Boost for London wildlife as rare fish spawn in Thames

Conservationists from the Zoological Society of London (ZSL) are celebrating after discovering evidence of one of the UK’s rarest fish species returning to spawn in the Thames.  

Smelt egg
Smelt egg

The team counted 74 smelt (Osmerus eperlanus) fry plus an additional 21 eggs over the two-day survey near Wandsworth Bridge in south west London, providing  new evidence of where these elusive fish live and breed in the Thames. ZSL will use this information to shape a conservation plan for the species, to ensure their continuing recovery in the wild. 

The smelt – a small fish that also holds the unusual distinction of smelling of cucumber – was once an abundant and commercially important species in many British estuaries but suffered significant declines from the early 19th century, eventually disappearing completely from many of the nation’s rivers.  Their decline was caused by a range of factors including water pollution, over-fishing and the destructive impact of engineering projects restricting up-stream migration and spawning habitats. 

Improved water quality in the late 20th century allowed smelt to gradually return to a handful of rivers in England, including the Thames, but still little is known about where and when these fish spawn. ZSL’s latest findings represent an important development, both in terms of understanding more about the elusive smelt’s behaviour but also underlining the ongoing recovery of the Thames as a valuable wildlife habitat. 

Joanna Barker, Europe Conservation Project Manager for ZSL, said: “While smelt are not the most iconic of fish, their presence is an important indicator of water quality and the overall health of the Thames. They represent the fantastic world of wildlife living in the Thames, and the fact they appear to be re-establishing themselves in the estuary is great news for conservation in the Capital.

“With the help of our team of volunteer citizen scientists, we have been surveying this stretch of the river since the beginning of March and were thrilled to find smelt fry just as they were hatching from their eggs. These juvenile fish are barely 6mm long so finding them in the Thames was no mean feat, and we’re delighted by the results.”

The Zoological Society of London (ZSL) has received a grant of £97,800 from the Heritage Lottery Fund (HLF) for the project, “The fish that smells of cucumber: conservation of smelt (Osmerus eperlanus) in the Thames Estuary”. Project partners include the Environment Agency, the Institute of Fisheries Management (IFM), Bournemouth University Global Environmental Solutions (BUG) and HR Wallingford. 

Smelt survey 2016
Smelt survey 2016

Learn more about smelt conservation

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