Survey of Cornish estuaries serves up some ‘fishy’ surprises

A survey of two of Cornish estuaries, the Fal and Camel, has revealed that some rare fish have taken up residence in local waters. Among those discovered by Environment Agency scientists are the Norwegian Topknot, Gilthead Bream and Seahorse.

The Agency started monitoring in 2007. The range, diversity and relative abundance of fish is an excellent indicator of water quality and health of the coastal and estuary environment.

So far 43 species of fish have been recorded on the Fal and 32 species on the Camel. The commonest fish are sand smelt, sprats and common gobies. Mullet, flatfish, rays, gobies and bass are also found in both estuaries. Dragonets, blennies, wrasse, sea-scorpions and fish belonging to the cod family have also been recorded in the Carrick Roads.

Catches on the Camel included the venomous Lesser Weever, two species of sandeels and a variety of pipefish - long-thin fish related to seahorses. The research is being carried out by the Agency’s ecological monitoring team under the European Water Framework Directive as part of a long-term ‘State of the Environment’ study.

The team uses a special shallow-draught boat that enables them to collect samples from parts of an estuary inaccessible to normal boats. Fish are caught in a seine net and, after being identified and examined, are returned to the water unharmed. A larger marine survey vessel is used to collect bottom living fish in the deeper stretches of water in Carrick Roads and the Camel.

As well as fish, scientists are looking at a range of ecological ‘indicators’ to gauge the health of the two estuaries. This year, in addition to water quality and phytoplankton sampling, scientists will be surveying saltmarsh and sea grass habitats. Seaweed surveys and studies of invertebrate creatures living on or in the seabed will provide an insight into the impact of chemical pollution on our estuaries.

The soft estuary mudflats exposed at low tide can be difficult to access. This is a particular problem on the Camel. The monitoring team are hoping to overcome this by using a small hovercraft to collect samples.

The Norwegian Topknot is a small flatfish that lives on rocky and stony ground. It is rarely caught by conventional fishing methods and could be more abundant than records suggest.

The Gilthead Bream is a warm water species that appears to be extending its range northwards possibly as a result of climate change. The seahorse was a single specimen caught during routine monitoring at Carrick Roads.

‘The large variety of fish recorded indicates that both estuaries are in a healthy condition. Long term monitoring provides unique and valuable information and will give us a much better understanding of these nationally important estuaries. The discovery of unusual species such as Norwegian Topknot and Gilthead Bream is especially encouraging,’ said Rob Hillman for the Environment Agency.

Data collected by the Agency will be shared with the Environmental Records Centre for Cornwall and the Isles of Scilly, the National Marine Aquarium and the Marine Biological Association.

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