The near-invisible lives of Ireland’s water beetles

In the ecological free-for-all following Ireland’s emergence from the last ice age, the first fish to penetrate the island’s lakes and rivers was almost certainly the northern world’s most cold-tolerant species, the Arctic char.

That's spelled with one "r" in Irish usage; elsewhere it gets two. But for all its long history here, Salvelinus alpinus remains, as in the title of a study for the Royal Irish Academy, "a secretive and threatened ice age relict".

To Google “charr” is to be offered pictures of giant trophy specimens straddling both arms of anglers, the fish’s big red belly (this only in breeding males) sagging between. Such monster specimens, up to 15 kilos, are caught in Canada’s northern lakes but still migrate to the sea for food. Ireland’s fish are now strictly dwellers in meagre trout lakes, feeding on zooplankton and occasionally each other.

At mostly up to 30cm, they have sometimes been termed "freshwater herring" – an indication of the "low numbers of encounters between Irish char and humans today", as the RIA paper put it. Written in 2014 by Fran Igoe and Swedish fishery expert Johan Hammar, it reinforced the appeal for conservation of char and the purity of deep, cold lake waters that are their vital retreat.

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Such pristine conditions are threatened by eutrophication, climate change and introduced predatory fish such as pike, and the past few decades have seen the extinction of entire populations. But in some lakes, says the RIA study, char may still actually outnumber the native trout.

The survivors may soon get some protection from a bylaw prohibiting their catch. This proposal, sought from the Minister of Environment by Inland Fisheries Ireland is now open to public consultation.

The char’s persistence at the southernmost fringe of its natural range makes its gene pool one of the oldest in western Europe and thus of particular interest to evolutionary biologists.

Such special histories mark others among the 1,000 Irish species considered "vulnerable", "near threatened" or "in danger of extinction" in Red Lists for protection. These were drawn up for the National Parks and Wildlife Service (NPWS) and the Northern Ireland Environment Agency.

The latest list of protected and threatened Irish species, published online (NPWS Wildlife Manual 116), took 10 scientists to compile, each a specialist in one branch of living nature. From seabirds and dolphins to dragonflies and lichens, the species were selected from an estimated 18,000-plus birds, animals, plants, fish and insects in the Republic alone.

Many of the man-made threats to their existence are known and even measurable, but the vagaries and intensities of climate change have yet to be experienced. Floods, droughts and heat waves will all have impact, for example, on the near-invisible lives of water beetles, which are such a distinctive part of Ireland’s natural world.

The study of Ireland's water beetles has a long and dedicated history, revived in recent years by the discovery of new Irish species in the lakes of the Burren and elsewhere

Until it sprang a leak and slowly sagged into a bog, my fabricated garden pond housed a host of water beetles. The largest and most fiercely carnivorous was the great diving beetle, which flies at night to avoid interception by birds. It is suggested that it looks for glints of reflected moonlight and has sometimes ended up in a water trough or flooded wheelbarrow.

Its pursuit of frog tadpoles is shared by its offspring, a singularly sinister style of prawn. I include the great diving beetle in my drawing. This was made in response to an experimental Irish recording of the chirps and stridulations of underwater life, captured by a dangled hydrophone. So beetles, like whales, can share the language of submarine song.

The study of Ireland’s water beetles has a long and dedicated history, revived in recent years by the discovery of new Irish species in the lakes of the Burren and elsewhere. Of some 240 known wetland species, almost 70 have been listed for Red List protection.

Scientific names come first, but English common names follow in almost very case – the Bubblegum Diver and Bald-beaked Sloth Weevil among them. The one exception in the NPWS list is the ciarogínbán, presumably named by the science team sifting the beetles from Ireland hardwater limestone lakes.

It discovered that Ireland holds most of the global population of Ochthebius nilssoni, a species never reported from Britain. This gives the country not only the right to award the beetle a native common name but also, as the team emphasises, “a responsibility to protect it”.

Between 2006 and 2016, the ciarogínbán was found in five Burren lakes and later in Co Mayo’s Lough Carra. There, in Ireland’s most famously pristine and closely studied karst limestone lake, the flea-sized (1.6mm) beetle browses on a spongy, bright cream-yellow biofilm on rocks called krustenstein.

A tiny Irish beetle in such a wild and whitish habitat does come together in a likely sort of Irish name, though krustensteinfloh might work well in certain foreign quarters.

* This article was updated on Wednesday, November 17th