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3 minute read
Sea lice management has long been a pressing issue in the aquaculture industry, and Northern Norway is currently experiencing one of the most significant outbreaks in recent years. According to a recent press release from Sjømat Norge, Norway's largest seafood trade body, unusually high sea temperatures have fueled one of the largest sea lice outbreaks in recent memory. The press release, titled "Unease about the lice situation in Northern Norway," highlights how these higher temperatures have contributed to the surge in sea lice.
As an organization that also monitors a number of these datapoints, our team at Manolin took a deeper look into these developments to try and understand what’s going on underneath the water.
This analysis looks at the detailed data points behind the outbreak and looks to address the following topics:
- How bad is this outbreak compared with previous years data?
- What has been the response to the outbreak?
- Could this outbreak have been predicted?
Data on Lice Outbreaks
The legal limit for adult female sea lice in Norway is 0.5 lice per fish, and exceeding this limit can lead to regulatory action. Over the last few weeks, a number of farming sites in Norway have reported breaches of this limit.
In Production Areas (PO) 9 through 12 in the last few months, the number of reports of sites exceeding the lice limit has increased sharply:
- PO9: 49 reports, matching the peak from 2021.
- PO10: 35 reports, higher than the previous peak of 28 in 2022.
- PO11: 18 reports, up from a previous peak of 2.
- PO12: 23 reports, surpassing the 2022 peak of 18.
These figures indicate the severity of the current outbreak. In many cases, reported female lice values have exceeded 4 lice per fish, compared to peaks of around 2 in previous years. Additionally, mobile lice (an earlier developmental stage) have reached values as high as 15 lice per fish, compared to typical peaks of 2-3.
Lice Pressure Across Regions
Total lice pressure, which measures the overall lice burden across a region, provides a more comprehensive view of the situation. This metric, used by industry experts to better assess regional lice impacts, shows a worrying trend.
For example, in PO10, estimates show over **30 million adult female lice** in the region, more than double the previous high of 14 million in 2021. This upward trend is consistent across other regions, with PO11 and PO12 experiencing lice pressure roughly three times the normal levels, while PO9 has seen smaller increases.
Efforts to Combat the Outbreak
In response to the outbreak, the industry is taking several actions. One potential solution is early harvesting, particularly of larger, market-size fish. Current data indicates that roughly 30% of the fish in Northern Norway are above 4 kg, a higher percentage than in previous years.
Despite the severity of the outbreak, the number of sea lice treatments—around 40 per week—has not significantly increased compared to previous years. This may be due to a limited availability of well-boats and treatment capacity, as many resources are already contracted to farms in southern regions, where lice issues have historically been more prevalent.
Could This Outbreak Have Been Predicted?
Both Sjømat Norge and the Institute of Marine Research have attributed the outbreak to record-high sea temperatures. While sea lice infections are difficult to predict, the data shows that unusually high sea surface temperatures were recorded as early as June, suggesting that the current outbreak may have been foreseen.
Surface temperatures in the region are now nearing 15°C, roughly 3-4°C above normal. These elevated temperatures have contributed to the explosive growth in sea lice populations. Comparisons to the Icelandic salmon industry, which experienced a similar outbreak following a heatwave in 2023, suggest that further issues could arise if lice numbers continue to climb.
Outlook
The ongoing sea lice situation in Northern Norway is concerning and will require continued attention from the aquaculture industry. As temperatures cool in the coming months, lice numbers will eventually decline, but the current outbreak is a challenge that we are currently in the middle of. Sea lice treatments will continue to be needed over the couple of months as farmers fight to keep the numbers down.
Our team at Manolin and the entire aquaculture industry will continue to monitor the situation closely and adjust strategies as necessary to mitigate the impact of lice on fish health and production.
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