The reproductive cycle of male atlantic cod (Gadus morhua L.) from Placentia Bay, Newfoundland

The timing of the reproductive cycle of male Atlantic cod (Gadus morhua L.) from Placentia Bay, Newfoundland, was determined from histological gonad samples collected throughout the year. Cycles in gonad mass, whole mass, and somatic mass indices were also determined. Results were consistent with a spring spawning population, with males having testes filled with spermatozoa as early as January. There was a short resting period following spermiation, during which residual sperm was resorbed, followed by rapid development so that some sperm was again evident in the testes as early as November. At first, the presence of spermatozoa was accompanied by cells in all other stages of development, but by spermiation the testes were filled mostly with spermatozoa. Gonad size was largest in April, smallest in October, and increased steeply again in November. Energy for gonad growth came from food intake, as well as liver lipid stores. Gonad development was, for the most part, finished prior to the winter reduction in feeding intensity.