Unalaska, AK – The National Marine Fisheries Service is continuing their research on Steller Sea Lions this summer. This time they are using high-resolution aerial photography to count the number of pups at rookeries and haul outs from Sitka to the western Aleutians. Biologist Lowell Fritz said they need to take the photos now, before the pups start swimming with their mothers. This year's survey is aided by new technology.

"Cameras are attached to a mount that actually compensates for the forward motion of the plane so that the image is perfectly still, so it's like it's on a non-moving platform," he said. "It slightly rotates and it also will take the pictures quick enough, so you get this overlap. So between the rocking motion and the overlap you get an entire swath of the beach and they're perfectly crystal clear as if you are standing or using a tripod."

With crisp images they can more distinctly see the animals. Fritz said in older surveys it was sometimes hard to distinguish between pups and rocks. The survey started on June 24 and it took only five days to go from Sitka to Unalaska. Then the crew was stuck in Adak for over a week because of bad weather. They were also unable to survey the far western Aleutians where sea lion populations are having the worst problems. Unlike in other parts of western Alaska, their numbers never rebounded in the early 2000s.

The NMFS sea lion research focuses on juveniles and adults some years, but those age groups seem to be healthy with high survival levels.

"So with survival being high and we're not seeing any real rebound in the population what we think is an impediment to recovery is pup production," Fritz said. "And from our modeling it looks as though pup natality rates are down about 30 to 35 percent from what they were in the 70s and this is why we're continuing to study this because at this point we don't know exactly why this pup production rate is going down."

Fritz said they need to study adult females to find out why they aren't reproducing and next year's research will focus on that. Currently scientists have three different theories on why birth rates are low. The first two - disease out breaks and environmental contaminants - don't have much evidence supporting them, but Fritz said they need to look into the contaminants theory harder.

"The third thing that could cause the drop in natality is some sort of nutritional stress, like from environmental changes or competition with fishing," he explained.

Fritz and others are looking into this theory. Researchers are also looking at sea lion scat to learn what different populations of sea lions are eating and how that's changing. They want to know if diet diversity effects survival or health. Fritz said they need to understand the physiology of females as well because the overall population survival depends on their reproductive success.

"In order to get recovery in the population we're going need to see an improvement in the birth rates. So right now, the stability that we're seeing in the population or even some of the increases is almost entirely due to better survival than we had in the past."

In addition to doing aerial surveys of sea lions, Fritz's team is also taking photos of the fur seal rookeries in the Pribilof Islands. Aerial surveys of the fur seals started 80 years ago and have continued on 20 year cycles.