Optimal sperm–egg ratios for successful fertilization using fresh and cryopreserved sperm in wild anadromous Atlantic salmon (Salmo salar L. 1758)

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In the context of production of organisms for restocking purposes, it is essential to maximise the use of male semen while maintaining a high level of genetic diversity. Good management of the sperm/egg ratio seems therefore crucial, both for fresh and cryopreserved sperm. Recent studies in salmonid species have shown the potential for assisted reproduction with low or very low sperm to egg ratios, but an optimal sperm to egg ratio for a good reproductive efficiency remains to be established for many fish species. Here, the reproductive success of Atlantic salmon was assessed after fertilization with five low sperm/egg ratios ranging from 5 × 103 to 5 × 105 and one control ratio at 106. With fresh sperm, good eyed stage and hatching rates were obtained with a low ratio of about 5 × 104 sperm per egg. Nevertheless, a high inter-individual variability was observed up to a ratio of 105, underlining once more the importance to select males according to their sperm quality. According to the results obtained, it seems wise to use a sperm to egg ratio of around 5 × 105, i.e. only half the concentration that is recommended for assisted reproduction of the tested species. Cryopreservation undoubtedly has a negative effect on reproductive success as shown by reduced sperm quality of cryopreserved semen. The reproductive success follows a linear regression that is highly correlated to the sperm/egg ratio clearly indicating that it is not feasible in this species to use low sperm/egg ratios with cryopreserved semen. According to the equation defined by the linear regression, it would be necessary to use a sperm/egg ratio of the order of 2.36.106, i.e. 5 times more concentrated than fresh sperm, in order to reach an equivalent reproductive success of cryopreserved compared to fresh semen.

langue originaleAnglais
Numéro d'article737758
Les DOIs
Etat de la publicationPublié - 25 févr. 2022

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