The call comes over the radio, “we have a few curious seals near the net.” And, then a few moments later, “we’ve got one!” After some time getting the seal into the boat and secured in a hoop net, we get the call to transfer the seal to our support boat for transport back to the R/V Norseman. For the most part, seals remain relatively calm during the short journey in our inflatable boat— surprising given this must be a Twilight Zone experience for them. Not many seals get a chance to ride in a boat, let alone a visit to the doctor.
Once alongside the Norseman, we move the seals into a larger bag that can be lifted with the crane. It’s a short ride through the air onto the deck. At this point, there are many similarities to a visit to the doctor or taking your pet to the clinic for a check-up. The first job is to record the seal’s weight with a scale on the crane. Getting a good mass measurement on a digital scale on a boat that is rolling around can be a bit of a challenge.
The next responsibility is for one of our veterinary team to start the sedation process. Midazolam is a sedative drug similar to valium that calms the seals, reduces their stress, and improves safety for the human researchers. It may also reduce their memory of the experience. Jen Rego, a registered veterinary technician with SeaWorld in San Diego, lets the data recorder know the dose that she administered and the time. Now, we monitor the seal closely and wait for the drug to take effect.
Basic data about the health of harbor seals in the western Aleutians are scarce, and this cruise is a valuable opportunity to gather more baseline health information. We begin with some additional measurements of length and girth. Then we use an ultrasound machine to measure how thick the seals’ blubber layer is. Most people don’t try to grow a thick layer of blubber, but seals don’t have thick hair or fur to keep them warm, and healthier seals usually have a thicker blubber layer. Our ultrasound is the same type that is used to examine people, but it is designed to be used in remote places, far from offices and hospitals. It is portable and waterproof, which has been crucial on this trip when we have processed seals in the pouring rain.
4 tigers, 3 blues, and 2 purples ready to go.
Collecting blood is a quick coordination between two people on the team. One person finds the particular location on the back where blood will be drawn, and the other assists by giving needles and tubes, as the person drawing blood needs them. Seals have a larger vein (also called a sinus) where vets and trained biologists can place a needle to collect blood. Several different blood tubes are filled in order to examine different properties of the blood, just like when you have blood taken for tests at the doctor’s office. The “tigers” refer to blood tubes designed to separate serum from red blood cells. The serum allows us to screen for particular diseases and pathogens. They are called “tigers” because the tube top is marked with tiger stripes. The blue top tubes allow us to separate plasma from red blood cells for examination of mercury and other exposure to contaminants. Finally, the purple top tubes are smaller tubes that provide blood for a wide range of additional health and condition screening.
After all the seals captured that day have been sampled, tagged, and released from the outer deck, we turn one of the rooms on the Norseman into a “lab”, where we process the blood and tissue samples. We have two centrifuges and a VetScan machine (a machine that lets us measure blood values right here on the ship) set up on one bench. We use centrifuges to spin the blood so we can then collect the different components (serum, plasma, red blood cells). As we look around the room, several people are busy using pipets to collect serum, plasma, and red blood cells into small vials, while others are making blood slides, spinning tubes in the two centrifuges, running samples through the VetScan, using a refractometer to measure protein levels in the blood, and organizing samples in boxes to be stored in the freezer.
On days when we catch a larger number of seals (5-10), the “lab” is a coordinated dance of activity amongst all of the research team; it can take several hours after the last seal has been tagged and released. Other than the VetScan—which provides some immediate analytical results—most of our blood is collected for later analysis as part of collaborations with other researchers or long-term archival. Thus, clear labeling of tubes and precise pipetting of samples is a big part of the evening lab work. The lab work ends with a trip down below to the walk-in freezer where we store samples until after the cruise when they will be shipped back to Seattle safely in liquid nitrogen.
We are optimistic that we’ll capture more seals and get more samples as we move into our last week. Stay tuned for more updates on our progress.
Meet the Bloggers
Shawn Dahle is a biologist at the Alaska Fisheries Science Center’s Marine Mammal Laboratory. Shawn joined the Lab's Polar Ecosystems Program in 2002 after completing his M.S. in Fisheries Conservation at the University of Minnesota. His research focuses on population monitoring and status assessments of seals in Alaska.
Josh London is a wildlife biologist at the Alaska Fisheries Science Center’s Marine Mammal Laboratory. He focuses on population assessment and ecology of harbor seals and ice seals. Josh received a B.S. and Ph.D. from the University of Washington.
Peter Boveng is the leader of the Polar Ecosystems Program for research on harbor seals and ice-associated (ringed, bearded, spotted, and ribbon) seals in Alaska. His primary research interests are in the estimation of fundamental quantities for population assessment, such as abundance, trends, and vital rates, and in satellite telemetry studies of movements, distribution, and foraging behavior. Peter received Ph.D. and M.S. degrees in biology from Montana State University and a B.A. from Cornell University.
Heather Ziel is a research biologist at the Alaska Fisheries Science Center's Marine Mammal Laboratory. She works in the Lab's Polar Ecosystems Program.