As the largest aquaculture industry in the U.S., catfish farming accounts for ~75% of total U.S. finfish aquaculture production, in which the channel catfish female by blue catfish male hybrid constitutes nearly 60% of the harvest. A major bottleneck for hybrid catfish breeding is high-quality sperm production as blue catfish reach sexual maturity in 4 to 7 years, and sperm is collected through a lethal testis removal procedure. The fact that sperm can only be obtained once from males creates a substantial investment in sperm production. Great variability has been observed between male sperm quality, cryopreservation success, and offspring performance from specific sires. Therefore, a major barrier to hybrid production is obtaining high-quality male sperm. Our objectives were to (i) examine parental contributions to larval morphological development and survival during early life using cryopreserved sperm, and (ii) identify fatty acids that predict sperm quality and cryotolerance to support hatchery production.
Sperm samples were collected from 44 males. Testes were dissected, weighed, and sperm extracted. An aliquot of sperm from each male was used for evaluation of fresh quality, while another aliquot was cryopreserved. Sperm kinematics and health indices were then quantified on fresh sperm and after cryo-storage. Sperm samples were also collected for fatty acid (FA) analyses. Cryopreserved sperm were thawed, then Males 1-15 were used to fertilize Female 1, Males 16-30 were used to fertilize Female 2, and Males 31-44 were used to fertilize Female 3, creating 44 families. Hatching success was quantified and larvae reared in triplicate (n = 50/tank) from each family. Survival, weights, and morphometrics were collected from 0-40 days post-hatch.
Preliminary results show that maternal and paternal variance both significantly contributed to body size in developing larvae, with increased paternal variance (increased coefficient of variation) throughout ontogeny (Fig. 1A). Relative FA concentrations of the fresh and cryopreserved groups showed significant differences (P<0.05) for saturated, MUFA, and n-3 FA with no differences in the n-6 and PUFA (Fig. 1B). Further data analyses will be presented. Together, these data will emphasize the need for high-quality male and female gametes and will result in a complete repertoire of lipid biomarkers for sperm quality and cryotolerance.