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This electronic thesis or dissertation has been downloaded from Explore Bristol Research, http://research-information.bristol.ac.uk Author: Nightingale, Jen A Title: Bolstering the wild populations of white-clawed crayfish Austropotamobius pallipes, through captive breeding, rearing and release of juveniles into favourable in-situ habitats General rights Access to the thesis is subject to the Creative Commons Attribution - NonCommercial-No Derivatives 4.0 International Public License. A copy of this may be found at https://creativecommons.org/licenses/by-nc-nd/4.0/legalcode This license sets out your rights and the restrictions that apply to your access to the thesis so it is important you read this before proceeding. Take down policy Some pages of this thesis may have been removed for copyright restrictions prior to having it been deposited in Explore Bristol Research. However, if you have discovered material within the thesis that you consider to be unlawful e.g. breaches of copyright (either yours or that of a third party) or any other law, including but not limited to those relating to patent, trademark, confidentiality, data protection, obscenity, defamation, libel, then please contact [email protected] and include the following information in your message: •Your contact details •Bibliographic details for the item, including a URL •An outline nature of the complaint Your claim will be investigated and, where appropriate, the item in question will be removed from public view as soon as possible. This electronic thesis or dissertation has been downloaded from Explore Bristol Research, http://research-information.bristol.ac.uk Author: Nightingale, Jen A Title: Bolstering the wild populations of white-clawed crayfish Austropotamobius pallipes, through captive breeding, rearing and release of juveniles into favourable in-situ habitats General rights Access to the thesis is subject to the Creative Commons Attribution - NonCommercial-No Derivatives 4.0 International Public License. A copy of this may be found at https://creativecommons.org/licenses/by-nc-nd/4.0/legalcode This license sets out your rights and the restrictions that apply to your access to the thesis so it is important you read this before proceeding. Take down policy Some pages of this thesis may have been removed for copyright restrictions prior to having it been deposited in Explore Bristol Research. However, if you have discovered material within the thesis that you consider to be unlawful e.g. breaches of copyright (either yours or that of a third party) or any other law, including but not limited to those relating to patent, trademark, confidentiality, data protection, obscenity, defamation, libel, then please contact [email protected] and include the following information in your message: •Your contact details •Bibliographic details for the item, including a URL •An outline nature of the complaint Your claim will be investigated and, where appropriate, the item in question will be removed from public view as soon as possible. Bolstering the wild populations of white-clawed crayfish Austropotamobius pallipes, through captive breeding, rearing and release of juveniles into favourable in-situ habitats Jennifer Anne Nightingale A dissertation submitted to the University of Bristol in accordance with the requirements for award of the degree of PhD in the Faculty of Life Sciences. School of Biological Sciences University of Bristol July 2020 Word count 35,544 i Abstract The white-clawed crayfish Austropotamobius pallipes, is a freshwater crustacean native to Europe and is endangered throughout its range due to habitat fragmentation, pollution, competition with the invasive American signal crayfish Pacifastacus leniusculus, and the associated disease, crayfish plague (Aphanomyces astaci). Production of captive-born A. pallipes for wild release into ark sites is a recognised conservation measure to help halt the decline of this species within the UK. The aim of this thesis was to optimise aquaculture methodologies to maximise ex-situ production of A. pallipes, whilst exploring effective techniques to monitor released individuals, so that their activity patterns and long-term survival could be assessed. A series of hatchery experiments were conducted investigating stocking density, grading and dietary regimes for rearing juveniles. Key findings were that young-of-the-year A. pallipes can be reared at high densities (300/m2) without compromising survival; however, the optimal stocking density that maximised growth and health was 100/m2. Juveniles exhibit sexual dimorphism as early as six-months of age, and sex, rather than size, was the main factor that led to dominance hierarchies and growth suppression in juveniles. Maintaining juvenile A. pallipes in single-sex groups was optimal. Live food was optimal for high survival and growth in hatchlings, and a plankton diet produced increased growth in juveniles than a pellet diet. Key findings for the tagging