In order that a clear answer is given to your question, the following points need to be touched on:

1. In the Tawdih al-Masa’il of the maraji’[1], where the verdicts of twelve marja’s have been gathered, it says if a fish with scales is taken out of the water alive and dies outside, it will be pak and its consumption permissible. If it dies in the water though, it is only pak and can no longer be consumed. As for fish without scales, they cannot be eaten regardless of whether they died outside the water or not.

2. The term ‘scales’ denotes both small and big scales that can be seen on the skin of the fish with the naked eye without using any instruments like the microscope.

3. Having scales means that firstly, the fish has scales in its original creation, even if not always throughout its life, and secondly, for the scales to be towards the head or tail or cover its entire body, to be little or many, small or big, and hard or soft in a way that they fall when caught in a net or when rubbed against something. In all of these cases, it is said that the fish has scales.

4. The way of ascertaining this is for one to know this himself, or for two just persons to testify this, or for an expert in this field to testify that a fish has scales.

5. If the Stellate Sturgeon has no scales whatsoever[2], if a competent practitioner says that the only way for treatment of an illness is for this fish to be consumed by the patient, it will be halal. (In this case, the fish becomes halal for this person because of extenuating circumstances).

6. Aside from the Stellate Sturgeon being food for people in the case of it being halal, it can also be turned into fish food for halal fishes or food for other halal meat animals.

7. In the case of it being haram, buying, selling or hunting it still cannot be haram, because the impermissibility of eating something is one thing, while buying or selling it is another; the two are distinguished issues. It is possible for the consumption of something to be haram, and yet buying or selling being permissible. Blood is a good example; its consumption is haram, but buying or selling it isn't. The reason being that the uses of things aren't limited to their consumption, rather, different things, such as blood, can have great uses other than that. Therefore, buying and selling isn't only for consumption and can have other reasons as well.

8. It is noteworthy that Imam Khumayni was asked in an istifta’ whether consuming Stellate Sturgeon is halal or not, and he replied: If it is a scaled fish, or it is uncertain whether it is scaled or not, it will be halal, otherwise, its consumption is impermissible.[3]

To conclude, those who follow marja’s such as Imam Khumayni, if it isn't known whether the Stellate Sturgeon has scales or not, then its consumption will be permissible, and those who follow those maraji’ who say it is haram, can buy and sell it for other purposes. Therefore, each person needs to follow his own marja’ on the issue.