The European smelt (Osmerus eperlanus) is a small predatory fish that inhabits cold-water estuaries. Once common in the UK, it has suffered significant declines since the early 19th century due to water pollution, over exploitation and destructive river engineering. Improvements to water quality in the latter half of the 20th century have allowed smelt to return to 36 water courses in England including the Tidal Thames. It is protected under a variety of regulation and can act as an indicator for good water quality due to its sensitivity to pollution.
The Zoological Society of London (ZSL) has just completed a two-year project to try and better understand the behaviour of smelt in the Tidal Thames. During the survey work, they caught a total of 455 smelt fry (photo top left) and 28 smelt eggs (photo bottom left), using two survey methods: ichthyoplankton netting (towing a micromesh plankton net just below the water surface to catch very small smelt fry – photo middle left) and seine netting (encircling an area of water by the foreshore with a sheet of net to catch all the fish in the enclosed area – see header photo). ZSL Citizen Scientists also took to the Tidal Thames foreshore to better understand the ecology of fish species in the region.
Joanna Barker, Europe Conservation Project Manager at the Zoological Society of London, said: “These data have been used to narrow down the most likely smelt spawning location to a 600m stretch of the Thames by Wandsworth Bridge. We have also shown that smelt are likely to spawn over an elongated period of 5 weeks from the beginning of March and provided information on smelt growth rates in the region. This is fantastic information which we will use with a variety of partners to better conserve smelt in the region.”
The outcomes of ZSL’s Smelt Conservation Project have been developed into a Guidance Document to conserve Tidal Thames fish through the Planning Process. Joanna Barker added “Over the course of the project, we realised that fish were often under-represented in local strategy documents and in some Biodiversity Action Plans. One reason for this could be due to the complexity of estuarine fish ecology, which is difficult to simplify for the non-technical user. To fill this gap, we produced a Guidance Document for Developers, Planners, Biodiversity of Environmental Officers in Local Government and Ecological Consultants to provide a single point of reference for information relating to fish conservation in the Tidal Thames. This document was developed through feedback from multidisciplinary stakeholders and we would like to thank everyone who has been involved both in this and the survey work.”
All photos (c) Zoological Society of London.