On several occasions, I have discussed the concept of ‘fishing down’ through marine food webs: starting with the top predator species, like tuna, and moving to smaller and smaller creatures as the big ones are depleted. In the waters around Antarctica, this process has come very close to reaching its logical extreme. Fishing for krill has become a big business.
Krill are shrimp-like marine invertebrates that make up a significant portion of the world’s zooplankton: the tiny creatures that eat phytoplankton algae. They, in turn, are eaten by all manner of other creatures, ranging up to large whales. Fishing them extensively risks knocking a whole tier out of the food web, with unknown but potentially severe consequences for all other forms of life in the ecosystem.
The krill that are caught are processed for fatty acids, used to make medicine, and fed to farmed fish. In particular, they are useful for giving farmed salmon more of a red colour, in contrast to the sickly looking pale pink much of farm salmon takes on. The current annual catch is estimated to be between 150 – 200,000 tonnes: much of that taken from the waters around Antarctica. Through the use of new technology, a planned new ship (the FV Saga Sea) will apparently be capable of collecting 120,000 tonnes annually. That is nearly one 1000th of the low estimate for the total global biomass of krill, and more such ships are planned.
While it may be that fishing for krill at this scale doesn’t pose a danger to marine ecosystems, it is worth noting that we have no scientific basis for being confident of that. An experiment is simply being performed in unregulated waters, which will have unknown future consequences. As with so many other instances of humanity’s engagement with the natural world, one cannot shake the sense that we are being awfully reckless.