Fish Survey on Orchard Lake and River Condition Assessment survey along a tributary of the river Thames at Radley Lakes.
FiveRivers were commissioned to undertake fish surveys on Orchard Lake and River Condition Assessment (RCA) surveys on a tributary of the river Thames in order to gather data to support a review of Old Mineral Permissions (ROMPs) application. Orchard Lake and the tributary are part of the Radley Lakes site which is considered a valuable green space that is rich in wildlife, particularly plants, birds, and insects.
Fish were surveyed using a combination of electric fishing, seine netting, and fyke netting methods, which aimed to target all species and life stages present in Orchard Lake.
The RCA surveys consisted of MoRPh5 surveys carried out at five sub-reaches along the tributary of the river Thames which recorded information regarding bank tops, bank faces, channel-water margin, and the riverbed. This data was combined with a desk study to provide a river condition score for each of the five sub-reaches.

Project requirements
The problem
The project required both fish surveys and River Condition Assessment (RCA) surveys to gather the necessary biodiversity data for the Review of Old Mineral Permissions (ROMPs) application. Fish surveys were to be carried out on Orchard Lake while the RCA surveys were to be carried out on a tributary of the river Thames that flowed past the lake. Reports detailing the results of the two different surveys were also provided to the client.

Our approach
The solution
Three different fish survey methods (electric fishing, seine netting, and fyke netting) were carried out by a team of qualified and experienced aquatic ecologists in order to target all fish species and life stages present in Orchard Lake. Electric fishing was used in the marginal habitat of the lake to target adult and juvenile fish. Fyke netting was used to target benthic (bottom dwelling) species and seine netting was used in the open water habitat of the lake to target adult life stages. On completion of sampling, individual fish were identified, measured, photographed, and returned to the lake. The data was then analysed to produce several metrics that were used to interpret the fish population in Orchard Lake.
An accredited River Condition Assessment (RCA) surveyor undertook five MoRPh5 surveys along a tributary of the river Thames to gather data on morphological and hydraulic features, vegetation structure, land use pressures, and human interventions along the river. Using the 32 indicators that are extracted from the MoRPh5 surveys and combining this with a desk study, a river condition score was produced for each of the five sub-reaches surveyed.

Project outcomes
The results
Four out of the five sub-reaches in the River Condition Assessment (RCA) surveys received a condition class of Fairly Good. The remaining sub-reach was given a condition class of Moderate. There were no human modifications to the channel, no non-native invasive plant species, and a diverse level of terrestrial vegetation and abundance of trees across the survey area. However, all sub-reaches were either dry or ponded with no flow resulting in no heterogeneity of hydraulic features which, along with the uniform nature of the banks, limited the condition class.
The combined fish surveys caught a total of 559 fish of 6 different species, with an estimated biomass of 9.24kg. The species caught were roach, perch, pike, rudd, tench, and bleak. Roach were the most abundant species caught, making up over half the total abundance. Tench and bleak had the lowest abundances. The size and age classes caught appeared to be representative of a normal population structure and the larger number of juveniles caught suggested there was adequate spawning and nursery habitat in Orchard Lake. This was likely provided by the large stands of emergent macrophytes around the margins, and submerged macrophytes across the lake which would provide cover for juvenile fish and present a spawning medium.
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Sean McGrogan
Monitoring Manager
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Telephone: 01722 783 041
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