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Sea lice levels across Norwegian salmon farms are mirroring last year’s record-breaking season, and in some ways, they’re already worse.
Manolin’s models show that 2025 mobile lice pressure is tracking at unprecedented levels, while female lice counts remain persistently high, almost identical to what farms faced at this point in 2024. Warmer waters have returned too, accelerating the lice lifecycle and tightening the window for effective intervention. In short, the conditions are primed for another difficult season. The question is: why does this keep happening?
A Missed Variable
Earlier this year, Manolin’s Observer report predicted sea lice trends based on historic farm data, environmental variables, and treatment behavior. Those forecasts weren’t far off, but they didn’t include global salmon prices as a variable in the model. Had they, the predictions would likely have aligned even closer to today’s reality.
The price of salmon has become a quiet driver of treatment strategy. With tighter margins, farms are under pressure to lower costs and treatments, especially large-scale ones, are an easy target. But the ripple effects of these decisions are becoming harder to ignore.
Treatments are Up. So is Fragmentation.
Data from both Manolin’s models and public sources shows that the number of cages being treated is increasing, yet the treatments themselves are shorter, smaller, and more frequent. Large-scale, synchronized delousings are giving way to fragmented efforts. Entire site treatments remain flat, while partial site treatments have surged.
The result is more treatments overall, but they’re fragmented: shorter, smaller, and often delayed. That pattern is allowing lice levels to climb across regions, even as farms continue to intervene.
Delayed Action, Rising Risk
One of the biggest shifts in recent weeks is the timing and duration of intervention. Farms appear to be waiting longer or switching to partial treatments to treat sea lice compared to previous years. Average lice levels (both mobile and female) are higher leading up to treatment than they’ve historically been during the same calendar period.
This trend points to a shift in strategy. Whether it’s to reduce stress on fish, limit chemical use, or cut costs, the intent behind delayed action may seem logical. But zoom out across a region, and the cost becomes clear. Mobile lice transfer easily between farms. Delays by one operator increase the reinfestation risk for everyone.
A Game Theory Trap
This is where game theory offers a useful lens.
The scenario resembles a classic Prisoner’s Dilemma. Each farm makes an individual choice: treat early and absorb the cost, or wait and hope for better timing. Acting early can reduce regional lice loads, but only if others do the same. If neighbors delay, early treatment loses its impact.
From the farm’s point of view, waiting often looks rational. From the industry’s point of view, it’s a trap. As more farms delay, regional lice levels climb, tools lose effectiveness, and even the farms that follow best practices suffer reinfestation.
What starts as a reasonable individual decision becomes a collective failure.
Economic Pressures Are Driving the Pattern
It’s not just strategy, it’s survival.
EBIT/kg figures across the industry show many farms hovering around break-even. Feed, labor, and treatment costs remain high. Prices, meanwhile, have softened. In this context, the instinct to delay or reduce treatments isn’t greed, it’s necessity.
But this cost-cutting has consequences. The higher the lice counts before action, the less effective treatments become. And with more fragmented efforts, reinfestations become harder to control. The net result: more treatments over time, not fewer.
So What’s the Fix?
There’s no silver bullet. But game theory doesn’t just diagnose the problem, it also offers a few paths forward.
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Coordination: Farms treating in sync, sharing data, and following common thresholds can reduce regional pressure. It’s difficult, especially across company lines, but historically effective when done right.
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Reputation: In repeated interactions, bad actors become known. That social pressure can nudge farms toward cooperation, especially when tied to partnerships or regional agreements.
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Rules and Enforcement: Regulations—like Norway’s traffic light system—can enforce shared action when voluntary cooperation breaks down. They’re imperfect, but they help level the playing field.
These aren’t theoretical solutions. They’ve been tested. In Manolin’s recent work with Cargill and Hofseth, farms used tailored models to guide their lice strategies. By acting based on predictive thresholds, they improved treatment timing and reduced reinfestations. It worked, not because the tools were new, but because the incentives were aligned.
The Bigger Picture
Sea lice management was never just about individual farms. It’s a regional problem with regional consequences. And when economics, environment, and behavior collide, the data tells a story: fragmentation drives pressure.
That story can change. The tools exist. The models work. The question now is whether farms can afford—not just financially, but operationally and politically, to act like part of a shared system.
Because the costs of inaction, as the numbers suggest, are already showing up on the scoreboard.