Somerset Wildlife Trust

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The Severn Estuary

A rich feeding ground

The large amounts of silts and other debris held in suspension in the Severn estuary is in fact the main key to its importance as a home for marine life. Vast amounts of tiny, but edible, fragments of animal and plant material come down the River Severn and its tributaries and mix with marine plankton brought in by the sea currents.

This mixture of silt and bacteria, microscopic animals and plants creates a nutrient rich feeding ground for literally billions of slightly bigger, but still very small marine creatures, which are then in turn eaten by marine worms, shelfish and fish, both big and small.

Across the Severn to Awre 8 Oct 2008 c Karen Lloyd2

Across the Severn Estuary

Fish nursery

The Severn Estuary is a vast fish nursery. Ten species of fish that are of economic importance use these waters at different times in their lifecycle, either for breeding or feeding. Herring, cod, plaice, sole, whiting, blue whiting, hake, horse mackerel, ling and saith all occur in the sea off the Somerset coast. Many of these fish will be caught later out in the open seas, by commercial fishing boats, after they have left the food rich, sheltered and shallow Somerset waters.

Migratory fish

Somerset’s sea also plays a critical role in providing a home to fish that live in the sea for only a part of their lives, moving up into the upper reaches of rivers to breed and spawn in fresh water. these are the Atlantic salmon, sea trout, allis shad, twaite shad, sea lamprey and river lamprey.

All these species have suffered big declines in their populations in the last hundred years due to a variety of reasons which include pollution, both in the sea and rivers, overfishing and structures such as weirs impeding their progress upriver to their breeding places.

The allis and twaite shad as well as sharing unfamiliar names are both members of the Herring family and grow to between 30 ­ 50 cm in length. Both species are very particular about, and faithful to their breeding rivers and also to which parts of the sea they will move out to and use for feeding. this has led, over many thousands of years, to the Severn Sea allis and twaite shad populations being genetically different to other populations of shad in the UK.

Photo © Karen Lloyd