The data on the diversity of fish species in London is outlined below. This is part of the water resources section of the London State of the Environment Report 2010.
About this indicator
We collected this data during routine fish surveys in rivers across London.
The indicator looks at the diversity of fish species present in the rivers surveyed.
Fish diversity and abundance depends on water availability, water quality and the presence of suitable habitat, as well as fish stocking by the Environment Agency and angling clubs.
In general, the more diverse the habitat, the more species are found, although this is sometimes affected by location.
The freshwater and tidal River Thames has a very rich fish community consisting of 125 species including freshwater, marine and migratory fish. Small numbers of salmon and sea trout annually migrate to and from the River Thames, reflecting the much improved water environment. However, there is great potential for more of these sensitive species to live in the River Thames and its tributaries.
Our plan for fisheries in Thames Region 2006-2011 (PDF, 990KB).
Overall trends
Fish populations in London’s rivers are varied and steadily improving. This is particularly true in the tideway where numbers of dace and bream have increased markedly in recent years. In addition shad and smelt, which are species of international importance, have become increasingly abundant in the estuary. Shad and smelt are particularly sensitive to pollution, and their increasing status is further evidence of improving conditions within the tideway over the decades.
In freshwater tributaries of the Thames the predominant coarse fish species are roach, dace, bream, chub, pike and perch. On the River Wandle, which suffered from a serious pollution event in September 2007, the fish populations have recovered well with the aid of some fish stocking. There is significant potential to further improve fish stocks on the River Wandle by improving habitat and migration conditions.
Brown trout are relatively scarce but present and spawning at discreet locations in the Rivers Lee, Colne and Wandle.
In small tributaries the most common fish tend to be minnows, eel and stickleback. On the River Quaggy where the Environment Agency has carried out a programme of habitat improvement works, the abundance of 3-spined stickleback has subsequently increased. This response is an indicator of longer term improvements in fish numbers likely to result from the work. On parts of the River Ravensbourne there has been a noticeable increase in the number of chub and dace during the last few years.
Barbel, an important and popular species fished for by anglers, is currently found in the Rivers Colne, Ingrebourne and Wandle.
Bullhead, a species protected under the EU Habitats Directive and a good indicator of favourable water quality, flow and habitat condition, are currently present in the Rivers Lee, Roding, Colne, Crane and Wandle.
The numbers of European eel, that have been migrating into our rivers, has been declining in recent years due to a number of complex factors. These include climate change, parasites, ocean currents and barriers to migration. Currently, the stocks in our rivers seem stable but we need to keep a close watch on populations. There is significant potential to extend the range of eel into habitats not presently occupied within London. The European Union are taking action to protect the eel from extinction and there is much work being done, including allowing eels to get over localised obstructions and into new habitat, in order to boost populations.
South London rivers – fish species and densities
North London rivers – fish species and densities
