Sensing salmon lice larvae with lasers

Through the past 3 years we have been working on a PhD with Josefine Nielsen and DTU Aqua understanding the potentials of our sensor technology in detecting salmon lice larvae (Lepeophtheirus salmonis) in aquaculture. The PhD is reaching the end, so what have we found and where will we take it from here?

Salmon lice are a problem in aquaculture because infected individuals will have increased mortality, weight loss and open sores in the skin paving the way for other diseases and trouble maintaining the salt balance. Also having many individuals close to each other increases the ability of salmon lice larvae finding a host. It might also post a higher risk to wild populations of salmon passing the aquaculture farms. Salmon lice only attach to salmon. The estimated cost of salmon lice control was found to be around 300 mio € per year in 2006 (Costello, 2009).

When monitoring salmon lice in today’s production, individual salmon are captured, and adult salmon lice attached to the fish are counted. This is labor intensive and time consuming and needs to be done regularly. Outbreak rates vary from year to year, but in Norway for instance there are strict regulations for monitoring, and a set threshold for when to treat the salmon population.

Detecting early appearances of salmon lice larvae could be an improved tool for monitoring, it might even be used to treat at an earlier stage, when the larvae change their shell. Also having real-time data could be of great importance to salmon farmers.

Salmon lice larvae will float in the water before attaching to the salmon and developing into adults, mixed with other zooplankton and algae. The first obstacle is how to find salmon lice larvae between all the other zooplankton in the water?

Most zooplankton eat algae, but the Salmon lice larvae will not eat until it finds a host. Chlorophyll (a major part of algae) is auto florescent when exposed to near UV light. With this knowledge Josefine has worked with two non-eating zooplankton (one being Lepeophtheirus salmonis) and four algae-eating zooplankton. Exposing the zooplankton to laser light and measuring cyan florescence and red florescence and determining the differences between them. Robustly determining if zooplankton contains algae gives a chance to find larvae from salmon lice. She has shown this can be done in filtered sea water.

So now what?

After finishing her PhD, Josefine will continue her work as part of FaunaPhotonics, further developing the sensor techniques. Focusing on moving the sensor from lab experiments to the ‘field’. From January 2020, Co-founder and director Frederik Taarnhøj will move a large part of his time and focus towards determining the business case around sensor detection of salmon lice larvae.

We have a patent pending on the basic principle of using laser to divide the two types of zooplankton.

One article detailing Josefines work with zooplankton and laser has been published here and another article is on its way.

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