We need a smaller shark (or a bigger boat)!

Well, after an exciting summer of 2018 where we captured and worked with nine Pacific sleeper sharks here in Resurrection Bay, we are at it again for the summer of 2019. Our capture efforts are for a research project funded by the North Pacific Research Board. The project is carried out in collaboration with the Shark Lab at California State University at Long Beach (CSULB).

Why in the world are we trying to catch sleeper sharks? Well, not much is known about these enigmatic sharks that may just be among the longest-lived vertebrates on the planet (more on that in a future blog). Even though it is possible and even likely that these sharks play a very important role in cold water marine ecosystems, most people have never heard of sleeper sharks. Even those that have often think of these elasmobranchs as sluggish, bottom-dwelling scavengers. But hold it – not so fast in your conclusions! Some evidence suggests that these slow moving sharks may occasionally attack, kill and at least partially devour fast swimming, agile sea lions – more on that in upcoming blog posts as well.

A Pacific sleeper shark (Somniosus pacificus) caught via an easily removable circle hook baited with salmon, next to our work boat, the Jubatus. The animal is floating on its back, and does not want to let go of the salmon bait.

Right now, we are working on developing a study that will allow us to learn more about these animals. Often times, when so little is known about a species, it can be very helpful to begin initial studies under ‘controlled access conditions’, in other words: in a lab. For example, there is no data on the metabolic rate of the Pacific sleeper shark: how much energy does a shark require to stay alive and for various functions, which leads to the question of how much they must eat. We don’t know. To find out, we must measure their metabolic rate, and the best, most accurate and safest initial way to do that is in a lab.

How do you get a shark to a lab?

Well, we’re working on figuring that out. Everything about this pilot project is experimental, so to speak. We have devised a plan to capture a small shark right here in Resurrection Bay, and transport it back to the Alaska SeaLife Center (ASLC). There we are hoping to maintain the shark for a few weeks while conducting ‘controlled access studies’, such as measuring the metabolic rate. After that, we will transport the shark back to where we captured it, and will release it. We will monitor all sharks after their release through satellite transmitters. By comparing the behavior of tagged sharks that stayed at the ‘Hotel ASLC’ for a few weeks, to sharks that did not stay at our facility, we will also be able to determine any effects of these manipulations, and hopefully confirm that the sharks don’t mind a few weeks of free food and lodging.

A key word here however is ‘small shark’. We feel we can safely handle and transport a smaller shark, maybe up to 1.8 meters in total length (about 6ft). We estimate that such a comparably small shark may weigh about 50 kg (about 110 lbs). However, while we have been able to catch a surprising number of sharks (9 animals last year), they were all too big: over 2.4 m (8 ft) in length, more than we can handle. The very last one we caught just a few days ago measured a whopping 3.5m (about 11.5 ft), and we estimated her weight at over 430 kg (over 950 lbs). So far, we have collected some samples (blood for health assessments, fin clips for genetic studies, and now muscle samples to study enzymes and muscle biochemistry), and we have placed markers (called spaghetti tags) and electronic tracking devices on the animals before they were released.

A 3.5 m long female Pacific sleeper shark captured in Resurrection Bay. To study this animal’s movement and behavior, researchers have attached a small acoustic tracking device (the grey cylinder visible to the left of the dorsal fin), and a satellite transmitter (floating in the water to the right of the dorsal fin). CSULB graduate student Taylor Smith is holding the shark via a wide strap just prior to releasing the animal.

We’re still working on finding, safely catching and transporting a smaller shark to the ASLC. And for those that might have questions about the study animals’ welfare: all our work is quite vigorously scrutinized by our institutional ethics committee, and is conducted under the authorization of this committee (AUP # R19-05-05) and by a research permit issued by the Alaska Department of Fish & Game (CF-19-085).

Check back with us throughout the summer for updates on this research project. And we are always open to donations for a bigger boat!

Written by: Dr. Markus Horning

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