Overfishing puts seabird population at risk
An international team of researchers has discovered that a wide range of coastal bird species is negatively affected when the supply of fish shrinks to below 33% of maximum capacity. Presented in the journal Science, the study's findings shed light on the association between predators and prey the world over.
Led by Philiippe Cury of the Institut de recherche pour le développement (IRD) in France, researchers in Canada, France, Namibia, Norway, South Africa, Sweden, the United Kingdom and the United States assessed data based on almost 450 cumulative years of observation. They compared the growth in the supplies of fish with the reproductive patterns of 14 species of coastal birds. Puffins, penguins, seagulls and gannets, to name just a few, feed mostly on sardines, anchovies, herring and prawns. All of these marine creatures, meanwhile, are feeling the crunch of overfishing.
The result? The loss of the fish biomass increases the threat against the survival of the birds and, in turn, of the ecosystem. When the numbers of fish fall, the birds stop reproducing. The opposite is not true, however. Even if the supply stays above the level, birds will not intensify their reproduction rate. The researchers suggest that other factors impact the reproduction rate, including how fast nesting areas fill up.
The researchers say all this information provides a reference level for the sustainable management of fisheries, which would help protect the bird population and ensure the well-being of the marine environments.
The study has successfully validated how ecosystems conform with similar laws. Experts in the past had an idea that this was happening, but this study helps substantiate a model of predator and prey behaviour.
The team investigated the bird species in seven ecosystems worldwide. Each of the ecosystem was assessed for periods ranging from 15 to 40 years. According to the researchers, it takes around 13 years of data to gain an accurate idea of what the maximum fish supply is in a given ecosystem.
It is the first study to assess such a wealth of data on the association between predators and prey. Key to the success of this study was the collaboration between experts from both the northern and southern regions of the planet.
According to the researchers, overfishing puts at risk the survival of higher-level predators including birds. Adding to this pressure is human activity, and in particular fishing. Around 80 million tonnes of fish are consumed by people and birds each year. Small bait like sardines, anchovies, herring, smelt and capelin used to make meal and oils in fish farming represent almost a third of today's catch worldwide. They add that the results of their study make it possible to establish a standard against which to measure the sustainable management of fish as global demand swells. This would lead to the sustainability of seabird populations over time.
Researchers in Europe have noted that an optimal way to determine if marine ecosystems are healthy is to assess the populations of seabirds.
Data Source Provider: Science; Institut de recherche pour le développement (IRD)
Document Reference: Cury, P. M. et al., 'Global seabird response to forage fish depletion - one-third for the birds', Science, Vol. 334 no. 6063, pp. 1703-1706, 2011.doi:10.1126/science.1212928
Subject Index: Biotechnology; Coordination, Cooperation; Environmental Protection; Scientific Research