Reproductive performance of alternative male phenotypes of growth hormone transgenic Atlantic salmon (Salmo salar)

Abstract

Growth hormone (GH) transgenic Atlantic salmon (Salmo salar) is one of the first transgenic animals being considered for commercial farming, yet ecological and genetic concerns remain should they enter the wild and interact reproductively with wild fish. Here, we provide the first empirical data reporting on the breeding performance of GH transgenic Atlantic salmon males, including that of an alternative male reproductive phenotype (i.e. small, precocially mature parr), in pair-wise competitive trials within a naturalised stream mesocosm. Wild anadromous (i.e. large, migratory) males outperformed captively reared transgenic counterparts in terms of nest fidelity, quivering frequency and spawn participation. Similarly, despite displaying less aggression, captively reared nontransgenic mature parr were superior competitors to their transgenic counterparts in terms of nest fidelity and spawn participation. Moreover, nontransgenic parr had higher overall fertilisation success than transgenic parr, and their offspring were represented in more spawning trials. Although transgenic males displayed reduced breeding performance relative to nontransgenics, both male reproductive phenotypes demonstrated the ability to participate in natural spawning events and thus have the potential to contribute genes to subsequent generations.

Effects of growth hormone over-expression on reproduction in the common carp Cyprinus carpio L.

“…The fertility of human GH-transgenic male mice was significantly lower than that of normal mice, and the female transgenic mice exhibited a prolonged vaginal cycle, and mated but failed to become pregnant or showed pseudopregnancy (Bartke et al, 1992(Bartke et al, , 1994. In fish, exogenous GH was found to influence the reproductive performance in some GH-transgenic species (Bessey et al, 2004;Fitzpatrick et al, 2011;Moreau et al, 2011;Rahman et al, 1998Rahman et al, , 2001). Rahman et al (2001) proposed that limitations in energy availability for gonadal development may be the mechanism for reproductive changes in GH-transgenic tilapia.…”

“…GH-transgenic coho salmon reach sexual maturation one year earlier than cultured non-transgenic fish, although some transgenic coho salmon display less courtship and reduced spawning capacity than their non-transgenic counterparts (Bessey et al, 2004;Fitzpatrick et al, 2011). Male GH-transgenic Atlantic salmon show poor nest fidelity, quivering frequency, and spawn participation, as well as overall fertilization success compared with their wild counterparts (Moreau et al, 2011). In our laboratory, the ''all-fish'' GH-transgenic common carp also have enhanced growth rate but with delayed gonadal development compared with their non-transgenic counterparts.…”

Transgenic Salmon: Science, Politics, and Flawed Policy

“…The reproductive performance of populations of male GH transgenic Atlantic salmon that are relatives of AquAdvantage Salmon, but are not triploid or all-female, has recently been assessed by Moreau et al (2011a). These investigators found that nontransgenic, wild anadromous (i.e., large, migratory) males outperformed captively reared transgenic counterparts in terms of nest fidelity, quivering frequency, and spawn participation.…”

Hybridization between genetically modified Atlantic salmon and wild brown trout reveals novel ecological interactions

“…Gametes from GH transgenic salmon [21] were provided by AquaBounty Farms (PEI, Canada). The gene construct used was a chimeric GH construct (opAFP-GHc2; EO1a line) that has been shown to greatly enhance growth [21], reduce reproductive performance among precocious mature males [22] and increase risk-taking foraging behaviours [23,24] in transgenic individuals. However, such phenotypic changes are known to be heavily influenced by gene-environment interactions [25,26].…”

“…Despite an observed successful first step, several lines of evidence from the literature combine to suggest that introgression of the transgene into the brown trout genome via backcrossing is unlikely. First, the reproductive abilities of transgenic salmonids are reduced compared to non-transgenic fishes [22,45,46]. Second, low natural rates of hybridization [15] and poor hybrid survival [19,36] further reduce the likelihood of transgene introgression into the brown trout genome.…”