Early immune response key to sea lice resistance in Pacific salmon, study finds

Study links Pacific salmon’s rapid immune response to sea lice resistance

Early and localized immune responses in Pacific salmon species may hold the key to improving sea lice resistance in Atlantic salmon, according to new research from the Norwegian food research institute Nofima.

The study, published in Cell and Tissue Research, examined the immune responses of various salmon species to sea lice infestations, intending to improve the resistance of Atlantic salmon. The findings suggest that early-stage immune activity plays a critical role in natural resistance, offering new insights that could inform future strategies for managing one of aquaculture’s most persistent challenges.

“When sea lice attach, certain Pacific salmon species mount a rapid and robust response, causing the lice to fall off,” said Lene Sveen, lead author at Nofima.

The study focused on coho salmon, a species long recognized for its natural resistance to sea lice. Rather than analyzing the entire immune system, the researchers concentrated on the initial site of parasite attachment: the skin. This localized approach revealed key insights into the early immune mechanisms that may underpin the species’ resilience.

“This is precisely where the battle begins,” said Nick Robinson, project leader at Nofima. “If the salmon can respond quickly enough, it can prevent the louse from gaining a foothold.”

The researchers found that coho salmon mount a strong inflammatory response within just two days of sea lice attachment. Immune cells rapidly accumulate at the site, creating an environment that hinders the parasite’s ability to establish and feed.

In contrast, Atlantic salmon exhibited a markedly weaker immune reaction, allowing sea lice to attach and develop with significantly less resistance. This disparity in early immune response may be a key factor in the differing levels of natural resistance observed between the two species.

From apps to traps, these innovations offer hope in the battle against sea lice plaguing aquaculture industry

The study also highlights that coho salmon are not alone in their resilience. Other Pacific species, including chum and pink salmon, demonstrated similarly robust defenses against sea lice.

A notable feature shared by these species is a high density of mucous cells in their skin, which may serve as an additional barrier to parasite attachment. During the experiment, researchers had to anesthetize the fish for sea lice to successfully attach, underscoring the effectiveness of their natural defenses.

“This suggests that their skin surface is inherently unsuitable for the parasite in some of these other species, and that several mechanisms are at play, making it difficult for lice to successfully establish,” Sveen said.

The research was carried out under the CrispResist project, a four-year international collaboration involving experts from both academia and industry. The project’s goal is to uncover the biological basis for the pronounced differences in sea lice resistance between Pacific and Atlantic salmon species.

Read the full study.