PhD Fellow René Alvestad at Nofima successfully defended his doctorate at the Norwegian University of Life Sciences (NMBU) earlier this week. His work involved analysing a very large production dataset sourced from a commercial salmon producer.

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Reidun Lilleholt Kraugerud  

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His work specifically focused on some of their sea cage production and slaughter data from northern Norway. The key aims of his doctorate were to identify risk factors for cause-specific and overall mortality, reduced performance during the seawater ongrowing phase and quality downgrading at harvest.

Uncovered connections in the data

Alvestad analysed a large commercial database from 2010 to 2018. He found that seawater transfer of smolts with a higher average weight (up to 200 grams) was associated with increased mortality due to the heart diseases HSMB and CMS, and mouth rot during this period. A higher proportion of salmon also died of mouth rot when the smolts were transferred to the sea at low and falling seawater temperatures in this specific region.

This historical data also suggested that mechanical de-licing contributed to increased numbers of mortalities associated with HSMB and CMS and also increased overall mortality. Winter sores were the main cause of downgrading at slaughter and were a persistent cause of mortality in the seawater phase of production in this region and timeframe.

Melanin spots were the second most important cause of downgrading at slaughter during the timeframe 2010-2018. Fish groups that had a higher proportion of deaths due to heart-related diseases also had a higher incidence of melanin spots in the fillet at slaughter.

”In summary, I have found that there are many drivers for reduced quality and mortality, but there is no single cause that particularly stands out. However, we do see that it is possible to demonstrate a connection between reduced product quality and certain production strategy factors when we get good access to data at a slaughter facility”, says Alvestad.

The doctoral thesis showed that the collection and analysis of production data can be a valuable tool for identifying risk factors for reduced fish welfare and reduced product quality in commercial salmon farming.

Need for digitisation and standardisation

Alvestad’s doctoral degree was based upon gaining access to a large number of daily measurements in a suitable format. These included a number of parameters such as environmental factors, smolt transfer factors, feeding data and cause specific mortality data, to name a few.

René Alvestad defended his PhD thesis about the challenges of analysing large scale commercial salmon farming data on 15th June 2021. Photo: Wilhelm Solheim © Nofima.
René Alvestad defended his PhD thesis about the challenges of analysing large scale commercial salmon farming data on 15th June 2021. Photo: Wilhelm Solheim © Nofima.

”What I do requires digitisation, and that there is actually data in the formats I need to analyse”, says Alvestad.

He believes there is a need to improve the infrastructure for collecting, handling and sharing data, so that it is easier to identify risk factors and implement measures to combat or circumvent them. This is a general issue for both aquaculture and many other industries.

”One thing we can see is that the industry takes the problem seriously. There are several ongoing initiatives for standardised data collection in the aquaculture industry.

Learned a lot about the challenges of the aquaculture industry

”I have learned that the conditions in commercial farming are much more complicated than one sees in isolation in experiments. I also learned a lot about the industry and some specific regional challenges. Mouth rot is so new and so poorly covered in the literature, that it was surprising that it was so extensive”, says Alvestad.

About the doctorate

René Alvestad, who is 35 years old, already has a master’s degree in aquaculture and management of marine resources from Wageningen University, and a bachelor’s degree in biology from the University of Bergen. His PhD programme was funded by Nofima and the Research Council of Norway. Alvestad defended his doctoral thesis on 15th June at NMBU. His main supervisor was Kristian Hovde Liland (REALTEK, NMBU), and the co-supervisors were Chris Noble and Ingrid Måge (Nofima).

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