Sonar and the Severn

The Severn Estuary is famous for having the second highest tidal range in the world. Its intertidal sandflats and mudflats are vital feeding and nursery grounds for a wide range of fish species. However little is known about how fish use different habitats in the estuary. Tools regularly used by researchers studying fish include baited, towed and drop-down camera systems. Many of these traditional methods are impossible to use in the muddy waters of the Severn. Devon and Severn IFCA are participating in two projects, led by Swansea University and Natural Resources Wales and Natural England respectively to trial the use of a high-resolution sonar camera to study fish and habitats in the murky waters of the Severn. The sonar camera was purchased by Defra in 2013 and is owned jointly by the ten IFCAs.

In early October Robyn Jones and Sam Rees of Swansea University, along with D&S IFCA officer Libby West, trialled the sonar camera as a baited camera, first in Swansea Bay and then in the Severn Estuary. Early results look promising with the camera clearly capturing schooling fish and dogfish in water too turbid for traditional cameras. Additional work with Natural Resources Wales and Natural England used the camera to map Sabellaria – a kind of reef-building worm- that is a protected habitat in the Severn Estuary European Marine Site.

This work will help improve knowledge of fish ecology in the Bristol Channel, essential for an Ecosystem Approach to management as described in D&S IFCAs Annual Plan. Robyn Jones is funded by the Kess2 project with support from SEACAMS2 and Ocean Ecology. Sam Rees is funded by the SEACAMS2 project.


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