Documentary based evidence for sardine run events, east coast of South Africa: 1946-2012

Abstract

The southern African sardine run is an annually recurring phenomenon involving vast schools of sardines travelling northwards along the east coast of South Africa. Climate change is assumed responsible for recently observed changes in the occurrence of sardine runs, yet data have been absent to quantify any phenological changes over time. The National Library of South Africa has extensive archives of Kwa-Zulu Natal based newspapers which were scrutinized to determine the annual arrival of sardines at specific places along the east coast between 1946 and 2012. In particular, ‘The Natal Mercury’, ‘South Coast Herald’ and ‘South Coast Sun’ newspapers were consulted. This yielded an uninterrupted sardine run record spanning 66 consecutive years. This is the first such study examining historical fish phenology in the southern Hemisphere. A variety of environmental conditions is thought to influence the sardine runs and may include, oceanic temperatures, oceanic currents, visibility of the water, wind speed/direction and air temperature. We thus also demonstrate historical climate variability and change along the east coast for the period between 1936 and 2012, based on data obtained from the National Oceanic and Atmospheric Administration (NOAA) and the South African Weather Service. In particular, we examine the parameters: temperature, wind, the occurrence of westerly wave disturbances (i.e. cold fronts), the El Nino Southern Oscillation, and the Southern Oscillation Index. The sardine run data are then compared against the various climate parameters to ascertain which variables most influence their phenology. It is found that the sardine runs have become more temporally delayed during recent years, particularly since the late 1960s/early 1970s, and may be associated with considerable increases in Sea Surface Temperatures (SST) since that time.