Unlike other fish species, where sex can be determined by temperature, feeding, sex competition… or species that start out as males and then become females (such as sea bream) or vice versa (such as rock grouper), in sturgeons their sex is genetically determined, so they will be male or female for life and regardless of external factors.
A priori it might be thought that this is great because from the beginning we would know which are male and which are female sturgeons and thus separate them. The reality is that they do not have sexual dimorphism, pay attention to the word.
What does it mean that they do not have sexual dimorphism? sight are exactly the same, they cannot be differentiated, since they do not have different colors, shapes or sexual organs that tell us clearly and without a doubt what sex they are.
There is a characteristic that can guide us a little about the sex of sturgeons, and that is that the As a general rule, females are larger than males, but this does not mean that there are large males and small females, which means that it is not a reliable method and if used as a technique to differentiate them, it would have a fairly high error.
So, how do we do it?
In our facilities we carry out a painless, fast and very reliable method to an experienced person. We use an ultrasound machine, which allows us to differentiate whether the animal has a testicle (male) or an ovary (female) internally.
This process, at our water temperature of 15º C, we carry it out at 8/9 years of age, since the gonadal tissue has not developed beforehand and we cannot know for sure the sex of the animals. Once their sex is determined, we separate them, males to some pools and females to others. After this process, it will still take several more years to produce caviar, which is only produced by females and to obtain it we will still have to wait another 10 years on average, that is, it will be a total process of 16-18 years. We also assess the size and optimal time of caviar production by ultrasound, as if it were a visit to the gynecologist.
Did you know the multitude of uses it has ultrasound in the world of sturgeon?
Ignacio Alba Alejandre
Vet