Sea lice are naturally occurring ectoparasitic copepods which can affect both wild and farmed fish populations. They are tiny, translucent fish parasites and do not affect humans. How planktonic stages of sea lice disperse and find new hosts is still not completely known but sea temperature, light, and currents are all major factors.

Sea lice attach to the surface of a fish's skin, usually behind sheltered areas such as the fins and gills. Once attached they will feed off the mucus, skin and blood which can cause the following pathogenic effects in salmon: skin damage, bleeding, a decrease in carcass quality at harvest, reduced growth rates, a loss of their physical and microbial protective function, and increased susceptibility to secondary infections due to the disruption of the epithelium (tissues) at the point of attachment.

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Aside from the direct damage to the fish’s skin, the potential for secondary infections to arise is a major concern for Scottish salmon farmers. Treating salmon for these parasites is paramount to maintaining fish health and welfare.

Keeping fish healthy is of primary concern to Scottish salmon farmers. The sector has invested heavily in recent years to develop a diverse and effective array of management methods, including the use of cleaner fish, that enable it to effectively control the numbers of wild sea lice.  

For more information please read: Sea lice and Scottish salmon farming.