Sea lice (Lepeophtherius salmonis) detection and quantification around aquaculture installations using environmental DNA

The naturally occurring ectoparasite salmon lice (Lepeophtherirus salmonis) poses a great challenge for the salmon farming industry, as well as for wild salmonids in the Northern hemisphere. To better control the infestation pressure and protect the production, there is a need to provide fish farmers with sensitive and efficient tools for rapid early detection and monitoring of the parasitic load. This can be achieved by targeting L. salmonis DNA in environmental samples. Here, we developed and tested a new L. salmonis specific DNA-based assay (qPCR assay) for detection and quantification from seawater samples using an analytical pipeline compatible with the Environmental Sample Processor (ESP) for autonomous water sample analysis of gene targets. Specificity of the L. salmonis qPCR assay was demonstrated through in-silico DNA analyses covering sequences of different L. salmonis isolates. Seawater was spiked with known numbers of nauplii and copepodite free-swimming (planktonic) stages of L. salmonis to investigate the relationship with the number of marker gene copies (MGC). Finally, field samples collected at different times of the year in the vicinity of a salmon production farm in Western Norway were analyzed for L. salmonis detection and quantification. The assay specificity was high and a high correlation between MGC and planktonic stages of L. salmonis was established in the laboratory conditions. In the field, L. salmonis DNA was consequently detected, but with MGC number below that expected for one copepodite or nauplii. We concluded that only L. salmonis tissue or eDNA residues were detected. This novel study opens for a fully automatized L. salmonis DNA quantification using ESP robotic to monitor the parasitic load, but challenges remain to exactly transfer information about eDNA quantities to decisions by the farmers and possible interventions.publishedVersio

Steps toward nation-wide monitoring of non-indigenous species in Danish marine waters under the Marine Strategy Framework Directive

This report is the outcome of MONIS 2 – or in full, “Monitoring of Non-Indigenous Species in Danish Marine Water, phase 2” – and includes three deliverable: (1) a national Target Species List including 50 species, (2) a draft Technical Guidance Report, and (3) in silico designed and tested primers and probes for 48 of the 50 species on the Target Species List. The list is based on discussions at a workshop and subsequent scoring and ranking of relevant species. The draft Technical Guidance report is anchored in existing Standard Operating Procedures (i.e. protocols for sampling, storage and analysis) and adapted to the requirements of the Danish NOVANA programme. In addition, the report includes suggestions for next steps to take to implement and improve monitoring and assessment activities in regard to non-indigenous species in Danish marine waters

Using eDNA to estimate biomass of bycatch in pelagic fisheries

Abstract In recent years, the analysis of environmental DNA (eDNA) has significantly improved, allowing for high‐resolution species identification and possible biomass quantification from water samples. Fisheries management typically requires monitoring of catches, including precise information about bycatch quantities to make sound assessments of exploitation rates. Bycatch assessment is particularly challenging in large catches (>500 T), and the current practice of visual assessment of subsampled catches is time‐consuming, requires extensive labor, and often has low precision. We explored the feasibility for applying eDNA‐based methods for studying catch composition using the pelagic North Sea herring fishery with bycatch of mackerel as a case. First, we experimentally simulate a series of catches using a range of herring and mackerel weight proportions to establish relationships under real fisheries scenarios. The relationship is subsequently used to estimate the biomass of mackerel bycatch from eDNA from three herring catches, by sampling and comparing processing water both onboard ships and at the processing factory. All samples are analyzed using species‐specific quantitative PCR (qPCR). The experiments reveled a strong correlation between DNA and weight fractions characterized by a constant overrepresentation of mackerel DNA compared to expected mackerel weight. We found that eDNA‐based and visual methods applied to the same landing reflect the within catch variability in species composition alike, however, the methods can show disparity in total estimates of mackerel biomass. Accounting for haul mixing within total landed catches increases the precision of the factory and ship eDNA‐based estimates for the same catch. We show that eDNA‐based bycatch estimates provide coherent quantitative data, and likely improve quality and reduce costs of collecting fisheries‐dependent data and thereby contribute to securing sustainable fisheries

Using eDNA to estimate biomass of bycatch in pelagic fisheries

In recent years, the analysis of environmental DNA (eDNA) has significantly improved, allowing for high-resolution species identification and possible biomass quantification from water samples. Fisheries management typically requires monitoring of catches, including precise information about bycatch quantities to make sound assessments of exploitation rates. Bycatch assessment is particularly challenging in large catches (>500 T), and the current practice of visual assessment of subsampled catches is time-consuming, requires extensive labor, and often has low precision. We explored the feasibility for applying eDNA-based methods for studying catch composition using the pelagic North Sea herring fishery with bycatch of mackerel as a case. First, we experimentally simulate a series of catches using a range of herring and mackerel weight proportions to establish relationships under real fisheries scenarios. The relationship is subsequently used to estimate the biomass of mackerel bycatch from eDNA from three herring catches, by sampling and comparing processing water both onboard ships and at the processing factory. All samples are analyzed using species-specific quantitative PCR (qPCR). The experiments reveled a strong correlation between DNA and weight fractions characterized by a constant overrepresentation of mackerel DNA compared to expected mackerel weight. We found that eDNA-based and visual methods applied to the same landing reflect the within catch variability in species composition alike, however, the methods can show disparity in total estimates of mackerel biomass. Accounting for haul mixing within total landed catches increases the precision of the factory and ship eDNA-based estimates for the same catch. We show that eDNA-based bycatch estimates provide coherent quantitative data, and likely improve quality and reduce costs of collecting fisheries-dependent data and thereby contribute to securing sustainable fisheries