A study led by the University of Helsinki has found that fishing for Atlantic salmon in the early part of the spawning season targets fish carrying a "large salmon genetic variant," which guides the fish to grow large and mature slowly. This selective fishing could lead to a rarer occurrence of this variant and younger, smaller salmon, potentially harming the diversity and viability of salmon populations. The research, published in Evolutionary Applications, suggests that the timing of fishing could have evolutionary impacts on wild fish, and highlights the need for fisheries management to take into account the targeting of salmon from upstream areas in the early season. The study was conducted in collaboration with several universities and institutes, and used samples collected between 1928 and 2020 from the northern Baltic Sea and its rivers.