A process for harvesting of fish eggs, comprising: a) providing a broodstock comprising sexually immature fish from at least one Salmo salar strain; b) rearing the broodstock in an aquatic environment comprising an aqueous medium that is suitable for sustaining life of the broodstock such that it proceeds to maturation, wherein the rearing is performed in life-cycle stages during which at least a light exposure and time span of each life cycle stage is adjusted, wherein the rearing includes at least a winter-summer period that comprises a winter life-cycle stage, within which the broodstock is exposed to light that simulates winter light exposure, and a subsequent summer life-cycle stage, within which the broodstock is exposed to light that simulates summer light exposure, wherein a total Accumulated Thermal Unit during the winter-summer period is no more than 5000; and c) harvesting eggs from the mature fish, wherein the winter life-cycle component of the winter-summer period comprises a total ATU of 1,600 to 3,500 units, and the summer life-cycle component of the winter-summer period comprises a total ATU of 400 to 1,500 units, wherein the simulated winter light includes light exposure for less than 12 hours in every 24 hour cycle, and the simulated summer light exposure includes light exposure for at least 12 hours in every 24 hour cycle, wherein during the winter-summer period, the summer life-cycle stage immediately follows the winter life-cycle stage, and wherein prior to the winter-summer period, the broodstock has been smoltified. a) providing a broodstock comprising sexually immature fish from at least one Salmo salar strain; b) rearing the broodstock in an aquatic environment comprising an aqueous medium that is suitable for sustaining life of the broodstock such that it proceeds to maturation, wherein the rearing is performed in life-cycle stages during which at least a light exposure and time span of each life cycle stage is adjusted, wherein the rearing includes at least a winter-summer period that comprises a winter life-cycle stage, within which the broodstock is exposed to light that simulates winter light exposure, and a subsequent summer life-cycle stage, within which the broodstock is exposed to light that simulates summer light exposure, wherein a total Accumulated Thermal Unit during the winter-summer period is no more than 5000; and wherein the rearing includes at least a winter-summer period that comprises a winter life-cycle stage, within which the broodstock is exposed to light that simulates winter light exposure, and a subsequent summer life-cycle stage, within which the broodstock is exposed to light that simulates summer light exposure, wherein a total Accumulated Thermal Unit during the winter-summer period is no more than 5000; and c) harvesting eggs from the mature fish, wherein the winter life-cycle component of the winter-summer period comprises a total ATU of 1,600 to 3,500 units, and the summer life-cycle component of the winter-summer period comprises a total ATU of 400 to 1,500 units, wherein the simulated winter light includes light exposure for less than 12 hours in every 24 hour cycle, and the simulated summer light exposure includes light exposure for at least 12 hours in every 24 hour cycle, wherein during the winter-summer period, the summer life-cycle stage immediately follows the winter life-cycle stage, and wherein prior to the winter-summer period, the broodstock has been smoltified. wherein the winter life-cycle component of the winter-summer period comprises a total ATU of 1,600 to 3,500 units, and the summer life-cycle component of the winter-summer period comprises a total ATU of 400 to 1,500 units, wherein the simulated winter light includes light exposure for less than 12 hours in every 24 hour cycle, and the simulated summer light exposure includes light exposure for at least 12 hours in every 24 hour cycle, wherein during the winter-summer period, the summer life-cycle stage immediately follows the winter life-cycle stage, and wherein prior to the winter-summer period, the broodstock has been smoltified.