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

Abstract 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.