Patagonian Ecosystem Threatened By Anchovy Fishing
Ms. Skewgar and her associates published a paper in Science about the threat to Patagonia wildlife posed by the opening of an anchovy fishery. Ms. Skewgar answers our questions.
How could opening the Patagonian coast to anchovy fishing affect the ecosystem?
Iím going to give you a two part answer, and first mention the importance of the anchovy in that ecosystem. Itís a forage fish, eaten by larger predators, and it dominates the level of the food web between those predators and the plankton. It plays a key role in transferring energy from the plankton level up to larger predators, which include other commercially important fish as well as several species of wildlife the Patagonian coast is famous for. We are concerned that if fishing for anchovy is expanded too much on the Patagonian coast, that the energy flow could be disrupted, and that the changes could be harmful to biodiversity.
In 2003, Argentinaís Federal Fisheries Council approved a plan by the Province of Chubut for an experimental small-scale trawler. How do trawlers affect fish species?
The type of gear used to catch anchovy are mainly pelagic trawls or purse seines. These are large nets that are dragged through the ocean or circled around schools of fish. The nets are brought to the surface, and the fish are removed. As with many types of fishing gear, there can be unintentional impacts from their use. In this case, other animals like penguins can be captured in the nets along with the fish, if they were hunting the same school that was targeted by the fishers. This often leads to injury or death for the penguin, which is known as incidental catch, or bycatch.
Can this opening of the Patagonian coast to fishing be stopped? What needs to happen next?
Our first message is one of precaution. We donít yet know enough about the food web interactions to predict quantitatively the effect of different magnitudes of expanded fishing. But because of the importance of the anchovy in that ecosystem, overfishing could have really damaging effects to biodiversity, other commercially important fisheries, and even ecotourism. Fishing anchovy is very likely to affect the recovery of Argentine hake, for example. In the absence of adequate knowledge of these consequences and with the risk of severe harm, itís especially important to apply a precautionary approach. We suggest that fishing not expand beyond current levels. More information about speciesí interactions is needed to inform future management decisions, and a precautionary approach will prevent overfishing while that information is gathered.
For our lay audience if you could explain the precautionary principle?
The precautionary principle is, in simple language, to leave a margin for error where you donít understand a system adequately. In order to make good management decisions, we need to evaluate our confidence in the quantitative predictions we can make about the system. When we lack knowledge, we need to acknowledge the uncertainty around the quantitative predictions. Itís important to err on the side of caution to avoid causing serious harm. Precautionary measures are not meant to be a permanent ban or freeze on fishing. As knowledge increases about the system, we then have more confidence in the predictions and we are able to reduce the precautionary measures that are necessary.
Skewgar, E. et al. Anchovy Fishery Threat to Patagonian Ecosystem. Science. 5 January 2007: Vol. 315. no. 5808, p. 45. DOI: 10.1126/science.1135767.
Ms. Skewgar is currently a graduate student at the University of Washington, Seattle.
Interview by: Thanh-Tam Candice Vu