Lobster Shell Disease

While out here on the Bigelow at the southern edge of the Northeast Channel, we’ve caught some lobsters, and just in time. Sailing with us is Joe Kunkel, a former professor and now professor emeritus at UMass Amherst, who is investigating a shell disease found on some lobsters.

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Map showing location of the Northeast Channel

Shell disease is an epizootic, or temporarily prevalent and widespread, disease found on lobsters.  Unofficially, it’s suggested to be caused by a bacterium called Aquamarina.  It’s denoted by circular lesions on the top part of the carapace.  The lesions start out microscopic, but once visible, hundreds of organisms, such as other bacteria, protozoans and nematodes, can be found living in the infected area.  During the 1980s, about 1 in 10,000 lobsters may have been seen with shell disease.  By the late 1990s, hot spots with up to 70% of the population showing signs of lesions were seen in the Narragansett and Buzzards Bay areas.

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Healthy lobster shell – no shell disease. Photo by Christine Kircun, NOAA Fisheries/NEFSC

Joe suggests that the prevalence of the disease increases as the lobsters’ vulnerability to it increases.  This means the shell’s protective ability plays an important role.  Minerals composing the shell include calcium, phosphate and magnesium.  The chemical reactions between these minerals dissolving in the surrounding sea water create a basic (high pH), ‘unstirred layer’.  Think of it as a barrier between the lobster and seawater where a lot of mineral mixing is happening.  Have you ever noticed that a lobster feels a little slippery?  The slippery feeling is that protective barrier.

In order to grow, lobsters molt their hard, exterior shell.  Leading up to molting, a reserve of calcium carbonate and minerals in the endocuticle, or inner shell layer, are resorbed through the epidermal cell layer.  A new, soft shell matrix is formed underneath the old shell.  Once molted, they eat their old shell, bringing all the rest of the minerals back into their body.  They use the resorbed and eaten minerals to establish their new shell.  It takes about seven days for the shell to feel hard, and it’ll be several more weeks until the shell reaches its maximum hardness.  But their new shell has to be bigger so they also need to consume more minerals from their diet.  This time of shell establishment is the vulnerable phase when shell disease may sneak in.

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Lobster with extensive shell disease on its carapace. Photo by Christine Kircun, NOAA Fisheries/NEFSC

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Lobster tail showing extensive shell disease. Photo by Christine Kircun, NOAA Fisheries/NEFSC

If a lobster isn’t able to consume enough added minerals, the new shell could be thinner or weaker in some areas.  As global warming changes the temperature and chemistry of the ocean, lobsters may find it increasingly difficult to obtain the necessary amount of minerals, added to what they already have stored, and regrow a shell to its maximum thickness and hardness as well as building reserves for its yet bigger shell next year.  Possibly, those areas of mineral thinness, or shell weakness, are spots of vulnerability to shell disease.  If the protective barrier isn’t as effective, the lobsters are rendered more vulnerable, giving the bacteria a chance to establish a lesion.

The mineralization is a process that spans multiple years, and the lobsters need an adequate mineral supply to achieve a healthy cuticle that is not vulnerable to infection.  We are making it harder for the lobsters by feeding them low-calcium bait.  We could possibly have a healthier lobster population in the face of ocean acidification if we feed them a higher calcium carbonate bait.  – Joe Kunkel

But if a lobster has shell disease, not all is lost!  If they are able to shed their shell, the disease goes with it, and they are safe.  Unfortunately, it’s not that simple.  First, younger lobsters benefit from multiple molts a year as they are growing very fast.  They are rarely killed because shell disease does not have the time to develop to advanced stages.  For older lobsters, molting is reduced to once a year in the summer.  This means that if the lobster is vulnerable to shell disease due to a compromised shell, it may develop lesions at some point during the year.  As a result, the most severe cases are expected right before molting.  As long as the infection hasn’t made its way through the epidermal cell layer, the lobster has a chance to molt the shell and have a new beginning, disease free with a new shell.  Otherwise, the infection enters the blood stream and kills the lobster.

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Minor shell disease is visible on this lobster shell. Photo by Christine Kircun, NOAA Fisheries, NEFSC

Females have an added hurdle to overcome because they don’t molt while carrying eggs.  Molting for these females may be delayed for up to six months!  This means any lesions on the shell have six more months to reach the blood stream.  Large, healthy and reproductively successful females are extremely important for sustaining a population, so it’s disconcerting to see this condition having an exaggerated effect on females.

