The Guardiana river, marking the lower border area between Portugal and Spain, is hosting a new visitor as a blue crab, found in the estuary in June, has been identified.
Researchers from the Centre for Marine Sciences confirmed the visitor was indeed a 'Chesapeake blue crab' from the US where it is valued as a food source.
This is the first time a blue crab has been found in the Guadiana and local fishermen have been asked by the researchers to be on the lookout for more examples.
The Chesapeake blue crab, Callinectes sapidus, also known as the Atlantic blue crab, is a species native to the waters of the western Atlantic Ocean and the Gulf of Mexico but has popped up in the strangest of places after being transported in ships’ ballast tanks.
The last recorded identification of a blue crab in Portugal was in the Sado estuary and researchers want to discover whether the species is establishing itself along the Portuguese coastline.
Callinectes sapidus is native to the western edge of the Atlantic Ocean from Cape Cod to Argentina and around the Gulf of Mexico.
The crab has travelled in ballast tanks to Japanese and European waters, and has been spotted in the Baltic, Mediterranean, North Sea and Black Sea. The first record from European waters was made in 1901 at Rochefort in France.
The crab is tasty and was an important food source for Native Americans and European settlers in the Chesapeake Bay area in the 1600s. later, they mostly were used as bait until advances in refrigeration techniques in the late 1800s and early 1900s increased the supply of blue crab across the US.
The declining blue crab population is now the subject of anxiety among fishermen in the US as over the decade between the mid-1990s to 2004, the estimated population fell from 900 million to around 300 million.
Many factors are to blame for low blue crab numbers, including high fishing pressure, environmental degradation, and disease. Hopefully the waters of the Guardiana will offer a safe haven for the delicious incomers.
