[February 22 AFP]The long-standing method of releasing juvenile Atlantic salmon (Atlantic salmon) artificially bred to secure fishery resources into the ocean actually reduces the breeding rate of wild salmon and is beneficial. Irish researchers have published findings that could ultimately have adverse effects.
According to a treatise published in October last year in the British academic journal Proceedings of the Royal Society B, salmon born in a hatchery in the Burrishoole catchment area in western Ireland On average, only one-third of wild salmon leave after leaving the Atlantic Ocean.
“O’s study also found that the greater the proportion of salmon from the hatchery in the annual catch, the less fertile the salmon in the wild environment the following year,” the main author of the paper said. Ronan James O’Sullivan, an evolutionary biologist at the University College Cork, told AFP.
The idea so far is that wild fish and hatchery-derived fish are “ecologically equivalent.” However, this study found that fish raised in cages for a period of time had some differences from wild fish.
Mr. O’Sullivan said he was “extremely worried” that the productivity (breeding rate) of salmon as a whole would “linearly decline” as the proportion of hatchery-derived fish in spawning salmon increased. Stated.
■ Decreased breeding rate, possible reasons
The release of salmon has continued for nearly 150 years in the North Pacific and Atlantic Oceans, and the area is home to several valuable endemic species. Over the decades, researchers have identified and sampled almost every salmon that passes through the lowlands of the intricate Barisur waters of lakes and rivers.
There are several possible explanations for why hatchery-derived salmon change rapidly and have a clear detriment to the number of wild fish. The first is the genetic effect.
In the case of artificial hatching, the fish do not choose their own mating partner, but the hatchery manager chooses a mating partner from a small group of wild fish. Its gene pool is so limited that genetic diversity is lost with repeated breeding. This is especially true if the salmon that were selected were hatched and released.
O’Sullivan speculates that the function of genes to adapt to the wild environment, such as overwintering methods, may eventually be suppressed or mutated.
The next thing to consider is the ecological impact. Although artificially hatched salmon are inferior to wild fish in adaptability to the wild environment, they grow in hatcheries where there are no natural enemies until they are released, so their bodies grow larger and females spawn more. “Wild salmon offspring may simply not beat hatchery-derived fish offspring in numbers and have been replaced,” said Osullivan.
Finally, material explaining the difference between wild salmon and hatchery-derived salmon may be found in the area of epigenetics, which studies the effects of non-genetic inheritance in offspring. However, this possibility is still a pure guess at this point.
Mr. O’Sullivan looks further and is also concerned about the impact of climate change. Previous studies have already confirmed a link between elevated water temperatures in rivers in northern Spain and southern France and the local extinction of Atlantic salmon in these areas. (c) AFP / Marlowe HOOD
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