But where there are problems, there are people seeking solutions.  One idea is to supplement their diets by feeding lobsters in their traps with bait that contains more minerals needed for shell growth.  Another idea is to harvest them sooner after they molt.  This may decrease the amount of lobsters caught with shell disease as it hasn’t had time to establish itself.  Lobsters with shell disease are usually either discarded or if abundant they are sent to the cannery.  Since the lesions are only on the cuticle, the meat is perfectly fine.   Lobsters with shell disease are not desirable for boiling in the shell because the lovely cherry red color is replaced with a rusted-metal look.

Christine Kircun
Aboard the NOAA Ship Henry B. Bigelow
SBTS HB18-02 Leg 4

Teacher Becomes Sea Student

A unique opportunity that’s offered for teachers to participate in the NOAA surveys is the Teacher At Sea (TAS) program.  It gives teachers from all 50 states, Puerto Rico, Guam and American Samoa the opportunity to participate on our surveys.  This leg, we were fortunate to have Thomas Jenkins from Ohio sail with us on the Bigelow during the spring bottom trawl survey.

With his positive attitude, creativity and excitement to learn, he was the perfect fit!  Aside from teaching 8th grade engineering and general science, he is the science laureate at Teaching Channel, an online community for teachers made up of teachers who provide videos to improve teaching practices, share references and create relevant content to keep up with changes in science, technology and engineering.  As science and engineering standards are increasing, Tom stays ahead of the game by participating in opportunities that give him first hand experiences that he can bring back to his students.

With not knowing exactly what to expect on a bottom trawl survey, Tom was greatly appreciative of everyone’s openness and eagerness to show and teach him everything.  For the most part, he thought the survey would mostly be recording length, weight and sex of the fish.  It was a surprise to find out how in depth the sampling was and how much more work needed to be done after the survey ends.  Most of the information and samples collected undergo further processing and analysis back at the NEFSC labs while other samples were requested from people working on research projects at outside labs or universities.  His excitement to learn was matched by the excitement of the scientific crew to teach.  “If you see something, say something.”  That is always told to everyone sailing.  Either during work-ups or after, everyone was always willing to answer questions and give explanations to any questions.

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Tom works with age and growth technician Jillian Price in the ship’s fish processing lab. Data are entered using the touch screen at right for easy retrieval when the cruise is completed. Photo by Christine Kircun, NOAA Fisheries/NEFSC.

Tom compared experiencing this survey to feeling like a 7-year-old and seeing everything for the first time.  It’s no picnic living in a marine environment, and to successfully thrive in this mysterious ecosystem, the adaptations marine organisms evolved are “so different and cool!”  “The diversity was amazing!”

In particular, he was fascinated with the monkfish.  It uses its illicium, a modified dorsal ray, to lore prey to its giant mouth and move it to its stomach using the many sharp teeth in the front and back of the mouth, like a conveyer belt.  Another animal that sparked Tom’s interest was the longhorn sculpin with its head covered with many sharp spines and the vibrating hum it makes when agitated.  Toward the end of the trip, we started catching lobster, and Tom was excited to hold a lobster whose one claw was the size of his hand!

His students are a clear passion!  In-between tows and after shifts, Tom could be found working on his blogs and collecting information and video capturing different phenomena, such as counter shading, eating habits, pressure changes, and defense mechanisms, to name a few.  He was constantly brainstorming ideas for interactive lesson plans that explain those phenomena.  For example, he mentioned a lesson that would have his students engineer different types of mouths and try to pick up various objects as a way to understand that examining a fish’s mouth is a great way to get an instant idea of their diet.

His students didn’t have to wait for Tom to be back in the classroom to be a part of this journey.  He used social media, Facebook, Instagram and Twitter to communicate informally with his 120 following students!  As he posted daily pictures and updates, they asked him questions and received a quick reply.  And the fun will continue when he returns to his classroom.

After 3 weeks of being away from family and friends, Tom was ready to go back and share everything he learned!  And with all his video footage, he’ll have plenty of work to keep him busy for a while.

