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.

Effectiveness of triploidy as a management tool for reproductive containment of farmed fish: Atlantic salmon (Salmo salar) as a case study

“…Although there is only limited literature on the production of neomales in Atlantic salmon (Johnstone & MacLachlan ; Lee et al . ), the effectiveness of this approach for yielding all‐female populations has been confirmed (Lee et al . ; Anon.…”

“…), the effectiveness of this approach for yielding all‐female populations has been confirmed (Lee et al . ; Anon. ) and is currently used in Australia for the production of all‐female triploid Atlantic salmon in the Tasmanian aquaculture industry.…”

“…Genetic females in such species can be treated with androgens or aromatase inhibitors to allow them to develop as functional males, and these 'neomales' yield all-female offspring when crossed with normal females (Benfey 2009). Although there is only limited literature on the production of neomales in Atlantic salmon (Johnstone & MacLachlan 1994;Lee et al 2004), the effectiveness of this approach for yielding allfemale populations has been confirmed (Lee et al 2004;Anon. 2010) and is currently used in Australia for the production of all-female triploid Atlantic salmon in the Tasmanian aquaculture industry.…”

Effects of aromatizable and nonaromatizable androgens on the sex inversion of red-spotted grouper (Epinephelus akaara)

“…Its unique difference from MT is the presence of 5 α -reduction, which prevents aromatazation. In salmon, Oncorhynchus kisutch ( Piferrer and Donaldson 1991 ; Piferrer et al 1994 ; Lee et al 2004 ), brook trout, Salvelinus fontinalis ( Galbreath et al 2003 ), Nile tilapia, Oreochromis niloticus ( Gale et al 1999 ; Wassermann and Afonso 2003 ) and European sea bass, Dicentrarchus labrax ( Blazquez et al 2001 ), MDHT treatment resulted in a higher proportion of sex-inversed males than MT treatment. However, co-administration of MT with aromatase inhibitor results in significant masculinization (97–98%) ( Piferrer et al 1994 ).…”

Transgenic Salmon: Science, Politics, and Flawed Policy

“…A genetic female can be induced to develop as a phenotypic male, or so-called neomale (XX), the milt from which will produce only genetically female offspring when crossed with a true female (XX). The monosex nature of the progeny derived from neomale-female matings has been demonstrated in several salmonid species, including Atlantic salmon and rainbow trout (Johnstone & Youngson, 1984;Johnstone et al, 1978;Johnstone & MacLachlan, 1994;Lee et al, 2004). In the AquAdvantage Salmon production process, 17α-methyltestosterone administered in the diet is used to produce AquAdvantage neomales.…”