Fish

Tompot blennies are charismatic, bottom-dwelling fish that live in rocky coastal habitats, often hiding in crevices and among seaweed-covered boulders. They’re most commonly found in shallow waters around Devon’s rocky shores and reefs. Tompot blennies are inquisitive and territorial, often returning to the same hiding spot and defending it vigorously from intruders.

They feed on small invertebrates such as worms, crustaceans, and molluscs, using their strong jaws to crush prey. Their mottled brown colouring and fringed tentacles above the eyes help them blend into their surroundings, making them hard to spot unless you know where to look.

Tompot blennies can be identified by the distinctive markings on their heads, which are unique to each individual, almost like a fingerprint. These markings have enabled researchers to track individuals over time without tagging, offering valuable insights into their behaviour.

Their breeding behaviour is equally fascinating. During spring and summer, males attract females to lay eggs in their chosen crevice. The male then guards the eggs for several weeks, fanning them with his fins to keep them oxygenated until they hatch.

Although not currently endangered, they are vulnerable to habitat degradation, especially from coastal development, pollution, and recreational disturbance. Their reliance on clean, structurally complex rocky habitats means they can be indicators of local marine health. Protecting these habitats is key to ensuring the survival of species like the tompot blenny.

Seahorses lead solitary and secretive lives in sheltered, shallow, coastal waters. The spiny seahorse and short-snouted seahorse live in Devon’s seagrass beds which are largely found on the coast around Torbay, Plymouth, the Exe Estuary and Kingsbridge. Sea horses are well-camouflaged, blending seamlessly into their surroundings and using their tails to anchor themselves to seagrass blades where they prey on small crustaceans such as shrimp and crabs.    

One of the most intriguing aspects of seahorses is how they reproduce. Unlike most fish, the males carry the fertilised eggs in a special brood pouch and give birth to live young.

Devon’s seahorses are both endangered species due to habitat destruction, especially the loss of seagrass meadows. Seahorses are often caught as bycatch in trawl fisheries and are also globally harvested for traditional medicine. The demand globally for seahorses in traditional medicine and the aquarium trade is higher compared to many other fish species. 

Habitat

Both shad species are members of the herring family and move from the sea into rivers to spawn between April and June. They spawn in gravels/cobbles in shallow areas (less than 1.5m) with high flows. Juvenile fish live in areas with low flows and very slow flowing water along the river edge (known as ‘dead water’).

Population

Though once widespread, in recent decades both species have declined significantly and allis shad is now critically endangered. The River Tamar (below and just above Gunnislake Weir) is the only confirmed spawning river for allis shad in England. Shad are now known to be present in the Taw and eDNA testing is being carried out to confirm the species and distribution.

Twaite shad are more widespread and not a threatened species. However records are still sporadic in Devon.

Both species are strong swimmers but struggle to leap over weirs and other barriers which can prevent them from reaching upstream spawning grounds. Other pressures include water quality, river modification and bycatch. 

Habitat

Atlantic salmon move from the sea to spawn in the middle to upper reaches of rivers where there is clean, cooler, fast-flowing water. They lay their eggs in shallow gravelly areas in nests called redds. Adult salmon usually die after spawning. Juveniles stay in freshwater for 1 – 3 years after which they migrate back to the sea. They feed on invertebrates and small fish. 

Population

Wild Atlantic salmon populations are in crisis, having declined by 70% in the last 25 years and Atlantic salmon is now endangered in Britain. In the 1980s there were 8-10 million adult salmon in the North Atlantic. Today there are 2-3 million.

There are 13 principal salmon rivers in Devon: the Axe, Exe, Teign, Dart, Avon, Erme, Yealm, Plym, Tavy, Taw, Torridge, Lyn, and Tamar. In 2022 all were classified as ‘At risk’ apart from the Tamar and Lyn which were ‘Probably at risk’. Particular pressures in Devon include barriers, water quality, sediments smothering gravel beds, higher water temperatures and altered flows. 

Habitat

Sea and brown trout are the same species. Like salmon, trout also require clean, well oxygenated gravel to spawn but prefer finer gravels and can also use smaller streams and rivers. They use vegetation and woody debris as refuges. Unlike salmon, trout don’t usually die after spawning. Some stay in rivers and are known as brown trout and others migrate out to sea and are known as sea trout. Many return to the same river to spawn, generally between June and October.   

Population

Due to the decline in sea and brown trout populations, byelaws have been put in place restricting the number of fish that can be kept and killed. Much of the data held on sea trout stocks in the UK is from fishermen who hold rod catch licences.   In Devon the Avon, Plym and Torridge are now classified as ‘At risk’ with the Dart, Erme, Yealm, Tavy, Tamar, Taw and Lyn classified as ‘Probably at risk’. Pressures for trout are very similar to those for salmon.

Habitat

Lampreys are an ancient order of jawless fish. They have a circular disc-shaped mouth, which sea lamprey use to attach themselves to a host fish they then feed on. Brook lamprey live in freshwater while river and sea lamprey spawn in freshwater and feed in coastal waters. However, brook and river lamprey could be the same species, with some fish staying in freshwater and some evolving to be able to migrate out to sea (similar to brown and sea trout).

Population

All three species are of international conservation concern. Brook lamprey is legally protected and all are UK Priority Species. There are no specific lamprey surveys in Devon, but an analysis of Environment Agency data from 1965-2024 showed:

– brook lamprey are likely to occur in most of Devon’s catchments

– sea lamprey were found in the Taw and other north Devon catchments, Axe and Tamar

– river lamprey were in the Lim, Axe and Torridge catchments.

The main pressures are river barriers preventing access to their spawning gravels, pollution and loss of habitat through straightening and deepening channels in rivers.

Habitat

Eels follow an opposite lifecycle to salmon, trout, shad and lamprey. They spawn in the Sargasso Sea and then travel across the Atlantic to mature in rivers for up to 20 years before they return to their spawning ground. They have a broad diet that includes fish, molluscs and crustaceans and are also known to scavenge dead fish. 

Population

Eels are found in rivers across Devon. However, they’ve seen huge declines and are now critically endangered in Great Britain. Threats to eel populations in the UK are barriers to migration, habitat loss, fragmentation and degradation, pollution, over fishing, illegal capture and climate change.

Habitat

Sturgeons migrate from the sea to freshwater rivers to spawn and need diverse habitats, including estuaries and intertidal zones, which provide critical feeding and nursery grounds. Some sturgeon species can grow to be over six metres long and weigh more than 1,000 kilograms.

They have long, torpedo-shaped bodies that are covered in bony plates rather than scales. Their mouths are on the underside of their heads and can extend to suck up small worms and crustaceans from sediments. Their feeding habits help to aerate the riverbed and redistribute nutrients.

Population

There have been at least ten records of sturgeon off Devon’s coastline in the last few years making this nationally very rare fish ‘fairly frequent’ in Devon. There are no known records of sturgeon within Devon freshwater habitats.