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Salmon in the Thames
Back in 1998 your Newsletter published an article by a River Thames expert, Mr G Armstrong, entitled The Thames Rehabilitation Scheme. This described the early attempt to clean up the Thames and repopulate it with fish stocks, including salmon. A later article by Peter Lane described tracking salmon in the Thames and in the autumn of 2000 Mr Darryl Clifton-Day contributed an article on the Thames Salmon Trust. In August of this year your President, Eva Lipman, wrote to the Environment Agency requesting an update on how successful the scheme had been in re-introducing salmon to our river, particularly since we had contributed towards the construction of one of the fish ladders.
A 2007 article for the BBC was not particularly encouraging. Darryl Clifton-Dey, of the Environment Agency (EA) said that “people do fish for salmon in the Thames but the population is so small at the moment that there’s not a great deal of chance of catching one. Hopefully if these come back, and if they breed and if the young from these come back, then in a few years time there’ll be quite a few salmon around”.
This project to re-stock the Thames was set up 30 years ago, not for the benefit of anglers but as a means of demonstrating that the capital’s river, for a century and a half a running sewer, was more or less clean again. The idea of restocking a new, cleaner, river with salmon was to demonstrate the success of this policy. Today, the project is not dead but its future is in the balance. Unusual rain patterns are thought to be to blame. Britain’s sewers are unable to cope with intense downpours, causing them to overflow into the river. The worst culprit — London — is also the closest to the river’s entrance, making the prospect for salmon even less enticing. “The difference between the Seine and the Thames is that all the industry on the Seine is far inland, near Paris. While the lower reaches of the Seine have mainly less problematic agricultural pollutants, the Thames carries domestic and industrial wastes,” said Darryl Clifton-Dey.
The project involves releasing juvenile salmon to areas of the River Kennet where the EA expect them to spawn, then monitoring the return of adults and using the presence of salmon in the river to encourage further improvements in the river environment for the benefit of all river species. Adult salmon have returned to the Thames in almost every year since 1979, although numbers have declined in recent years.
To reach the breeding areas of the River Kennet adult salmon must negotiate 20 weirs on the River Thames and then a further 17 weirs on the Kennet. With the help of the Thames Salmon Trust and the National Lottery funding of good causes, fish ladders were completed on all of these weirs in the year 2000. Most of these passes have been designed to allow as many fish species as possible to migrate upstream, not just salmon. The fishpass at Boulters Weir in Maidenhead on the River Thames was one of the last of the chain to be constructed, but it has been in place for about 8 years now and the EA believe that it is working well. A report was received not long ago from an angler who saw three salmon jumping at the fishpass one evening. This report also appeared in the local Maidenhead paper. It cannot be confirmed that the fish were salmon, but it is possible that they were.
Now that the chain of fish ladders is complete and allows access to salmon breeding areas, EA expect adult fish to start using them. A few years ago they fitted small radio transmitters to some salmon and tracked them upstream. This information, and catches by anglers, have demonstrated that some salmon are swimming up through Maidenhead and reaching the River Kennet. Unfortunately this is likely to be very low numbers of fish at the moment: returns of adult salmon to the Thames have been low for the last decade. There are a number of reasons why this might be, including climate change and generally higher mortality rates in the river and at sea. The EA are currently investigating these and trying to produce more fish in the river. In the meantime they are continuing to build fish ladders so that all of the fish species in the Thames can benefit. In fact Richard Oates of the Thames Rivers Restoration Trust says that the Thames is still not in good enough condition to support the return of significant numbers of salmon. This is a great pity, particularly since the fish are apparently returning in good numbers of their own volition to the river Seine. All Europe’s great Atlantic-facing rivers once ran thick with salmon, and all lost them when they became choked by sewage and other pollution. But unlike the Thames, the Rhine and other rivers, no efforts have been made to restock the Seine with salmon. Before salmon begin to run beneath Tower Bridge in London in any number, it seems that the capital’s new sewer system must be completed. That is not expected to happen until 2020 at the earliest.“We won’t see salmon returning to the Thames until then,” said Richard Oates.
Eva Lipman
