Space invaders: Searching for invasive Smallmouth Bass (Micropterus dolomieu) in a renowned Atlantic Salmon (Salmo salar) river

Abstract

Humans have the ability to permanently alter aquatic ecosystems and the introduction of species is often the most serious alteration. Non‐native Smallmouth Bass (Micropterus dolomieu) were identified in Miramichi Lake c. 2008, which is a headwater tributary to the Southwest Miramichi River, a renowned Atlantic Salmon (Salmo salar) river whose salmon population is dwindling. A containment programme managed by the Department of Fisheries and Oceans, Canada (DFO) was implemented in 2009 to confine Smallmouth Bass (SMB) to the lake. We utilized environmental DNA (eDNA) as a detection tool to establish the potential escape of SMB into the Southwest Miramichi River. We sampled at 26 unique sites within Miramichi Lake, the outlet of Miramichi Lake (Lake Brook), which flows into the main stem Southwest Miramichi River, and the main stem Southwest Miramichi River between August and October 2017. We observed n = 6 positive detections located in the lake, Lake Brook, and the main stem Southwest Miramichi downstream of the lake. No detections were observed upstream of the confluence of Lake Brook and the main stem Southwest Miramichi. The spatial pattern of positive eDNA detections downstream of the lake suggests the presence of individual fish versus lake‐sourced DNA in the outlet stream discharging to the main river. Smallmouth Bass were later confirmed by visual observation during a snorkeling campaign, and angling. Our results, both eDNA and visual confirmation, definitively show Smallmouth Bass now occupy the main stem of the Southwest Miramichi.

Comparing CRISPR‐Cas and qPCR eDNA assays for the detection of Atlantic salmon (Salmo salar L.)

“…In the eDNA space, there seems to be a lack of consensus regarding how many positive qPCR replicates are required to deem the species present in the sampling site (Ficetola et al., 2015; Giguet‐Covex et al., 2014; Willerslev et al., 2014). Due to the risk of taxa being present at low densities, some accept a single positive qPCR replicate (O'Sullivan et al., 2020), although Goldberg et al. (2016) suggest that results of this variety, which cannot be replicated, should be interpreted with caution.…”

“…As previously stated in Carim et al. (2016), the protocol employed has been used to collect >5,000 samples and no field contamination has been reported (see also McKelvey et al., 2016; O'Sullivan et al., 2020; Wilcox et al., 2016). At each site, 3.5 L of water was pumped through a pre‐packaged filter (cellulose nitrate membrane filters: Whatman—47 mm diameter/0.45 μl), housed within a Nalgene 145‐2020 Analytical Test Filter Funnel—250 ml capacity.…”

“…S. salar numbers in the Miramichi are in steep decline, with causes including overfishing, habitat degradation, high water temperatures, and low discharge (DFO, 2018). An additional stressor to the Miramichi S. salar population will undoubtedly be the presence of Smallmouth Bass ( Micropterus dolomieu), an apex predator whose presence was confirmed in the main Southwest Miramichi during 2017 (O'Sullivan et al., 2020). Human activities, such as pollution but dams, in particular, have had a significant impact on S. salar as exemplified by the Jacques‐Cartier River (CBJC, 2020).…”

Environmental DNA: What's behind the term? Clarifying the terminology and recommendations for its future use in biomonitoring

“…This definition also recognizes that samples of eDNA contain both intra‐ and extracellular DNA of microbial and macrobial species, and that the type of DNA captured may depend on capture method (Deiner et al., 2015). On the other hand, the definition of eDNA sensu stricto only referring to (mostly or even exclusively extracellular) DNA of macrobial organisms is especially used in conservation biology to monitor invasive and/or endangered species (Borrell et al., 2018; Lacoursière‐Roussel & Deiner, 2019; O'Sullivan et al, 2020), as well as in ecology to survey animal and plants communities and to study biodiversity patterns in aquatic ecosystems (see Deiner et al., 2016; Nguyen et al., 2020). Sometimes, the eDNA concept also includes the DNA extracted from bulk samples (see, for example, Lynggaard et al., 2019; Nielsen et al., 2019, both studies working on bulk samples but published in a journal dedicated to eDNA).…”

Ecological genomics of divergence, admixture, and fitness in the smallmouth bass (Micropterus dolomieu)

“…Conversely, they may be exceptionally tolerant of new environmental conditions because of evolution over an extensive geographic range. In some cases, as with the Northern pikeminnow and Pacific salmon in parts of the Pacific Northwest, USA, and Atlantic salmon in southeastern Canada (O'Sullivan et al 2020) invading Smallmouth Bass have outcompeted native fish or decimated other species through predation (Fritts and Pearsons 2004;Tabor et al 2007;, leading to population declines and ecosystem instability.…”