The Overlooked Sharks

Dive into research on mysterious deep sea sharks. They're not what you're expecting. 

By Melissa Nehmens

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 A small-eyed rabbitfish (hydrolagus affinis). Photographs courtesy of  the  Pacific Shark Research Center

A small-eyed rabbitfish (hydrolagus affinis). Photographs courtesy of the Pacific Shark Research Center

Even after completing my second year of graduate school, I still don’t know how to respond to people after I tell them I study sharks.

I imagine there is a perfect response, one that would launch us into lively conversation about chondrichthyans (sharks, skates, rays, and chimaeras), but people usually want to know if I study great whites, “man-eaters”, or shark attacks.

“I don’t actually study those kinds of sharks,” is my standard (quietly heartbroken) response, “but they are beautiful” or “but I’m sure you’re safe on the shore at the beach.”

  Wedgefish

Wedgefish

The research I do at Moss Landing Marine Laboratories in central California focuses on lesser-known deepwater sharks impacted by fishing along seamounts just south of Madagascar in the Southern Indian Ocean . The species I study in this area come from four families: kitefin sharks, gulper sharks, lantern sharks and sleeper sharks, all of which are presumed to have slow growth, late sexual maturation, and low reproductive rates that leave them especially vulnerable.

I am trying to understand how long individual sharks live and how fast they grow to predict how heavily they can be fished.

These shark species are of interest to science due to the sheer amount of information we are missing about even some of their most basic characteristics. For some of my study species, we don’t even know how big they get, how many pups (baby sharks) they have in one litter, or when their breeding season is. This means huge knowledge gaps in our basic understanding about what these sharks do, where they spend their time — and, importantly, how they react to pressures such as fishing.

So no, I do not study those big, beautiful, charismatic whites, tigers, or bulls (although they deserve a kind of respect entirely their own). My interests lie with the lesser-known deep-sea sharks of the world. They may not be quite as recognizable, but they’re every bit as intriguing.

 Ninja lantern shark 

Ninja lantern shark 

One of the species I study, the southern lantern shark, is bioluminescent — meaning that it creates its own light (like a firefly) and glows in the dark — which comes in handy as it lives at a staggering 250 to 1,500 meter depth, that's 5 to 30 Olympic swimming pools. And it’s not just sharks that inhabit the deep: Chimaeras can be found down here as well. Like sharks, chimaeras are chondrichthyans, but have long snake-like tails, huge eyes, batty fins, and venomous dorsal spines.

Like their shark counterparts, chimaeras may also be susceptible to fishing pressure from above. And like their shark relatives, we know shockingly little about them. In fact, given the technological advances humans have made in the last century, it’s crazy just how little we know about deep-sea species in general. Chondrichthyans are still being discovered at an increasingly rapid rate , at least 4 species for 2016; but who knows how many more species remain unknown to the scientific community. And we aren’t just talking about microscopic animals — these ones are big and they’re weird looking, and there are plenty we haven’t named or even seen.

The deep ocean, particularly the life-abundant Indian Ocean, is an untapped area of knowledge just waiting to be investigated.

In the Southern Indian Ocean, these sharks are vulnerable to mounting fishing pressure. Historically, fishermen were limited by available technology; they didn’t have the tools and equipment to haul in a huge catch for every net they set. An increase in fishing pressure in coastal areas and unprecedented advancements in fishing technology came to fruition in the 1950’s, and round-the-clock commercial fishing on larger vessels became common place.

  roughskin shark

roughskin shark

This continued unchecked for several decades (and arguably continues today). But in the late 1980’s and early 1990’s scientists, fisherman, and international agencies had what you could call an “uh-oh” moment: we realized we had depleted most of the coastal stocks of edible fish. So what could be done next? Catch fish farther from shore and in deeper water, of course! The technology was available, the fish were out there — why not?

Well… the ocean isn't limitless, and we can drive fish stocks to collapse. We should proceed cautiously. And to do that, we need information. This is where my work comes in.

As we fish environments we know very little about, science can help paint a picture of how human fishing practices influence the fish we catch (yes, sharks are fish!). That information will then supply policy makers with the tools they need to assess what the next step should be.

Once we understand how these deep-sea species live, we can figure out how to protect them – or if they even need protecting. A management plan would set rules and regulations about how many, when, or if a species can be legally caught. Sometimes research shows that a species should never be caught because it grows and reproduces too slowly to maintain a healthy population if fished. On the other hand, research can also show that a species grows and reproduces quickly – and that fishing has only limited impacts on their population.

There are so many other types of shark out there just waiting to be the center of attention: sharks not much bigger than a quarter, and sharks over 50 feet long; adorable sharks and… not so adorable sharks. They inhabit waters from only a few feet deep to the deepest depths your mind can imagine, and anywhere in between. So to explore your world, start with the sharks you've never heard of.

 Cookiecutter shark

Cookiecutter shark

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Melissa Nehmens studies little-known deep sea sharks as a graduate student in marine science at Moss Landing Marine Laboratories, in Moss Landing, California (a staggering 26 miles down the coast from her undergraduate institution: UC Santa Cruz).

She spends her time chasing mysteries of the deep, and daydreaming of the watery worlds just beyond her grasp. Email her at mnehmens@mlml.calstate.edu

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