Francis LeBlanc

Environmental DNA (eDNA) is transforming biodiversity monitoring by enabling the generation of high‐volume, machine‐readable biological data. When standardized and accessible, these digital assets can support ecosystem management through advanced computational methods, data integration, and temporal analytics. While substantial methodological guidance exists for eDNA field and laboratory protocols, a major unresolved challenge is determining the optimal timing of sampling. Inadequate alignment between sampling schedules and species‐specific phenology or DNA persistence can result in false negative detections, inefficient resource allocation, and misinterpretation of ecological patterns over time. To address this gap, we developed GOTeDNA (Guidance on Optimal Timing for eDNA), an interactive Shiny application that creates a dynamic loop where user‐reported observations inform evidence‐based guidance on eDNA methods. Here we describe the tool's core functionalities, including standardized data templates and statistical models developed from extensive inshore and offshore eDNA datasets spanning the Atlantic Maritime region to the Eastern Canadian Arctic. GOTeDNA provides detection rates for DNA metabarcoding, capabilities for high‐level field, laboratory, and bioinformatic protocol comparisons, and guidance on optimal sampling times for each method. Key features include: (1) Protocol exploration, (2) monthly species detection probabilities, (3) sampling effort recommendations, (4) seasonal detection heatmaps, and (5) data variability assessments. Users can explore their own data or query the Ocean Biodiversity Information System (OBIS)‐GOTeDNA database. As the database grows, the tool's guidance accuracy will increase. We outline a framework for future expansion, including the development of customizable dashboards and the integration of more advanced analytical tools. Finally, we discuss how the GOTeDNA workflow has the potential to advance the achievement of standardized data formats and computational approaches to enhance the reliability, comparability, and reproducibility of rigorous eDNA‐based decision‐making in ecosystem management.

After collapsing in the late 1990s, the southern Gulf of St. Lawrence population of striped bass (Morone saxatilis) is recovering. Here, we evaluate the use of under-ice eDNA sampling to monitor the population and confirm overwintering locations. From 2018 to 2020, water samples were collected from transects spanning 35 km of the Miramichi River system, accounting for the effects of sampling site, month, sampling depth and tidal influence on eDNA concentration. We examined the distribution of eDNA in a complex tidal river system with a time series consisting of 12 h of continuous sampling throughout a tidal cycle, in conjunction with the use of artificial DNA tracers and acoustic Doppler current profiler flow measurements. The eDNA distribution correctly identified overwintering grounds based on acoustic tag data, including a perceptible upstream shift in 2020. Overall, there was no significant effect of year, sampling month (February or March), sampling depth or tidal phase on eDNA concentrations. The tidal time series revealed only weak patterns of eDNA recirculation. Monitoring eDNA concentration and distribution allows for a relative comparison of population size and location between years, and has the potential to be expanded to other river systems more easily than traditional acoustic fish tags and surveys.

The sole member of the Piscihepevirus genus (family Hepeviridae) is cutthroat trout virus (CTV) but recent metatranscriptomic studies have identified numerous fish hepevirus sequences including CTV-2. In the current study, viruses with sequences resembling both CTV and CTV-2 were isolated from salmonids in eastern and western Canada. Phylogenetic analysis of eight full genomes delineated the Canadian CTV isolates into two genotypes (CTV-1 and CTV-2) within the Piscihepevirus genus. Hepevirus genomes typically have three open reading frames but an ORF3 counterpart was not predicted in the Canadian CTV isolates. In vitro replication of a CTV-2 isolate produced cytopathic effects in the CHSE-214 cell line with similar amplification efficiency as CTV. Likewise, the morphology of the CTV-2 isolate resembled CTV, yet viral replication caused dilation of the endoplasmic reticulum lumen which was not previously observed. Controlled laboratory studies exposing sockeye (Oncorhynchus nerka), pink (O. gorbuscha), and chinook salmon (O. tshawytscha) to CTV-2 resulted in persistent infections without disease and mortality. Infected Atlantic salmon (Salmo salar) and chinook salmon served as hosts and potential reservoirs of CTV-2. The data presented herein provides the first in vitro and in vivo characterization of CTV-2 and reveals greater diversity of piscihepeviruses extending the known host range and geographic distribution of CTV viruses.

