Opportunities and challenges related to sperm cryopreservation in Atlantic salmon gene banks

• Published in: Conservation Science and Practice
• Main Authors: Kristin Bøe, Bjørn Bjøru, Marthe Tangvold Bårdsen, Anveig Nordtug Wist, Steffen Wolla, Arne Sivertsen
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2021
• Subjects: Atlantic salmon; effective population size; fish conservation; frozen gene banks; live gene banks; population restoration; Ecology; QH540-549.5; General. Including nature conservation; geographical distribution; QH1-199.5
• Online Access: https://doi.org/10.1111/csp2.552; https://doaj.org/article/13837b94a3ae4fcca22c2747776d54b0

Abstract Atlantic salmon are facing population declines and loss of productivity within populations due to anthropogenic impact factors and reduced survival at sea. Biobanking is an increasingly used tool to conserve the genetic integrity and diversity of populations threatened by extirpation. The aim of the current article is to discuss the opportunities and challenges that increased use of cryopreservation brings to biobanking activities, using the Norwegian Gene Bank (NGB) for Atlantic salmon as a model system. The NGB was established in 1985 and involves a traditional living gene bank, as well as “frozen gene bank” where paternal germplasm is stored as cryopreserved sperm. Cryopreservation is a method where cells or tissues are frozen in liquid nitrogen to temperatures where all biological processes are paused, thus allowing the cells to remain viable after later warming/thawing to temperatures above 0°C. Cryopreservation is therefore used in long‐term preservation of genetic diversity and characteristics of wild populations. Until recently, implementation of large scale use of cryopreserved sperm in the live gene bank has been limited by a lack of protocols/capacity to preserve larger portions of sperms. More recent developments in cryopreservation methodologies, now enables preservation of samples sufficient for mass fertilization. Mass fertilization by cryopreserved sperm opens new opportunities to gene bank operations, including increased capacity to restore lost populations, mitigation of genetic changes in broodstock fish, as well as increased capacity at live gene bank facilities through the replacement of older males with frozen sperm. Knowledge demands regarding potential genetic damage to cryopreserved milt and potential epigenetic effects caused by the cryopreservation procedure should, however, be addressed.