A Greater Weever (Trachinus draco) has been found in a stretch of the Thames estuary in Great Britain. The species, which is native to the Eastern Atlantic, the Mediterranean, and the Black Sea, is one of many signs of the improving health of the Thames estuary.

The weever was found after a two-year investigation carried out by the Environment Agency and Zoological Society of London and is the 60th new species found in the Thames since 2006. “The diversity and abundance of fish is an excellent indicator of the estuary’s health”, says Environment Agency Fishery Officer Emma Barton.

Flowing through London and several other urban areas, the Thames has a long history of being heavily polluted. In the so called ‘Great Stink’ of 1858, pollution in the river was so severe that sittings at the House of Commons at Westminister had to be abandoned.

So, should we fear this semi-new addition to the Thames estuary? No, there is no need to panic. This fish can deliver a very painful sting and should be handled with care, but the sting is rarely dangerous to humans – especially not if you seek medical attention.

The Greater Weever has venom glands attached to both of the spines on its first dorsal fin, and to the spines of the gill cover. The spines are equipped with grooves through which venom is driven up if the spines are pressed. A person that receives a sting from a Greater Weever can develop localized pain and swelling, and the result has – in a few rare cases – been fatal. Fortunately, there are several things you can do to make the situation less dangerous for a stung victim.

· If the wound bleeds, allow the wound to bleed freely (within reason of course) to expel as much venom as possible.

· Soak the affected limb in warm water because the toxin produced by the Greater Weever is sensitive to heat. There is no need use extremely hot water it and risk scalding the skin, because the toxin will deteriorate at a temperature of 40° C / 104° F.

· Seek medical attention.

The pain is normally at its most intense during the first two hours after being stung and even without treatment, the severe pain normally goes away within 24 hours. It is however possible for some pain to last for up to two weeks, and it is also possible for the spine to break off and get stuck inside the stung limb where it can continue to cause problems until it is removed.