New report reveals unnaturally high mortality in aquaculture hatcheries

Publisert 06.09.2019

Unnaturally high juvenile mortality and poor reporting are among the main findings of Dyrevernalliansen and the Norwegian Veterinary Institute's project "Småfiskvel".

Yngel engelsk

Vulnerable small fish: Recently hatched salmon. The mortality rates are highest at this stage, when the fish weigh less than 3 grams.

Photo: Steinar Johansen, Midt-Norsk Havbruk

Unnaturally high juvenile mortality and poor reporting are among the main findings of Dyrevernalliansen and the Norwegian Veterinary Institute's project "Småfiskvel".

In the project "Småfiskvel", Dyrevernalliansen have asked the Norwegian Veterinary Institute to analyse national mortality data from the juvenile stage of salmon farming. The high mortality rates and high numbers of individuals in this stage of production indicate a large potential for high-impact welfare improvements.

Click here to download the full report.

The project was supported by a grant from the Open Philanthropy Project.

altZoologist Susanna Lybæk has been leading the work on the Småfiskvel project.

For zoologist and scientific advisor Susanna Lybæk, who has been leading the project for Dyrevernalliansen, it is good to finally shed light on the welfare challenges in salmon hatcheries.

– There is such a high number of individuals in juvenile salmon production, they are actually among the very largest livestock groups we have in Norway. The mortality rate is even higher than for the salmon in the sea, yet they receive little attention. It is high time to put the spotlight on the smallest fish!

Norway is the largest producer of Atlantic salmon worldwide (approx. 52% world market share in 2017), and the highest numbers of individuals are found in juvenile Atlantic salmon production. However, compared to the production of farmed salmon at sea, less attention has been given to mortalities reported from production of juvenile salmon in Norway.

The project aimed to correlate mortality rates with operating conditions in hatcheries. The goal was to identify which operating conditions are connected to mortality or poor welfare, and which can be described as success factors. Production form, biosafety, water quality, causes of mortality and welfare were among the topics covered.

High variation in mortality rates

altClick here to download the Småfiskvel report.

The highest mortality rates were found in the smallest weight group, in the juveniles weighing less than three grams. At this stage of life, the fish are moved from a protected life where they can hide in "astroturf" in the tanks to open, naked tanks with 24h light. The high mortality rate may indicate that the transition is a challenge for the small fish.

The mortality data from the Norwegian Food Safety Authority also revealed clear differences between the hatcheries. Not only is there a variation in mortality rates among the sites, but some sites consistently report high mortality rates over several years. The fact that some facilities manage to operate at significantly lower mortality rates than others indicates that it is not biology, but rather production methods and routines that cause the fish to die.

– The very smallest fish are very vulnerable. Many have interpreted this to mean that it is natural for many to die and that they cannot be helped. In this project we found that this belief is wrong. There are some producers that stand out and do a better job of looking after the fish. It is crucial that we learn from them, says Lybæk.

Poor reporting

The reports from the hatcheries to the Norwegian Food Safety Authority consist of the number of fish in each tank, average fish weight and the number of dead fish in the previous month. Data from year 2011 to 2018 were included in the project. However, an unexpected main finding was that the data is of less than desired quality. In order to make good analyses, reporting and data quality must be improved.
Apart from significantly higher mortality rates in the weight group below 3 grams and an increase in total monthly mortality in the period after year 2014, no significant differences were found between modes of operation and other conditions in the hatcheries. It is important that the way mortality data is reported to the Norwegian Food Safety Authority is revised. Changes in reporting of the data will make it possible to find both success factors and conditions that increase the risk of poor animal welfare in hatchery production.

Moving forward

Dyrevernalliansen will work for the introduction of daily or weekly reporting that will allow fish to be monitored throughout the production. Quality control of data will be central. This will make the reporting process easier for both producer and government officials.

In order to find the cause of the high mortality rate, further research is needed. Dyrevernalliansen will continue its efforts to improve the welfare of juvenile salmon.

Lybæk is concerned about the high mortality rates in hatcheries.

– Dyrevernalliansen helps those animals who need it the most. Juvenile salmon need help and the findings in the Småfiskvel project show that focusing on helping the smallest and most vulnerable will make a difference.

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