You've seen the Thames. It's brown and dirty and pretty choppy but you might be surprised to know quite how many living creatures call it home.
In fact surveys by Zoological Society London (ZSL) show life is thriving underneath the murky surface.
In 2017 so far there have even been 7 sightings of dolphins in the Thames, with 38 spotted since 2014.
Dolphins have been spotted near Battersea Bridge, Hammersmith, Chiswick, two near the rail bridge in Chiswick and in Brentford.
ZSL also report sightings of 19 harbour porpoises, 61 harbour seals and 106 grey seals this year.
These big, exciting species don't tell the full story though.
The Thames isn't just a hard-flowing backwater that animals get sucked into.
According to ZSL, which has been surveying the Thames since 2004, there are a number of species that have been spotted in the river.
You can find an interactive map of mammal sightings and information on life in the Thames at the ZSL website .
Among the species which call the Thames home are:
- Atlantic salmon - These used to migrate from northern waters to the Thames but went extinct in the river after heavy industrialisation in 1833. They're back now and research indicates that's thanks to improving water quality.
- Bullhead - A small fish often found in freshwater streams and rivers.
- Common smelt - Once one of the most common fish in the country and a popular food source. One of the few significant colonies lives in Greater London.
- Depressed river mussel - This large mollusc species loves the north side of the Thames, between Richmond and Twickenham.
- European eel - Once common in - you guessed it - Europe, this species is now critically endangered. Some small eels, known as elvers, still swim up the Thames each summer.
- Flounder - Usually found near the estuary, the marine fish has been known to swim much further upstream.
- River lamprey - These primitive fish have no jaws and need relatively clean waters to breed. That means they were all but extinct from the Thames but a resurgence may be under way.
- Brown trout - 2011 saw a record number of these fish swimming up the Thames to spawn.
- Short-snouted seahorse - Usually preferring warmer Mediterranean waters, there is believed to be a small colony in the Thames.
- Twaite Shad - A narrow, streamlined fish which is struggling to recover from the pollution in the Thames.
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