Species Identification

There are plenty of resources available to divers interested in learning more about the underwater life they see in Irish waters. This is far from an exhaustive list and if you spot anything that’s missing or want to highlight a resource you’ve used email us at SeasearchIreland@gmail.com and we’ll add it to the list.

Seasearch Ireland Species Identification Sheets

These species identification sheets aimed at identifying the most commonly seen species in Irish waters or those that have an unusual distribution.

Cnidarians – Anemones and Jellyfish
Molluscs – Sea snails, nudibranchs & cephalopods
Echinoderms – Starfish, urchins & cucumbers
Tunicates – Sea squirts

Miscellaneous – Sponges, worms etc.
Crustaceans – Lobsters and Crabs

The Seasearch Ireland Guide to Wrasse is a short guide to the 5 most commonly seen wrasse species in Irish waters.

Guide Books

The first port of call for most divers and generally easiest to use as you can flick through pages muttering “it was a orangey thing, where’s the photo of an orangey thing?”. Guide books are a great tool as they can be accessed in the most remote locations unlike online resources and pored over while you’re still wet. Below is a list of some of the most useful books available, all are avaialbe from the Marine Conservation Society bookshop by clicking on the image.

The Diver’s Guide to Marine Life of Britain and Ireland – 2nd edition

This replaces the old Observer Guide to Marine Life and it is jam packed with everything a novice recorder needs to know. Over 250 species, information on depth, habitat, size and distribution of species to narrow down your options.Particularly useful is the key features section and similar species so you can know what can be reliably identified visually in the field and what requires a bit of learning.

Great British Marine Animals – 4th edition

We’re now on the 4th edition of Naylor and this one is even bigger and better. This book is supplied as part of the Adopt a Site workshop training program and is a must for any serious recorder though it does needs to be combined with Seaweeds of Britain and Ireland.

Seaweeds of Britain and Ireland – 2nd edition

The most comprehensive guide on Seaweeds available without delving into the world of scientific keys this book contains virtually every algae species you’re likely to find on a stretch of coast. While it’s a must have to really expand your knowledge of seaweeds it does come with the caveat that it is perhaps too detailed and you can find yourself confused between numerous different species of fiddly reds. For a novice approach with caution and the Biodiversity Ireland swatch would be the best place to start.

A Field Guide to the Marine Fishes of Wales

Quick confession I love this book and think it has been the most helpful in terms of coming to grips with the fish I see diving. While written for Wales this book encompasses all of the most common fish you’re likely to see in Irish waters and a few uncommon ones you’re likely to never see, as well as regional oddities and the fiddly small guys. Whether it’s you want to tell the difference between a John Dory and a Basking Shark or start identifying your Callionymus lyra from your Callionymus reticulata whatever your level of fish knowledge I’d highly recommend this book

Sea Anemones and Corals of Britain and Ireland

Exactly what it says on the tin this book is a comprehensive guide to the 77 sea anemones and corals found in British and Irish inshore waters. Once you’ve mastered the common anemones (Dahlias, Jewel, Plumose, Devonshire Cup Coral etc.) this guide is essential for expanding your knowledge of the rest.

Seasearch Guide to Bryozoans and Hydroids of Britain and Ireland

One for the real anoraks this. Bryozoans and Hydroids are criminally overlooked by divers. This guide can help you identify over 120 species of stuff you’ve probably never really looked at before. If you’re at this stage you’re heading for “weirdo at dinner parties” level of recorder. Good for you.

Scottish Nudibranchs – Jim Anderson & Bernard Picton – Available as an eBook only

“A photographic guide to the nudibranchs and other sea slugs recorded around the coast of Scotland. 107 species are described and illustrated, with up to 8 images for each species, including their spawn and food, and general information on the main groups. There are also distribution maps for 102 species and reproductions of the illustrations from Alder & Hancock’s 1845-55 monograph for 74 species. All 107 species are illustrated in the Kindle version. Both versions now have the latest taxonomic updates.”

A Field Guide to Nudibranchs of the British Isles

This would have been much higher up the list in years gone by but unfortuanetly it is a) out of print and b) out of date on some species. Thanks to the sterling work of people like the authors we know far more about species structure of various genera of nudibranchs in Britain and Ireland a lot of species have been renamed and what was previously thought to be one species is now 2 or 3 or 4 species. Still an excellent resource for learning the tricky terminology in relation to identification of nudibranchs.


Encyclopedia of Marine Life of Britain and Ireland

The Encyclopedia of Marine Life of Britain and Ireland is edited by Bernard E. Picton and Christine C. Morrow and hosted by the University of Ulster. Excellent for all groups with the exception of worms and crustaceans this website is particularly useful for sea squirts and marine molluscs (nudibranchs in particular).

MarLIN – The Marine Life Information Network

Typically contains much more detailed information than the Ulster Museum website the only complaint that could be aimed at this website is that is only covers a much smaller selection of species.

The International Union for the Conservation of Nature Red List of Threatened Species

Unfortunately due the bias in conservation towards terrestrial vertebrates there are not many entries on the list relating to marine creatures and those that are tend to be fish. However extremely detailed information for the entries that are there as well as information on conservation status.

National Biodiversity Data Centre

In addition to their mapping system the Data Centre’s website contains information on Irish species. However the entries here are almost entirely restricted to invasive species.

World Register of Marine Species

Useful for checking scientific names for species and updates in taxonomy.

Ireland Nudibranchs and Sea slugs

A picture gallery of 58 nudibranch and sea slugs found in Ireland

Facebook groups – Some useful groups for posting queries or photos of difficult to identify species

Seasearch Identifications

Seasearch Ireland Identification and Recording Group – Not currently an active group but you could be the one to change that.

British Marine Life Study Society

NE Atlantic Nudibranchs

Other resources

Irish Sport Fishes – A guide to their identification

Intended for anglers rather than divers this useful tool was published by the Central Fisheries Board in 2003.

Irish Red List for Cartilaginous fish [Sharks, skates, rays and chimaeras]

Published in 2016 the most up to date overview of sharks, skates and rays in Irish waters.

National Parks and Wildlife Service – Irish Wildlife Manuals

Specific reports on various species or sites in Ireland.