**Author details**

The observed decrease in sperm motility might be due to decrease in the percentage of sperm viability, high damage of sperm cells, or decrease in ATP content following cryopreservation. Similarly, Alavi et al. [54] determined that almost all studies on sturgeon sperm cryopreservation showed significant lower sperm motility and fertilizing ability of frozen/thawed sperm

On the other hand, when fish spermatozoa are released into water or activation medium, they have a brief spermatozoal activity period [55]. For instance, in fresh sperm, the duration of spermatozoa motility in several cyprinids have been reported to last 120 s [56]. Similarly, in case of silver barb, the maximum motility period was observed until 150 s after water activation [4]. However, in case of frozen/thawed sperm, duration of mean post-thaw spermotozoa motility (32.0 ± 8.16 s) of the Nile tilapia was determined as lower than the results assessed with mirror carp [57] but higher than that of scaly carp [46] when DMSO, DMA, and glycerol were used as cryoprotectant. Similar results for the motility parameters of frozen-thawed spermatozoa were reported in fish in some experiments [48, 58, 59]. On the other hand, it is interesting to note that Godinho et al. [60] reported 241.2 ± 57.3 s post-thaw spermatozoa motility duration in glucose-based cryosolution containing 10% methanol in Nile tilapia.

sperm, which probably resulted in excessive sperm concentrations in all batches. However, according to Lubzens et al. [48], the concentration of frozen/thawed sperm to be used to achieve optimal fertilization and hatching success is approximately 100 times higher than for fresh semen. This may be due to differences in extender compositions, cryoprotectant types, equilibration periods, egg quality, or applied protocols. In the present study, high positive correlation was determined between post-thaw spermatozoa motility and fertilization. This situation was consistent with the results that obtained from turbot (*Psetta maxima*) [61],

In conclusion, Nile tilapia sperm can be successfully cryopreserved in a glucose-Tris–based cryosolution containing 10% DMA with 0.5-mL straws. The applied protocol can be used in commercial hatcheries to facilitate artificial reproduction of Nile tilapia due to acceptable postthaw motility and fertility results obtained. On the other hand, additional researches are needed to examine the growth and survival of the larvae originated from cryopreserved sperm.

This research was funded by the Mustafa Kemal University Scientific Research Fund (Project

common carp (*Cyprinus carpio*) [49], and African catfish (*Clarias gariepinus*) [62].

:1 for fresh as well as frozen/thawed

compared to that of the fresh sperm.

84 Cryopreservation in Eukaryotes

**5. Conclusion**

**Acknowledgements**

No: MKU BAP-384).

In the present study, the applied sperm/egg ratio was 1×105

Yusuf Bozkurt1\* and İlker Yavaş2

\*Address all correspondence to: yfbozkurt@hotmail.com

1 Faculty of Marine Sciences and Technology, Department of Aquaculture, İskenderun Technical University, İskenderun, Hatay, Turkey

2 Faculty of Veterinary Medicine, Department of Reproduction and Artificial Insemination, Mustafa Kemal University, Antakya, Hatay, Turkey
