Fish farming may have been devised as a remedy to reinvigorate dwindling fish stocks but this human solution has spawned another problem: lower genetic diversity.  New research shows that the genetic makeup of Atlantic salmon populations from a century ago compared with the current stock across 13 Swedish rivers is more genetically similar than distinct, which researchers say could compromise the ability of the fish to adapt to climate change. Click here (open access).

Salmon chosen by hatcheries are generally the same, selected for fast growth but with less survival skills than embodied by wild stock.  If reared salmon escape their pens or stray away from their designated water body, and end up mixing with wild species, they all but guarantee their offspring an inferior draw in the genetic lottery.  The study’s results show that stocking practices of salmon in the Baltic Sea have led to the homogenization of populations over the last century, potentially compromising their ability to adapt to environmental change.

Stocking of reared fish is common worldwide, and our study is a cautionary example of the potentially long-term negative effects of such activities.  “It is another nail in the coffin of stocking, the … techno-arrogance approach to salmon conservation, one that simply addresses the symptoms (fewer fish) and not the causes (less water, less habitat, more fragmented rivers) by simply releasing fish,” said Carlos Garcia de Leaniz, the director of the centre for sustainable aquatic research at Swansea University.  “This is a very solid study that adds to the growing body of evidence that shows that stocking is at best a waste of time, at worst an additional problem for the same populations it is trying to restore.”  Click here.