I was away last week so missed doing my weekly blog, looking back at an element of our 50 year history. However, it was quite fortuitous that I am a little late in writing it, as events this week make it even more poignant.
My focus this week (or last week) is eels. Perhaps not something that necessarily springs to mind when you think of Leighton Moss, but they are actually an incredibly vital part of the reserve ecosystem and we would be in trouble without them. They are the main food source for bitterns and otters and herons and all manner of reedbed favourites, so they are really really important.
Eels have an incredible story. They begin life in the Sargasso Sea on the other side of the Atlantic. They drift across on the Gulf Stream which brings them into Morecambe Bay. They are microscopic when they start out but when they get to this side, they have grown a bit and are around 1-2 inches in length. They are known as glass eels at this point as they are completely see-through. Another name for these young eels is 'elvers'.
A glass eel by Ruth Watts
The main dyke that runs out of the reserve is used to connect up the pools and control water levels. There is a sluice gate part way down it that allows us to either let water out, or keep water in depending on the conditions we want to try to achieve in the reedbed. This main dyke is also the eels motorway into the reserve from Morecambe Bay. However, the sluice gate presents an obstacle for them, so how do they get past it? We have a couple of eel ramps up the side of it. Eels are actually pretty good at manoeuvring when out of the water, so they wriggle up these ramps to get into the reserve. The eel run begins in about March and can last all summer in a good year, but is often waning by the end of June. We need to be able to monitor their numbers to find out whether they are having a good or bad year. To do this, we have a couple of eel traps, that the eels fall into once they've wiggled up the ramps. Our Warden David, has been surveying these eels at Leighton Moss since the 1990's and has the most detailed study in the country. He checks the traps every day, counts how many are in it, and then releases them into the reserve. Provided they don't get eaten, the eels will then grow to around a metre or more in length. They will then make the return journey across the Atlantic, back to the Sargasso Sea, where they spawn and die, and the whole cycle begins again. It's fascinating isn't it!
Eel ramp by David Mower
So how are the eels doing? Well like a lot of our wildlife, they have good years and bad years. An average year sees about 15,000 elvers coming into the reserve. The worst year we ever had saw only 2,500 in the whole season, and the best year ever was last year, with 51,000!!! So far this year, it is looking like we could have a repeat of 2013. 5,000 eels were recorded on Monday morning, and if you add that to those caught last month and yesterday, we already have over 15,000 so far this year! Looks like the wildlife will be feasting this year.