Regime Shifts of small pelagic fishes involving anchovy and sardine have been identified in many places around the world, mainly in the Pacific Ocean (Kuroshio, California and Humboldt Currents) and in the Eastern South Atlantic (Benguela Current). The reasons why sardine stocks flourish while anchovy stocks collapse and vice-versa remain uncertain, but some researchers have tried to relate these fluctuations to environmental variations. Despite the Engraulis anchoita (Argentine anchovy) and the Sardinella brasiliensis (Brazilian sardine) co-occurrence in the Southeastern Brazilian Bight, there are no studies comparing the population size fluctuations and distribution of both species in the area. Thus, the objective of the present project is to investigate the fluctuations in the distribution and abundance of eggs and larvae of E. anchoita and S. brasiliensis during different regimes and to relate them with the environmental conditions and the climatic regimes alternations. Two temporal scales will be considered for a detailed diagnosis of these fluctuations: 1) long-term: from 1974 to 2010, comparing different spawning seasons; and 2) medium-term: comparing different months within the same spawning season. This will be achieved with the analysis of data from 18 oceanographic cruises that occurred during late spring and summer months from 1974 to 2010 in the Southeastern Brazilian Bight. Ichthyoplankton samples were collected by oblique hauls using bongo nets coupled with a flow meter. Temperature and salinity measured in situ were obtained from Nansen bottles and reversing thermometers until 1988 and after this date, from a CTD (conductivity-temperature depth profiler). Additional information, as sea surface temperature (SST), surface chlorophyll-a concentration (SCC), El Niño and La Niña conditions, Pacific Decadal Oscillation (PDO) and other climate indices will be obtained through specialized web pages, reports and papers.
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