The Teacher At Sea program is a great way to establish networks and opportunities between Tom, his current and future students, the Teaching Channel community, and the crew and scientists on the ship.  It’s always important to encourage and empower a strong scientific community.

Overall, Tom would definitely come back if the opportunity presented itself!  “Meeting people who are excited about what they do and who they work with, and learning something new re-energizes me, and makes me want to share the information.”

Christine Kircun
Aboard the Henry B. Bigelow
SBTS HB18-02 Leg 3

Safety First!

Note: The NOAA Ship Henry B. Bigelow is currently at sea working along the Northeast U.S. shelf south of New England on the annual Spring Bottom Trawl Survey.

All images and text by Christine Kircun, NOAA/NEFSC

Safety is an issue that everyone on the ship takes very seriously.  Fire extinguishers, fire stations, emergency escape breathing devices (EEBDs), immersion suits, defibrillators, and personal flotation devices (PFD) can be found all throughout the ship.  Drills are designed by an officer who creates an emergency situation which could be a fire or chemical spill.  The emergency is always in a different area, and sometimes if it’s a fire drill, a smoke machine is used which definitely adds an element of reality!

Drills are practiced once a week, and every single person aboard ship has a job during the drill.  It could be investigating the emergency, directing communications/activities, or mustering to a safe place, to name a few.  Once the alarm for the fire drill is set off, one ten-second tone, everyone immediately stops what they’re doing and heads directly to their assigned muster.  The ship crew split into on-scene, damage control (DC) locker forward, DC locker aft, engine room, and bridge groups.  The on-scene group is first on the site to assess the emergency.  Depending on where, what, and severity of the emergency, people from the DC lockers will assist with any needed equipment or personnel.

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Emergency Escape Breathing Devices (EEBDs, orange boxes at left)) and defibrillators (black bag) are part of the ship’s safety equipment.

Meanwhile, the bridge is monitoring the events and guiding the responders.  The crew in the engine room have the ability to control the electric grid to either divert electricity from the hazardous area or make sure there is power for some other necessary task.

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When the fire is extinguished and area secured, a fire hose is cleaned out by shooting water over the side.  This tests the pump and keeps the inside of the hose clean.  After the crew remove their gear and clean up the tools, the abandon ship alarm sounds with six short and one long tone.  The crew grabs some Emergency Position Indicating Radio Beacons (EPIRBs) and joins the scientific party on the bow.  We practice dressing into our immersion suits to make sure it fits, there are no holes, and there’s a light and whistle attached.  When everyone is finished, the captain announces “secure from drills and heed all further alarms,” and it’s back to regular ship life.

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Members of the science party practice dressing into immersion suits, sometimes called Gumby suits, to make sure it fits, there are no holes, and there’s a light and whistle attached.

Occasionally, we’ll practice a man overboard drill which is announced by three long tones.  For this drill, a dummy or some floating object is thrown overboard.  The science crew musters to the flying bridge as lookouts.  Some crew are stationed at the hospital room and others ride out in a Rigid-Hulled Inflatable Boat (RHIB) to retrieve the “man overboard”.  The cold water makes a fast retrieval paramount for the victim’s survival, so it’s best to avoid falling over!

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A Rigid-Hulled Inflatable Boat, or RHIB, on the Bigelow is used for science and ship operations, including drills for a “man overboard.”

There is a chemical hood onboard for preserving stomach and gonad samples.  Gloves are always worn when filling sample jars, but in case of an accident, there is a spill kit and body/eye wash station nearby.

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Chemical hood with safety equipment, including gloves and goggles (left) and the eye wash station (right).

PFDs (personal flotation devices, or life jackets), helmets and man over-board beacons (MOBs) are always worn while working on the back deck.  When wet, the MOB sends a signal to the bridge that someone is in the water.

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Man overboard beacons (MOBs)

Safety drills aside, we are also encouraged to be mindful of tripping hazards, heavy weather doors, wet stairs, hot electrical boxes, slippery floor surfaces, dryer lint traps and in general, keeping one hand free to help you move around the ship.  One rogue wave could easily throw you down a staircase!  Ultimately, a successful trip is one where everyone comes back uninjured and alive.

Christine Kircun, biologist
Onboard the NOAA Ship Henry B. Bigelow
HB 18-02 Leg 3