Diel variation in catches of Euphausia superba Dana 1854 early larvae: Vertical migration or avoidance reaction?

• Main Authors: Marschoff, Enrique R., Calcagno, Javier Angel
• Language: unknown
• Published: 1998
• Subjects: Distribution; Euphausia superba; Net avoidance; Vertical migration; avoidance reaction; larva; temporal variation; trawling; zooplankton; article; ecology; environment; nonhuman; shrimp; statistical analysis; Southern Ocean; Euphausiacea; Argentina; Weddell
• Online Access: https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00220981_v228_n1_p107_Marschoff; https://hdl.handle.net/20.500.12110/paper_00220981_v228_n1_p107_Marschoff

Samples were obtained with two pairs of black and white nets towed simultaneously at varying light conditions in the Weddell-Scotia confluence region. The statistical analysis (ANOVA, Regression and Kruskal-Wallis test) of the log transformed counts of Euphausia superba calyptopes larvae (CI, CII and CIII) shows that the significant difference between the white and black nets found in daytime are not present in darkness. A negative regression coefficient was detected between the difference in catches and sun's height, pointing to a light dependent avoidance reaction. These results demonstrate that the day/night differences in observed densities of krill larvae are due to net avoidance rather than to vertical migration, a result confirmed by hydroacoustical observations; and that the habitat of these stages is restricted at all times to the upper layers of the ocean. Fil:Marschoff, E.R. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Calcagno, J.A. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.