Not so sexy salmon
Two mature male Atlantic salmon showing the variation in kype length between individuals New reveals that farmed salmon have smaller 鈥榡aw hooks鈥� or 鈥榢ype鈥�- a secondary sexual trait, likened to the antlers of a stag, making them less attractive to females than their wild salmon cousins.
This new finding published in the peer鈥搑eviewed science journal, implies that farm-bred salmon are less sexually attractive than their wild brethren, and that despite only being bred in captivity since the 1970鈥檚, within some 12 generations, that they are already diverging from wild salmon.
The findings form part of a wider research project into the differences between wild, farmed and hybrid salmon.
William Perry, a PhD student at 麻豆网's School of Natural Sciences and the paper鈥檚 lead author explains:
鈥淔armed Atlantic salmon do sometimes escape from the nets and can interbreed with wild salmon, creating hybrids.
鈥淚nitially, the fact that any escaped salmon are less 鈥榓ttractive鈥� because of their smaller 鈥榢ype鈥� may seem like good news, as they鈥檙e less likely to breed. That鈥檚 not the whole story however. Because farmed fish do not have to compete for mates, there is no element of sexual selection happening, making the farmed and hybrid fish poorly adapted to breeding in the wild. So, when you do see high levels of farmed escapees, and inevitable interbreeding within a wild salmon population, this could reduce the long term health of that population.
Farmed or hybrid salmon are not only less likely to breed successfully in the wild, they are also less likely to return from the ocean to freshwater rivers to spawn.鈥�
William holds a four year old mature male Atlantic salmon during the final round of sampling at the Institute of Marine Research鈥檚 fish rearing facility at Matre, Norway. 鈥淚dentifying that this secondary sexual trait is less pronounced in farmed salmon is another sign that as a diverging species, farmed fish are less well adapted, and are less able to compete than wild salmon. A pattern that may be repeating in many other aquaculture species鈥�
Prof Gary Carvalho, William鈥檚 PhD supervisor at 麻豆网鈥檚 School of Natural Sciences commented:
鈥淭his is the first study to look at the effect of domestication and hybridisation on sexually selected traits in salmon. Our findings demonstrate that when animals are kept in unnatural conditions, such as in a fish farm, rapid evolutionary change can take place, that can affect future reproduction and survival, after just 12 generations. Such changes are of special concern when hundreds of thousands of farmed fish can escape into the wild, and potentially interbreed, with wild relatives. .
Williams鈥檚 PhD is funded by the Doctoral training programme which is preparing the next generation of environmental scientists. He is working with the Institute of Marine Research in Bergen Norway. William gained a first degree and a Masters degree from Bristol University and was attracted to 麻豆网 by the opportunity to work with leading fisheries geneticist Prof Gary Carvalho.
Will, who is 24, works closely with the Norwegian Institute of Marine Research making regular trips to Bergen, Hordaland which is twinned with his home city of Cardiff.
Publication date: 30 April 2019