Ocean upwellings are an important, resource-rich event in the lives of many marine animals. They occur as cool and warm waters mix and nutrients are driven to the ocean’s surface, causing plankton to bloom, and this sudden abundance attracts an entire food-web. One such upwelling, the Canary Current Large Marine Ecosystem (CCLME), occurs off the West coast of Africa. It is a hot-spot for marine life, and many predators, like seabirds, will travel enormous distances to feed there.
A recent study has shed light on just how important the CCLME is as a seabird foraging ground. Over a period of 11 years, between 2000 and 2011, 123 birds from eight different species were tracked to investigate their foraging behaviour. The species in this long term study included the Northern gannet (Morus bassanus) from the UK and the South polar skua (Stercorarius maccormicki) from the Antarctic. All eight of the species were found to have visited the CCLME, including 70% of all individual birds that were tracked.
The convergence of winged visitors from across Europe, Africa and Antarctica emphasises the importance of these upwellings to marine birds. Not only has the study highlighted the area as a biodiversity hotspot for migratory seabirds, it has demonstrated the interconnectivity of these species that traverse the Atlantic to take advantage of this feeding ground.
These upwellings form hotspots that take up less than 1% of the ocean surface, but provide around 20% of global fisheries catch. The CCLME is a vital food and economic source for much of West Africa, including some of some of the world’s poorest countries. In efforts to support the demand for food, the CCLME area is fished extensively. This fishing effort is not only from the nearby African nations – the resource-rich area is also targeted by China’s distant water fleet.
We are beginning to understand how heavily seabirds rely on this area, but it is still unclear to what extent humans also do. Illegal fishing is under-reported, as is the catch of the Chinese distant water fleet. “It is unlikely that both a large diversity of marine vertebrates and intense fisheries exploitation can be sustained in this region,” suggest the study authors.
The conflict between humans and marine predators is particularly intense in the CCLME. Under such great human pressure, conservation management is crucial if this region is to be targeted without detriment to migratory seabird populations. Many seabirds travel extensively and pay no heed to international borders, making their conservation notoriously difficult. The confirmation of its importance for so many species, though, suggests that the CCLME upwelling region should be a conservation priority. Such an undertaking, aiming for sustainability, will require co-operation across multiple nations, and will likely run counter to the aims of the commercial fisheries that operate in this area. For the many species that make the most of this ocean bounty, including humans, only time will tell.
Grecian, W.J., Witt, M.J., Attrill, M.J., Bearhop, S., Becker, P.H., Egevang, C., Furness, R.W., Godley, B.J., González-Solís, J., Grémillet, D. and Kopp, M., 2016. Seabird diversity hotspot linked to ocean productivity in the Canary Current Large Marine Ecosystem. Biology Letters, 12(8), p.20160024.