Monday, September 1, 2014

Basking sharks, Bioacoustics, and the Bay of Fundy

A basking shark -- immensity and amazingness.  (GMWSRS photo -- I wish mine came out this good!)
It is glassy calm on the Bay of Fundy, and the crew of Eucheta are debating whether they are seeing a basking shark in the distance or not.  Researchers Heather Koopman and Andrew Westgate are out tagging and biopsying these giants today with their assistant Karina Ortiz, and they have invited me along for the ride.

This is how calm it was!  We are passing a herring weir on the way out to the bay, and it's hard to tell what's water and what's sky.
Heather and Karina surveying for basking sharks in the calmest Bay of Fundy ever.
The problem is not that basking sharks are hard to see under these conditions.  Rather, there are so many things going on around us, we have to take a moment to get our bearings.  It's an embarrassment of charismatic megafauna.

"Okay," says Andrew, pointing to a surface disturbance on Eucheta's port side.  "That's a grey seal over here."

"Right," we agree in unison, then we turn our eyes ahead, raising our binoculars in unison.

"I'm pretty sure that's a mola over there," says Karina, indicating a large fin flopping up and down on the surface.

Mola molas are my favorite, but I contain my enthusiasm as we hone in on the basking shark.  We will have plenty of time to visit Mr. Mola after we find our basking shark.

"He's right there, straight ahead, past the harbor porpoises,"  says Heather.

Carefully approaching a basking shark; her dorsal fin and tail are both visible above the water.
Indeed, a basking shark swims along the surface about a quarter of mile away, her dorsal fin rising above the water by a couple of feet.  We approach carefully as she lumbers along, smoothly cutting the surface of the water with her dorsal fin while her tail -- trailing at least a dozen feet behind -- occasionally slices the water.  As we draw near, it becomes apparent just how large this shark is.  She's much bigger than our boat, with a beefy body, massive head, and dorsal fin the size of a manhole cover.  This shark is probably twenty feet long, and we can only guess how heavy she is. Ten tons? Twenty tons?  Who knows.  A lot.

Basking sharks are the second largest fish in the world, just behind the whale shark in size. Amazingly, they grow to such massive sizes by consuming plankton -- in these waters, copepods. They are slow moving grazers, similar to right whales in many ways.  Despite their enormous size, very little is known about basking sharks, and today we hope to put a tag on one animal and biopsy as many more as we can find.

"It's hard to imagine an animal this size that we know so little about,"  Heather tells me, and she is right. Basking sharks are as big as whales, on which decades of research have resulted in thousands of scholarly papers, dozens of textbooks, and millions of photographs.  Compared to this body of research, scientists know absolutely nothing about basking sharks.  How long do they live?  How fast do they grow?  Where do they reproduce?  What are their migration patterns?  And on and on.  So many questions remain unanswered about the second largest fish.  Heather and Andrew have their work cut out for them.

Following close behind the shark, we prepare equipment for a tag deployment.  Andrew is an expert tagger, having worked extensively on dolphins and whales before becoming curious about basking sharks.  On the bow of the boat, he prepares a tag, which records temperature, depth, speed, pitch and roll.  These tags are a rather extraordinary feat of engineering, allowing researchers to track an animal's movement through the water column and ask questions we could only dream of asking ten year ago: How much time to they spend at the surface?  How deep are they diving?  How do they behave underwater?  How do they react to differences in the water column, like temperature?  Tags like this allow us to spy on animals under the surface as we never have before.  Andrew's tag is cucumber-sized and designed to harmlessly attach to the shark, ride along with her for a few days, then pop off and float at the surface.  When that happens, it sends a signal to orbiting satellites, telling Andrew where it is, and he then retrieves it -- or loses the data stored on it.  Thus far, he hasn't lost a tag on a basking shark, which is quite an accomplishment.

I am handed a camera with a massive lens, and I madly snap shots of the shark's dorsal fin as we track along behind the animal.  Variations in dorsal fin morphology allow researchers to identify sharks individually, just like bottlenose dolphins can be identified by their dorsal fins, or humpback whales by their fluke patterns.  Being able to identify an individual allows researchers to track that individual over time -- and ask where it's been, what it's doing and how long it lives.  Knowing how important these photos might be, I take dozens of photos as Heather carefully pilots the boat along beside the shark. As soon as I think we have enough, the expensive camera is put away in its waterproof Pelican case, lest the shark splash water into the boat when she is tagged.

Andrew makes tagging a shark the size of an airplane look extraordinarily easy, although I've seen enough tagging to know this is rarely the case.  We approach closely as Andrew kneels over the bow of the boat with a long pole, which he uses to attach the tag just behind the shark's dorsal fin.  We all brace for a reaction from the shark, but there is none.  She just swims placidly along, trailing the tag a few feet behind her.  Karina, who is hanging over the starboard side of the boat with a GoPro on a long pole, is filming her the entire time (this is how we know it's a female -- no claspers, which only males possess, were observed on this footage).  The shark gives us a bit of a show, slowly circling the boat, surfacing on the starboard side, then diving under us and appearing on the port side. It's a bit unnerving, but Andrew is elated; the tag looks perfectly placed and the shark seems completely unaware of its presence.  We drift along with the shark for a few more minutes, jot down data from the encounter, and continue to watch in wonder before calling this encounter a success.

I ask Andrew what question he would most like to answer about basking sharks.  He is quick to answer -- where do they reproduce?  He has his suspicions about this.  Andrew thinks they head out of the Bay of Fundy to reproduce, swimming south until they reach the edge of the continental shelf, diving deep to swim below the Gulf Stream, and then heading out to somewhere near the Sargasso Sea.  The tag he deployed today won't reveal this information, but this question can be answered with other tags -- if the money can be raised to deploy them.  

