Denise Harrington: Big Sharks Bite, Itty Bitty Sharks Intrigue – May 11, 2016

NOAA Teacher at Sea
Denise Harrington
Aboard NOAA Ship Pisces (In Port)
May 04, 2016 – May 12, 2016


Date: Saturday, May 11, 2016


Dr. Trey Driggers shares a great white shark jaw with me.  Photo courtesy of Kevin Rademacher

My children sometimes complain when they find a bird in the freezer next to their frozen waffles.  Yet in Pascagoula, Mississippi, relentless digging in the freezer is how discoveries are made.


Mark Grace, in his office.

Mark Grace has been a biologist with NOAA for 30 years.  If he counted all his time at sea, excluding volunteer and international research, he spent “seven solid years floating.” Out of 200 surveys with NOAA, he was the field party chief for 41 of those projects.  In all of those years, he had never discovered a new species, almost no one ever does.   Yet, in 2013, he discovered an extremely rare, tiny species of pocket shark that had been identified only one other time, in 1979 off the coast of Peru.

pocket shark

This photo of the pocket shark shows its remarkable pocket, just behind the pectoral fin, and some skin damage in front of the eye that may have occurred from the pressure of being harvested from the depths.  Credit J. Wicker NOAA/NMFS/SEFSC

Scientists happened to find the 5 ½ inch shark while doing research on sperm whale feeding habits in the Gulf of Mexico in 2010.    The pocket, unnoticed at first, is what makes this shark so unique. Jesse Wicker took this photo in 2010, aboard NOAA Ship Pisces during the whale survey while processing mountains of sea creatures.  Scientists must pay meticulous attention to detail as they document and photograph specimens at sea.  You never know when your photo may prove crucial to scientific discovery.

The Discovery

The specimens collected in 2010 were identified and then placed in freezers to preserve them for further analysis.

freezer of fish

Photo courtesy of Mark Grace

Mark began to work through the specimens, but it took much longer than he had imagined.  He’d undo a bag, and there would be a hundred fish to process. Each bag seemed bottomless.  By the time Mark got to the last bags, the shark had been in the freezer for three years, eight months.  Brrr…..

Yet he knew the fish weren’t worth much if they stayed in the freezer. He was particularly interested in the cookie cutter shark named after the cookie shaped bites they leave in their prey.  He kept on.

cookie bite

NOAA photo The round mark left on the back of this toothed whale is a telltale sign of a cookie cutter shark, such as this one below.

cookie cutter shark

Cookie Cutter Shark, NOAA’s Fisheries Collection, Photo taken aboard NOAA Ship Pisces.

A shark caught his eye. The shark was identified as belonging to the Dalatiidae family (kitefin sharks), many of whom share luminescent features.

pocket shark bottom

Kitefin shark harvested in 2010 aboard Pisces. Credit: J. Wicker NOAA/NMFS/SEFSC 2010

Yet this shark did not look like the other cookie cutter sharks he had studied.  It had a remarkable fold of skin behind the pectoral fin that did not look like an injury or parasite.  Once Mark saw a matching feature behind the other fin, he realized this shark was like no other species he had ever seen.  Looking in his reference books, he could not find this shark, because it did not exist in any book on his shelf.


Photo credit: Mark Grace – The pockets behind the pectoral fin of the 2010 specimen.

pocket shark diagram

Over hundreds of millions of years, shark adaptations have helped them survive.  They have become smoother, faster, and better at sensing out their prey.  Many sharks have the hard, smooth, scales on their skin called denticles that increase their speed and reduce noise, just like my friend’s fast blue Sterling fiberglass kayak compared to my noisy, orange, plastic Avocet kayak.

Just below the snout, this shark had has a translucent denticle, or scale, at the center of surrounding denticles, giving the appearance of a flower.

pocket shark denticle

Magnified photo of modified denticle.

Mark hypothesized that this unique adaptation might be a pit organ, used to sense currents, or prey.  Scientists have many thoughts about the purposes for this organ.  Each unique feature of the shark inspired Mark to research further.

bioluminescent creatures

Composite of images of bio luminescent species collected with pocket shark by Mark Grace.

One adaption many creatures of deep ocean waters is they glow.  Small photophores, or organs on their body, emit light and signals to communicate with other animals.  In this picture, Mark created a composite of several of the other glowing animals that were pulled up in the trawl net with the pocket shark (middle).

In 30 years, he had never seen a species this rare.  A vitelline scar, like the belly button of a human, indicated that the five and a half inch fish was only a few days to no more than a few weeks old when it was born near the place it was harvested. It was a baby. There had to be at least one other fish like it somewhere in the world.

Connections to others

After a little research, Mark connected this pocket shark with the only other pocket shark ever recorded, in 1979 off the coast of Peru and Chile in the east Pacific Ocean.  His research was particularly challenging because Dolganov, the scientist who first identified the new species pocket shark, wrote up his findings in 1984, in Russian.  Mark had to find a Russian scientist to translate the document to English.


