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MILJØFORSK-Miljøforskning for en grønn samfunnsomstilling

Targeted strategies for safeguarding the noble crayfish against alien and emerging threats

Alternative title: Målrettede strategier for ivaretakelse av edelkreps mot fremmede og framvoksende trusler

Awarded: NOK 6.5 mill.

TARGET aimed at developing cost-effective and environmentally friendly monitoring tools and control strategies for a better protection of endangered European noble crayfish. In work-package 1 (WP1), we developed methods for simultaneous environmental DNA (eDNA) detection of noble crayfish and its biological threats, including Aphanomyces astaci (crayfish plague) and several alien carrier crayfish species (Agersnap et al 2017; Strand et al 2019, Rusch et al submitted) through national and international collaboration. We compared eDNA with classic surveillance methods (Strand et al 2019), and implemented eDNA methodology in the monitoring program for crayfish plague (Vrålstad et al 2017-2018). TARGET further contributed to the coordination of the surveillance programs for crayfish plague, noble and signal crayfish (Johnsen et al. 2018), where synchronized fieldwork and the joint use of eDNA data contribute to a holistic and efficient monitoring. Simultaneous screening of crayfish and crayfish plague provides a good snapshot of habitat status regarding presence and threats (Strand et al 2019). We also tested mobile technology that enables the detection of crayfish plague and different crayfish species in field with rapid eDNA results on-site. Aquarium experiments with infected signal crayfish were conducted to measure the concentrations of eDNA from A. astaci and signal crayfish under various environmental conditions and life stages. The study showed that temperature, microbiological activity in the water, and various parts of the crayfish life-cycle affect eDNA quantity more than individual density (Laurendz 2017). A study comparing traditional crayfish trapping and eDNA data showed that eDNA detects crayfish equally well as trapping, with a high probability of detecting crayfish eDNA even at very low population densities provided a sufficient sample effort. However, it was not possible to develop eDNA predictors for population density. Both field- and aquarium studies showed that biological factors such as moulting, mass mortality, reproduction, and environmental factors such as rainfall, water quality and turbidity, affect the detectable amount of eDNA more than population density does. Three papers and one master's thesis were published from WP1, one paper is submitted, and two are in preparation. In WP2, we evaluated if toxin-producing cyanobacteria pose a risk to crayfish health and to people eating crayfish. We analysed crayfish from Lake Steinsfjorden after a cyanobacterial bloom in 2015, and conducted exposure- and feeding experiments with noble crayfish. The results from Steinsfjorden and the feeding trials revealed high amounts of toxin in the stomach, intestine and "liver", whereas edible tail muscle contained very low toxin levels. The exposure trials did not result in significant uptake of microcystins. This indicates that noble crayfish eat large amounts of toxic cyanobacteria. The experiments showed that the toxin amount in the crayfish did not decrease after two weeks of non-toxic feed and clean water. This was not problematic from a food safety perspective. The microcystin content in 100 g of crayfish tails from Lake Steinsfjord was below the tolerable daily intake (TDI), but we recommend removing the intestine from the tail before consumption as it contains high levels of microcystins (Vrålstad & Haande 2016). High doses of toxic cyanobacteria did not affect mortality or behaviour of noble crayfish. From WP2, one paper (Foss et al. 2018) is published, and two papers are in preparation. A Master thesis (Matre 2018) used WP2-material to compare ELISA and LC-MS methods for quantification of microcystins in crayfish. In WP3, we tested if ultrasound technology can eliminate crayfish plague in water and signal crayfish. We performed co-habitation experiments with noble crayfish and infected signal crayfish exposed to different ultrasound treatments. We obtained promising results for one of three ultrasound programs tested, but lacked sufficient confirmation in the control groups. We therefore carried out experiments with infected signal crayfish during the moulting phase where we analysed the degree of infection elimination by ultrasound treatment, and in controlled infection experiments where noble crayfish were exposed to known doses of A. astaci spores with continuous ultrasound treatments. The results showed that tested ultrasound treatments did not eliminate crayfish plague in water or signal crayfish (after carapax replacement). On the contrary, the infection load seemed to increase in the ultrasound treated signal crayfish, and in the infection trials, some treatments resulted in faster noble crayfish mortality compared to the infection control group. This remains to be statistically tested. The results will be summarized in a paper. In summary, TARGET has succeeded in developing surveillance tools that are now in use in the management of noble crayfish and crayfish plague in Norway.

TARGET har forbedret mulighetene for tidlig oppdagelse av sykdom og fremmede arter av ferskvannskreps. Prosjektet har ledet til implementering av et nytt konsept for miljø-DNA overvåking av krepsepest og ferskvannskreps, og i praksis eliminert bruk av levende edelkreps for overvåkning av krepsepest fra 2017. Det gir bedre dyrevelferd og mer etisk forsvarlig forvaltning. Fra 2018 ble miljø-DNA metoder tatt i bruk i nasjonal overvåkning av edelkreps og spredning av signalkreps. Overvåkningen ble samkjørt med krepsepest-overvåkningen slik at felles miljø-DNA prøver benyttes. Dette er kostnadsøkonomisk og fremmer samarbeid mellom forvaltningen og aktørene som utfører overvåkningen. Kompetanseoppbyggingen medfører også muligheter for andre fagfelt, og konseptet kan få bredt anvendelsesområde innen fiskeoppdrett og villfiskovervåkning. Miljø-DNA metodikken tas også i bruk i flere Europeiske land, og er publisert og tilgjengelig for foretak som er med anbudsprosesser om overvåkningsoppdrag.

The use of environmental DNA (eDNA) for detection and quantification of aquatic organisms is a rapidly growing field with a great potential for streamlined inventory- and monitoring purposes. TARGET aims to implement eDNA approaches for rapid and reliable "all-in-one-water-sample"-monitoring of the red-listed Noble crayfish and its threats. These include alien invasive disease-carrying North American freshwater crayfish and crabs, the crayfish plague pathogen Aphanomyces astaci, and possibly toxin-producing cyanobacteria that during blooms may pose a risk to crayfish health and crayfish as secure food source. TARGET will build on experiences and filtration approaches from a previous project, and test the "all-in-one-water-sample"-eDNA approach in vitro and on real-life water samples from relevant sites in Norway and Europe. Here, we will benefit on synchronized sampling efforts with classic on-going monitoring programs and research projects on the national and European level. Comparative studies using synchronously obtained classic (CPUE) data and eDNA quantities will be used for identification of eDNA predictor values for 1) relative crayfish population densities and 2) relative prevalence and infection load of A. astaci in the infected crayfish population (inferred from eDNA ratios of crayfish/A. astaci). Such approaches may allow effective large-scale, non-invasive surveillance programs that monitor not only the threatened noble crayfish and/or its threats, but also substantiate the absence of crayfish plague or toxin-producing cyanobacteria, or alternatively alert on their presence and quantities. TARGET will further elucidate how toxin-producing cyanobacteria may affect crayfish health and crayfish as food-source. Finally we will explore innovative environmental measures for mitigation and prevention of the crayfish plague agent in water and in carrier crayfish through pilot studies using ultrasonic technology.

Publications from Cristin

Funding scheme:

MILJØFORSK-Miljøforskning for en grønn samfunnsomstilling