Original Articles

Monitoring of seabirds in the Benguela upwelling system: can seabirds be used as indicators and predictors of change in the marine environment?

Published in: South African Journal of Marine Science
Volume 12, issue 1, 1992, pages: 959–974
DOI: 10.2989/02577619209504755


Historical and contemporary data on Benguela seabirds assumed to be responsive to changes in food availability are reviewed as potential indicators and predictors of change in the ecosystem. Cyclic variations in the annual yields of seabird products evident at decadal long time-scales may reflect fluctuations in prey populations at similar periods. However, no such relationship has been demonstrated and consequently the value of such annual yields as indicators is not proved. More recently, interannual variation in diets, foraging effort, breeding success and chick growth of two of the three most abundant species of seabird in the ecosystem have been examined in relation to changes in prey abundance. Although the relative abundance of important forage species in the diets of both species of seabird have reflected regional changes in the absolute abundance of these prey, changes in the values of other parameters thought to reflect food availability were not consistently correlated between and within species. This indicates poor potential for their use as indicators of change at least over the range of abundances experienced in this study. Under present management protocol, data from seabirds do not nor are likely to provide abundance indices that may be used directly in stock assessment of commercially important species. To date, insights into distribution and migration of pelagic fish provided by seabird-derived data probably represent the most valuable contribution of birds to fisheries scientists studying the Benguela system.

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