Sheiko pocket shark

The only other known pocket shark, harvested in 1974, is not in great condition.  Photo 2013, Boris Sheiko


pocket shark with ruler

Look at those unique photophore clusters on the shark’s underside.  Photo credit: J. Wicher NOAA/NMFS/SEFSC, 2010

The older pocket shark was a female, and probably an adult, at 20 inches long. Between the two sharks, there were many similarities, but also many differences.


In second grade, we like to make Venn Diagrams in situations such as these.  So I drew this one, comparing the shark harvested in 1974 to the shark harvested in 2010.

Once again, I find myself swirling in a sea of questions.  Are these two pocket sharks, which lived far away from each other, of the same species?  Are their morphological (physical) differences enough to make them unable to reproduce with each other?  Scientists ask similar questions to determine if they have found a new species.

What makes a species unique?

Species identification is no easy task.  Mark reached out to experts, as we all do, with his questions.  At the Hollings Marine Laboratory, Gavin Naylor began to collaborate with Mark as part of his global effort to collect DNA of all living things.  He added the pocket shark to the portion of the tree of life he manages at  John Denton, of the American Museum of Natural History, and Michael Doosey and Henry Bart from the Tulane University Biodiversity Research Institute became part of this group of five scientists who would be connected for life through this 5 ½ inch shark. Together they read many books, sliced and diced the shark digitally, and traveled around the world to meet with other biological explorers. They determined that the specimen collected in the Gulf of Mexico, like specimen in the east Pacific, was a pocket shark, Mollisquama.

pocket shark ct

This three dimensional image obtained by Gavin Naylor through a high resolution CT scan at the Hollings Marine Laboratory allows Mark and Gavin to share their research digitally, with scientists around the world, while keeping the baby pocket shark intact.



The American Museum of Natural History in New York used a three dimension printer to obtain a model of the shark from the CT scan.

The most intriguing part of the scientists’ research lies in the title of their work, hidden in Latin: Mollisquama sp., the name for our Gulf of Mexico baby, and Mollisquama parini, its Russian relative. I notice that the second part of their name is different! Yet in order to establish our shark as a new species of Mollisquama, these scientists will have to write a paper that is “strong enough to withstand many layers of peer review,” says Mark. They will need to demonstrate that the physical differences (e.g. teeth and vertebrae) are significant enough to support a new species identification.

If they are successful in proving their pocket shark is different than its eastern Pacific Ocean relative, what should he name this species of shark?  Mark suggests an international competition, as it will take many minds “to be good enough for NOAA.”

Mark reminds us that when we learn about this shark, we realize that the one great interconnected ocean and its inhabitants are a still a place of mystery and discovery.  We have much more to learn about the ocean and its inhabitants than we know.

Personal Log

Often the greatest discoveries come when you least expect them, hiding in expectations dashed, problems, or the path less traveled. While the Pisces was scheduled to depart last week, the crew continues to work on long and short term projects on the ship and in the lab.

me on screen

Photo courtesy of William Osborn

I am being supervised by Engineering Department Chief “Chief” Brent Jones, on one of many cameras around the ship, as I “assist” the engineering crew get through their list of duties.  His words of wisdom? “Hands off!”

Here, Dana Reid, General Vessel Assistant, and I are opening up the aft valve, so that Travis Martin can switch out the strainers in the main water system.  Dirty strainers get hosed out at least every other day.  Today we caught a small eel in the strainer.

righty tighty

Photo Courtesy of William Osborn


cleaning the strainer

Travis Martin, TAS Denise Harrington, and Dana Reid are switching out the strainer, while Farron “Junior” Cornell, Fisherman, photo bombs us.

Acronyms abound at NOAA, and teachers are affectionately referred to, not by our names, but as “TAS,” for Teacher at Sea.  I’d like to name a new species of this family of adventuresome NOAA educators, “TIP” for those Teachers in Port who adapt by learning about all the amazing discoveries that take place on land following successful projects at sea.  I want to extend a big thank you to Mark Grace and the fishery biologists in the lab who did not know they’d be hosting a TIP.

While in port, I have been able to explore the various land based habitats which are much easier to study than their underwater counterparts. Standing on the water’s edge at David Bayou, I wondered how the area would look from a kayak.  I posted a message to the Mississippi Kayak Meetup Group. Both Eric and Keigm Richards and their friends responded, sharing their knowledge and boats, showing me parts of the watershed very few people see. Coincidentally, Eric was one of the talented NOAA Ship Pisces builders, and knows everything from the finest detail of an itty bitty kayak skeg, to the gigantic architecture and versatile features of the Pisces.

Here is a slideshow of the one of the most unspoiled, diverse and scenic estuaries I’ve paddled.

This slideshow requires JavaScript.

Most of the were taken by Eric.  Notice the changes in vegetation as we travel away from mouth of the Pascagoula River, up the estuary.  The decreasing salinity has a remarkable effect on the flora and fauna of the area.  Mississippians are proud of the Pascagoula, “the last unimpeded river system in the continental United States.”


Most, around 80%, of the creatures in the water column are bio-luminescent, or emit light.  They can vomit out the glowing liquid, hold and release it from a pouch, and/or send it out through photophores (organs like eyes which emit light instead of collecting it).


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