Semen cryo-bank of the Malaysian Mahseer (Tor tambroides and T. douronensis)

Abstract

Ex situ conservation of Malaysian Mahseer (Tor tambroides and T. douronensis), the ecologically threatened freshwater fish species in Malaysia via semen cryo-banking was started in 2008 with the mature Tor species from four different locations in Peninsular Malaysia. At current stage, a total of 150 ml semen sample was collected from male fish of 73 T. tambroides and 15 T. douronensis and kept cryo-storage in liquid nitrogen (LN2) in the semen cryo-bank at Freshwater Fisheries Research Centre (FFRC). Sperm motility after cryo-preservation was found to be reduced by an average of 15 and 30% for T. douronensis and T. tambroides respectively; i.e. with pre-frozen motility 87.8 ± 7.9% (n = 73) and 88.8 ± 6.7% (n = 15), and post-thaw motility 54.9 ± 14.3% (n = 73) and 74.0 ± 11.2% (n = 15) for T. tambroides and T. douronensis respectively. The mean fertilization and hatching rates by using cryo-preserved semen in T. tambroides were 36.4 ± 10.5% (n = 360) and 34.5 ± 11% (n = 360) respectively; whereas were 89.8 ± 10.2% (n = 360) and 80.2 ± 16.6% (n = 360) respectively for fresh semen. Meanwhile, the survival rate of fry produced from cryo-preserved sperm (97.6 ± 3.1%, n = 360) was equally good (P > 0.05) when compared to the use of fresh sperm (99.7 ± 0.5%, n = 360). Sperm motility (%) during milt collection, before freezing and after thawing of each cryo-preserved semen samples was recorded. These tests were done with sperm from all semen samples and kept up to date into the Fishery Information Network System (INFOFins). The subsequent fertilization capacity and hatching rates of eggs fertilized with sperm from selected cryo-preserved semen sample were also quantified and recorded into INFOFins. Future prospects of the semen cryo-banking of Malaysian Mahseer is also reported and discussed in the present paper.