British Wildlife of the Week
Lurking in the depths of a select few lakes in England and Scotland is our rarest freshwater fish. Known as the vendace, this truly is a relic from the past. The few isolated populations that remain are the last vestiges of a species that was much more widespread during the last Ice Age. In our warmer modern world, only large, deep glacial lakes can provide the cold, clean, well-oxygenated conditions that these fish need to survive.
The term ‘vendace’ is commonly used to refer to two species of freshwater whitefish: Coregonus albula (widespread in northern continental Europe) and Coregonus vandesius (found only in Britain). The two species are so closely related that they are, arguably, one and the same. But if, as some experts believe, Coregonus vandesius – ‘our’ vendace – is indeed its own distinct species, it makes it a fish of great importance. Not only is that because the UK has very few endemic animals – and even fewer endemic vertebrates – but it would also make the vendace globally endangered.
Only four native populations of vendace have ever been recorded in the UK: two in the Lake District in England (at Bassenthwaite Lake and Derwentwater) and two near Lochmaben in southwest Scotland (Castle Loch and Mill Loch). But, probably thanks to water pollution, rising temperatures, and the introduction of non-native fish that utilised the vendace as a food source, the Scottish populations died out during the 20th century, while those in England were in decline.
In the 1990s, prompted by concerns of habitat deterioration at Bassenthwaite, a refuge population of vendace was established in Loch Skeen to save the fish from possible extinction. This may have happened just in time because the vendace in Bassenthwaite seemingly died out at the dawn of the 21st century. Meanwhile, more fish were translocated from Derwentwater to other bodies of water in both England and Scotland to establish further safeguard populations.
Today, fortunately, the vendace is faring slightly better than it has in the past. In 2013, after a 12-year absence, the species was rediscovered living in Bassenthwaite Lake (first, a juvenile was found and then, a year later, a couple of adults turned up), while the population in Derwentwater is thought to be stable. And it’s even better news north of the border because the vendace introduced to Loch Skeen have thrived. According to a survey carried out by the Centre for Ecology and Hydrology, Loch Skeen now boasts the healthiest population density of this fish, with ten times the number of vendace per hectare as Derwentwater.
I will almost certainly never see this highly secretive fish with my own eyes, but it’s still strangely thrilling knowing that, hidden away in just a few special bodies of water, there is a rarity here in the nature-depleted country I call home that may live nowhere else in the world.
In the next British Wildlife of the Week, we’ll be looking at our two smallest birds – the goldcrest and the firecrest.