Sea Lice: The Science Behind the Hype

Sea lice infestations are one of the most widely publicized issues regarding farmed fish in British Columbia. These small invertebrates have starred in documentaries, an advertising campaign, and even a popular US television show. But do these small parasites warrant all this attention? Current research reveals that Pacific salmon are less susceptible and more resilient to sea lice than Atlantic salmon. Furthermore, research into the actual effects of sea lice on Pacific Salmon is, as yet, inconclusive.

What Are Sea Lice and Where are They Found?

The term sea lice is a generic name, often with unpleasant connotations, use to describe a range of marine invertebrates that are generally small, and which have, for some reason, become part of popular culture. In southern Africa, sea lice is the common name for mole crabs, from the genus Emerita, which are innocuous burrowing crabs found on sandy, high energy shores and used as fishing bait. In the southern US, sea lice are planktonic organisms related to jellyfish and sea anemones. In this incarnation they pose a serious threat to human health because they sting thousands of swimmers every year. (There is burgeoning industry providing suntan creams that negate the stings of these little jellyfish.)

In BC and other regions around the world where salmon are indigenous, the term sea lice (also called salmon lice) refers to the parasitic copepods often found on wild and farmed salmon. But even within the communities that encounter these copepods, there is an obvious problem of sea lice identification as there is frequently some confusion as to what they really are. Amongst some sport salmon fisherman and even salmon farm workers, harmless Cumacean shrimps (closely related to copepods) have been confidently identified to the authors as sea lice. The sea lice identification problem is exacerbated by conflicting reports in both the media and scientific publications on the impact of these lice on salmon health and even wild salmon returns.