Tagged Blue Claw Crabs

 

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Tagged Blue Claw crab … photo from Lori Wyatt

You have heard of, seen and even found tagged horseshoe crabs, but have you ever seen or found a tagged blue crab?  Lori Wyatt and her crew were crabbing in Delaware recently and came across a tagged blue claw crab, but the day didn’t end with that one, eventually they had thirteen of these tagged crabs.  They called the number on the tags and reported their catch.  There is a reward for reporting the tags from five up to fifty dollars for a reported and sometimes returned specimen.  So not only did they have a great day crabbing with a nice feast for their efforts, but they also made a few bucks to boot.  I was rather intrigued by these tags since blue crabs molt, how did the tag stay on?  I wanted to know how and why this program was started.  From the SERC website … “Thank you for your participation in the Smithsonian Environmental Research Center’s blue crab research program. Our blue crab tracking studies focus on understanding habitat use and crab migrations, as well as better understanding fishery dynamics. To learn more about SERC’s blue crab research, visit our Blue Crab Ecology website and follow our crab tracking updates at the Blue Crab Blog.  Our blue crab tags consist of 1″x 2″ hard pink or white plastic disks attached to the back of the crab with stainless steel wire wound around the spines. High-reward tags ($50) are marked accordingly on both sides of the tag.​”  If you find a tagged crab follow the instructions on the tag, the pink tags they just want the data and the white tags they want the whole crab.  Recreational crabbers in Maryland are not allowed to keep mature female crabs, just send in the data if it is a white tag.  Commercial crabbers can retain mature female crabs and are encouraged to send in the whole specimen.

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Tagged crab marked with a $50 reward .. photo from Lori Wyatt

I contacted the Smithsonian Environmental Research Center (SERC) Animal Tracking Studies and spoke to Rob Aguilar to learn more about this tagging program.  Over the past decade this program has been done in some of the Chesapeake bay’s tributaries.  Male and female crabs are tagged, so their movements can be tracked and other fishery information.  They are collecting data on recreational and commercial crabbing, as well as types of gear used to catch crabs.    My first question concerned molting, I assumed these crabs would lose this tag in a matter of a month, but apparently that is not the case.  Female crabs will no longer molt after their last prepubescent molting.  Male crabs molt less often the larger they get or full size.  The tags are usually attached to crabs that recently molted so thetag will stay on as long as possible.  You can tell a crab recently molted by how white the legs appear.  Some large male crabs may take all season to molt, not monthly like most people think.  Many of these crabs have made it as far as the Core Sound in North Carolina, from the Chesapeake bay.  That is a long trip for a crab.

 

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Tagged blue claw crabs, 13 caught .. photo by Lori Wyatt
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The researchers are also studying the micro chemistry of the water in the tributaries where these crabs were tagged.  A few crabs are kept from the bunch that were tagged to study the water chemistry in the shells of the crabs as a control group.  When a crab molts and grows a new shell it will take in the chemistry of the water in which it regrows a new shell.  This is important data to study growth and allows the researchers to see a chemical signature.  They want to know if this signature stays with the crab after it has moved into other waters.  The crabs the researchers retain when tagging are the control group for each tributary to see the differences in chemical signatures.  Water quality for any marine species is a factor for spawning, molting, feeding and everything in their daily lives.   If you find any tagged crabs, please follow the instructions, send in the data, and if possible the crab.

 

sponge crab, female blue claw crabs, delaware, sussex county, indian river inlet, inland bays, sook crab
Sponge crab caught in the surf in Delaware

Female crabs stop molting once they reach a certain age, but they can produce more than one sponge in their lifetime.   When females mate with a male crab it is only once and then they are done, but they will store the male’s sperm and can create a sponge at anytime.  This is seen more often in warmer waters where the crabs do not have to winter, like Florida.  This information certainly reinforces the fact you should not keep female blue claw crabs, many people think they only sponge once in their lifetime.  The larger the male, the more sperm the female can get from it to store for future sponge production.  The researchers are working on a study to see if the amount of sperm stored by a female matches her potential to produce sponges during her lifespan.  Smaller males produce less storable sperm and a smaller sized male crab population could determine the numbers of crabs produced in a season.  So the collected specimens are also being studied for sperm numbers, to see how it matches up with the population of crabs.  So to answer the age-old question, apparently size does matter in the crab world.

Fish On!!

Rich King

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