AVALIAÇÃO HIDROACÚSTICA DOS EFEITOS CAUSADOS POR BANCOS SUBMARINOS E ILHAS SOBRE A DISTRIBUIÇÃO E DENSIDADE ACÚSTICA DE ORGANISMOS PELÁGICOS, NA ZONAECONÔMICA EXCLUSIVA DAS REGIÕES CENTRAL E NORDESTE DO BRASIL.
Seamounts are the main topographical features of the oceanic bottom. With a considerable range of heights and top depths, and a variety of substrata and different habitats, constitute important ecosystems. Along the ExclusiveEconomic Zone (ZEE) of the Central and Northeast coasts of Brazil several oceanic banks and islands exist and are the geographical area of the present study where two acoustic assessment cruises were carried out. The aims of thisstudy are the classification of the echo records, to evaluate possible alterations in the thermohaline structure due the presence of banks and islands, and the analysis of the relationship between the presence of these features and thedistribution and abundance of pelagic organisms. Hydroacoustic, environmental and biological data derived from such cruises were used. The echo records were classified in the Oceanic Layer, Myctophidae, Oceanic Layer withMyctophidae and Cloud of Break echo types. Evidences were not found of the effects of the presence of banks and islands in the local thermohaline structure, with the available data. A clear pattern was not observed in the distribution of the recorded acoustic density around the features, indicating local differences associated to the same ones. Strong and important vertical migration events were frequently observed and recorded. Acoustic densities observed from thesurface down to 500 m, maximum assessed depth, were higher during the night compared to daylight hours. Such events are, probably, ecologically very important in the studied area.
Advisor:José Guilherme Bersano Filho; José Henrique Muelbert; Lauro Antonio Saint Pastous Madureira; Paulo de Oliveira Mafalda Júnior
School:Fundação Universidade Federal do Rio Grande
Source Type:Master's Thesis
Keywords:ecotipos hidroacústica Bank effect echo types exclusive economical area of central and northeast coast Brazil hydroacoustic REVIZEE
Date of Publication:02/24/2006