Boobies and Gannets

Guano is a commercially important product obtained by digging the surface of the huge colonies of Peruvian boobies and other seabirds off northern South America, and at colonies of Cape Gannets off South Africa. Guano is a natural, phosphorus-rich compound derived from the excrement of seabirds, and is used as a fertilizer.

For many years, gannets, and to a much lesser degree boobies, were considered to be serious competitors with humans for commercially important marine fish. For this reason, gannets were often killed, and only a few decades ago their numbers were perilously small. This sort of indiscriminate killing is not much of a problem anymore, except in a few remote places.

In some regions, gannets and boobies may be killed for their meat and feathers, and where they are accessible, their eggs may be collected for eating.

Boobies and gannets are also vulnerable to collapses in the populations of the fish that they feed upon. For example, Peruvian boobies and other seabirds have suffered precipitous population declines when their most important prey of anchovies collapsed as a result of oceanographic changes associated with El Niño. El Niño is a warm-water phenomenon that impedes nutrient cycling, greatly reducing the productivity of phytoplankton, and ultimately, causing a collapse of fish stocks.

Since the beginning of the 1990s, there has also been a collapse of many fish stocks in coastal waters off eastern Canada. The reasons for this ecological change are not known for certain, but the leading hypotheses include the effects of overfishing and climate change. The collapse of the fisheries of the northwest Atlantic has led to severe economic hardship for many people who are dependent on that natural resource for their livelihood. However, there have also been severe effects on northern gannets and other seabirds, which depend on those fish stocks as a source of food, particularly when they are raising their young. Consequently, these birds have experienced unsuccessful reproduction, and this may pose a threat to the longer-term health of their populations in that region.