Counting down the days

Emily Collins – Research Student

As the newest member of the Conservation team, I’ve barely had time to lace up my boots before having to, quite literally, wade into the deep end. Having studied Picture 1Biology for two years at The University of York, I will be spending the next thirteen months working alongside Simon Hirst (River Esk Project Officer) and Rona Charles (Senior Ecology Officer) on numerous National Park projects as part of my Year in Industry, replacing Sam Jones who leaves at the end of August. A major focus of my year will be on helping Simon with the Pearl Mussel encystment project which aims to counter the declining numbers of rare Freshwater Pearl Mussels in the River Esk.

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As you might have read in Sam’s earlier post, this is an exciting time of year for the Pearl Mussel encystment project. The project revolves around the stage in the mussel life cycle which usually occurs between July and early September, in which glochidia (baby mussels) are released by adult mussels so that they can latch onto the gills of passing salmon or trout. They then grow on the gills for nine months before they are large enough to drop off and survive on the riverbed. A couple of weeks back, with August fast approaching and the release of the glochidia from adult mussels just around the corner, we called in mussel experts Ian Killeen and Evelyn Moorkens, to gives us some vital advice and training on how to artificially induce the encystment process ourselves.

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Picture 4So far this year we have found no evidence of natural encystment occurring in the Esk, something which we feared might be down to the fact that the female mussels weren’t producing eggs at all. All is not lost, however, for Evelyn having gently prised the mussel shell open with special tongs, was able to study the gills of a number of our mussels with an otoscope and show us that, to our relief, we still have some healthy egg-producing mussels in the Esk! What’s more, we found that many of the males have become hermaphrodites (egg-producing) due to the sparse distribution of mussels (a natural process that can sometimes occur). Picture 5

Picture 6Picture 7Ian and Evelyn also showed us how to extract fluid from the gills of the mussel using a pipette. The fluid can be studied under a microscope and any glochidia within it identified. At the moment our glochidia are in stage 2-3 of development so, using estimations from previous studies, we can predict that they will be at stage 5 – the ‘snapping’ stage – and ready to be released within a fortnight.

pictureNow that we have a date for the encystment, it’s vital that the whole encystment team, including the Environment Agency’s electro-fishers, are on standby so as not to miss the moment of release. On the day, we hope to visit the two sites which Evelyn believes to be good juvenile habitat and collect glochidia from the mussels by placing them in buckets and increasing the temperature of the water slightly to stimulate release. The mussels will then be replaced in the river and the glochidia mixed with salmon and trout in the buckets for fifteen minutes until the majority of them have ‘snapped’ onto the gills of the fish. The fish are then released. We will then return in the spring to see if any of these fish have glochidia still growing on them and whether the encystment has been a success.

Now we’re just counting down to the big day.

1 thought on “Counting down the days

  1. Pingback: Saving our Pearl Mussels: assisting encystment | The official blog for the North York Moors National Park

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