Mackerel-like coastal fish which returns upstream to spawn in freshwater.

In brief

• Mackerel-like fish with dark spots behind gill opening
• Lifecycle involves both a freshwater and marine stage.
• Internationally listed species.
• Very few records from the island of Ireland, Northern Irish records may be fish that belong to the Scottish population.

Species description: This fish superficially resembles a mackerel with a moderately deep and compressed body, usually 40-50 cm but can reach up to 70 cm. Scutes (bony plates/modified scales) visible along the belly. There is usually a dark spot behind the gill opening, with one or two further along the body, although some or all of these may be absent.

Life cycle: There is limited knowledge of marine requirements for this species, it spawns in freshwater.

Similar species: Could be confused with Alosa fallax but it has 4-8 dark spots behind the gill opening.

How to see this species: This species is coastal, and found in open water from 10 - 150 m, but returns upstream to spawn in freshwater. Juvenile fish may be found in estuaries.

Recorded around most coasts of Britain, with some documented spawning sites. Very few records exist from the island of Ireland. Recorded from Lough Foyle and commercial fishing nets off County Down; 2003 record from Mourne River and 1896 record from Donaghadee.

Current status: Unknown. There are very few marine records from the island of Ireland. Northern Irish fish could derive from spawning population in Solway rivers (Scotland).

Why is this species a priority in Northern Ireland?

• Criterion 1: Internationally listed species.

Threats: Main threats to this species are from river or estuarine pollution and habitat destruction, e.g. from dredging and barrages at tidal limits of rivers.

Action: Records of new sites for this species, with details of habitat and population are always valuable. Observations with a photograph can be recorded using iNaturalist, find the MBDP-NI iNaturalist project here.

Alternatively, records can be sent to CEDaR, National Museums Northern Ireland, 153 Bangor Road, Cultra, Holywood, County Down, BT18 0EU. Tel 028 9039 5257, e-mail cedar.records@nationalmuseumsni.org, or via the online portal.

Objectives:

• Monitor population and establish if there is one in Northern Ireland or if these fish are part of the Scottish population.
• Improve estuarine habitat and safeguard against pollution.

Conservation:

• Protected under Bern Convention Appendix 3.
• Protected under Habitats Directive Annex 2.
• Protected by The Conservation (Natural Habitats, etc.) Regulations (Northern Ireland) 1995 Part III.
• Covered under Global (LC) Fisheries Acts.

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

iNaturalist: Alosa alosa at iNaturalist World Species Observations database.

WoRMS: Alosa alosa at World Register of Marine Species. Accepted name: Alosa alosa (Linnaeus, 1758). AphiaID: 126413.

Classification: Biota; Animalia; Chordata; Vertebrata; Gnathostomata; Osteichthyes; Actinopterygii; Actinopteri; Teleostei; Clupeiformes; Clupeoidei; Alosidae; Alosa