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

In brief

• Mackerel-like coastal fish which returns upstream to spawn.
• Internationally listed species.
• Limited knowledge of their true distribution in Northern Ireland.
• Main threats are from river and estuarine pollution, habitat loss and tidal barrages.

Species description: This fish superficially resembles a mackerel with a moderately deep and compressed body, usually 30-40 cm but can reach up to 60 cm. Scutes (bony plates/modified scales) visible along the belly. There is usually 4-8 dark spots behind the gill opening, although some or all of these may be absent.

Life cycle: There is limited knowledge of marine requirements for this species. Adults live in coastal water and return upstream to spawn in freshwater.

Similar species: Could be confused with Alosa alosa but it does not have 7-8 dark blotches along its side.

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.

They have been recorded from Lough Foyle, Belfast Lough and the County Down Coast.

Current status: Vulnerable. There is limited information on their true distribution in Northern Ireland marine waters. They are known to be in decline across western Europe.

Why is this species a priority in Northern Ireland?

• Criterion 1: Internationally listed species.
• Criterion 3: Rare or restricted range – rare breeding species confined to 5 hectads or less (based on expert judgement).

Threats: Main threats to this species are from estuarine and river pollution, habitat damage and tidal barrages.

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 5.
• Protected by the Conservation (Natural Habitats, etc.) Regulations (Northern Ireland) 1995 Part 3.
• Listed as Vulnerable on Irish and European Red Lists.
• Covered by Fisheries Acts.

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

iNaturalist: Alosa fallax at iNaturalist World Species Observations database.

WoRMS: Alosa fallax at World Register of Marine Species. Accepted name: Alosa fallax (Lacepède, 1803). AphiaID: 126415.

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