Sea anemones and stalked jellyfish

To be finalised during Consultation.

What we need to do and where
Glaucous pimplet - Keith Hiscock

Glaucous pimplet, Keith Hiscock

St. John's jellyfish, Eleanor Goodall

St. John’s jellyfish, Eleanor Goodall

Snakelocks anemone

Snakelocks anemone

1. About

Devon’s shorelines are teeming with life, much of it hidden beneath the waves or nestled among its rocky shores and estuaries. From the exposed headlands to the sheltered coves, these coastal environments support a rich tapestry of marine biodiversity, particularly within the intertidal zone. 

Devon’s intertidal rock pools are more than just a place to spot crabs; they are vibrant microecosystems brimming with life. Along sheltered rocky shores, these pools support a diverse array of invertebrates, including colonial bryozoans, sea squirts, encrusting and branching sponges, brittle stars, sea urchins, chitons, sea slugs, bivalves, and more. 

Among the most visually striking invertebrates found here are the sea anemones and stalked jellyfish. These soft-bodied species belong to the cnidarian group and are especially well suited to life in shaded crevices, beneath overhangs, and in other sheltered spaces. All cnidarians are equipped with specialised stinging cells, also known as cnidocytes, which they use to capture prey and defend their territories. Despite their delicate appearance, they are remarkably well adapted to the dynamic and often harsh conditions of the shoreline. 

Particularly significant habitats for these species include: 

Rocky shores 

These areas provide ideal habitats for many sea anemones, which anchor themselves in crevices, beneath overhangs, and in shaded rock pools to avoid drying out during low tide. 

Tidal pools 

Retaining water at low tide, these pools offer a stable microhabitat for more delicate cnidarians such as stalked jellyfish and smaller anemones. Unlike their free-swimming relatives, stalked jellyfish attach themselves to seaweed or rocks using a stalk and gently pulse to capture tiny prey. 

Seagrass and seaweed beds 

In more sheltered estuarine areas, dense growths of seagrass and seaweed provide excellent attachment points for stalked jellyfish. These habitats offer both camouflage and a consistent supply of food. 

Noteworthy locations in Devon, such as Wembury and Northam Burrows, are important hot spots for these species. With a combination of rocky outcrops, tidal pools, and sheltered estuarine zones, these areas provide ideal conditions for both sea anemones and stalked jellyfish. 

Devon Species of Conservation Concern

Eight species of cnidaria are listed as Devon Species of Conservation Concern: 

  • Glaucous pimplet (Anthopleura thallia) 
  • Sea Fir (Hartlaubella gelatinosa) 
  • Trumpet anemone (Aiptasia couchii) 
  • Scarlet and gold star coral (Balanophyllia regia) 
  • Kaleidoscope jellyfish (Haliclystus auricula) 
  • Spotted kaleidoscope jellyfish (Haliclystus octoradiatus) 
  • St John’s Jellyfish (Calvadosia cruxmelitensis) 
  • A Stalked Jellyfish (Calvadosia campanulata) 

Key pressures and opportunities

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Coastal development

Construction of sea defences, harbours, and housing near the coast can lead to habitat loss, especially in intertidal zones. This disrupts the natural structure of rocky shores and estuaries, reducing the availability of crevices, pools, and sediment types that these species rely on. 

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Pollution

Runoff from agriculture, sewage discharge, and marine litter (especially plastics and microplastics) can degrade water quality. Cnidarians are particularly sensitive to chemical pollutants, affecting their survival and reproduction. 

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Climate change

Rising sea temperatures and ocean acidification can alter species distributions and disrupt reproductive cycles. For example, cnidarians may experience stress or bleaching. 

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Recreational disturbance

Rockpooling, trampling, and boating can physically damage fragile habitats. Even well-meaning visitors can unintentionally dislodge sea anemones from their substrates. 

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Invasive species

Non-native species, such as xxx, introduced through ballast water or aquaculture can outcompete or prey on native cnidarians, altering the balance of intertidal ecosystems. 

2. What we need to do and where

Priority

Increase the abundance and distribution of sea anemones and stalked jellyfish particularly those identified as Focus Species.  

Focus species

Glaucous pimplet - Keith Hiscock

Glaucous pimplet

Anthopleura thallia
Read more

To be finalised during Consultation. 

The glaucous pimplet is a small but distinctive species of sea anemone found on wave-exposed rocky shores in the north coast of Devon, such as Lee Bay, Croyde and Westward Ho! Notably, Devon hosts one of the highest populations of this species in the UK, making it a key region for its conservation and study. 

Its typically found in  shallow rock pools, crevices, and areas among dense mussel beds, often partially buried under gravel or sediment. Its tall, trumpet-shaped body is dotted with sticky bumps, also known as verrucae, that trap sand and bits of debris, helping it blend in with its surroundings. 

