Aspectos bioecológicos del ictioplancton en la estación fija "La Libertad" durante 1997
Luzuriaga de Cruz, M.
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El presente trabajo se refiere a las variaciones observadas en el ictioplancton presente en la estación fija "La Libertad" desde febrero de 1997 hasta diciembre del mismo año. Los datos se relacionan con las observaciones ecológicas hechas en base a indicadores de masas de agua, formaníferos planctónicos, presentes en las mismas muestras.The present paper deals with the bioecology study of the ichthyoplankton at the fixed sampling site "La Libertad" located 10 miles offshore of Salinas-Peninsula de Santa Elena, Ecuador. Plankton samples analysed were collected every 20 days, from february to december 1997, onboard of boats belonging to the National Army. During 1997 the following dominant families of fish larvae were found: Scaenidae (18%), Engraulidae (9%), Bregmacerotidae (6%) and others beloging to the suborden Pleuroronectoidei (8%). The Clupeidae family decreased from 17% (until 19969) to 2% during the "El Niño" event 1997. The highest concentration of fish larvae was found during june, july and august, between 490 and 700 org.m², fish eggs were found in february, 23000 org.m² and june, august and octuber. The following species larvae of commercial value were found in the present study: Cetengraulis mysticetus (chuhueco), Scomberjaponicus (macarela) and Sardinops sagax (sardina del sur). In relation to the past years, important changes in the composition of species of ichthyoplankton and zooplankton were found specially into planktonic foraminifera. The dominant species in the planktonic foraminifera group were: Globigerinoides sacculifer, G. ruber, Globoquadrina dutertrei, Globigerinella aequilateralis which are related to warm, oceanic and poor nutrient waters, properties observed in surface water from february to december 1997 with light mix of cool water as is indicated by the increase of Globigeina bulloides during july, august, september and november 1997. In general, according to biological markers, the "El Niño" 1997 event conditions has shown rising effects in the zooplanktonic fauna up to december, effects associated to morphologic changes in the population of foraminifera and the presence of larvae of tropical and oceanic fishes.