Aquaculture systems—whether ponds, land-based fish farms, or floating cages—are all susceptible to accidental (and sometimes intentional) escapes of farmed fish. In Chile, farmed salmonids (Atlantic salmon, Coho salmon, and Rainbow trout) are exotic or non-native species, as they did not evolve in the country’s natural environments. This poses a threat because escaped fish can move freely, potentially harming biodiversity and ecosystem processes through predation, competition, and disease transmission. [1]
Paradoxically, Rainbow trout were introduced to Chile in the early 1900s by the government to promote recreational fishing, and their reproductive periods are now protected, allowing them to thrive in most Chilean rivers [2]. Another layer to this paradox is that escaped salmonids can also enter the recreational fishing “ecosystem”. A prime example is Chinook salmon, which was farmed in Chile in the early 1980s—even using ranching practices where juveniles were released into the ocean to be caught upon their return to rivers for spawning [3]. Today, Chinook salmon provides an important economic alternative for artisanal fishers in coastal areas of the Araucanía and Los Ríos regions, where overfishing has depleted native species.
Amid ongoing debate and controversy over salmonid escapes, we recall a policy proposal published in 2021 by INCAR in collaboration with INVASAL, which made specific recommendations for recapture and monitoring of escapes—measures that should be considered by authorities and salmon producers.
Continuing these efforts, a multidisciplinary research team led by INCAR conducted a large-scale geographic analysis using the best available data to assess environmental risks from escapes in the Los Lagos, Aysén, and Magallanes regions. This study, published in Reviews in Aquaculture under the title “ Environmental risk assessment of non-native salmonid escapes from net pens in the Chilean Patagonia” [4], found that risks vary by species:
The study also identified priority rivers and basins (such as the Palena, Cisnes, Aysén, and Exploradores rivers) where monitoring for escaped fish and spawning events should be intensified to enable early detection and control of potential invasions.
However, a persistent challenge in monitoring is distinguishing whether a salmon originates from aquaculture or wild populations—a dilemma that also affects recreational and artisanal fishers.
A recent study led by researchers at Oregon State University (with participation from INCAR) proposes adipose fin clipping as a simple, low-cost, and minimally invasive marking method [5]. This can be done during vaccination, reducing costs and stress on the fish, and could be enhanced with technological innovations for easier implementation.
Monitoring and reporting salmonids with clipped adipose fins could be extremely useful in guiding management strategies, preventing new invasions, and promoting a balance between salmon farming, artisanal fishing, recreational fishing, and nature conservation.
[1] https://centroincar.cl/wp-content/uploads/2021/04/PB7-INCAR.pdf
[2] https://www.scielo.cl/pdf/rchnat/v79n1/art09.pdf
[3] https://www.scielo.cl/pdf/rchnat/v80n1/art07.pdf
[4] https://onlinelibrary.wiley.com/doi/full/10.1111/raq.12711
[5] https://onlinelibrary.wiley.com/doi/10.1111/raq.70105
