Early warning: detection of exotic coho salmon (Oncorhynchus kisutch) by environmental DNA and evidence of establishment at the extreme south of Patagonia

Abstract

The global expansion of aquaculture is a constant propagule pressure that enables the establishment of exotic species in freshwater and marine environments. Here, we provide the first report on the presence of exotic coho salmon (Oncorhynchus kisutch) at the extreme south of Patagonia, in the island of Tierra del Fuego (TDF). During the last 6 years, 43 juvenile coho salmon were captured along the Beagle Channel, while one adult was captured in fresh water. Scale analysis showed that migration from fresh water as smolt would occur during their first winter of life. Mitochondrial DNA analyses revealed two haplotypes previously reported in North America and a new haplotype not reported before. We developed an environmental DNA assay for detecting coho salmon DNA from fresh water, obtaining positive results in three rivers. Additionally, one of these rivers was monitored monthly for a year, and we detected coho salmon DNA over 7 months, revealing the probable occurrence of coho salmon juveniles in fresh water. These results suggest the potential establishment of self-sustaining populations of coho salmon in TDF.

Southernmost distribution limit for endangered Peladillas (Aplochiton taeniatus) and non‐native coho salmon (Oncorhynchus kisutch) coexisting within the Cape Horn biosphere reserve, Chile

“…Habit et al proposed that if O. kisutch escapes from the salmon industry continued to increase, this species would be able to settle and naturalize in southern Chile due to an increase in propagules and optimal habitats. In this context, and in accordance withChalde et al (2019), we hypothesize that the establishment of O. kisutch at 55 S is due to escapes reported from salmon farms located in the Aysen region at 51 S, the closest region in Chile in which this species is farmed. We report that O. kisutch is co-inhabiting with two native and endangered species with significantly lower abundances within the area sampled.…”

“…In this context, and in accordance with Chalde et al . (2019), we hypothesize that the establishment of O. kisutch at 55°S is due to escapes reported from salmon farms located in the Aysen region at 51°S, the closest region in Chile in which this species is farmed. We report that O. kisutch is co‐inhabiting with two native and endangered species with significantly lower abundances within the area sampled.…”

“…Chalde et al . (2019) described its presence through eDNA in Tierra del Fuego, Argentina. Here we report its southernmost distribution point at 55°S.…”

Degradation modeling of water environmental DNA: Experiments on multiple DNA sources in pond and seawater

“…To detect and quantify the DNA of O . kisutch using qPCR, the forward and reverse primers for a 120‐bp fragment of the COI region of the mitochondrial DNA were prepared according to Chalde et al (2019) and we designed a TaqMan probe using Primer3Plus (http://www.bioinformatics.nl/primer3plus). The sequences of the real‐time PCR primers and TaqMan probes are shown in Table 1.…”

“…A Sterivex filter was used to filter 500 ml samples of water, and 1.5 ml of the filtrate from each bottle was collected. After extracting eDNA, the copy number of each type of DNA was estimated by qPCR All primer specificities for the three fish species were confirmed by each study that developed the primer-probe set (Chalde et al, 2019;Takahara et al, 2012;Yamamoto et al, 2017). While we tested the specificity of our designed O. kisutch probes, we also checked them in silico using homologous sequences from other Oncorhynchus that inhabit Japan (National Center for Biotechnology Information, NCBI; http://www.ncbi.nlm.nih.gov/).…”