Andrew examining a sample.  He wears a GoPro to document the research.
Heather finding us another shark.
By eleven we have gotten biopsy samples from two sharks, and our attention begins to wander.  In the distance, a fin flutters on the surface of the water, a telltale sign of a mola.  Even seasoned researchers are charmed by these odd fish, and we can't resist taking a closer look any longer.  We motor over to the mola and shut down the engine, drifting along as the fish swims around us, flopping his fins and laying on his side occasionally.  He looks as if he is observing us as much as we are observing him.

"Just a little one," Andrew says.  At about three feet long, Andrew is right.  Someday, I'll see a monster mola, and will be able to die happy.  Until then, I catch a quick video of our friend before we move on.

Porpoises popped up all around us, puffing as they went.
Mola mola were everywhere!  These freaks are my absolute favs.  Squee!  Squee!  (That's me squealing in delight!)

By ten o'clock we are halfway to Nova Scotia, way out in the middle of the Bay of Fundy.  Although we are looking for basking sharks, we are delighted to instead find an unusual visitor to the Bay -- a sperm whale.  A couple of these amazing animals -- the largest of the toothed whales -- have been reported in this area, and when we see a puffy, asymmetrical blow rise above a whale on the horizon, we know we have found one.  Their single blowhole isn't found in the midline of their head, as is the rule for other groups of whales, but has migrated to the left side of their head.  (Here's a great pic of this oddity.)

Sperm whales are rather extraordinary creatures.  They are deep divers, sometimes reaching depths of over a mile, and can go without breathing for well over an hour.  They typically forage on prey items at depth, with giant squid being the prey they are famous for pursuing, but they take many other animals, particularly fish.  Finding food in the deep oceans is a challenge, as light doesn't penetrate very far into the water column.  The sperm whale has therefore evolved a spectacular ability to echolocate, using sonar to sense the environment at depth and locate individual prey items.

We sit quietly near the whale, watching as it breathes repeatedly on the surface.  Today, the research team has brought along a hydrophone -- a microphone that works underwater -- and we decide to toss it overboard to eavesdrop on the whale.  Sperm whales are the loudest of all the animals on earth, broadcasting sounds at over 230 decibels.  That's loud -- imagine a shotgun being fired by a neighbor standing next to you.  If this whale is making any noise, we're likely to hear it.  (Interested in sperm whale acoustics?  Google "sperm whale monkey lips".  Go ahead, do it.)

Notice the bushy, assymetrical blow, typical of a sperm whale.
A sperm whale sounding.
The whale dives just as we toss the hydrophone over, and the first thing we hear is a series of clicks that sounds like a depth finder from a boat.  But it isn't; it's our sperm whale clicking away; either echolocating or communicating with another whale.  Soon this sound grows, and we hear a series of Ka-pams, which sound much like a gunshot.  All of us on the boat are transfixed as we listen to the whale.  The clicking and "gunshots" go on for about five minutes, then the pace of clicking changes dramatically, and we hear what is called "creaking" -- clicks coming so close together it sounds like a squeaky door closing in a ghost story.  This becomes quite frenzied, then suddenly stops. 

"He's found something . . ." Andrew says quietly.  "Aaaaaand . . . Chomp!"

We speculate on what our sperm whale might be eating.  Big cod?  Some other fish?  Probably not a giant squid, that much is for sure.  Whatever it was, we are all thrilled to have had the chance to hear this sperm whale's noisy hunt.  Even for seasoned field biologists like Heather and Andrew, this was a special event to witness, a day we will remember for a long time.




Eventually Karina picks up her binoculars and starts to scan the horizon for basking sharks.  She is a hard worker and will be a good biologist as her career progresses.  Our brief distraction is over, and we pull the hydrophone out of the water and head on our way.  We have a few more promising leads, but are unable to approach them before the shark dives below the surface.  Soon the wind picks up.  The tide turns, and in the Bay of Fundy this is a big deal.  The strong currents of the outgoing tides are opposing the light wind, whipping up a chop on the water.  Suddenly we are unable to find any more fins rising above the water, and we decide it's a waste of time and gas to continue.  Andrew turns the boat towards home, where plenty more work must be done.  After a quick ride back to North Head, we unload the boat, carry gear back to the field station, and clean it to prevent salt water residue from destroying it.  Pictures are downloaded and categorized; samples are carefully loaded into freezers, and notes are transcribed onto computers.  This is the part of marine biology no one thinks about, the glamour-free part, but is as essential as the field work.

After this work is done, we break out some beverages and talk over the highlights of the day.  For me, it has been extraordinary.  The massive sharks, the charming molas, the seabirds flitting around us, the sperm whale are all dancing around in my head.  We talk about what we know about the animals we've seen, and what we don't know.  The things we don't know are the most interesting part of our discussion -- science is, after all, about questions.  There are plenty more questions to be asked about basking sharks.  We stay up late hypothesizing and speculating.  I try to put in a plug for starting to study molas, which Heather sees through in a heartbeat.  But maybe I can convert them.  I mean, basking sharks are cool, but molas -- over the top.

Whatever questions they ask about in the future, I hope I'll get to hear about Heather and Andrew's progress in answering them.

Nuf' said.
For more information about the Grand Manan Whale and Seabird Research Station (like how to donate a few clams to help them out), go to their website.

Fin.  The end.

4 comments :

  1. That settles it - I am definitely coming up there to visit all my Bay of Fundy biology buddies next year.

    --Sarah K

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  2. When I was I kid, I remember herring weirs here in Belfast Bay..long gone now, along with the sardine carriers that used to haul them to the sardine plant..Stinson Canning

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  3. Oh, yes, they used to be here. I'm not sure if any weirs are active in Maine anymore. But up in Grand Manan, there are still quite a few being fished. A fascinating industry.

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