images of Steller sea lions (Figure 2). The challenge with developing a similar approach for northern fur seals has been deciphering small black fur seal pups from the black boulder substrate common in the Pribilof Islands—northern fur seals are much harder to count in images!
We have a few objectives for our project to get us closer to our goal: (1) assess a heavy-lift hexacopter with longer flight times and ability to carry heavier payloads, (2) evaluate imaging capabilities of a thermal sensor for northern fur seals, and (3) conduct an on-the-ground assessment of the feasibility of multi-spectral imaging for distinguishing northern fur seals from their background.
In August of 2018 during the shear-sampling surveys on St. George Island, we were able to test the APH-28 hexacopter (Figure 3) (Aerial Imaging Solutions) mounted with the FLIR DUO Pro R thermal sensor and conduct aerial surveys of a small rookery (Figure 4). We completed redundant surveys of this rookery with this thermal sensor and also with a high-resolution mirrorless digital camera. We will soon count northern fur seals from these two sets of imagery and be able to compare the counts to our traditional ground-survey estimates.
During this same trip, we worked with GeoThinkTank to collect spectral measurements using a handheld spectroradiometer (loaned by NESDIS) of northern fur seals (pups, adult females, and a deceased adult male) and the substrate (rocks, grass, driftwood, etc.) (Figure 5). Collecting measurements like these is a normal procedure for plants and other substrate (e.g., for calibrating satellite imagery), but as far as we know, has never been done for wildlife.
Collecting these spectral measurements in the field in Alaska was made easier by our preliminary trip to Mystic Aquarium in May of 2018. The Mystic Aquarium allowed us the opportunity to collect more measurements of northern fur seals (from animals far more cooperative than those we encounter in the wild) and in a more controlled environment to help us streamline our methods for the harsher field conditions in Alaska (Figure 6). These spectral measurements will be used to model a virtual northern fur seal rookery environment to run various aerial survey simulations. This will allow scientists to test various bands beyond the typical four bands customary to off-the-shelf multi-spectral UAS sensors. If optimal bands are identified and multi-spectral imaging is found to be effective, this will guide our next steps towards developing a custom UAS-mounted sensor.
Assessing optimal imaging capabilities will guide sensor selection and further development of an observing system. Once we have a handle on the best sensor payload option, we can explore which UAS platforms would be most effective for abundance surveys, and eventually replace and improve upon the current traditional survey method.
I have been a biologist in NOAA Fisheries Alaska Fisheries Science Center studying Steller sea lion population abundance and life history for over 10 years. I am an FAA certified remote pilot and have been flying marine mammal surveys with our hexacopter since 2014. I earned my B.S. in Aquatic and Fishery Sciences at the University of Washington and my Master in Coastal Environmental Management at Duke University.