Spend your days criss-crossing the Thames via various bridges, but never stopped to contemplate what lies beneath? Despite its murky brown appearance, the water quality of the Thames has steadily improved since sewers were repaired in the 1960s, and is home to seals, otter and even seahorses.
Species of fish
According to Ian Tokelove of the London Wildlife Trust, there are 125 types of fish in the Tidal Thames (from the estuary mouth to Teddington Lock). Ed Randall of the Thames Angler's Conservancy names bream, perch, pike, roach, rudd, dace, ruffe, barbel, native and non-native carp, chub and gudgeon among them.
- The once-prevalent salmon is now rare due to overfishing, but is occasionally spotted on Environment Agency camera traps migrating upstream between October and January, such as at Molesey Weir near Hampton Court.
- Non native species such as zander are occasionally spotted around Teddington. In 2010 the now-defunct British Waterways organisation identified it as one of the non-native species most likely to harm native wildlife along rivers in Great Britain.
- Sturgeon have been caught occasionally, like the non-native Siberian sturgeon which was caught in the Thames near Dartford last year.
- Trout are sometimes hooked — sea trout migrate upriver from the estuary to spawn, whereas brown trout tend to stay up the river. The River Wandle, a tributary of the Thames, is a known trout-spawning ground in the Croydon area. Non-native Rainbow trout also occur, but have usually escaped from lakes or fish farms.
- Non-native Wels catfish are rare but were introduced to the river in the 1930s and persist to this day, occasionally making headlines due to their size. In 2008, Brett Ridley landed a Wels catfish on the Kingston stretch of the river, believed to be the largest fish ever caught in British waters. In 2013, Chiswick RNLI was called to reports of a body on the foreshore in Barnes, which also turned out to be a catfish.
- Eels migrate up the River Thames every year between April and October, but face many hazards and obstacles and are regarded as critically endangered. They are usually found close to the estuary, travelling as far as Greenwich.
Other information about record-breaking or rare fish in the Thames is hard to come by. Anglers are notoriously secretive about specimen catches, as publicity may attract too many others and spoil the fishing in a favourite spot.
- In September, it was announced that seal numbers in the Greater Thames Estuary had increased almost back to their natural rates thanks to a conservation project, after being hunted for fur and meat. While they do mainly hang around in the estuary, Tokelove tells us that they've been seen as far west as Teddington Lock.
- Famously, in 2006, a Northern Bottlenose Whale swam up the Thames until becoming stranded near Battersea and sadly not surviving. It is now in the National Research Collection at the Natural History Museum.
- In 2013, a pod of porpoises was spotted near Tower Bridge and a small pod of dolphins was seen in Bermondsey. In 2001 a lone dolphin also made the trip, spotted between Wapping and Blackfriars. Recent improvements in water quality and availability of fish brings these animals to the Thames in search of food. What's the Thames Barrier to stand between a porpoise and its lunch?
- Otters are often the hardest to reintroduce to a habitat, so the fact that sightings are on the up (one was spotted on the River Lee a few years back, and they are approaching the western boundaries of the Thames catchment), shows that the waters are once again in excellent health, providing plenty of fish for Tarka and co. to get stuck in to. However, buildings, walls and roads create barriers that they cannot currently get around, accounting for why they are often seen in urban Thames areas.
- In 2011, a rare seahorse from the Canary Islands and the Mediterranean was found at Greenwich, leading to theories that a breeding population existed in the Thames.
- Pipistrelle and Daubenton’s bats will feed over bodies of water such as the Thames, but can be difficult to spot. Tokelove recommends signing up for a bat walk which uses electronic bat detectors to track them down.
- Where there are fish, there are birds, so a few species to keep an eye out for are swans, grey herons, cormorants, Canada and Egyptian Geese, mallard, grey wagtails and pied wagtails. London Wildlife Trust's Species Explorer has photos of each bird to help with identification — and could be great to keep the kids occupied on a riverside walk.
Can I fish?
If we've got you hooked, it's worth knowing that there are quite a few Environment Agency national and regional byelaws (PDF) to abide by. Fishing is not permitted at all during the closed season, which runs 15 March-15 June inclusive ,and all fishing in England and Wales requires an Environment Agency rod licence.
Finders keepers, right?
Legally, you can take some of the fish that you catch, but British anglers generally catch and release. Randall says, "There's a real cultural thing that you just don't do it. You've had your sport stalking the fish and it deserves to be treated with respect and put back in the river quickly and unharmed". Plus, fishing is not sustainable: there are simply not enough fish in our rivers to support widespread removal.
So what's the future for watery wildlife? "The Thames has made an amazing comeback since the 1950s, but significant investment will be required to sustain this progression. "Without investment in the city’s sewage management, life in the river and on the riverbanks will diminish as sewage and pollution levels rise," says Tokelove.
See also: Non-native animals that are on the loose in London and our review of A Field Guide To East London Wildlife