BRDs: Saving One Diamondback Terrapin At A Time

Mar 29th, 2012 | By | Category: Make a Difference!

Today, we are learning about a challenge that faces the only turtle in the world that lives exclusively in brackish water:  the imperiled diamondback terrapin.  The challenge we are talking about isn’t habit loss or destruction, it’s not live predators, and it’s not boats!  We are going to talk about crab pots and the lethal trap they can be for diamondback terrapins.

A crab pot is a cage-like-box with an opening that crabs go into, but can’t get out of.  They can’t get out because the metal wires on the opening face inwards.  Crabbers throw crab pots into the water where they sit until they are checked about 24 hours later.  A buoy is attached to the top of the line so the crab pots can be found again (because it would be really hard to have to snorkel around to try to find them!).

The problem for the diamondback terrapins is that the openings on most of the crab pots are too big!  The large openings allow both female and male diamondback terrapins to pass through, and when high tide comes, they are trapped!  Diamondback terrapins are sexually dimorphic, which means the females are larger than the males.  So when females go into a crab pot to get food, the males follow them, and then they both get trapped and drown.

If the opening of the crab pots were just a little smaller, at least the large female diamondback terrapins that carry the eggs would not be able to pass through. This means that they could still lay their eggs and repopulate!  Of course, some males would still go into the crab pots and drown, but at least the eggs would be saved.

So you might ask, why doesn’t the manufacturer of crab pots just make the crab pot openings smaller?  The reason is probably because the crabbers are worried that a slightly smaller opening will prevent them from getting as many crabs;  however, this is not true, and there is another way to minimize the size of a crab pot opening in existing crab pots.  That solution is a Bycatch Reduction Device (BRD).  BRDs are plastic and rectangular, and can be attached to crab pot openings quickly and easily.  You can see one in the picture to the right.

BRDs do not change the amount of crabs you catch, and better yet, they save 73.2% of Diamondback Terrapins that could have gotten trapped in the pot.  How do we know this?  In 2003-2005, Dr. Joseph A. Butler and George L. Heinrich did a study about how BRDs on crab pots reduced how many diamondback terrapins were captured or killed.  Their paper was published in 2007.  Their results showed that BRDs help save diamondback terrapins but did not reduce the amount of crabs caught!

So now crabbers have a way to be heroes in the conservation world by using BRDs!  So where can crabbers get BRDs?  Well, if they are in Florida, recreational and commercial crabbers can get them for free from the Florida Turtle Conservation Trust ( with the funding from the Tampa Bay Estuary Program.  I got to go to a workshop they organized called “Management and Conservation of Diamondback Terrapins in Tampa Bay:  A Symposium for Environmental Professionals” a couple of months ago, and it was great learning a lot of this information!

One more thing!  Sadly, some crab pots get lost and turn into ghosts.  Not the type that you might see in a haunted house, but the type that is called a ghost pot, or ghost crab pot.  There are many different reasons this happens, like if the buoy breaks off or a strong storm moves it, but basically they are called ghost pots because they are no longer being checked.  Since they don’t get checked, the animals inside of them do not get released, and they eventually drown.  Diamondback terrapins are often one of these unfortunate animals.

I hope you have learned something new.  If you know a crabber that crabs in brackish water, please tell him or her about how they can help be conservation heroes of diamondback terrapins!

Diamondback Terrapins of Tampa Bay: an Educator’s Guide developed by George L. Heinrich, Timothy J. Walsh and Dr. Joseph A. Butler
Florida Turtle Conservation Trust (

Me with a diamondback terrapin
With a BRD
With Dr. Joseph A. Butler and George L. Heinrich

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