Preliminary Assessment of Sex Inversion of Farmed Atlantic Salmon by Dietary and Immersion Androgen Treatments

Dietary and immersion treatments with the androgens 17α- methyltestosterone (MT) and 17α-methyldihydrotestosterone (MDHT) were assessed for their efficacy in the masculinization of Atlantic salmon Salmo salar. Dietary treatments with MT at 1 or 3 mg/kg food or MDHT at 1 mg/kg food for 800 degree-days resulted in 100% masculinization of all female stocks. Single or double immersion treatments of alevins in MDHT at 400 μg/L for 120 min during the period 0-28 d after median hatch resulted in significant masculinization. Immersion treatments were most effective when conducted more than 14 d after median hatch. Two immersion treatments 7 or 14 d apart resulted in masculinization levels of up to 100%, whereas single immersions yielded levels up to 77%. Immersion treatment resulted in the production of significantly more sex-inverted males with patent sperm ducts than did dietary treatment. The study shows that immersion treatments are simple and effective for androgen-induced masculinization of Atlantic salmon, that they are suitable for commercial-scale use in hatcheries, and that they offer advantages in production efficiency over dietary treatments.