Studying Steller sea lion scat requires getting up close, personal

REID BREWER

April 25, 2008 at 10:54AM AKST

For the Dutch Harbor Fisherman

When most people think of marine-related research, they think that because it is called "research" that it must be highly technical and hence difficult to understand.

In fact, most research is very simple and logical when it is put in the proper context. In the coming months, I will be describing several marine research projects with the intent of de-mystifying science to show what really happens and why.

To determine the distribution and diet of Steller Sea lions, researchers such as Lowell Fritz, of Alaska Fisheries Science Center, have a less-than-pleasant job to do, but he certainly doesn’t mind.

For this project, the first thing that happens is that researchers must perform aerial overflights of a specific area to determine where sea lions are hauled out.

Cameras fixed to a plane take photos of the haul-outs so that researchers can confirm the number of animals in attendance and also to some degree their age and sex. Flights are performed at between 600-1,000 feet to photograph the entire haul-out in one pass and reduce disturbance to the animals.

While the flights are going on, another group led by Steve Barbeaux of the Alaska Fisheries Science Center is in a research boat loaded with oceanographic and acoustic instruments. With the acoustic instrumentation, the researchers are able to determine what kind of fish are in the water column around the areas where the sea lions are hauled-out.

When the first group from the overflights has completed the aerial surveys and haul-out site attendance is determined, they board another research boat and visit the haul-out sites photographed.

From a distance, researchers count the number of animals and also look for ones that have been marked by hot branding, which is part of another study to determine survival and reproductive rates.

Sea lions are gently urged off of the haul-out, generally just by approaching them in a skiff or on land with arms outstretched. Once there, researchers using spoons and trowels scoop the sea lion excrement or scat into labeled plastic bags. Bags are sealed and transported back to land-based labs for inspection later.

Once researchers and scat have arrived in the lab, samples are inspected for hard parts that might indicate what the sea lions are eating.

Most of the evidence from these samples is in the form of fish bones, including vertebrae, ribs and ear bones, called otoliths. By counting the types and number of each in the scat and cross-referencing the information from the acoustics survey, researchers are able estimate at least a portion of the diet for sea lions.

So the process for determining Steller sea lion distribution and diets is fairly straight forward: Overflights to see where the sea lions are, acoustics to see what prey is locally available, scoop the scat off of the sites and analyze scat for remnants of prey eaten.

Note, though this process seems extremely simple, there is a tremendous amount of training and permitting required to approach Steller sea lion haul-outs.

Reid Brewer of Unalaska is a marine biologist with the University of Alaska Fairbanks Marine Advisory Program. He can be reached at 581-4589 or reidbrewer@hotmail.com.