Scientists have discovered something new about the basking shark, which lives in Cape Cod waters during this time of year.
Jaida Elcock of the Woods Hole Oceanographic Institution is the lead researcher for this study.
CAI's Gilda Geist spoke with her to get the latest on basking sharks.
Gilda Geist Compared to a species like the great white shark, basking sharks are not a species that has a particularly large presence in the mainstream. Can you introduce us to the basking shark?
Jaida Elcock The basking shark is one of my favorites. It is the second largest fish on the entire planet, second only to the whale shark. They can get to be, like, 30-ish feet long, so they're pretty large. A lot of people are a bit unnerved by that—just the sheer size of a shark that big—but they're filter feeders. I always like to remind people that they couldn't swallow you even if they wanted to. They feed on things like copepods, really small zooplankton, some really small fish, things like that. So, they're pretty harmless. One of the things that I think is really cool about them is they can launch themselves out of the water, which is not something that I focus on in my research, but it's something that I think is really interesting about them. I think with their mouth open, they look like a giant windsock, and when they have their mouth closed, they look like an old man that doesn't have his dentures in. I just think that they're one of the coolest species out there.
GG Do we have basking sharks in our local waters right now?
JE Yes, absolutely. Basking sharks tend to hang out around the continental shelf of the East Coast of the United States and Canada between spring to fall, and they start to migrate during fall and spend the winter out in deeper water in like the Sargasso Sea, the Caribbean Sea, near the coast of South America and things like that. Currently, I think that a really good time to see basking sharks, if you're out recreationally fishing, would be probably June to early July. I, disclaimer, have still not seen one in person. I have tried many times and they are sometimes elusive, but other people just seem to have a bit better luck than I do. So, maybe you'll see one.
GG What new information did you and your fellow researchers learn about basking sharks?
JE So, we know that they migrate thousands of kilometers and we know that while they're migrating, they're spending time in some really, really deep water. So, they leave the continental shelf and now they're in the very deep Sargasso Sea and they can access a lot deeper water. What we are finding is that not only do they overlap with the primary deep scattering layer, which is probably around 500 to 700 meters [deep], they're also overlapping with the secondary deep scattering layer, which is like 800 to 900 meters deep in the ocean twilight zone. And so, this is really impressive because being able to dive to those depths is physiologically challenging. But we have these giant sharks [with], you know, a large surface area to body volume ratio, meaning that they can retain heat a little bit easier. They have the capacity for endothermy so they can keep themselves a little bit warmer. They're able to feed on really small things in these really deep waters. A lot of the biomass is really small, like a ton of really, really tiny fishes. And so, if you're a predator that's hunting fish individually, basically going after M&Ms one at a time maybe isn't the best way to go about it. But if you're a basking shark that can kind of hoover up a ton of them all at once, maybe that's a really beneficial place to be. So, we think that they're going down there potentially for foraging purposes. Not many other predators that we know of are accessing depths that deep for foraging. They're kind of staying within the primary deep scattering layer. But this is something new among predators that we're finding here. And it's really interesting that basking sharks are able to overcome some of those physiological challenges to get that deep.
GG What is the significance of this new finding?
JE So, I think that a big thing is understanding what resources basking sharks rely on so that we can better protect basking sharks. The more information we know about an endangered species, the better we are able to protect it. The tough thing with basking sharks is they are highly migratory. So, like I said, they can go from Canada down to Brazil. You're crossing so many different borders of protected areas in so many different countries, and so it's really difficult to conserve a species when it can swim so easily out of a protected area and now it's no longer protected. I think that the ocean twilight zone—there's still so much that we don't know about it. We're doing a lot of really awesome work to better understand it. We know that it plays a really big role in transporting carbon down to the deep sea, and we know that there's a lot of really intricate food web dynamics happening in that zone. If we want to be able to continue to benefit from the ecosystem services of this region that that we are still learning about, we need to be able to better understand it. If we can understand more about the ocean twilight zone and the basking shark, I think that will kind of help protect both of those things.
