The ever-increasing temperature and salinity level in the Guadiana River is driving away eels and lamprey while more exotic species are moving in to take their place.
Changes in the world's climate are having a direct effect on the Guadiana river that defines the Algarve’s border with Spain. More than a dozen new species have been detected in recent years, including the recent sighting of the Chesapeake blue crab' from the US along with fish, clams, jellyfish and prawns that, normally, should not be there at all.
The blue crab is a seasoned traveller and has been found in the Baltic, Mediterranean, North Sea and Black Sea. Luckily, this crab is tasty and was an important food source for Native Americans and European settlers in the Chesapeake Bay area in the 1600s.
The researchers are looking at how this and other invaders, can be encouraged and harvested, rather than eradicated as the changes in the Guadiana are permanent for as long as climate change continues and waters warm up.
The river is being monitored by a team from the University of the Algarve's Sea Science Centre (CCMAR) in a long-running project in which water samples are collected, temperatures and salinity levels are measured and local fishermen are asked if they can catch and hold on to species in the Guadiana that should not be there.
The studies started in the late 1990s when the Alqueva dam was constructed. Now, water Ph, temperature, salinity and oxygen levels are recorded monthly, and fish larvae and crustaceans are taken to be analysed in the laboratory.
With ever-higher salt levels in the river, fish that typically live in the sea, such as sea bass, are being found in the Guadiana and habitués of river systems such as the eel and the tasty lamprey, are in decline.