and tracking studies were that A. pallipes with a carapace length of 21 mm and above can be safely injected with passive integrated transponder (PIT) tags without survival or growth being compromised. Detection of PIT-tagged crayfish is limited to 150 mm, which is reduced to a 45 mm detection range when crayfish are within refuges. Long-term tracking using acoustic telemetry can provide useful data on activity patterns; A. pallipes are strongly nocturnal and are most active in spring and autumn. However, the methodology may be limited when used in still-water sites possibly due to interference from surfaces or other sound waves. The findings from this thesis have influenced the aquaculture methodologies now used at the Bristol Zoological Society’s crayfish hatcheries. This has led to increased productivity and more wild releases, which are significantly contributing to the conservation effort for this species, helping to halt its decline in south west England. ii Foreword This PhD study has been funded by the Bristol Zoological Society and Mohammed Bin Zayed Conservation Grant. Throughout the course of my studies I continued working in my role as UK Conservation Manager at the Bristol Zoological Society, overseeing the crayfish hatcheries at Bristol Zoo Gardens, Priddy and Ubley, whilst delivering practical crayfish conservation within my role as a lead partner of the South West Crayfish Partnership Programme. I was also part of several research collaborations including co-supervising a MSc, investigating terrestrial movements of A. pallipes and assiting with ex-situ and ark site detection of A. pallipes using environmental DNA. In total, I have led the writing and analysis for four scientific papers published during my PhD, and a fifth paper has been submitted and is currently under review. A sixth paper is currently being written up for publication. Scientific publications: 1. Nightingale, J., Stebbing, P., Sibley, P., Brown, O., Rushbrook, B., & Jones G. (2017). The use of ark sites and associated conservation measures to secure the long-term survival of white-clawed crayfish in the UK. International Zoo Year Journal, 51, 50-68. 2. Nightingale, J., Stebbing, P., Taylor, N., McCabe G., & Jones, G. (2018). Determining an effective density regime for rearing juvenile Austropotamobius pallipes in a small-scale closed system hatchery. Aquaculture Research, 49, 3055-3062. 3. Nightingale, J., Stebbing, P., Taylor, N., McCabe G., & Jones, G. (2018). The effect of size-grading for rearing young-of-the-year white-clawed crayfish Austropotamobius pallipes. Aquaculture Research, 49, 3116-3122. 4. Nightingale, J., Stebbing, P., Taylor, N., McCabe G., & Jones, G. (2018). The long-term effects and detection ranges of passive integrated transponders in white-clawed crayfish Austropotamobius pallipes. Knowledge and Management of Ecosystems, 419, 20-28. iii Dedication and acknowledgments I would like to dedicate this thesis to my family. To my mother Iris Nightingale and my father, ‘Pops 88’, who encouraged me so much and patiently listened to my incessant ramblings, at every stage of my studies; forever enthusiastic and willing to impart guidance. I am so sorry and sad that you did not witness me reaching the end of this journey, but thank you for helping me to get here; I know how proud you would both be to witness this moment! To my sisters Claire and Sarah for believing in me and showing kindness and support all the way through this journey. To Timmo, my amazing best friend and husband; it was you who told me I could (and should) do this, and who gifted me a shed to make it so. Thank you for your plumbing skills, your patience, your love and support, for helping us maintain some kind of ‘normality’, amongst all the crazy busy. I am not sure this would have been possible without you, by my side, every step of the way! To Maya and Wilf, our amazing little people, who have been so positive about every new graph and every new crayfish arrival at our house; you are the most incredible human beings and I hope I have inspired you to be curious about all the marvels of our natural world, to question and explore, rather than put you off science completely! You have been so kind and supportive to your mummy over all these years and I am so looking forward to all the awesome adventures that are waiting patiently for us. Let’s go and make some more magical memories, all four of us together…! Thank you to my supervisors, Gareth, Gráinne and Paul. Thank you Gareth for agreeing to supervise me for a second time, many years on, for allowing me the freedom to create my own set of studies and for taking a chance on a crustacean rather than a mammal! Thank you Gráinne, for having the daunting task of being both my supervisor and manager throughout this journey; your guidance and support has been amazing! Thank you Paul, for all your crayfish expertise along the way and for your complete faith in my abilities! Thank you to all three of you for taking me on and indulging my crayfish passion.