Ammodytes marinus is a shoaling species which alternates between lying buried in the sand at night and hunting for prey in mid water during daylight. It feeds mainly on plankton and high activity periods are associated with strong tidal currents when they leave their burrows and form large shoals. During low light intensity periods such as at night or in winter they bury themselves into the bottom. They have neither a swim bladder nor fins. A. marinus is of great importance as a food source; however it is also important as a component in animal feed and fertiliser. Overfishing is causing problems for natural predators as is climate change and potential renewable energy developments.

In brief

• Found widely distributed throughout the UK and Ireland. Extremely common offshore in northern European Seas and occasionally found, mostly as juveniles, in inshore habitats
• Typically found at depths greater than 30 metres in sand and fine gravel
• Important food source for a wide range of predatory fish and sea birds such as terns, guillemots and puffins
• Has seen a marked decline in commercial tonnes landed in UK waters
• Main threats are overfishing, climate change and renewable energy developments

Species description: The body shape is thin and elongated with diagonal skin folds across the body and an upper jaw which can extend outward. The lower jaw is distinctively longer than the upper jaw and there are no teeth on the roof of the mouth. There is a single long dorsal fin and the anal fin is half the length of the dorsal fin. The pelvic fin is absent and the tail fin is small and forked. The lateral line is high on the body. Scales are absent from a median band forward of the dorsal fin and from the base of the caudal fin, the ventral sales are loosely arranged. A. marinus can reach a maximum length of 25 cm it is a green-blue colour on top, blue on the sides with a silver tinge and silver on the belly. Dorsal soft rays 56-63 and anal soft rays 29-33.

Life cycle: Spawning usually takes place in winter between November and February. The eggs are laid in sticky clumps on sandy substrates at the bottom of the sea. The hatched larvae remain in the water column before settling near the seabed approximately 2-5 months after hatching. Tagging experiments have shown there is little movement between spawning and feeding grounds indicating fishing and spawning grounds may coincide. Maturity is attained mainly at the end of the second year with some maturing in the first year. It is a relatively short lived species living up to 9 years. It feeds upon worms, small crustaceans and plankton, including fish eggs and larvae.

Similar species: A. marinus has often been confused with another very similar sand eel A. tobianus however it differs by having irregular rows of scales on its belly, no scales on the lobes of the tail fin and it has more vertebrae, dorsal and anal rays. In addition the pectoral fin does not reach beyond the first three dorsal rays.

How to see this species: In spring A. marinus emerges from the sea to feed on plankton. The availability of suitable seabed substrate is an important factor driving sand eel distribution and in addition the highest sand eel densities have been found where zooplankton concentrations are also high. The best way to spot sandeels from the land are in the beaks of returning seabirds feeding their young.

Current status: Decline in the UK waters.

Why is this species a priority in Northern Ireland?

• Listed as a UK priority species
• Declining

Threats: Overfishing is a threat to the sandeel and in addition climate change is increasingly viewed as an emerging human pressure. There is strong evidence that sandeel stocks are affected by bottom-up processes involving climate and changing plankton stocks. An increase in renewable energy developments also has the potential to affect sandeel numbers in terms of locating wind farm developments in its preferred habitat.

Objectives: Choose seafood from sustainable sources

Conservation:

• Potential protection of sandeel habitat (sand banks) through designation of new MPAs under the Marine Framework Directive Strategy
• Consultation on future marine aggregate extraction and offshore wind farm proposals
• Research is currently being conducted on local sandeel abundances and their effects on seabirds nesting on Rathlin island
• Effective fisheries management to protect remaining sandeel stock

Distribution Map from NBN: Ammodytes marinus at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Ammodytes marinus at iNaturalist World Species Observations database.

WoRMS: Ammodytes marinus at World Register of Marine Species. Accepted name: Ammodytes marinus Raitt, 1934. AphiaID: 126751.

Literature:

Greenstreet, S.P.R. et. al. (2006). Variation in the abundance of sand eels Ammodytes marinus off southeast Scotland: an evaluation of area-closure fisheries management and stock abundance assessment methods. ICES Journal of Marine Science 63, 1530-1550.

Van der Kooij, J. et al. (2008). The effects of environmental factors on daytime sand eel distribution and abundance on the Dogger Bank. Journal of Sea Research 60, 201-209.

Wheeler, A. (1969). The fishes of the British Isles and North-West Europe. London: Macmillan. 250-252.

Classification: Biota; Animalia; Chordata; Vertebrata; Gnathostomata; Osteichthyes; Actinopterygii; Actinopteri; Teleostei; Perciformes; Uranoscopoidei; Ammodytidae; Ammodytes