Several factors regulating activation of spermatozoon motility in Eurasian burbot, Lota lota, including osmolality, calcium (Ca2+) ions, and temperature were investigated. Spermatozoon motility in Eurasian burbot, Lota lota was assessed at 4 and 30 degrees C in seminal fluid, isotonic media (with and without Ca2+) and hypotonic media (with and without Ca2+). Spermatozoa were spontaneously activated in seminal fluid at 20 degrees C and the maximum motility was recorded at 30 degrees C, which is out of the spawning temperature range, indicating that no risk of activation occurs during routine semen handling in artificial insemination. Initiation of spermatozoon motility in L. lota is mediated by Ca2+ and sensitivity to Ca2+ is dependent on temperature.