Causal analysis of escapement of farmed salmonids in southern Chile

Escaped salmonids are considered among the most serious threats to the aquatic environment. One hundred and nine escape incidents were reported in Chile from 2004-2021, representing some 8.53 million escaped salmonids. Of this total, 5.73 million were Atlantic salmon Salmo salar (67.2%), 0.83 million coho salmon Oncorhynchus kisutch (9.8%), and 1.96 million were rainbow trout O. mykiss (23.0%). It is estimated that 70.1% of the escaped salmonids were recorded in the Los Lagos Region, 23% in the Aysén Region, and 4.6% in the Magallanes Region. In total, 80.5% of the escapes were recorded from seawater facilities, while freshwater units accounted for 19.5%. The highest percentage of escaped salmon recorded in seawater over 2004-2021 was 1.71% of harvested salmonids in 2013. Some 39.5% of the escapes in 2015-2021 were attributed to rupturing of net cages, mainly due to adverse climatic conditions. The additional regulations introduced in 2020 by the Chilean authority, has helped to minimize the escape of farmed salmonids. As a consequence, just one escape event was reported in 2021, corresponding to 3.85% of the total number of escapees recorded from 2004-2021.