World Aquaculture - June 2024

66 JUNE 2024 • WORLD AQUACULTURE • WWW.WAS.ORG In the salmon aquaculture world, the battle against sea lice is heating up. With the introduction of stringent sea-lice standards, Norway is leading the charge to protect wild Atlantic salmon populations from the tiny parasite. But at what cost? This study dives into the murky waters of salmon farming regulations, analyzing whether adhering to these strict lice limits is truly making a splash in the fight against sea lice infestation among wild salmon, or if it’s simply stirring the pot. Salmon Farming Salmon farming has experienced rapid expansion from its early days, evolving from an emerging sector to a significant global industry. In 1990, worldwide production stood at merely 230,000 tons of Atlantic salmon, while today that number has increased to more than 2.2 million tons. Leading the industry in production are Canada, Chile, the Faroe Islands, Norway and the United Kingdom, with Norway being the largest producer, responsible for just over half of the global supply. Seafood is Norway’s second-largest export, and in 2023 seafood exports totaled more than $160,021,000, with Atlantic salmon accounting for over 70 percent of this figure. The primary method of salmon farming involves open net pens, with around 1000 such sites along the Norwegian coastline contributing to annual production of about 1.3 million tons of salmon. Environmental Concerns Salmon farming in open net pens, while economically important, poses several environmental challenges. Genetic mixing of escaped farmed salmon with wild populations may potentially weaken the genetic diversity and resilience of wild salmon. Waste from open net pens, including uneaten feed, feces, and chemicals used to treat diseases and parasites can accumulate in the surrounding environment. Furthermore, antibiotics can leach into the surrounding environment, potentially affecting non-target marine species. In Norway, a tiny but troublesome parasite known as the sea louse (Lepeophtheirus salmonis) takes center stage as the leading environmental concern in salmon farming. Every year, the industry invests hundreds of millions of kroner into battling this minuscule menace. The Sea-lice Challenge Sea lice are natural parasites that have coexisted with salmon for millennia. However, the expansion of salmon farming may tip the ecological balance, providing a bounty of hosts for these parasites and leading to escalated infestations. In net pens, each farmed salmon typically hosts very few or no lice at all. However, the problem arises because of the millions of farmed fish at each site. The dense gathering of hosts at the farm sites allows for the release of a vast number of lice larvae from mature sea lice into the water column, which then spread throughout the fjord system, carried by currents. As wild salmon smolt navigate from their natal rivers to the open sea, they may pass through a gauntlet The Environmental Effectiveness of Sea Lice Regulation in Salmon Aquaculture Mari Lie Larsen FIGURE 1. Map representation of PA 1 to 13, farm sites (light gray circles) and key wild Atlantic salmon rivers (orange circles). Source: Modified from, assccessed: 21.04.2022 URL: FIGURE 2. Proportion of production sites within the Production areas PA 3, 4, 5 and 7 kept below or above an average of 0.2 sea lice per farmed fish, 2014- 2019. Source: Based on data from Barentswatch, January 2020. URL: