"She'll be right, Mate" - Shark Tagging with NOAA/NMFS

This summer marked another great shark tagging cruise for NOAA/NMFS’ Large Pelagics Group, with over 200 blue, short fin mako, and common thresher sharks tagged. The Ventura II set out near the Channel Islands for a ten-day trip under blue skies with a great crew, in hopes of catching  as many juvenile sharks as possible. As a bio undergrad with hopes of doing research, it was an awesome experience to be able to handle and tag some of these shark and all three of the interns- Mackenzie Merkel, Nathan Mertz and I- saw firsthand the importance of planning and execution for research. I feel extremely fortunate to be have been under the wing of John Hyde and Natalie Spear from NOAA/NMFS, and Paul Rogers from Flinders University in Australia- all three very motivated scientists and good people. This high tagging tally forms the basis for a large pool of information and samples that can be obtained from these annual juvenile surveys- DNA samples, muscle biopsies, length, condition and sex of sharks, as well as stomach contents and a few organs from dead specimens. Also collected this trip were parasitic copepods for  Paul Roger’s continuing study of mako sharks. These copepods found on the skin and fins of both mako and blue sharks are being studied as possible biological markers to indicate interactions of different shark subpopulations or species.

For a student who doesn’t quiet have her sea-legs yet, what would seem mundane for seasoned scientists was more than new for me, from baiting 200 hooks with sleepy eyes to the actual tagging of sharks. I had also never participated in long lining before and with all the negative perceptions surrounding this industry, it was surprisingly less invasive in terms of by-catch than I had expected. With two sets a day for ten days, the total tally of 202 animals included 1 opah, 1 pelagic ray and 1 Mola mola, the latter two of which were thankfully unhooked at the rail and swam away. This personal realization about long lining, which although based on a very small sample-size using only a fraction of the industrial hooks, could be testament to the gap between an assumption and the actual experience. I would like to avoid sounding cliché, but it’s amazing how much more you learn from hands-on experience than from just reading about it. No book has or can describe the smell of blue shark under the fingernails at the end of the day, or the pure muscle that makes up the body of even the smallest sharks we tagged. I really loved the actual handling of the sharks, which on our busiest set, was up to 43 blues in a row! It was the mako’s however, that were my favorite, their black eyes and the way they thrash violently from side to side was plenty more aggressive than the characteristic wriggling of the blue sharks.

One set in particular stood out not only because of the low count of two sharks, but for the healthy dose of adrenaline it gave us. The first, a small mako, appeared to be dead as we pulled it on deck and the water running over its gills thankfully paid off. With time and attention, what seemed to be a lifeless little mako turned into a lively one. The next shark was memorable for its 202 cm length paired with how feisty it was. Once on the cradle, it demonstrated its teenage angst by biting through one of the four supporting ropes of the cradle. The rope broke completely off the hydraulic pulley and all of us just looked at each other with wide eyes, surprised.  We sprang into a chaotic impromptu rearrangement of shark, personnel, and ropes, and the cradle was  fixed onboard to bring up the shark. The shark had tired out enough for everyone to hold it down, but as the first big fish of the trip, it definitely made its debut one to remember. I was quickly reminded of the awesome power and agility of these sharks that had been somewhat diluted by handling so many docile juveniles up to that point- a much needed paradigm shift to say the least.  

All but one of the sharks was given a conventional tag- a metal arrow-shaped anchor about a centimeter long attached to a six-inch flexible plastic flag label. These metal anchors are placed in the muscle next to the dorsal fin, from which a small fin clip was taken. The largest mako was given a GTOPP-funded SPOT tag (Smart Position and Temperature Tag), which unlike the conventional plastic tags, can transmit to the satellites which calculate a position. Because of its large size, this mako was given the tag in the assumption that it would  move through different territories more so than juveniles might. The team affixed the plastic tag onto the dorsal fin to keep the oval, battery-operated device from falling off, yet to not be invasive in the shark’s daily behaviors. Hopefully in the near future, the shark we brought onboard on that very day can indicate to the team its movement patterns and where it spends most of its time.

The shark deterrents we picked up in Avalon, Catalina, were tested in our lone night set, with an  outcome differing from our expectations. We clipped a deterrent- a plastic cylinder wrapped in foam, containing a battery-induced electrical field- on almost every other lead going out on the mainline. Unfortunately, the ratio of sharks on deterrent hooks to total number of deterrents used was about 16:21. This high ratio could indicate that improvements are needed for these to effectively repel shark, however, the sample sizing was also very small. Regardless, the possibility of using shark deterrents on future surveys and in commercial fishies could help reduce shark bycatch.

The waters of the Southern California Bight have not only been my personal playground since childhood, but also for sailors, divers, and commercial fishermen, due in part to the biological diversity of pelagic predators. The Ventura II was flanked by a pod of dolphins almost every day, not to mention the pod of white scarred Risso’s dolphins, giving us false hope of nearby swordfish. About three whale spouts were seen returning into coastal waters, almost greeting us before diving down deep. Every night and day, we saw salps forming large stringy colonies that feed on phytoplankton blooms. These salps were joined by a transluscent pink pyrosoma we found during the night set, a column-shaped and hard tunicate that are closely related to salps. It was refreshing to see this kind of life throughout the cruise, especially with the amount of juvenile sharks tagged, because all members of this pelagic environment play a role in the health of the environment. On two occasions, we saw evidence of the predatory instinct of the sharks in the area. We pulled up a mako hooked in the mouth but missing its body from the gills down; the bite marks were testament to an attack from a larger shark. Another live shark was pulled on deck with a large bite mark on its back, while the opah also had a cookie cutter shark bite. All these were seen above water, however we were itching to see some underwater action. Paul and I rigged up a classy little contraption we called the “Ghetto-Pro”, a makeshift version of the professional “Go-Pro” cameras, by duct taping and zip-tying my digital underwater camera to a gaff. Running video over the rail, we were able to see some footage of hooked sharks- a small mako and a large blue- along with a pretty cool sequence of a mola mola being unhooked and swimming away in their odd manner.

Needless to say, the cruise was a blast, I’m still grinning about the experience. With the information gathered not only on this cruise, but from years past and years to come, the abundance and distribution of juveniles sharks in the Southern California Bight might be better understood for scientists and the general public alike.

-Liana Heberer

Nature Paper Receives Extensive Media Coverage

On June 22 the paper "Tracking Apex Marine Predator Movements in a Dynamic Ocean" was published on-line in the journal Nature.  It appeared in the printed edition July 7.  The result of a decade of biologging research on 23 species in the North Pacific Ocean, this paper described for the first time the marine hotspot of the California Current, which extends along the West Coast of North America from the US-Canada border to the tip of Mexico's Baja Peninsula.

As we had hoped, the paper generated broad media coverage in newspapers around the globe.  Click on the links below to read some of the coverage:

Washington Post: West Coast boasts underwater Serengeti, study finds

New York Times: Oceans Imperiled But Still Teeming

San Francisco Chronicle: The Pacific Ocean's 'Corridors of Life'

San Jose Mercury News: California Coast is Hot Spot for Marine Life

MSNBC: Where do Ocean's Predators Roam? The Amazing Answers

Santa Cruz Sentinel: Study: Marine Life Population Rich But Fragile

Sign On San Diego: Marine Predators Flock to California Coast

Oregon Live: In Pacific's Fertile California Current, Marine Predators Bountiful, Study Shows

Big Country Comes to Town

(This is a cross-posting from our Tag A Giant blog, courtesy of TAG Scientist Robbie Schallert)

The TAG team was back on the water Friday in search of more bluefin. After a long run past The Point in some sporty seas, Captain Dale put us on the fish immediately...in fact we had a tuna hit the flat line as it was being let out! Anglers Daragh Brown and Erin Wright, having been trained by living legend Peter Wright, brought the fish in with ease. Once to the back of the boat, Alan "Big Country" Scibal took charge of the leader and wired the fish to the transom door. Dr. Dre surgically implanted the tags, and with a couple of quick stiches, the fish were ready to head out the door to show the school their new hardwear. By the end of the day, we had 4 fish tagged, all in the 220-260 pound size range. It was a long ride home as we battled a head sea the whole way but no one seemed to mind after a great day on the water. You can see some of the action below...

Luck of the Irish

Our Tag-A-Giant team is currently off the coast of North Carolina tagging bluefin tuna.  I'm going to be cross-posting their blog entries here, or you can follow them directly at the Tag-A-Giant blog.  This first one is courtesy of TAG Scientist Robbie Schallert.  Go TAG Team!

TAG-A-Giant 2011 got underway with four bluefin tagged on a gorgeous North Carolina day. The Sensation, captained by Dale Britt and Mate Alan Scibal, hooked a double header to kick off St. Patty's Day with Irish scientist Daragh Browne in the chair. Duke grad student Caitlin Hammer fought the next two fish under guest captain Peter B. Wright's tutelage. The ocean was filled with life on the other side of the Gulf Stream with schools of hammerhead sharks, mantas and tuna exciting the crew. There were literally hundreds of tuna surfing down swell...a site to behold! It is great to get the season started...hopefully the weather will hold through the weekend!

White Shark Team Take Census of Northern California Population

The white shark research team has published two papers in the past few days, documenting the ability to recognize individual sharks year after year by the distinctive shapes and markings on their dorsal fins; and then using this information to estimate the total size of the white shark population in this region.

The first study, which was published March 1 in the journal Marine Biology (Anderson et. al., 2011) shows that it is possible to positively identify the same shark year after year - even over time periods as long as 15-22 years!

Figures a and b show the fin of a single shark in 2007 and 2008;

Figure c shows a different shark in 2008 - illustrating how

distinctive the fin edge shape can be.

  The second study, published today in the journal Biology Letters (Chapple et. al., 2011), uses fin photographs like those above to calculate the total size of the white shark population that returns to northern California each year - and the estimate was just 219 individuals.

Because this marks the first census of this population, we have no way of knowing whether this number is typical, or if it is unusually low (or even unusually high).  What it provides, however, is a baseline that can be used in the years ahead to monitor changes in the adult white shark population - which will be a key step in managing and, if needed, protecting these animals in the wild.

As one might expect, we've had a lot of media interest in the story.  You can check out the latest news coverage at the GTOPP website.

GTOPP data to be integrated into Ocean Observing System

Back in the early days of TOPP, one of our goals was to see if it might be possible to one day use the data we get from tagged animals to help us understand the ocean itself. This concept, which we dubbed "Animals as Ocean Sensors," came a giant step closer to reality last week, with the birth of a new partnership between GTOPP and the national Integrated Ocean Observing System (IOOS).

The concept behind the partnership is simple: electronic tags often carry a variety of environmental sensors to detect light, temperature, pressure and sometimes even salinity or other ocean chemistry. When we attach these tags to an animal - especially one like an elephant seal that dives continuously throughout its journeys - it provides an exceptionally rich dataset, profiling regions of the ocean that would be expensive and logistically difficult to access by human oceanographers.

In a series of meetings held March 2-3, 2011 at the NOAA Fisheries Service lab in Santa Cruz, California, biologging scientists worked directly with the IOOS team to discuss how best to begin the process of integrating animal tagging data into the Ocean Observing System. On Friday, March 4, we were joined here at the Hopkins Marine Station by the IOOS Director Zdenka Willis, to share the results of the meeting with the media and the public. You can see highlights of these discussions at the links below:

Monterey County Herald:  Agencies Join Forces to Track Marine Animals in Monterey Bay

TOPP Researchers Describe Habitat Preferences of Leatherback Sea Turtles: A Key First Step in Open Ocean Conservation

 

Today in the scientific journal Marine Ecology Progress Series, Stanford University marine biologist, and Center of Oceans Solutions’ Marine Spatial Planning Director Dr. George Shillinger and his colleagues published their findings from a three-year study of leatherback sea turtles tagged with satellite transmitters at Playa Grande, Costa Rica.  By following the movements and diving behavior of these turtles, in the context of the oceanographic conditions around them, the researchers were able to identify the habitat most suitable for them.  With this information, it is possible to predict where leatherbacks will go in the open ocean based on oceanographic conditions – and thus to help reduce mortality through interactions with fisheries or other human activities on the high seas.

 

Leatherback sea turtles are the largest and widest-ranging turtle species, and they spend most of their long lives in the open ocean.  Unfortunately, their numbers have declined precipitously in the wild – especially in the Pacific.  This decline is attributed to a variety of human activities, including habitat loss, poaching of both turtles and their eggs, and fisheries bycatch.  Although there have been significant conservation efforts aimed at protecting the turtles on their nesting beaches, little information has been available to help protect them at sea where they spend the majority of their time.

 

Working on the beaches of northwest Costa Rica, Shillinger and his colleagues attached electronic tags to female leatherback sea turtles that had come ashore to lay eggs.  A total of 46 turtles were tagged from 2004 to 2007.  After leaving the beaches, the turtles were followed for an average of 217 days as they traveled offshore into the southeastern Pacific Ocean. During these journeys, the tags recorded information about location, depth and temperature – giving the researchers a detailed profile of their behavior in the wild.  By studying the frequency and depth of their dives, the researchers were able to identify specific behavior types – some of which appeared to be characteristic of traveling, and others of foraging for food.

 

Using a sophisticated computer model, the turtle behavior data was combined with satellite-based measurements of oceanographic conditions including sea surface temperature, chlorophyll a (indicative of the presence of microscopic plant life called “phytoplankton,” which forms the base of the ocean food web), and Ekman upwelling – which is associated with the presence of nutrient-rich water rising to the surface.  By analyzing all these factors together, the researchers demonstrated that the turtles’ foraging behavior was associated with regions of cooler surface temperatures, higher chlorophyll aconcentrations, and strong upwelling – all of which can be observed from earth-orbiting satellites.

 

“The ability to predict where leatherback sea turtles go is a critical first step in being able to protect these animals in the open ocean,” says Shillinger.  “Our improved understanding regarding the forces that shape their movements,  will help to inform our efforts to reduce fisheries-turtles interactions,  and to advance  ecosystem-based marine spatial planning efforts in the Pacific.”

 

One of the fundamental goals of the TOPP program was to explore whether ecosystem-level tagging studies, carried out on multiple species over an extended time period, could help inform ecosystem-based resource management.  This study demonstrates the viability of such an approach.

 

You can read an excellent article about this study on the Stanford News website here, or read the paper itself here.