Transient Juvenile Steller Sea Lion Studies

November 26, 2010 6:52 pmComments OffViews: 16
 
 
The captive juveniles permit NMFS 14335
The captive juveniles permit NMFS 14335

 Part Two:
By Heidi Zemach for SCN 
  

The Alaska SeaLife Center has been temporarily housing and studying five wild “transient” juvenile Steller sea lions captured by divers near haulouts in Resurrection Bay and Prince William Sound They are the latest subjects to be studied in eight years of research on transient Steller sea lions from Resurrection Bay and Prince William Sound in order to better understand the decline of the area’s sea lion populations, and the cause of high juvenile sea lion mortality. This particular study of juvenile sea lion mortality using transmitters has only involved 27 sea lions thus far, but ASLC plans to try to capture and release six more in late May, 2011. The sea lions, which were captured October 18-25th 2010, will soon be released into their home environment. They are permitted to remain at the center for up to three months, but are released earlier whenever possible. They will be carrying intra-abdominal transmitters designed to allow researchers to learn more about their health history, and their probable cause of death, said ASLC lead researcher Dr. Jo-Ann Mellish, an associate research professor and UAF scientist.   

 Once the sea lions arrive in Seward, they are quarantined at the “Steller South Beach” facility—a set of four round outdoor pools where they can swim together or visit one another in a different pool, or remain in isolation. Standing just outside the Alaska SeaLife Center, one can sometimes hear their barks mingling with the captive sea lions, Woody and Sugar, and the center’s many sea ducks and birds. One can also view them the distance from the center’s second-floor viewing window, below.   

 In keeping with strict federal permit guidelines, and the conditions that Mellish helped design for their care, ASLC keeps these sea lions as close to wild conditions as possible while minimizing their contact with humans. They are fed live fish in order to maintain their fishing skills, but aren’t given man-made toys to play with. All food is delivered remotely through ‘fish cannons’ tied into the plumbing system so they won’t associate food or treats with humans. The gates between the tanks are opened and closed by remote pulley systems. The amount of time humans spend on the deck nearby is limited to only that necessary for cleaning and husbandry. The humans who do come into contact with the quarantined marine mammals also must follow strict quarantine procedures. Mellish, who had been working with the quarantined sea lions earlier in the day, asked to be interviewed by Seward City News in a location outside ASLC, as she could not enter the main part of the ASLC building for fear of cross-contamination.   

 The juvenile sea lions visit the veterinary clinic once a week at most. They are given gas anesthetic during their health check, as it is more humane, Mellish said. This particular group was studied primarily for their implants, with some sample collection taken for ongoing studies of nutritional biomarkers.As the only facility in the United States federally permitted to capture and research captive sea lions, the ASLC in Seward has become one of the important forerunners for juvenile sea lion research anywhere, and its scientists have been able to obtain data not collected anywhere else, according to the ASLC website. The eight years of data collected thus far has been shared among many teams of researches in Alaska and Outside participating in many different scientific projects, Mellish said. The Transient Juvenile Steller Sea Lion Project is just one of a series of broad categories of research focused on the possible reasons for decline of sea lion populations in western and south-central Alaska. They include studies on whale predation, endocrinology and contaminants, foraging ecology, population, and nutrition—all of which may be a factor in their decline. Overall, the center has housed, researched and released 60 juvenile sea lions since the program began in August 2003. They have caught, studied and released about 60-70 more in the field as controls, Mellish said.   

  Of the 27 sea lions captured and released over the past few years with these new abdominal implants, nine are known to have died. Of the nine, eight apparently died very suddenly, as evidenced by the rapid cooling of their body temperatures. (Some of the juvenile sea lions also had been identified by ASCL staff shortly before their demise via Chiswell Island’s video monitors, appearing very much alive and well.) The researchers studying the data believe that the eight juveniles were killed by larger predators, probably Orca or “Killer” whales. When Orcas attack a sea lion or seal, they slash it up into smaller pieces, or throw their prey into the air in a visually dramatic display rather than consuming it whole. The abdominal transmitters fall off in the process, and then begin to transmit the information collected since it was implanted, via satellite, Mellish said.   

For the past decade or more, the cause of the Steller sea lion’s steady decline in Western Alaska has been a particularly searing debate by affected fishing communities, as commercial Pollock and Groundfish fishing has been increasingly restricted around sea lion breeding grounds to protect them. Fishermen who have witnessed Orca feeding frenzies have long suspected these whales, as well as broader changes in the sea’s climate—rather than commercial fishing competition, so the ASLC’s latest findings might interest them.

A sea lion haulout

 

But 27 transmitter-animals is a relatively small sample size, and these sea lions have all come from PWS or Resurrection Bay, so one can’t really attribute the decline in the Western Alaska Stellar sea lion population to Orca predation, Mellish said. One can only possibly attribute the high rate of mortality among juvenile sea lions in Kenai Fjords or the Prince William Sound area to Orca predation. “There’s never going to be a smoking gun” pointing to one causal factor for the entire Western Alaska sea lion decline, Mellish said.For those concerned with the ethics of using live marine mammals as research subjects, Mellish said; “One thing that I always try to impress upon people is that people researching these animals do it because they care about the well-being of the species as a whole, and at an individual level.” Perhaps as a result of the careful parameters of their care at the center, the brief time in captivity and the transmitters don’t seem to affect their lives once released. Past experience has shown that within two weeks of release there is no difference between individuals that have been in the program and wild animals of the same age and location that have not, Mellish said. (hzemach@gmail.com) (Scroll back to last week to view Part l)

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