Uncovering Alderney's Rocky Shore Secrets: My First Crab Survey with AWT

Ever wondered what a crab survey with AWT is like? Read Thanh’s sharing about her first crab survey with AWT at Braye (East end) below.

‘That’s a really big one!’ I exclaimed in delight at the size of an Edible crab under the rock that Lou has just turned.

Last Wednesday, I joined Mel, the AWT Living Seas Coordinator, and Lou, a seasoned citizen scientist, for my first ever crab survey at Braye's rocky shore (east end) during low tide.

To start with, a transect line was set from the shore to the water mark. Lou then walked along the transect line, stopping every 2 meters to selectively turn a big rock near the transect line. The team identified and recorded crabs and other species found under each rock. We found plenty of crabs, mainly broad-clawed porcelain, furrowed, and a few Chancre crabs. The furrowed and Chancre crabs were then put into separate buckets, measured one by one and then carefully put back to where they were.

The data collected for each crab included species name, male/female, presence of eggs, measurements of the carapace, crusher, and the distance between two hind legs, as well as an assessment of their health (a healthy crab receives index 3, while an unhealthy one receives index 4). This detailed data helps track population changes, understand the health of the crab population, and gain valuable insights into the overall health of Alderney's rocky shores.

I was taught how to hold crabs and how to measure them! It was super fun! It takes skill to measure pinchy crabs and patience and dedication to record data regularly and precisely. The crab survey data has been collected for over 2 years, with the survey conducted roughly every 3 months.

Apart from crabs, we spotted many marine species like shore clingfishes, super-fast gobies, well-camouflaged shannies, oyster thieves, scaleworms, barnacles, sponges, painted top shells, flat top shells, dog whelk eggs, and, of course, various seaweeds.

Taking part in the crab survey made my day!

Joining a citizen science project with the AWT is a fantastic way to contribute to vital research and learn more about Alderney's incredible marine life. Whether you're interested in crabs, Pacific oysters (an invasive species), eelgrass, or diving with Seasearch, contact Mel at [email protected] and get involved!