Exciting Research on Juvenile Sea Lions

By Heidi Zemach for SCN

A group of researchers and divers from the Alaska SeaLife Center had another great adventure October 18-25th capturing juvenile Steller sea lions near their haul outs in Resurrection Bay and an area in north Prince William Sound. The five juvenile sea lions captured are being carefully studied, and cared for at the “Steller South Beach” a four-tank outdoor facility at ASLC. These wild juveniles captured on this trip would have had their first birthday in July. They have recently been implanted with intra-abdominal transmitters. When they die, the transmitters will relay information via satellite on their health history and on their possible cause of death, said ASLC lead researcher Dr. Jo-Ann Mellish, an associate research professor and UAF Scientist. ASLC plans to release them back to the wild next week.

The Capture:
Being chosen to participate on the sea lion dive team is a highly coveted position among the divers because it is so interesting and challenging, said Chip Arnold, ASLC’s dive safety officer. The divers he selects for each trip must be extremely comfortable with the underwater equipment and dive techniques, and must have the required scientific diver ratings certified by the American Academy of Underwater Sciences.

Three boats carrying researchers, divers and veterinarians/lab technicians participate in these collection trips. After arriving within range of a well-populated Steller sea lion haulout, two divers aboard a dive boat descend to 20-30’ feet below the surface and wait patiently for the juvenile sea lions to come find them. Groups of these intelligent, most curious youngsters will approach the divers to watch, play, or nip at their fins, Arnold said. The more sea lions there are in the area, the higher their confidence level, and the closer they dare approach. They eventually come close enough to allow divers to poke inside their mouths. While juvenile, they are playful underwater rather than aggressive, Arnold says. But those they typically catch for research, one to four year-olds, can weigh between 180-560 pounds, and an overly friendly bump or nibble can inflict serious damage to a divers’ suit, Arnold said. One might get hold of a piece of a divers’ suit, and tug with his teeth like a puppy, breaking an X- seal, for example. One of the teams’ divers has twice had his suit punctured and flooded, necessitating his quick retreat to the surface. “It gets pretty cold pretty quick,” Arnold said.

While engaging with the youngsters, the divers try to select a good specimen for the research. Checking their teeth, which sea lions will bear during play, helps verify their age. A juvenile sea lion generally looses its baby or milk teeth after being weaned, when it’s about 12 months, and then it begins to develop its large, canine teeth.

Once a sea lion is chosen, and is in a good position to catch, the divers will slide a slip-noose on a large pole around its neck. The noose is attached to a line with a buoy on the other end marking its location on the surface. Usually the sea lion doesn’t like this, and will immediately take off in the opposite direction. The diver will hang onto the end of the line to make sure that it is securely fastened before letting go, allowing the animal to swim away—its buoy in tow.

“It’s actually really exciting to noose them,” Arnold said,“…and they’re not small animals! We do have to hold onto that line and make sure it’s secure, so we kind of go for a little bit of a ride for a few seconds.” The scariest thing that Arnold can remember has happened to an ASLC diver over the 14 sea lion capture trips was the time the line of a fleeing juvenile got tangled around Chip’s tank valve, pulling him backwards through the water! If anything should go wrong, divers need to be able to keep their heads, not panic, and wait for a couple minutes, because eventually the animal will tire and take a breather, Arnold said.

Once the divers are sure that the sea lion’s buoy is not tangled in the line, and that the diver isn’t tangled either, they will send up another buoy to let the six people in the center’s catcher boat Jubatus know where they are, and that it’s O.K. to make chase. Noosed sea lions can travel possibly as far as the length of an entire haulout area of maybe a couple hundred feet before they tire and stop swimming, Mellish said.

Once the buoy stops, the catcher vessel will move in closer, and someone in the front will lean forward and catch its hook line with an extended pole, and then pull the animal in just close enough for the others to drop a net under it. Then they scoop it up much like a fish, and bring it into the boat. As the catcher boat can only hold two juvenile sea lions at a time, a third “mother” vessel, even larger than the other two, waits nearby to accept the captured animals. There, a medical team with portable surgical equipment will anesthetize the sea lion, examine it and take a blood sample, its weight and measurements. Some sea lions will be kept for further research, while others are released on site data have been taken. The team has only a 48-hour window following each capture to get each sea lion safely back to Seward in good health, so they must be efficient.

(Coming soon in Part Two: How the juveniles are cared for at ASLC, and what the latest research is showing.) hzemach@gmail.com



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