Seasonal variations in seminal plasma and sperm characteristics of wild-caught and cultivated Atlantic cod, Gadus morhua

The objective was to investigate changes, throughout the spawning season, in body size attributes and quantitative semen characteristics of wild-caught and cultivated Atlantic cod, Gadus morhua L. Sperm velocity increased significantly throughout the spawning season of cod from both origins. Curvilinear velocity (VCL; 30 sec post-activation) increased from 78.9+/-6.5 to 128.2+/-6.5 microm/sec (mean+/-SEM) between the beginning and end of the spawning season, respectively, for wild-caught cod, whereas for cultivated fish, it increased from 26.6+/-2.4 to 48.9+/-3.1 microm/sec between January and March. Spermatocrit did not undergo a significant seasonal change in wild-caught cod but did thicken for cultivated cod (24.6+/-4.2% in January to 40.5+/-4.4% in April; P<0.01). Sperm head area, perimeter, length, and width declined significantly at the end of the spawning season of cod from both origins (all P values<0.01). Seminal plasma osmolality and Na(+) ion concentration followed a dome-shaped function through the spawning season for both wild-caught and cultivated cod (P<0.05). For cultivated cod, seminal plasma pH was significantly lower at the start of the spawning season (P<0.001), whereas Ca(2+) increased then decreased (P<0.05). Body size attributes, spermatocrit, and seminal plasma constituents had significant relationships with sperm activity variables. These relationships varied as a function of time post-activation, month, and fish origin. Our findings may be used to (i) assess spermiation stage without killing males; (ii) optimize semen collection for hatchery production; (iii) characterize the potential impact of farming on sperm quality; and (iv) improve success of sperm cryopreservation and short-term storage.