Barndoor skates, once a textbook example of overfishing, have recovered enough to allow fishing

Barndoor skates were once thought to be so overfished that a highly-publicized paper from 1998 noted that they had been “driven to near extinction without anyone noticing.” One of the largest skates, barndoor skates can reach over 5 feet in wingspan, which is large enough that their diet includes small sharks like spiny dogfish; for a skate, that’s about as close as it gets to charismatic megafauna!

Recently, NOAA Fisheries announced that Barndoor skate populations off the Northeastern United States had finally recovered enough that fishing for them could resume. This move comes after a 2009 NOAA Fisheries report showed that the species had begun to recover enough that they could be removed from the species of concern list, though they remained protected at the time. “This is good news,” Mike Ruccio, a Supervisory Fishery Policy Analyst for NOAA Fisheries Greater Atlantic Regional Fisheries Office, told me. “Rebuilding overfished stocks is one of the cornerstones of the US domestic policy on fisheries.”

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Ancient fish farming and popular invasive species: Thursday Afternoon Dredging, October 18th 2018

Cuttings (short and sweet):

Spoils (long reads and deep dives):

Please add your own cuttings and spoils in the comments!

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How goats got the bends, a new ship for VIMS, a new deep-sea submersible for all of us, our looming destruction, and more! Monday Morning Salvage: October 15, 2018.

Foghorn (A Call to Action!)

Flotsam (what we’re obsessed with right now)

Bends in the foreleg of a goat after experiments performed by physiologist John S. Haldane, published in the Journal of Hygiene Vol. 8, 1908.

Bends in the foreleg of a goat after experiments performed by physiologist John S. Haldane, published in the Journal of Hygiene Vol. 8, 1908.

Submersible. Photo courtesy Discovery.

Photo courtesy Discovery.

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We haven’t earned the right to quit. Monday Morning Salvage: October 8, 2018

Foghorn (A Call to Action!)

We are slouching toward somewhere around 3 or 3.5C. That's probably not extinction-level, but it will cause enormous human suffering & irreversible changes that make the biosphere less welcoming to life. We could easily drive half of earth's other species to extinction.

  • And yes, this is a dark, dark report. There’s no hearty, feel-good dose of Earth Optimism today. Maybe it’s discouraging. Maybe you just want to curl up in a ball and hide from the world. Well too bad. You haven’t earned the right to give up. None of us have.

That’s it. There is nothing else.

Banning Arctic fishing and protecting public beach access: Thursday Afternoon Dredging, October 4th, 2018

Cuttings (short and sweet):

Spoils (long reads and deep dives):

Please add your own cuttings and spoils in the comments!

If you appreciate my shark research and conservation outreach, please consider supporting me on Patreon! Any amount is appreciated, and supporters get exclusive rewards!

Dear Shark Man, are the relative sizes of sharks in the “baby shark” dance scientifically accurate?

Welcome to  Dear Shark Man, an advice column inspired by a ridiculous e-mail I received. You can send your questions to me via twitter (@WhySharksMatter) or e-mail (WhySharksMatter at gmail).

Dear Shark Man,
Are Daddy and Grandpa sharks really morphologically bigger than Mommy and Grandma sharks?
Sincerely,
Addicted to “Baby Shark” in Arizona


Dear Addicted,

Thank you for a great question, which allows me to continue teaching science from things that go viral on the internet. First, let’s make sure that everyone’s on the same page about what precisely you are inquiring about.

You’re referencing the viral song “Baby Shark,” which has been made popular recently by the online educational company Pinkfong. (Though, let’s be clear here, the song is much older, I remember singing it at summer camp 25 years ago). The Pinkfong version of the song is an undeniable hit, inspiring remixes, educational parodies, clothing, food,  and even the baby shark challenge.

In case you haven’t seen it yet, you’re welcome:

Anyway, in the song and associated dance, a series of shark age classes are named, and the dancer moves their hands and arms progressively larger to signify an increased gape size (size of open mouth) associated with changes in shark life history. Baby shark is the smallest, mommy and grandma shark are the next largest, and daddy and grandpa shark are the largest. Additionally, both grandma and grandpa shark are shown to have no teeth.

So let’s get back to your question, Addicted. How accurate is the dance associated with “Baby Shark” in terms of portraying the relative dimensions of gape sizes associated with different life history stages of sharks?

Is the gape size of a reproductively mature shark (male or female) larger than that of it’s newborn offspring, which are called either “pups” or “young of year ” or “neonates”? Yes, because the whole shark would be larger. This makes intuitive sense, I hope! Indeed, a mommy or daddy shark would have a dramatically bigger mouth than a baby shark. The size disparity becomes a little blurrier when you’re talking about not-quite-reproductively-mature juveniles and have-just-become-reproductively-mature young adults, but the difference between baby and mommy or daddy sharks is noticeable.

