Environmental risk assessment of non‐native salmonid escapes from net pens in the Chilean Patagonia

Abstract

Here, we review extensive information to estimate environmental risks from escaped non-native salmonids based on the assessments of hazard, sensitivity and exposure of discrete water bodies in Chile. In 2020, the country harvested about 1 million tons salmonids from net pens located along 1500 km of highly biodiverse coastline. We base our analysis on existing scientific information and authors' expert opinions including an assessment of knowledge gaps and uncertainties. Risks of environmental impacts differed by salmon species, being lowest for Atlantic salmon due to its estimated lower survival, lower ability to feed after escaping and lower reproductive capacity in the wild compared to coho salmon and rainbow trout. Overall risks due to escapes of any of the species were highest in areas of both high farming intensity and low capacity of mitigating escapes (by wild predators and fishers) such as Aysén District. At same time, risk was higher in the most farmed areas that also presented suitable habitats to support reproduction and juvenile salmonid rearing. However, the risk estimation certainty differed among species being lowest for Atlantic salmon due to insufficient monitoring of their fate in the wild. Monitoring the fate and impacts of escaped salmonids, specially in higher risk areas is recommended to improve risk projections and to prevent and mitigate further impacts. Since Atlantic and coho salmon are not yet successful invaders in Chile, research attention is urgently needed to assess the environmental consequences of escapes of these species. The present approach can be applied to any aquaculture system given the availability of information on farmed species and receiving ecosystems.

Sea lion and fur seal interactions with fisheries and aquaculture in South American waters: threats and management perspectives

“…Farming of Atlantic salmon Salmo salar , coho salmon Oncorhynchus kisutch , and rainbow trout Oncorhynchus mykiss (Salmonidae, hereafter salmonids) has expanded rapidly in the last three decades in southern Chile (Quiñones et al 2019). The aquaculture industry, both in size and in the number of farming facilities, is rapidly expanding further south to remote areas of Chilean Patagonia (Soto et al 2022). The high density of fish stocked inside the salmonid pens (16–20 kg/m 3 ) constitutes a strong attractor for various predators, including the SASL (Sepúlveda & Oliva 2005, Vilata et al 2010).…”

Quantifying habitat overlaps between native and non-native fishes in the Himalayas using MaxEnt models optimized for data-deficient stream networks

“…The only supplementary data needed are species occurrences. Fortunately, even in situations where occurrence data is absent, experts knowledge about species ecology can be used to model the intrinsic potential of habitat to support sh populations 23,24 . The SNE tool can extract instream variables (discharge, gradient, and valley con nement) for modelling the intrinsic potential of streams to support species-speci c habitat based on ecological knowledge of species requirements.…”

“…These reachscale, spatially continuous stream segments are extracted in vector format, which preserves the hierarchical linear structure of the stream network. In addition to climatic requirements of species, topographic variables derived from DEM adds information to the model about the intrinsic potential of streams 22 to support different sh species 23,24 . SNE can be used to extract critical habitat features along the hierarchy of the stream network including reach gradient, total upstream gradient, and stream order, which are often associated with hydrological features, and are important for shaping the distribution of shes 34 .…”

“…But, high resolution digital elevation models (DEM), which are freely available for most parts of the world, can be used to extract instream and topographic variables. These variables can describe the intrinsic potential of habitats 22 that differentially support both native and non-native species 23,24 , and be used as inputs to implement ENMs in data poor regions.…”

An environmental resistance model to inform the biogeography of aquatic invasions in complex stream networks

“…by salmon farming production in marine net-pens between 2010 and 2019. We summarised historical data of massive salmon escapes and total aquaculture production (a surrogate for leakage escapes) at aquaculture management zones from Los Lagos and Aysén districts (41-47°S), where most coho salmon aquaculture exists (Soto et al, 2022).…”