Live Preservation of Fish Gametes

Abstract

The term cryopreservation is used to describe the freezing and long-term storage of living cells, tissues and organs. Successful cryopreservation is well established for sperm cells from many fish species, but a technique for true cryopreservation of fish ova has proved elusive. Cryopreservation or longterm storage of fish eggs or embryos would be beneficial to the fish aquaculture industry. It would provide a method of retaining specific genetic lines of fish without the expense of maintaining broodstock populations and would provide a secondary source of a genetic line in case of broodstock loss or would allow the preservation of endangered genetic lines in wild populations (Jamieson 1991 and references below). Reports of successful freezing of viable Rainbow Trout (Oncorhynchus mykiss=Salmo gairdneri) eggs to -55oC (Zell 1978) or to -20oC (Erdahl and Graham 1980) were subsequently interpreted as supercooling (Harvey and Ashwood-Smith 1982). Successful hatching from vitrified embryos has been claimed for sea perch (Lateolabrax japonicus) (Tian et al. 2003) and Japanese Flounder (Paralichthys olivaceus) embryos (Chen and Tian 2005). However, the protocol of Chen and Tian (2005) was not found to be successful for Japanese flounder (Paralichthys olivaceus) embryos (Edashige et al. 2006) and although (Zhao et al. 2005) achieved some successful hatching the larvae had only a short survival. Vitrification of Turbot (Psetta maxima=Scophthalmus maximus) (Robles et al. 2003b) and red sea bream (Pagrus major) embryos also failed to produce viable larvae (Ding et al. 2007). A novel procedure involving vacuum equilibration for viable freezing of fish eggs to -196oC was introduced by