Are reproductively mature adults old enough to have reproductively mature offspring going to be approximately the same size as their reproductively mature offspring? In other words, are grandma sharks the same size as mommy sharks, and are grandpa sharks the same size as daddy sharks? No. Sharks have what’s called “indeterminate growth,” which means that they continue growing throughout their lives. Therefore, grandma sharks would be larger than mommy sharks, and grandpa sharks would be larger than daddy sharks. This difference in size (and associated gape size) would not be as drastic as the difference in size between that of mommy/daddy sharks vs. baby sharks, however, because growth rate slows down as sharks age.

Next, are reproductively mature adult male sharks larger than reproductively mature adult female sharks? In other words, are daddy sharks bigger than mommy sharks, and are grandpa sharks bigger than grandma sharks? Typically not! In many (I’m always hesitant to say “all” because sharks are weird, but I don’t know of a counterexample) species of sharks, the females are larger than the males. The reasons for this are complex, but if you think of it in terms of how much energy and effort and space it takes to make sperm vs. eggs (or how much energy and effort and space it takes to have pups grow inside you), it makes some intuitive sense. In some other fish species, the smaller younger individuals are all males, and they *turn into* females when they age and grow, a phenomenon known as protandrous sequential hermaphroditism. (This happens with clownfish, which would have made Finding Nemo a very different movie if they paid a little more attention to scientific accuracy).

Finally, would older grandma and grandpa sharks have lost all their teeth as they aged? In reality, many shark species can continually regrow new teeth throughout their lifetime (sometimes going through thousands of teeth per individual shark). This is good, because when you’re a wild predator and you don’t have any teeth, you can’t eat and you, um, die.

So in summary, Addicted, “Baby Shark” is catchy as hell, but is not a new song, and the associated dance is not scientifically accurate. Put another way, the song is not quite right, doo doo doo doo doo, not quite right, doo doo doo doo doo, not quite right doo doo doo doo doo, not quite right.


If you appreciate my shark research and conservation outreach, please consider supporting me on Patreon! Any amount is appreciated, and supporters get exclusive rewards!

What to do after the first fatal shark bite in Massachusetts since 1936: 3 experts respond

Two weeks ago, tragedy struck in New England as a boogie boarder was killed by a great white shark. Though shark bites* in general and fatal shark bites* specifically are incredibly rare (Mr. Medici was the first person killed by a great white shark in Massachusetts waters in 82 years), emotions are running high. Some Cape Cod residents are explicitly calling for a cull (targeted killing) of great white sharks.

Such a cull would be devastating for a recovering but still protected shark species, has been shown not to effectively reduce shark bites, and is opposed by shark experts around the world, but what, if anything, should local governments do instead? I’ve written in the past about alternatives to lethal shark control here and here, but not every solution is applicable for every location; local oceanographic conditions vary, as well as local laws and cultural norms. I reached out to three experts to ask what, if anything, they think should be done here. Here’s what they had to say:

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SeaWorld versus OSHA versus Brett Kavanaugh, sea lions and sucker punches, this dumpster whale is all of us, and more! Monday Morning Salvage: October 1, 2018.

Foghorn (A Call to Action!)

Flotsam (what we’re obsessed with right now)

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Angry Canadian Crabs and Extinct Australian Sea Stars: Thursday Afternoon Dredging, September 27(8)th 2018

 

It’s a special Friday morning edition of Thursday Afternoon Dredging because I was traveling!

Cuttings (short and sweet):

Spoils (long reads and deep dives):

Rules of the road (news about regulations governing the ocean) 

SCALLOPPPPPPPPPPPP WARRRRRRRRRRRRRRRRRRR (An update on the brewing BREXIT-related war over scallop fishing rights between the UK and the EU): 

Please add your own cuttings and spoils in the comments!

If you appreciate my shark research and conservation outreach, please consider supporting me on Patreon! Any amount is appreciated, and supporters get exclusive rewards!

High octopuses don’t love you back, sextants in space, protect our ocean monuments, and more! Monday Morning Salvage: September 24, 2018

Logo for Monday Morning Salvage.

Foghorn (a call to action)

Flotsam (what we’re obsessed with right now)

  • Gulper Eels are amazing. Amazing.
There are approximately 30 vaquitas left in the world Illustration: Mona Chalabi

There are approximately 30 vaquitas left in the world
Illustration: Mona Chalabi

  • There are sextants on the International Space Station and I can’t stop thinking about it.

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