Shore Clingfish vs Cornish Sucker
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| Cornish Sucker Lepadogaster purpurea (top) Shore Clingfish Lepadogaster lepadogaster (bottom) Figure: A revision of the status of Lepadogaster lepadogaster (Teleostei: Gobiesocidae): Sympatric subspecies or a long misunderstood blend of species? |
As with virtually every contemporary tale of misidentification, it starts with a "Google said"; two words which send a chill down my spine every time I hear or read them. What may feel like a comfort blanket of confirmation bias to some, can mean an investment of hours for science communicators, who often need to access (sometimes quite obscure or costly) papers or surveys to effectively relay the relevant information over, and then summarise why the Google algorithm frequently pushes incorrect or dated material, even from reputable sources, to the top of the search. Sci-comm is generally a rewarding experience, as with every delve into a study, we learn more and become better communicators; though, in this "Age of Information", every peer-reviewed paper is countered with a more popular webpage lacking in any references.
In the context of ichthyology, there are tens of hundreds of known species this applies to, at least. It used to be a problem limited largely to field surveys and the literature which followed, but with the growth of the aquarium trade, and its (understandable) inability for exporters to keep up with the ever-changing nomenclature, it has led to incorrect husbandry for countless species. Even in our own angling, we're seeing a demand for fish identification, with swathes of users giving out incorrect IDs on social media. Thankfully there are many wonderful users who are able to drown this out with accurate identification, or even their honesty in admitting to not knowing (a rare thing to see these days). This stuff isn't new, of course, but it has certainly seen a rise due to the growth in anglers taking up light rock fishing (LRF) targeting the lesser-known micro fishes, and the increase in sea temperatures due to climate change, pushing unfamiliar Mediterranean species into the southern coasts of British waters.
One such group which has fallen victim to perpetual misidentification (and the focus of my attention for this article), have been the gobiescoids; and no, those aren't gobies, they are the clingfishes! A colourful and diverse family comprising of nearly 200 species ranging from the tropical zone to the southern reaches of the temperate zone. At the time of writing, we in the UK have a humble four [verified] clingfish species; and for the longest time, anglers and academics alike have been reporting a species we may not actually have.
When you think of British clingfish, your immediate thought might be of the Lepadogaster genus, which includes the relatively well known:
- Connemara Clingfish (Lepadogaster candollei)
- Cornish Sucker (Lepadogaster purpurea)
Or perhaps you're a species hunter whose every waking thought turns to one of the two more elusive species:
- Small-Headed Clingfish (Apletodon dentatus)
- Two-Spotted Clingfish (Diplecogaster bimaculata)
Whichever is the case, you may have heard the Cornish Sucker (Lepadogaster purpurea) referred to by another name, the Shore Clingfish. This is a misnomer, as the Shore Clingfish is Lepadogaster lepadogaster, the type species of the genus, whose range likely doesn't extend into the British Isles. I say "likely doesn't" as they mirror eachother's range in the Mediterranean and parts of the East Atlantic, but this has not been evidenced in the British Isles.
I always advocate for the use of scientific names, but I can't deny how powerful a communication tool colloquial (common) names are. Whilst there is some overlap between colloquial names with species, it is generally a force for good. In the case of the Shore Clingfish, it isn't just one common name that two species share, it is a name for one species which has been erroneously applied to another. This is where Google comes in, as when you search for one or the other species, you're greeted by websites, such as The Wildlife Trusts which use both names for one species. Errors by reputable sources like this have a snowball effect to the online (and even printed) medium, and academics who are fallible themselves may end up applying even the wrong scientific name for a species in a study. I can list half a dozen papers which have been affected by this, with a notable example (on polypterids), linked here—thankfully amended several months later.
Now, as we don't have Shore Clingfish in the UK, I wouldn't normally go through all this trouble to effectively just say "stop using this name for the Cornish Sucker", as there's not really any harm in it (at least not for anglers and the general public), but knowing these two species mostly share the same distribution, and paired with our "recent" Mediterranean invasion; it's a possibility we do have this species, or will do soon. Therefore, it's important, for the sake of gathering accurate data about what lives along our coastlines, to recognise the differences.
Cornish Sucker (Lepadogaster purpurea) & Shore Clingfish (Lepadogaster lepadogaster) - What's the difference?
Pictured below (B), is the Cornish Sucker (Lepadogaster purpurea), the same native to our waters. Note the two large ocelli on the dorsal side of its head. Markings have a habit of varying somewhat in fishes (especially location to location), but the ocelli are generally a good indicator as to what you've encountered.
On the underside of the fish (D), are the papillae on the sucking disc region. These are far harder to see for your average angler, but if you have a good zoom on your phone camera and a steady hand, you should be able to see them. They will have 5–6 rows of these small papillae; this is considered to be the most definitive way to correctly identify them.
Pictured below (A), is the true Shore Clingfish (Lepadogaster lepadogaster), the species which has not yet been verified in the British Isles. As you can see, the ocelli marked here are much smaller; again, as with all markings, this is not definitive (due to the overlap and variation), but perhaps a good indicator.
Once again, looking at the underside of the fish (C), we turn to the papillae around the sucking disc. This species has 3–4 rows of them, and you may notice they are larger than that of the Cornish Sucker.
Figure A, B, C & D: Lepadogaster purpurea (Actinopterygii: Gobiesociformes: Gobiesocidae) from the eastern Mediterranean Sea: Significantly extended distribution range
Of course, there is a range of other ways to tell them apart, but hardly any being practical in the field, at least not without severely distressing the fish. These include, incredibly subtle differences in morphology and further meristics—best left to lab work.
For the ichthyological bibliophiles out there, you may be aware that they were both originally described as a single species, Cyclopterus lepodogaster in 1788, then were later split into Lepadogaster lepadogaster and it's subspecies Lepadogaster lepadogaster purpurea, and more recently (in 2002) they were considered distinct species (citing subtle physical differences), and their names changed to what we know today, and in 2008, there was molecular evidence to support this.
Hopefully this has been insightful, and encouraged a few anglers and citizen scientists to look at what they find even closer; who knows? You might record a new species.
