According to most media outlets there is little in the way of good news for the world’s fisheries. We hear of over fishing, nations flouting treaties and in the worst instances, of mismanagement to the point of fishery collapse. So perhaps understandably there is often resistance to the idea of fishing the Southern Ocean for fear these highly productive waters will succumb to overfishing the same way as, for example, the North Atlantic and its cod fisheries. What cod fishery I hear you ask? Exactly my point.
One particularly contentious topic has been the sustainability of harvesting krill from the Southern Ocean. It makes a sensational headline that harvesting krill will decimate the base of the food chain, and subsequently cause the collapse of not only the broader piscine population but populations of the most iconic of Antarctic species: the seal, the albatross, the penguin and the whale. (Gasp, one more step and you’ll be pro-whaling!!!) But perhaps we are better off listening to the advice of an organisation, such as the Commission for the Conservation of Antarctic Marine Living Resources (or CAMLAR to its friends), that actually monitors and manages those who seek to feed the human population by exploiting that of the fish. Read on and I promise to tone down the hyperbole.
What has this to do with earth science? Everything. The Southern Ocean is one of the most biologically productive regions on our planet due to ocean circulation. As the deep ocean circulates around the ocean basins organic matter constantly rains down from the surface waters above. As it breaks down, it replenishes the deep water with nutrients. Large scale upwelling of this nutrient rich water occurs around the Antarctic continent fuelling phytoplankton growth (microscopic marine plants) that in turn supports the krill. Life abounds in the Southern Ocean and higher trophic levels do indeed depend on these crustacea for survival, but these fisheries are NOT presently in danger of collapse, nor are they likely to be so. Antarctica is an expensive destination, and krill too prone to decomposition to entice rogue fishing vessels to hunt down such a low value commodity.
As it stands CAMLAR currently sets legally binding catch limits to 620,000 tonnes per year. Seems like a lot, but considering this is estimated to be around 1% of the total biomass it’s not exactly a tipping point for the species. And these limits are not presently being met so there is no point in expanding the fishery further. CAMLAR also sets limits according to region, ensuring a smaller catch limit from coastal areas, as although krill may be more abundant this is where they support penguin and seal colonies. Larger quotas are allowed in the open ocean, but this is not as economically sustainable due to lower abundance.
CAMLAR’s scientific committee advocates conservation and the sustainable management of our most southern fisheries. While I support environmental activism in its many guises, I feel in this instance it is entirely misplaced.