YouTube video about sea lice and salmon

The Farmed Salmon Cases decision a couple weeks ago (blogged here), which I was asked to write about for FindLaw (here) has me thinking more about salmon. I wrote briefly about the sea lice problem in my guest commentary for FindLaw:

Another reason consumers might be interested in making an informed choice between farmed and wild salmon is that salmon farming can endanger native salmon species. Salmon is an anadramous fish, which means that it lives its adult life in salt water, then returns to freshwater streams to spawn and die. In the spring, the eggs hatch, and the little fish (called "fry," but not worth frying) start to grow and make their way out to the ocean. The adults never see their offspring.

This is a fine system for salmon. Blood-sucking sea lice often attach themselves to adult salmon, but the tiny parasites are not a big deal on a big fish. Moreover, sea lice can't live in fresh water, so they die off when the salmon go upstream to spawn. By the time the fry make it out to the ocean, they are big enough to withstand occasional sea lice, and the really small fish never encounter large numbers of sea lice.

However, when salmon farms are located near salmon migration routes, the large numbers of adult fish swimming close together mean that sea lice infestations are inevitable. The problem that has made headlines recently is that small fish swimming out to sea encounter large numbers of sea lice on the way out. The fry, which can't withstand large numbers of lice, never make it to adulthood. In some areas, this means that natural populations are declining in the face of salmon farming. Interestingly, the California Supreme Court's decision may indirectly help rectify this situation somewhat if labeling causes more consumers to choose wild salmon over farmed salmon, thus decreasing the viability of salmon farming and the negative effect on migration.

The video below shows sea lice up close.  Towards the very end, the researchers sing a rousing rendition of "Salmon Swims Tonight" (based loosely on In the jungle, the mighty jungle, the lion sleeps tonight).