Skip to main content
Unsupported Browser Detected

Internet Explorer lacks support for the features of this website. For the best experience, please use a modern browser such as Chrome, Firefox, or Edge.

The Pribilof Pup Count: From Land & Air - Post 5

September 07, 2021

Join Alaska Fisheries Science Center staff as they test the viability of aerial surveys via uncrewed aircraft systems to advance methods used to estimate northern fur seal pup production on the Pribilof Islands.

Photo of male and female adult fur seals and pups on rocks next to the water. Fur seals at Zapadni Rookery. Credit: NOAA Fisheries.

The Big Picture

In my final blog post I’d like to share some perspective on the big picture of why we study northern fur seals. I also want to share my own reactions and experiences over the last couple weeks on this amazing island.

One of the first questions I asked our lead scientists (Rolf and Rod) is, given the limited crew and capacity to sample this year, how did they choose which rookeries we would sample for the pup production study? To recap from earlier blogs, the five rookeries we sampled were Morjovi, Polovina, Reef, Zapadni Reef, and Zapadni.

Image
Satellite photo image of St Paul Island with fur seal rookery locations named and labeled.
Map of northern fur seal rookeries on St. Paul Island. Names are, for the most part, derived from Russian words. Credit: NOAA Fisheries.

Looking at a map, it may seem obvious: the rookeries are spread out among the northeast corner, the east coast, the southeast peninsula, and English Bay on the southern shore. Geographic representation from different regions of the island is certainly a strong driver for site selection, but there are many other factors as well. These include sampling rookeries of different sizes, access for our smaller crew, and special interest, such as sites with focused tagging efforts like Zapadni Reef Rookery. And finally, from years of satellite tracking data from females with pups, we now know that females in these 4 regions have unique foraging patterns and diet. Considering all of these factors gives us confidence that our sampling effort will be representative of the island as a whole.

Image
Map image of the Bering Sea with radiating arrow lines from the Pribilof Islands, green lines labeled P or V and red lines labeled R or T from St Paul Island, and yellow lines labeled E, N, S or Z from St George Island.
Foraging patterns of nursing mothers. Credit: NOAA Fisheries.

Understanding what’s going on in these four regions of the island may also provide some very telling insight as to the health of the prey populations in each of their respective foraging areas in the Bering Sea. For instance, if we found that pup mortality in one region of St. Paul was much higher than others, or pup weights were much lower, that may indicate that females are having a harder time finding food and nourishing their pups.

This goes for the tagging studies too. If we’re finding differences in survival or reproduction  from one rookery vs. another, we may be able to tease out the reasons why, or this may inspire new areas of study for future years. This is timely and important research because the population trend on St. Paul has been going steadily down for the past couple decades.

Image
St. Paul vertical error bar point chart with Pups born (1,000s) on Y axis and years (1974-2016) on X axis.
Pup production on St. Paul Island from 1974 through 2018. Credit: NOAA Fisheries.

Ultimately, the goal is to help these fascinating animals thrive, and be sure that we are managing our actions to ensure their sustainability. And we do this through ecosystem-based management. This means NOAA Fisheries manages the total allowable catches in different fisheries based on continuous analysis of both fish populations and the predators that depend on those fish, as well as environmental factors like climate, oceanographic conditions, and weather patterns.  Understanding the estimated rate of decline of this fur seal population and the factors that may be contributing to that decline are critical to develop strategies for a hopeful recovery. 

After the 2018 census, we estimated there were about 350,000 northern fur seals on St. Paul Island (not just pups). That is a far cry from the 2 million that were here in the 1940s. While some other rookeries are growing today (see our 2019 Field Blog from Bogoslof Island), St. Paul Island still hosts the largest congregation of northern fur seals on the planet. It will be interesting and exciting to see how this year’s estimates of pup production compare between the traditional mark-recapture method vs. the aerial surveys. And time will tell which method or methods will continue contributing to this important long-term dataset.

As we wrap up this blog series, I’ll leave you with some fun photos and observations that our crew shared while on St. Paul Island. Thank you for following along and for your interest in northern fur seals and our research!

Image
Photo of northern fur seal adult male on rocks next to sea.
Adult male fur seals often come out of the water and shake their heads. In doing so, they get a hilarious sideways mohawk. It’s pretty funny looking. Credit: NOAA Fisheries.

 

Image
Photo of northern fur seal pup looking out from a small cave created by large rocks.
You’ve got to hand it to northern fur seals. They are tough animals growing up in tough conditions. It’s no surprise they don’t take lightly to being woken up. While scanning the beaches, we sometimes encountered sleeping pups. If we happened to wake them, they would pop up ready for battle! Credit: NOAA Fisheries.

 

Image
Photo of adult male northern fur seal surrounded by females and pups on rocks.
Adult males are extremely aggressive and territorial, and huge, especially compared to the pups. Pups often find safety tucking under rocks. Credit: NOAA Fisheries.

 

Image
Photo of northern fur seal scratching its chin while sitting on a large rock.
Fur seals have fingernails and toenails just like us. On their hind flipper (homologous to our feet), their toenails are in the center of their flipper. Webbing extends beyond their nails to help with swimming. Credit: NOAA Fisheries.

 

Image
Photo of northern fur seal adult female nursing a pup.
Image
Photo of northern fur seal adult female nursing a pup among rocks.
What’s sweeter than a mom and baby? With pups having to wait multiple days between feedings, it’s always sweet to see nursing. Credit: NOAA Fisheries.

 

Image
Photo of a northern fur seal rookery with scattered groups of seals on rocks and grass.
As we get later into August, most, if not all of the pups have been born and mating has taken place. At this point, the territories held by the adult males break down, and animals spread freely throughout the rookery. Credit: NOAA Fisheries.

 

Image
Photo of northern fur seals on rocks fanning themselves with hind flippers.
When we get hot, we sweat. Fur seals don’t have this option so they pant and wave their hind flippers. This is their thinnest skin and their best opportunity to lose heat! When the sun comes out, it’s time to flipper fan! Credit: NOAA Fisheries.

 

Photo of a northern fur seal resting at the water's surface.
Northern fur seals often rest in the water in a unique “jug handle” position. Seeing this just makes you smile. Credit: NOAA Fisheries.

 

Photo of northern fur seal pups among rocks.
You can often find fur seals looking to the sky, and flopping their head back and forth, or around in circles. Some speculate that they are actually learning navigation with this behavior. Who knows? Credit: NOAA Fisheries.

 

Image
Photo of northern fur seals scattered across sandy beach.
Haulout of fur seals south of Polovina Rookery. Credit: NOAA Fisheries.

 

Previous: The Pribilof Pup Count: From Land & Air - Post 4

Meet the Blogger

Insight

Understanding Ecosystem-Based Fisheries Management

Ecosystem-based fisheries management is a holistic approach that recognizes all the interactions within an ecosystem rather than considering a single species or issue in isolation.

Captain-John-Boats-with-humpback-WDC.jpg