The steroidal levels are detected from the blood of fish and this is explained in this paper:

Study on sexual maturity and levels of gonad steroid

hormones in female kutum

Rutilus frisii kutum

(Kamenskii, 1901) during spawning season from river

Sefid-Rood of the southern Caspian sea

Further, you can go through the papers of Prof. Neeta Sehgal, Dept. of Zoology, University of Delhi.Here is the link, the relevant information is available:

https://www.researchgate.net/profile/Neeta_Sehgal?_iepl%5Bdata%5D%5Bposition-1%5D=1&_iepl%5BviewId%5D=587f52aded99e1a0e6191216&_iepl%5BinteractionType%5D=searchItemClicked&_iepl%5Bcontexts%5D%5B0%5D=searchItems

The steroid levels in the circulation may give you more information

I think the best method to steroid assay is using serum, because hormone is secreted from endocrine gland and enter circulatory system.

thank you all for your help