SKJERJEHAMN, Norway — As a teenager, Ola Braanaas kept a few fish in an aquarium in his bedroom. Now, at 55, he keeps a lot more of them: about 1.2 million in a single windswept spot off the stunning coast of Norway, a giant farm with six large, circular structures each containing about 200,000 fish.
Once a rarity on global dinner tables, salmon is a staple today, thanks to a fish farming industry that has expanded at breakneck speed in recent decades. In Norway, about 1.18 million metric tons of salmon were produced in 2016.
But now, Norwegian fish farmers face new curbs designed to protect the country's stocks of wild salmon, rules that have angered both the industry and its opponents, prompting threats of court challenges from both sides.
Wild Norwegian salmon are members of an ancient species that heads downriver early in its life cycle, swimming through Norway's famous fjords, and out to saltwater feeding grounds, before returning to their native rivers to spawn.
In recent years, however, the wild salmon population has more than halved, partly because of the spread of sea lice, parasites that feast on the mucus and skin of the fish before moving on to the muscle and fat, making the fish vulnerable to infections and sometimes killing them.
Sea lice, like the salmon, have existed in the ocean for eons but have emerged as a huge problem for the fish farms. They multiply there in such numbers that they kill farmed fish and endanger young wild salmon as they pass the pens on their way to the open sea.
The lice problem is so bad that the worldwide supply of salmon on sale, the overwhelming majority of which is farmed, fell significantly last year, with Norway, the largest producer, hit especially hard.
To contain the problem, a system took effect Oct. 15 in Norway, in which production by farms in regions where wild salmon are judged to be severely threatened will be frozen and potentially, in future years, cut. If the lice are brought under control, then output can be increased.
Braanaas, the owner of Firda Seafood, says that there are already rules to control the lice, and that he will go to court if he is ordered to reduce production because of problems from other farms in his region. It is, he says, a "Stasi system," a reference to the secret police of the former East Germany.
Norway's biggest producer, Marine Harvest, is also unhappy with the new protocol, which it describes as premature, and wants more work done on the methodology used to decide when there is a lice problem that needs to be addressed.
Yet, environmentalists seem unimpressed as well. One group, SalmonCamera, plans to challenge the system in court, arguing that it is too lenient. Kurt Oddekalv, leader of the Green Warriors of Norway, says the system is a sign of "panic from the Fisheries Ministry."
Sea lice kill an estimated 50,000 adult wild fish a year in Norway's rivers, and the wild salmon population has fallen to 478,000 from more than 1 million in the 1980s, according to one study. So depleted are stocks of wild salmon that about 100 of Norway's 450 salmon rivers are closed to anglers.
But there are other problems, too, beyond sea lice. Rune Jensen, the head of SalmonCamera, says that wild fish, like cod, congregate around salmon farms, attracted by the food there. These predators eat the young wild salmon in greater numbers than normal as the migrating salmon make their way out to sea. Sometimes the predators even force the young fish into farm cages.
But activists say the biggest threat is the genetic effect of farmed fish that escape from their pens, reproduce with wild salmon and produce offspring ill-equipped to survive.
During the past decade, fish farmers have reported that more than 200,000 salmon escape on average each year, though the real figures may be as high as four times that in the years 2005-11, according to one study.
The effect has been observed by Norway's anglers. Few people know the fishing grounds of the Dale River as well as Inge Sandven, the head of the Dale Hunters' and Anglers' Club. In just 15 minutes at one river pool, set against a spectacular backdrop of tree-covered hills, he had three bites but no catches.
Then, the rod strained, and he slowly reeled in a small, shiny, olive brown salmon weighing a couple of pounds. Just by looking at it, as it thrashed in a net, Sandven could tell a lot about the fish: It was male and had probably spent three years in this river and one winter at sea.
But what he could not say: whether it was a pure wild salmon.
"It's impossible to tell. It looks good, but I don't know," Sandven said, when asked whether it might have genes from farmed salmon. "It's a 50/50 chance — that's the experience of this year," he added, before releasing his catch.
Sandven knows this because he supervises a wild salmon hatchery, and takes DNA samples from fish caught in this river before they are used for breeding. Recently, about half have failed the wild salmon purity test.
Previously, pollution was a huge problem in aquaculture, he said, but now "the only threats that are not under control are the genetic impact from escaped fish and sea lice."
The fish farmers argue that they play a vital role in feeding the planet, and that they produce a crop worth $8 billion annually to Norway, accounting for about 8 percent of the country's exports.
The Norwegian government already has rules requiring farms to test the quantity of sea lice in pens and to take action if they exceed the limits.
Marine Harvest uses cleaner fish that feed on sea lice to help combat the problem. It is also investing in new techniques designed to eliminate the risk of escapes by farmed salmon and to cut lice numbers.
These include novel ideas such as the "egg" — a solid oval-shaped pen, yet to be constructed, which is enclosed, preventing any risk that salmon can escape and making it harder for sea lice to enter and spread.
Information on the health of Norway's farmed fish is publicly available online. But so divisive is the debate that environmental groups do not trust statistics provided by the farmers, and the two sides do not agree on the facts.