Appropriate condition for the preparation of captive sturgeon’s brood stock for artificial propagation

Development of sturgeon’s brood fish gonads depends to a large extend on the quality of feed, mostly animal proteins and rearing condition specially the water temperature. In the feeding of brood fish, in addition to vitamin levels, omega-۳ fatty acids and amino acid profiles are also important. It is necessary to feed brood stock, from the beginning of the stage III of sexual maturation until a few months before the hormone injection (stage IV) with food containing ۴۸-۵۰ percent protein. Totally, the sexual maturation of brood fish, needs to keep them ۱-۲ months in water with a temperature below ۱۰ ۰C. The final ripening, is done by increasing the water temperature to more than ۱۴ ۰C. In other words, optimum conditions for spawning are a water temperature of ۱۳-۱۷ ۰C. Depended on the species and conditions, males spawn every year and females every ۲-۴ years. Nutrition and rearing condition of brood fish at stage III, where yolk formation takes place, play an important role in the quality and quantity of reproductive material. Usually, this stage includes more than ۲ years of the brood fish maturation period. In the maturation stage IV, ovulation occurs at water temperature below ۷-۸ ۰C (wintering). During this period, the eating is completely stop. The length of this period is shorter than the Stage III. Brood fish that are constantly placed in water with a temperature of below ۶ ۰C or above ۱۵-۱۸ ۰C can’t reach sexual maturity and/or resorb their eggs. Brood fish with ripe eggs that didn’t get the spawn opportunity for several consecutive times, they will be lost. To increase the efficiency of artificial propagation, at least ۲ years before sexual maturation, brood fish should be selected and placed in special rearing condition (feeding, water quality and temperature, duration and intensity of light). In order to provide the appropriate condition, it is necessary at least in the last ۲ years before the final maturation, from the beginning stage III and stage IIII of sexual maturity, seasonal changes in water temperature provided. This temperature range start of about ۲۶ OC in the summer and about ۸ OC in the winter. In the case of sudden changes in the weather or the entry of well water that has a different temperature from the surface water, the damages to the brood stock will be irreparable. This situation can cause a decrease in the probability of success, a decrease in the quality of the eggs, sexual maturation outside the breeding season, and a sharp decrease in the survival of eggs and larvae. This issue can even have a severe adverse effect on the survival of the juvenile from such spawners and it may cause their death. In the absence of surface water with optimum temperature fluctuation, suitable cooling and heating equipment can be used to change the water temperature and bring a limited amount of water to a suitable temperature by a few degrees.

Keywords:

Appropriate condition , sturgeon’s brood stock , artificial propagation