The use of environmental DNA (eDNA) is a promising approach for the detection of aquatic species, including species at risk. One freshwater mussel species of interest in Atlantic Canada, the brook floater (Alasmidonta varicosa), is listed as being of Special Concern under theSpecies at Risk Actin Canada and as Vulnerable on the International Union for Conservation of Nature Red List. Further scientific data regarding species distribution and critical habitat is needed for the protection and conservation of this species. The aim of this study was to design, optimize, and apply a species‐specific quantitative polymerase chain reaction assay for the detection of brook floater from eDNA samples, and to assess temporal variability in brook floater eDNA quantities. Through an eDNA survey performed in New Brunswick rivers in 2017 and 2018, brook floater DNA was found at a total of 16 out of 56 sites sampled. The amount of brook floater DNA detected at all 16 sites was always below the theoretical limit of detection of the assay, and, as such, results were classified as either ‘inconclusive’ or ‘suspected’. The co‐detection of eastern pearlshell (Margaritifera margaritifera), a more abundant freshwater mussel species in Atlantic Canada, was successfully used as a natural positive control. Temporal variability in the amount of eDNA found in the water was also assessed at a site with a known brook floater population and minimal variability in eDNA quantities was observed from May to September. These results provide researchers and managers with a new tool for the detection of the brook floater in support of conservation and monitoring efforts.

The infectious salmon anaemia virus (ISAV) is capable of causing a significant disease in Atlantic salmon, which has resulted in considerable financial losses for salmon farmers around the world. Since the first detection of ISAV in Canada in 1996, it has been a high priority for aquatic animal health management and surveillance programmes have led to the identification of many genetically distinct ISAV isolates of variable virulence. In this study, we evaluated the virulence of three ISAV isolates detected in Atlantic Canada in 2012 by doing in vivo‐controlled disease challenges with two sources of Atlantic salmon. We measured viral loads in fish tissues during the course of infection. Sequences of the full viral RNA genomes of these three ISAV isolates were obtained and compared to a high‐virulence and previously characterized isolate detected in the Bay of Fundy in 2004, as well as a newly identified ISAV NA‐HPR0 isolate. All three ISAV isolates studied were shown to be of low to mid‐virulence with fish from source A having a lower mortality rate than fish from source B. Viral load estimation using an RT‐qPCR assay targeting viral segment 8 showed a high degree of similarity between tissues. Through genomic comparison, we identified various amino acid substitutions unique to some isolates, including a stop codon in the segment 8 ORF2 not previously reported in ISAV, present in the isolate with the lowest observed virulence.

The infectious salmon anaemia virus (ISAV) is an important viral disease of farmed Atlantic salmon that has caused considerable financial losses for salmon farmers around the world, including Atlantic Canada. It is listed as a notifiable disease by the World Organization for Animal Health, and to this day, culling of infected cages or farms remains the current practice in many countries to mitigate the spread of the virus. In Atlantic Canada, ISAV was first detected in 1996 and continues to be detected. While some outbreaks seemed to have arisen from isolated infections of unknown source, others were local clusters resulting from horizontal spread of infection. This study provides a description of the detected ISAV isolates in Atlantic Canada between 2012 and 2016, and explores the phylogenetic relatedness between these ISAV isolates. A key finding is the detection for the first time of a North American‐HPR0 ISAV subtype, which was predicted to exist for many years. Through phylogenetic analysis, a scenario emerges with at least three separate incursions of ISAV in Atlantic Canada. An initial ISAV introduction follows a genotypic separation between North America and Europe which resulted in the NA and EU genotypes known today; this separation predates the salmon aquaculture industry. The second incursion of ISAV from Europe to North America led to a sublineage in Atlantic Canada consisting of EU‐HPR∆ isolates detected in Nova Scotia and New Brunswick, and the predominant form of ISAV‐HPR0 (EU). Finally, we observed what could be the third and most recent incursion of ISAV in Newfoundland, in the form of an isolate highly similar to ISAV EU‐HPR0 isolates found in the Faroe Islands and the one isolate from Norway.