Although it has been no secret that zander had infiltrated the Thames it has now been officially confirmed by the Environment Agency.
The fingerling zed, just 3 inches long, was discovered when a party of primary school teachers watched a fish survey demonstration on Teddington Lock Island.
It is the first time a zander has been officially recorded in a survey and it brings the total number of fish species in the tidal Thames to 119.
An EA spokesperson commented: “The freshwater zander was legally brought over from Western Europe and introduced into the Great Ouse system in the mid twentieth century to improve angling but it has spread to other waters and caused substantial ecological changes in some locations.
“Although a species in its own right, it is also known as a pike-perch because it appears to be a hybrid between these two native predatory species. Zander hunt fish of between four and six inches in length, often as a shoal, and because of their good eyesight, they can hunt in extremely poor visibility.
The zander joins the Chinese mitten crab and signal crayfish as new residents of the Thames. Populations of both have significantly increased in recent years, making a considerable impact on their new environment and requiring much research to further understand these species and their effects.”
EA Fisheries Officer Steve Colclough said: “We are not sure how the zander came to be in the upper tidal Thames. It may have entered ‘naturally’ through fresh water streams from stocked locations. We hope that anglers will help us gather more information by reporting any sightings or captures to the Environment Agency.”
Since the return of the twaite shad and sea lamprey to the Thames was reported in May, further reports of both have been received from the public.
Thames Species List