This anemone varies in colour (green, brown, or greyish) with tentacles that can be similarly muted or subtly patterned. It possesses up to 100 retractable tentacles arranged in whorls around a central mouth, and small outgrowths called acrorhagi that are armed with stinging cells for defence. Though not widely distributed, it can be locally abundant and is thought to reproduce asexually, forming clonal clusters. 

The glaucous pimplet is small and often buried or camouflaged, making it vulnerable to trampling or being accidentally removed. Anthopleura thallia often lives among mussels, therefore any decline in mussel populations (due to harvesting or environmental stress) could reduce their habitat. Consultation Q: What are the key pressures? 

Stalked jellyfish

Read more

To be finalised during Consultation. 

Stalked jellyfish are a rare and unusual type of jellyfish that attach themselves to seaweed, seagrass, or rocks instead of floating freely in the water. They are often small, growing up to 5 cm in width, and can be hard to spot, blending in with their surroundings in shallow coastal areas. 

There are ten species recorded in the UK, with four commonly found in Devon. Each has a central body with eight arms, and at the end of each arm are clusters of tentacles. In some species, these tentacles are filled with stinging cells that help catch tiny prey like plankton, which are then passed to the jellyfish’s central mouth. 

Spotted kaleidoscope jellyfish

Haliclystus octoradiatus

To be finalised during Consultation. 

The spotted kaleidoscope jellyfish is a small, stalked jellyfish that inhabits the shallow, sheltered waters of Devon’s intertidal zones. Unlike typical jellyfish, it does not drift through the water column but instead anchors itself to seaweed, seagrass, or small stones using a short stalk. Its body is bell-shaped and vividly patterned, often displaying a mosaic of translucent greens, browns, or oranges with distinctive white spots, features that give it its common name. 

This species is typically found in rock pools, estuarine lagoons, and seagrass beds, where it uses its tentacles to capture tiny invertebrates. Though small and easily overlooked, it plays a role in the local food web and is an indicator of healthy, undisturbed intertidal habitats. Its presence suggests good water quality and intact microhabitats, making it a valuable species for monitoring environmental change. 

Kaleidoscope jellyfish

Haliclystus auricula

To be finalised during Consultation. 

St. John's jellyfish, Eleanor Goodall

St John’s jellyfish

Calvadosia cruxmelitensis

To be finalised during Consultation. 

Calvadosia campanulata - Keith Hiscock

A stalked jellyfish

Calvadosia campanulata

To be finalised during Consultation. 

Actions for all sea anemones and stalked jellyfish

Habitat creation and management

Intertidal invertebrates are found across Devon’s coastlines and will benefit from the actions set out on the Coast page. Anyone who is managing or creating habitat for sea anemones and stalked jellyfish should be aware of their needs. For more detailed information see the list of Devon Species of Conservation Concern and Find out more below. 

Protect sensitive intertidal invertebrate habitats 

  • Identify and map areas where sensitive intertidal invertebrates, such as the glaucous pimplet, are known to occur, particularly wave-exposed rocky shores with gravelly rock pools. 
  • Include these habitats in local marine conservation designations and shoreline management plans. 
  • Use signage, codes of conduct and public education to promote responsible rockpooling and coastal recreation in areas with vulnerable species. 
  • Collaborate with local tourism operators to reduce trampling and disturbance in sensitive intertidal zones. 

Research and monitoring 

  • Fund research into reef resilience, climate change impacts, and potential restoration techniques. 
  • Explore pilot projects for reef restoration in degraded areas using natural or artificial substrates. 

3. Inspiration

Case studies

Wembury Marine Centre (Devon Wildlife Trust) 

Focus: Marine education and habitat awareness. 

What it does: Offers guided rock pool safaris and educational outreach, helping the public identify and understand the importance of intertidal species like sea anemones and stalked jellyfish. 

Impact: Builds community support for marine conservation and encourages responsible shoreline behaviour. 

Where to visit

Always follow the Countryside Code and stick to footpaths and sites which are managed for public access.  

Wembury 

Nestled along Devon’s stunning south coast, this rocky shoreline is one of the best places in the UK to discover the hidden wonders of marine life. At low tide, the rock pools come alive with colourful sea anemones, darting shrimp, feathery worms, and even the occasional starfish or sea urchin. 

Lee Bay 

The bay’s peaceful setting and rich biodiversity make it an ideal spot for rockpooling, nature walks, and discovering the fascinating invertebrates that call this coastal haven home. 

For information on these and other sites which are open to the public please see the Explore Devon website.    

4. Find out more

Ask for useful links during the Consultation  

Marine Invertebrates – Field Studies Council 

Beneath the waves | Devon Wildlife Trust 

Home | Wembury Marine Centre 

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