September 22, 2017

Common Shore Crab (Carcinus maenas)

Continuing the theme of invasive species explored elsewhere in the blog, the Common Shore Crab, a native of British waters, has been recorded on almost every other continent.

World domination aside, I have very fond memories of this species. As a lad, each summer we used to take day trips to Sand Bay, a stretch of the north Somerset coast just north of Weston Super Mare. My Dad had spent some years of the second world war living there with my Gran to avoid the Luftwaffe’s bombing of Bristol, so the place itself had good memories for him.

Whilst my parents busied themselves having picnics and other dull things, I used to spend my time prising Limpets (Patella vulgata) from the carboniferous limestone to use as bait on my crab line.

Occasionally I’d catch an Edible or Brown Crab (Cancer pagurus) but most of the time, these deep green Shore Crabs made up the body of my catch. Spending time trying to encourage them out of the submerged crevices of rock polls by dangling a line with a morsel of Limpet on it, needs a fair bit of patience and is an excellent way into learning about the ecology of the inter tidal zone.

At the end of the day my catch would be returned to their respective pools, but as I learned more about the other seashore creatures I got less and less comfortable with the requisite Limpet butchery.

Some years later, whilst working for a conservation charity on the island of Flat Holme in the Bristol Channel, I learned a deep respect for the humble Limpet. We marked individuals and their home positions, then moved them to a different part of the beach to demonstrate that they could move considerable distances. I’m still not sure how they navigated back to their original positions, but they mostly did.