Can changing the sex ratio of signal crayfish help us control their numbers?

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A guest blog by Connor Wood, a 2015 PTES intern at the University of Aberdeen, on his project on American signal crayfish.

Invasive signal crayfish are having a devastating impact on our native species, which is now in real trouble. The non-native animals need to be removed from our waterways but just removing large numbers of them isn’t working. We need to understand how the sex ratio impacts on the reproductive ability and success of the crayfish and then adjust our efforts accordingly. For instance some trapping methods attract mostly males. However studies have shown that changing the sex ratio to a high proportion of females actually increase reproductive output! PTES awarded me an internship grant in 2015 to look at this issue more closely and see if I could make some useful findings, whilst also gaining new skills that will help me to get a job in the conservation sector.

american signal crayfish by Connor WoodWorking on this PTES internship has been a highly rewarding experience. Having the responsibility for planning and managing a long-scale project was a fantastic opportunity that I can transfer to my future career in academia and science. This project has offered me personal and professional challenges which, not too long ago, I wouldn’t have thought myself capable of handling.

Firstly, the sheer amount of work my workmate and I took on was remarkable! Each day we were waking up at the early hours of morning (early for me, at least!), faced with 8, 10, sometimes 12 hours of trekking up and down a river bank, hauling out traps and counting crayfish. It was physically exhausting work for a couple of scrawny guys like us! What’s more, half the time we were sleeping in tents overnight, from which I learned perhaps the most important lesson of all – if you’re going to be camping in the Highlands, spend more than £30 on your tent! This work taught me perseverance, far beyond what I’d ever shown before, and for that I am proud and grateful.

Without a doubt, though, the most demanding work was constructing the cages. This was a mammoth undertaking, considering neither of us were experienced in design and construction. We set ourselves the ridiculous task of hand building 20 giant bamboo-net cages and somehow, with a little help from some lovely volunteers, we managed to pull it off. It was a trial-by-fire for design and construction, and it proved to be a valuable, skill-building experience; the ability to conceive of a design intended for my own specific project, select the appropriate materials, construct it from scratch and put them to use.

This project also helped me develop my ability to work as a team. Every aspect of the project required highly co-ordinated team work, as there was always some task to be done and we had to know who was doing what at all times. We each had our roles, and we were constantly communicating and co-ordinating in order to increase our work efficiency. On multiple occasions, we had a third person volunteering to help us for the day. This offered me the chance to work as a team leader, explaining tasks to someone who did not usually work with us and managing them to work effectively in the group. I thoroughly enjoyed working in such a close-knit team dynamic.

Finally, through this project I was offered the opportunity to produce and present a poster at the Findhorn, Nairn & Lossie River Festival. The festival itself was a delightful and entertaining day, and it gave me the chance to communicate complex scientific ideas to the public in a digestible manner. This is an invaluable skill in the scientific community.

I couldn’t have done this without the help of my supervisors and workmates, Rupert Houghton and Prof Xavier Lambin, mostly for putting up with me for so long but also for the incredible help they’ve provided from the very start of the project. Fiona and Simon Calvin at Ecocamp Glenshee, and everyone at the Findhorn Village Hostel, were wonderfully hospitable and provided me with a home away from home. Ann-Marie and Ben were exceptional helpers with the field work.

This PTES internship has been a truly remarkable experience – I recommend anyone starting out on their conservation career path consider it. It’s been a hugely rewarding experience.

You can read more about Connor’s project on signal crayfish on our internship grants page here.

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