Effects of global climate change on the recruitment of Anchovy in the Southern Benguela upwelling system
Master Thesis
2001
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University of Cape Town
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Abstract
Changes to global climate patterns, as predicted by many climatologists, will impact on ecosystems in numerous ways. The nutrient-rich waters of marine upwelling environments enable prolific plankton growth, which in turn supports vast shoals of pelagic fish. The nutrient supply is dependent on the strength and direction of winds, which govern the upwelling process as well as turbulence. A change in climate may thus affect the food supply and feeding conditions required by pelagic fish populations. This thesis investigates predicted changes in wind patterns in the southern Benguela system and assesses how these changes may impact on the recruitment of the Cape anchovy, Engraulis capensis. A general circulation model (NCAR Climate System Model) is used to compare a future simulation under double C02 conditions with a simulation of the present day wind regime. Climate change effects on anchovy in the other main upwelling systems, off the coasts of California, Peru and Morocco are also examined. Wind speeds and turbulence off the Agulhas Bank in the southern Benguela system are expected to remain suitable and potentially become even more conducive to spawning in the future. The results show similar mean wind speeds to present day values, a decrease in mean turbulence, a decrease in the frequency of extreme wind speeds and a decrease in the frequency of extreme turbulence during the anchovy spawning season (i.e. September-February). An increase in Lasker events is expected at the Eastern Bank Grid Cell, which suggests that this area may become the preferred spawning habitat in the future. The Cape Town Grid Cell also shows suitable conditions in the future simulation for anchovy spawning and may thus become an alternative spawning location. The West Coast shows an increase in alongshore wind stress and thus an increase in upwelling in the future simulation from November - February. This is likely to increase planktonic food availability and ultimately anchovy recruitment. Future simulations from the Climate System Model show that the upwelling systems off the coasts of California, Peru and Morocco are likely to continue supporting anchovy spawning and may become even more suitable in terms of wind and turbulence regimes.
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Includes bibliographical references.
Reference:
Young, S. 2001. Effects of global climate change on the recruitment of Anchovy in the Southern Benguela upwelling system. University of Cape Town.