Britain’s Rarest Fish

Yesterday I arrived back from a week-long trip to the Lake District, which I thoroughly enjoyed. The landscape of the Lake District, with all the fells and lakes, is absolutely stunning, but so is the wildlife. In this post I will be writing about 2 of the fish that we saw on our trip, out of the 4 new species I have so far added to my Pan-species list. I am very pleased with the addition of these new species as it raises my fish list from only 7 to 11. Despite this still meagre total, I am very proud to say that following my trip I now have the 2 rarest fish in the British Isles on my list, the Schelly and the Vendace!

Schelly

The Schelly is a very rare fish , being endemic to the United Kingdom and even Cumbria. In fact it is only found in four lakes worldwide, Red Tarn, Haweswater, Brotherswater and Ullswater, and is classified as endangered. The combined area of those lakes forms the species’ area of occupancy, which is a tiny total of 20 km². That’s equivalent to half the size of Portsmouth!

During our trip to the Lake District we visited two of the lakes where the fish lives, Haweswater and Ullswater. In Haweswater, the population has been in decline unlike the other 3 lakes where the population is stable. According to the website of the International Union for the Conservation of Nature’s Redlist, which assesses species trends etc. and assigns them a category such as endangered or vulnerable, the two main reasons for the decline of the Schelly from the reservoir is water abstraction and predation from the humble cormorant. Water abstraction is the taking of water, permanently or temporarily, from a water body. The fact that Haweswater is a reservoir means that water abstraction is often practised, and this process can harm the environment. The good news is that conservation actions are taking place to conserve the Schelly, namely reducing water abstraction in Haweswater and taking control measures on Cormorants, according to the IUCN website.

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Clouds looming over Ullswater

Vendace

Now, the Vendace is the rarest fish in Britain. As a native species, confined to only two lakes globally, both in the Lake District, and introduced to one more in Scotland. The combined area of the two lakes where it is found in the Lake District is just 9.9 square km, making its native distribution area 10 times smaller than Paris! The Vendace used to be found in two further lakes, both in Scotland, however both populations were extirpated due to eutrophication. Eutrophication is the excessive abundance of nutrients in the water of a lake which causes very dense growth of plants. Eutrophication is often due to run-off from the surrounding land.

The main threats to the population of Vendace is the Ruffe, an introduced fish which feeds on the eggs of the Vendace. However, the Ruffe has only been introduced to Lake Bassenthwaite, not Derwentwater, the other lake in which it inhabits. Luckily there aren’t any clear threats to the population in Derwentwater, and fishing of this species has been banned. The Bassenthwaite population of this species even seems to be increasing. The species was declared locally extinct in Bassenthwaite in 2008 after the last fish had been recorded in 2001, but had been rediscovered a few years ago. It is possible that the fish found in Bassenthwaite come from the Derwentwater population and had travelled down the river from Derwentwater to Bassenthwaite.

The introduced population in Scotland, in Loch Skene, is doing very well, with a larger population than Derwentwater. The precise figure is nearly 10 times more Vendace per hectare than in Derwentwater, which is excellent! The species was introduced to Loch Skene when the population in Bassenthwaite Lake was seen to be very unstable due to the severe decrease in the habitat quality in the lake. This is a very good example of a successful conservation action.

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Looking across Derwentwater

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The gravel shores where I saw the young Vendace

I’m very pleased to have had the privilege to have seen these two fish as they are both in danger of extinction. Before I visited the lakes where these two fish are found I had no idea either of them even existed. Rare species like this are usually extremely poorly known by the general public and they don’t get the publicity that they deserve as they aren’t all that impressive, like tigers or pandas. However, just because they aren’t impressive it doesn’t mean that they don’t deserve to be saved from extinction. I think we should raise more awareness for these not very well known species in order to conserve them for future generations to cherish and enjoy.

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