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Salt Marsh Mud

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The salt marsh mud is vital to the shoreline birds and marine creatures too! It is full of millions of mud dwellers on which they feed.

Beasties in our salt marsh mud

Mud Shrimp
mud shrimp

Mud Shrimps (Corophium volutator) are the most abundant creatures in estuary mud. There can be up to 100,000 per sq metre. They live in semi-permanent U-shaped burrows.

They feed on bacteria, alga and organic matter, but what feeds on mud shrimps. Well they are a very important food for many species including dunlin, redshank, shelduck, flounders,  shore crabs and larger brown shrimps.

They are quite small, 11m in length and only live for one year. In that year the female can have between 2 and 4 broods with 20 to 50 offspring in each brood. The young develop in a brood pouch and emerge as fully formed miniature shrimps.

For more information on the Mud Shrimp see

Mud Snail

mud snail

The Mud Snail (Hydrobia ulvae) also known as the Laver Spire Shell is the next most abundant species in the mud with up to 42,000 per sq metre. They feed on detritus and algae.

In turn they are food for creatures like the Shelduck, which are regulars in the estuary. So an important mud creature.

The males are larger at around 0.3 – 6mm in size and have a visible penis. Life expectancy is generally 1 to 2.5 years.  They move around the shore by crawling, climbing and even floating. They might even be found amongst the high tide strand level.

More information about the mud snail can be found at


Ragworms (Hediste diversicolor) are one of the most common marine worms. It is perhaps one of the most important too.  Ragworms are a valuable food source for wading birds. Curlews and at least fifteen other wading birds feed on them. It is not just wading birds though, flatfish like flounders and sole also feed on them.

Usually a reddish brown colour they are typically between 6-12 cm in length.  Its body appears flattened with a prominent dorsal blood vessel.

They live in a U-shaped of J-shaped burrows up to 20 cm in depth.  The deeper the burrow the safer they are from probing beaks. A burrow depth of over 15 cm is likely to be deep enough to escape the long beak of the curlew. Ragworms typically feed on mud, detritus, plankton and microfauna by scavenging or filter feeding on suspended particles. They can even be carnivorous.

More about ragworms at

See our hands-on mud sampling at the bottom of this page. . .


Lugworm (Arenicola marina) is also know as Blow lug.  They feed on algae, small invertebrates, detritus and bacteria. They are another very  important food for wading birds and flatfish and even ragworms which will eat small lugworms.  Lugworms will grow to between 11 – 20 cm with a Lifespan of 5 – 10 years.

They live in J-shaped burrows with a vertical shaft and horizontal limb. The worm lies head up so it can capture food at the mouth of the burrow.

More about lugworms at


The Catworm (Nephtys hombergii) is 10-20 cm long  with a life span of 2-5 years. Unlike lugworms and ragworms, they don’t have a permanent burrow. Instead they move about in the sediment forming a network of temporary burrows 5-15cm deep.  The catworm is a predator and scavenger feeding on molluscs, crustaceans and other worms.

Like ragworms and lugworms they are preyed upon by waders and fish and are a popular bait for fishermen.

More about cutworms at

Mud Sampling

During our 2021 Portishead Salt Marshes Day we did a bit of mud sampling. We wanted to see what was in the mud.

We found mainly ragworms . . . which is good news as our wading birds love to eat these!

Read more about our salt marshes at the salt marsh hub

Reference and further reading: