Sea Lice – How fresh is fresh?

Sea Lice?

Salmon and steelhead fishers commonly look for sea lice on fish they catch and use the presence of these parasitic copepods as an indicator of  fish fresh-from-the-ocean.  Well, it turns out that sea lice can hang onto our fish as they migrate upstream for days or perhaps even a couple of weeks.

I’m no expert on these critters, but I am writing a short article for the Oregon Fly Fishing Blog describing what I have observed regarding the transition one may see in the appearance of sea lice as they begin to die after our fish enter freshwater.

You may view the article (after it is completed and posted) at

This photo shows a really fresh-from-the-ocean copepod nestled at the base of the anal fin of a Sixes River Chinook.  This fish probably entered the estuary less than 24 hours before this photo was taken.

I’d love to hear what you know about how long sea lice can survive in freshwater and where you have caught sea-lice-bearing salmon and steelhead in Oregon.


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