Sleeper Shark Season Wrap-up

Lessons learned and new horizons

Well our first season of researching sharks is wrapped up! It has been a roller coaster and an example of teamwork in action. Since our first efforts at camera deployment and attempts at fishing, we have logged over 20 days on the water, from 3 different boats, and with a crew of over 20 staff members from 7 departments.

There were empty hooks:

sharks1
Jane and Jared after pulling up another empty hook.

and ones that got away:

sharks2
Jared demonstrating that our bait (salmon) caught a halibut…which almost caught us a shark!

So after all of that, what have we learned?

That we are really, really good at catching sharks that are too big for our study.

As mentioned in previous posts, we originally planned to catch ‘small’ sharks ranging from 4-6ft in length. This size selection was partially to accommodate handling and logistics of temporarily housing the animal at the ASLC, but also because that was the size we were told was most commonly caught in Resurrection Bay.

It turns out that in over 150 hooks we set, we were able to catch 9 Pacific Sleeper Sharks in total: all of which were 8-11ft in length!

shark3
Getting ready to take an estimate of the length of the shark as well as other measurements that might help in aging these animals.

Even though these animals were too big for the primary study, we still have an amazing opportunity to learn from them and address some other questions. For example, we were able to tag two adults with satellite tags. One tag has already popped off (more on that coming soon!), but another tag is still with its shark…wandering around the depths of the Gulf of Alaska fjords until 6 months from now it detaches and we are able to learn what our shark was up to! So be sure to check back in in February when we hopefully hear from that tag!

We also seem to have improved upon and mastered our technique at catching sharks. If you remember, there was a fair bit of trial and error at the start of the season with many days of waiting on the water only to have empty hooks. By the end of the season, the placement of our buoys, bait, and technique was resulting in almost 1 shark caught every time. For much of this success, we can thank our partner Andy Mezirow who helped get us set up! Now we just have to take that information and assess if we can change it at all to catch smaller sharks. Should we try shallower areas of the bay? Different bays? Different times of the year?

There are at least 9 sharks in Resurrection Bay.

Sharks_2018
We caught 9 sharks in 2018 (7 are shown here) from April-September.  Five were females, and four were males.

This might sound like a simple piece of information, but one of the main questions managers have regarding Pacific Sleeper Sharks is actually “how many of them are there?” Pacific Sleeper Sharks are incidentally caught by commercial fishing operations (e.g. ‘bycatch’) but there is very poor availability of data on these and other sharks in Alaska to understand what impact bycatch has on shark populations, or on the ecosystems if they are removed.

shark4.png
A spaghetti tag is attached to the shark so if we re-catch an animal, we know it is one we already sampled. So far we haven’t re-caught any sharks.

To help improve our knowledge, we attached what is called a spaghetti tag—or a small nylon or metal line with a unique number on it—to each of the sharks we caught (except for one that slipped off the hook too soon). The tags were provided by our partners at the Alaska Fisheries Science Center who are also interested in Pacific Sleeper Sharks. Not only do these tags help us to identify if we catch the same shark twice, they also can inform bigger population-level and management questions. For example, if we eventually have a big enough sample of tagged animals and effort, we could use these tags to do a mark-recapture analysis to determine local population size.

So what are our plans moving forward?

We are pausing our field efforts over the winter—mostly because team members are going to be travelling for other work, and because the waters of Resurrection Bay in the winter are less ‘calm’. But this gives us a good opportunity to look-back on this season, reflect on what worked, what didn’t, and what horizons we can aim for next spring.

IMG_8246
Kenny and Markus working on letting a shark go.

Until then, check out our new website for the project “Somniosus” created by our summer Science Communication Fellow, Philina. We will continue adding to the site over the winter and this is where we will be posting more information about our work, background on Sleeper Sharks, telemetry, and the team. You can also find all the previous and upcoming blogs on this project on that website!

 

Oh, and the last thing we learned?

The “Here Sharky sharky sharky” call is not an effective fishing technique.

Sorry, Markus.

 

shark_sp1809_gopro

______

Written by: Amy Bishop

Thanks to the 2018 Sleeper Shark Team: Jared Guthridge, Richard Hocking, Kenny Regan, Chuck DiMarzio, Sarah McMillen, Jane Belovarac, Natalie Rouse, Caitlin DeGrave, Julianna Kim, Sadie Ulman, John Maniscalco, Holly Hermann-Sorensen, Shea Steingass, Chloe Rossman, Alex Havens, Tyler (fellow), Rebecca (fellow), Lisa (fellow), Philina (fellow), Brett Long, Brandon Russell, Amy Bishop, Renae Sattler, Andy Mezirow, and Markus Horning.

Offsite Team: Chis Lowe and Taylor Smith (California State University, Long Beach), Cindy Tribuzio (National Marine Fisheries Service).

This work is funded by a grant from the North Pacific Research Board.

All activities pictured and described here were permitted under ADF&G Aquatic Resource Permit #CF-18-041

 

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