Marine Scotland

Marine Scotland Scientists Contribute to Management and Control of Important Salmon Parasites

December 4, 2015 by No Comments

Marine Scotland scientists have recently carried out two studies, funded by the Scottish Aquaculture Research Forum (SARF), to determine the effectiveness of hydrogen peroxide (H2O2) against important parasites of marine salmonids – Lepeophtheirus salmonis, often referred to as the salmon louse, and Paramoeba perurans, which is responsible for amoebic gill disease (AGD). As well as laboratory and aquarium experiments, the projects included a literature review of target structures and physiological processes in lice, and the requirement to organise and report on a workshop involving the salmon farming industry.

Laboratory and aquarium-based trials revealed that H2O2 had varying effects against different L. salmonis lifecycle stages. Exposure of egg strings to H2O2 resulted in high levels of hatching failure and, where hatching did occur, numbers of larvae making it through to the infective stage were greatly reduced. While H2O2 did not kill adult stages at higher temperatures (13 °C rather than 10 °C) and concentrations over 1500 ppm, treatment resulted in an extended period of inactivation, which reduces the risk of re-infection of the treated site. Tank trials also demonstrated that although H2O2 did not kill the chalimus stages (Stages 4 and 5 of the parasites 8 stage lifecycle), it did cause a one-stage delay in maturation.

The H2O2 thresholds required for killing amoebae were determined in laboratory trials. Then aquarium trials showed that both H2O2 and freshwater treatments were effective at reducing amoeba numbers. While neither treatment fully eradicated the amoebae, early intervention was found to be more effective for successful treatment of AGD.

In independent peer reviews the projects scored highly, with reviewers very complimentary about the work undertaken by MSS in terms of our understanding of the issues, the open-minded but informed approach to the work, the standard of the output and incorporation of extras which added value. The findings in the reports will contribute to establishing criteria to support existing sea lice and AGD management strategies.

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