Invasive Non-Native Species (INNS)
We have many non-native species living in the UK. Non-native species are those which are living outside their normal range. Many are favourite garden plants or popular wild mammals. Some, both on land and in the sea, are causing problems and are then called Invasive Non-Native Species (INNS).
The routes for non-native marine species are varied from shipping and recreational boating, to marine plastic floating across oceans or hitchhiking on introduced commercially farmed species.
The problems when species are deemed invasive are also multitude, from harming native marine life (outcompeting, feeding on and bringing in diseases) to affecting economic activity (fouling ports and hulls, interacting with farmed species and blocking outlets). They can also affect the DNA integrity of native species.
Monitoring present and expected species is an integral part of the plans to deal with them.
Lists of priority species have been compiled in line with their likely impact to our environment. There are plenty, so we’re introducing a few as we begin and move through our training.
Searching for INNS using the timed species search (see section on surveys) is an ideal activity to add to a survey or, if your time is short, to use as the Shoresearch survey you do that day.
For a training session during our Living Seas Champions weekend in 2020 Chloe Powell-Jennings (NRW) gave an online workshop which covered many of the most relevant species to North Wales and perhaps the most important to focus on. The full video is accessed via the link below (recommended), but to focus in on information about the four species we mention here, please see the timings below to jump to.
chinese mitten crab @ 22mins 50seconds
slipper limpet @ 29mins 14seconds
pacific oyster @ 32mins 16seconds
wireweed @ 39mins 49seconds
Four INNS to start
wireweed/sargaswm (Sargassum muticum)
©North Wales Wildlife Trust
- found in rockpools and on low shore areas
- very thin (wire-like fronds)
- yellow-brown in colour
- floats are apparent along “branches”
- plant floats on surface in shallows.
- possible comparisons are sea oak, mermaid’s tresses (for wireweed, look for small leaf-like shapes and floats)
- dies back in winter except for holdfast
- can look like another group of algae called Cystoseira, but look for lack of spines, clear bladders attached on their own and less dense appearance to ID wireweed
- this species is assessed as medium priority in terms of the risks it poses to ecosystems and economies in Wales
slipper limpet/ewin mochyn (Crepidula fornicata)
©Marine Conservation Society
- low shore, especially likes sheltered areas
- look for tall mass of pale coloured shells,
- can be orange-striped shells or low-growing shells attached to rocks or other shells
- peak is off-set in young, then curls over towards the shell opening, as grows
- shelf across opening, which provides the reason for the species name
- when small can look like other limpets, but look for orange patterning and bending peak.
- this species is assessed as high priority in terms of the risks it poses to ecosystems and economies in Wales
chinese mitten crab/cranc menigog (Eriocheir sinensis)
©Great Britain Non-Native Species Secretariat
- connected to areas close to estuaries
- green/brown coloured
- up to 6-7cm wide carapace
- carapace quite square-looking
- crab with distinctive, dense hairs on its claws, forming rounded “mittens”
- hairs on legs, which are long
- lives in rivers, but migrates to breed in estuaries in autumn, remaining there until the adults and juveniles migrate back in spring.
- looks similar to shorecrabs, so look out for the mittens.
- this species is assessed as high priority in terms of the risks it poses to ecosystems and economies in Wales
pacific oyster/wystrysen portiwgal (Magallana gigas)
©Great Britain Non-Native Species Secretariat
- grows up to 30cm in length
- teardrop-shaped shell
- each growth layer frills at edges
- off-white, yellow or grey in overall colour with patches of purple
- this species is assessed as medium priority in terms of the risks it poses to ecosystems and economies in Wales
- looks like another INNS oyster (Crassostrea angulata) which is also elongated and has purple patches. The Native oyster (Ostrea edulis) is more rounded, brown/blue colour patches and is less strongly frilled
The next section is the quiz. Click to begin the quiz, the questions will appear below. For the fill-in-the-gaps questions, make sure you spell the same way as the word/phrase in the list, but don’t worry about using capitals or not. If you get any one question wrong within each quiz page, the you will be marked as wrong for the whole page. Answers will appear one you’ve finished each question.
You will be tested on what you’ve learnt so far using the reading and video info. Don’t worry too much, as once you’ve been out on the shore, the ID features you’ve learnt about will make more sense and after a couple of visits you should feel more confident about your ID.
Good luck!