Development of germplasm cryopreservation and transplantation techniques for sturgeons

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Sturgeon are among the most valuable fish in the world. They are also the most endangered vertebrate group in the world. This is a direct result of human activities including pollution, damming, river fragmentation, climate change, and fisheries persecution, through directed fisheries, by-catch and illegal activities such as poaching. While efforts are being made to stop these activities, they are not fast enough or on a scale large enough to ensure sturgeon survival. Fortunately, advances in cryobiology have allowed us to expand the potential for preservation of wild and domestic stock variability through cryobanks. I propose to develop germplasm cryobanking protocols for 3 species of Canadian sturgeons that are of both aquaculture and conservation interest: shortnose (Acipenser brevirostrum), Lake (A. fulvescens), and White (A. transmontanus) sturgeons. First, we will develop sperm cryopreservation protocols for these species. Sperm cryopreservation procedures can be used to: synchronize gamete availability, conserve sperm volume, resolve space issues needed to meet genetic diversity targets by reducing number of broodstock held in hatcheries, reduce the risk of disease transfer, aid in spawning multiple males with several females throughout the spawning season, extend generation interval (gametes outlive the donor), provide insurance against extinction, and conserve genetic variability to reduce the risk of inbreeding in domestic and wild populations. Second, we will develop protocols for germplasm collection. Current germplasm collection protocols rely on sacrificing donors. This is not good when trying to generate rescue programs for endangered fish. Based on previous work in our lab, we will develop a preselection protocol based on sturgeon morphology and ultrasonography to select suitable candidates for non-lethal laparoscopic removal of small amounts of gonadal material for development of germplasm cryobanks. Third, we will develop cryopreservation procedures for oogonial cells (OC) from female sturgeon. In sturgeon, females are the heterogametic sex (ZW); in order to preserve genetic diversity we must cryopreserve OCs. Fourth, I propose to develop protocols to generate offspring directly from cryopreserved germplasm. We will develop procedures to transplant cryopreserved OCs into a sterile triploid surrogate, the blue tilapia (Oreochromis aureus). Blue tilapia were chosen because of the ease in generating sterile triploids and their very short time to maturation. They mature in under six months, unlike sturgeons that take 6-25 years to mature. Donor OCs will develop as either male or female gonads based on the sex of the surrogate (blue tilapia). When the surrogates mature, they will produce eggs and sperm of the donor species (sturgeon). This program will provide a roadmap for development of germplasm cryobanks for sturgeons and other fishes in Canada. One PhD, 3 MSc and 10 Honours students will be trained during this research program.