THA Aquatic tests fish monitoring equipment for Cardiff tidal lagoon

THA Aquatic has been hired by Tidal Lagoon Power to assess the application of acoustic telemetry for monitoring fish in the Severn Estuary and surrounding rivers.

Tidal lagoon Cardiff seeks to harness the power from the rising and falling tides in the Severn Estuary. The lagoon will have a c. 3,000 MW generating capacity capable of fulfilling Wales’ entire annual domestic electricity requirement for up to 120 years, the company explained.

As part of the Environmental Impact Assessment for tidal lagoon Cardiff, modelling is required to estimate the proportion of fish that will encounter the project’s turbines. To achieve this, a combined hydrodynamic and behavioural modelling approach using Individual-Based Models (IBMs) can be used to simulate fish movements in the Severn Estuary once the lagoon is constructed.

Few existing studies have collected data on fish movements that are representative of both the species and macrotidal conditions found in the Severn Estuary.

With the second highest tidal range worldwide, the Severn Estuary presents a unique combination of challenges for monitoring fish, such as high current velocities, turbidity and debris, heavily navigated areas, mobile sand banks and protected reef habitat. After reviewing the existing technology available for monitoring fish movements in these conditions, THA Aquatic are testing fixed passive acoustic receivers in the Severn Estuary.

To detect fish movements, acoustic receivers will ultimately be deployed in a line or array across parts of the Estuary. The present study aims to identify the maximum spacing required between receivers for an array to detect a variety of fish species and life stages.

Since the focus at this stage is to test the equipment under a range of environmental conditions in the Severn Estuary, fish are not tagged. Instead, receivers and tags are deployed from moorings at set positions on the seabed and retrieved using an acoustic release system.

This study will also assess the performance of a variety of receiver mooring methods.

After two weeks of deployment covering a full cycle of spring and neap tides, THA Aquatic, with the assistance of Titan Environmental Surveys, have retrieved the equipment and downloaded the data for interim analysis. The equipment has been redeployed at a second location to obtain data across a range of environments and conditions.

If data analysis reveals passive acoustic telemetry to be a successful monitoring method in the Severn Estuary, Tidal Lagoon Power plans to tag and track a number of fish species and life stages over the coming years.

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