SGER: Impact of Severe ENSO Events on Insular Endemic Shorefish Populations

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Recent meteorological predictions indicate that a severe El Nino/Southern Oscillation will develop during that latter part of 1997 and extend through 1998. This ENSO event is predicted to be comparable or more intense than the 1982/83 event the strongest ENSO recorded in this century. This SGER study will gather baseline data for investigating the effects of this ENSO on recruitment and population dynamics of reef fish populations in the Galapagos Islands. Of particular interest is the effects of hybridization and introgression observed between invading mainland species and island endemics that resulted from the 1982/83 ENSO. Recent work has found evidence to indicate that extensive recruitment of the mainland damselfish species, Stegastes acapulcoensis in Galapagos occurred during 1982 83. Currently extant populations of S. acapulcoensis coexist in Galapagos alongside the island endemic, Stegastes arcilrons. Otolith analyses of adult fish indicate that the first cohort of these adults arrived in 1983. The population has subsequently grown, presumably from local recruitment. In addition, a significant proportion of hybrids have been detected by electrophoretic protein analyses. Dr. Wellington predicts that another invasion will occur in early to mid 1998. He add associates will document the distribution and intensity of recruitment of S. acapulcoensis in the Galapagos Archipelago. These data will provide invaluable information needed to predict potential effects of climate change on insular marine organisms.