Biologists last spring counted 1,895 Steller sea lions at Sea Lion Rock, the highest number since systematic counts started there in 2004.
That number is 25 percent higher than the next highest count in 2014. Sea Lion Rock is a nickname for Gran Point, a rock ledge on the east wall of Lynn Canal 10 miles southeast of downtown Haines used primarily by females and juveniles.
“There’s no obvious reason that would explain it to my knowledge. The best guess is that the food was particularly good here or bad elsewhere. Sea lions are very good at finding patches of forage fish,” said Kelly Hastings, a Fish and Game sea lion biologist based in Haines.
Sea Lion Rock is one of 20 major “haulouts” in Southeast Alaska, places sea lions use primarily to rest. They congregate there between May and July after arriving in Lynn Canal to feed on eulachon, herring and other forage fish.
Including this year’s count, the numbers of sea lions using Sea Lion Rock is growing at 3.5 percent per year, Hastings said.
That’s slightly higher than the 3.1 percent growth since the 1970s of the eastern Steller sea lion population, a genetically distinct population that extends from Southeast Alaska to southern California.
The numbers are consistent with recent studies that show a northward expansion of the population and its breeding range, as well as establishment of new breeding and birthing areas – called rookeries – in Southeast.
There are five rookeries on the outer coast of Southeast, up from just one prior to the 1980s. Breeding sea lions use places like Gran Point to fatten up before heading to rookeries, as during breeding and birthing, animals can go weeks without eating.
According to recent studies, Southeast rookeries account for more than half the pups in the eastern population.
At two new ones, Graves Rocks outside Glacier Bay and White Sisters Islands on western Chichagof Island, sea lion counts are growing at a much higher rate. In the Glacier Bay-Cross Sound region, sea lion numbers are growing at 8 percent annually. “That’s a high growth rate for sea lions. That high growth area includes the two newest rookeries, with high survival and big pups,” Hastings said.
White Sisters became a major rookery in the early 1990s and the rise of the Graves Rocks site dates to 2005, Hastings said.
Biologists have “no definite answer” on why the eastern population is doing so well, Hastings said. “We know they’re not suffering disease, but other than that, we really don’t know.”
Extrapolating a 2002 population estimate of 46,000 to 58,000 individuals, the current eastern population may be between 67,500 and 85,000, Hastings said. The population was listed as a “threatened” species until 2013, but the listing was largely due to a dramatic drop in a separate population of sea lions in western Alaska.
The western population dropped from 250,000 animals in the late 1970s to 40,000 in 2004, and scientists have yet to explain why that happened.
About 2,000 sea lions from the eastern population have been branded, and 236 branded ones were seen at Sea Lion Rock last spring. Of those, 98 percent were born in Southeast Alaska rookeries and 2 percent were born in Oregon, Prince William Sound, Barren Islands or Marmot Island (Kodiak area).
Although numbers haven’t been computed, many of the branded sea lions at Sea Lion Rock were from rookeries in southern Southeast, including Forrester Island near Dixon Entrance and Hazy Island near Cape Ommaney.
Although Graves Rocks is the closest rookery to Sea Lion Rock, biologists see relatively fewer animals from there, Hastings said. “They stay close to Graves Rock. It’s a good spot.”
In total production, rookeries in southern Southeast rank higher than ones nearby, Hastings said. Forrester Island produces about 4,000 pups per year compared to 2,000 at Hazy Island, 440 at Graves Rocks and 850 at White Sisters.
Studies have shown sea lions can travel quickly through the region. A sea lion cow spotted at Gran Point with a juvenile was seen five days later at Forrester Island giving birth, Hastings said.