A new study — which is part of a broader project into the differences between wild, farmed, and hybrid salmon — reveals that male farmed salmon are “less attractive” than their wild counterparts thanks to their smaller “jaw hooks,” also known as “kype.” Per Phys.org, these hooks are a secondary sexual trait similar to the antlers of a stag, and their smaller size is less desirable to females than the larger hooks on their wild salmon cousins.
The findings were published in the Royal Society Open Science and suggest that farm-bred salmon are less attractive than wild salmon. Although they have been bred in captivity for a relativity short time in evolutionary terms — since the 1970s, which is equal to 12 generations of the fish — the results suggest that they are already starting to diverge from wild salmon.
“Farmed Atlantic salmon do sometimes escape from the nets and can interbreed with wild salmon, creating hybrids,” said William Perry, a Ph.D. student at Bangor University’s School of Natural Sciences and lead author of the paper.
And while Perry says that the idea that any escaped salmon are less attractive at first seems like a benefit thanks to the reduced likelihood of reproduction, he claims it’s not that simple.
“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.”
Perry claims that farmed or hybrid salmon are also less likely to make the journey from the ocean to freshwater rivers to reproduce. He believes that the revelation that farmed salmon have a less pronounced jaw hook suggests that farmed fish are less adapted and less able to compete compared to wild salmon — a pattern he suggests could be happening in other aquaculture species.
Professor Gary Carvalho, William’s Ph.D. supervisor at Bangor University’s School of Natural Sciences and one of the senior authors of the study, believes the new data shows that “rapid evolutionary changes” can occur when animals are kept in unnatural conditions, such as farms. Not only that, he says these changes are significant enough that they “can affect future reproduction and survival.”
Carvalho added that the changes discovered in the study are concerning when considering the fact that hundreds of thousands of farmed fish can escape into the wild and interbreed with wild relatives, suggesting that they could be a danger to other salmon populations.