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Citizens Count Crabs & We Count on Them

Feb 11, 2019 | Get Involved, Informed Citizens, Mission-Aransas, Texas, Reserves

Citizen scientists reconstruct a blue crab collector. More than 60 locals supported a study that found that less than 1% of blue crab larvae make the journey from the ocean to Texas bays. Watch a video about this project. 
All media courtesy of the Mission-Aransas Reserve.

Most young adults don’t plan on moving back home, but for juvenile blue crabs in Texas, moving back to the estuaries of their parents is part of their complex life-cycle. Thanks to a collaboration between local citizens and scientists from our Mission-Aransas Reserve, we’ve set an important baseline for understanding the movements of this commercially important shellfish.

Texas blue crab populations have been on the decline since 1987 due to pressures that likely include reduced fresh water in estuaries, habitat loss, and predation. Management actions to protect blue crabs requires a better understanding of their complex life cycle and their incredible journey.

Every year, thousands of raindrop-sized larval crabs ride the currents from the Gulf of Mexico into the state’s estuaries. With tiny claws, they cling to anything they can catch hold of: seagrass, oyster reefs, bathing suits (ouch!), and most recently, collection stations designed by Reserve researchers and monitored by citizen scientists.

Thousands of blue crab larvae make the journey from the ocean into Texas estuaries every year.

“We wanted to get a picture of what the populations are doing,” says Ed Buskey, the Mission-Aransas Reserve research coordinator and professor at the University of Texas Marine Science Institute. “Are there a lot of blue crabs at a certain time of the year? Are we not getting as many crabs in our bay as in the past? How many actually survive?”

To answer these questions, the team installed hog hair collection stations—named for their hairy texture but made from air conditioning filters—in the ocean off Port Aransas and throughout Aransas Bay. By counting the crabs at the stations each day, researchers hoped to track how many baby crabs were returning to the estuaries, how far they travelled, and when they did so. 

The Reserve team knew they were going to need a lot of help to make it work. Fortunately, more than 60 citizen scientists volunteered more than 2,000 hours of service to collect and process the hundreds of samples involved in the project.

“I had never heard of a blue crab before, but learning how the effects of tide, temperature, season defined their population was fascinating and startling,” says Francie Henderson, who volunteered with the project. “My part in it was gratifying, and I was glad to help. I would definitely participate as a citizen scientist again.”

Reserve Scientist Tracy Weatherall counting samples in the lab.

Reserve scientists Tracy Weatherall, Lindsay Scheef, and Ed Buskey recently published the results of the study in Estuarine, Coastal and Shelf Science. They found that less than 1% of the larvae released into the ocean make their way back into the bays. They also found seasonal patterns to the larval crab’s movements. The return of the commercial blue crab species, Callinectes sapidus, peaked in the fall, and another common species known as the lesser blue crab, Callinectes similis, peaked in the winter.

Incredible journey: Blue crab larvae travelled on currents up the estuary, but their numbers were highest at the mouth.

I’ve always had a strong interest in nature and science, but ended up pursuing a career developing computer software applications,” says Chris Muckey, another citizen scientist volunteer. “This project allowed me to rekindle that interest. I took away a better understanding of the complexity of the food chain. Even the smallest crab larvae can impact the survival of endangered species like the Whooping Crane.”

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