Extensive diel fish migrations in a deep ultraoligotrophic lake of Patagonia Argentina

RECHENCQ MAGALÍ; SOSNOVSKY ALEJANDRO; MACCHI PATRICIO JORGE; ALVEAR PABLO ANDRES

HYDROBIOLOGIA

SPRINGER

Lugar: Berlin; Año: 2011 vol. 658 p. 147 - 161

0018-8158

Andean Patagonian lakes are ultraoligotrophic,highly transparent water bodies with very lowdensities of organisms at the different levels of theirtrophic food webs. Little is known about spatialdistribution and habitat use by fish in these lakes.Hydroacoustic and active sampling techniques wereused to study the distribution, composition, anddisplacement of organisms in an Andean lake throughoutthe diel cycle on two different moon phase days.Sound scattering layers (SSLs) were found both in thenear-shore and pelagic habitats at different times of theday. These SSLs, formed by galaxiid larvae and adults,underwent displacement during the time periods ofdawn and dusk, giving rise to the redistribution oforganisms in the different habitats. The organismsshow high sensitivity to light intensity, displayingdifferent behaviors depending on moon phases.Extensive diel vertical migrations show that the deeppelagic habitats provide diurnal refuge for nativegalaxiids in Andean Patagonian lakes. Due to the highdensities of galaxiid larvae and adults, it is likely thatdiel migrations generate an active flow of energy andmatter between habitats, which could have a profoundinfluence on whole lake dynamics.