© 2004 by ICES/CIEM International Council for the Exploration of the Sea/Conseil International pour l'Exploration de la Mer
Diel vertical distribution of fish larvae during the winter-mixing period in the Northwestern Mediterranean
Institut de Ciències del Mar (CMIMA-CSIC) Passeig Marítim de la Barceloneta 37-49, 08003 Barcelona, Spain
*Correspondence to A. Sabatés: tel: +34 932309500; fax: +34 932309555. e-mail: anas{at}icm.csic.es.
The vertical distributions of the larvae of shelf and oceanic fish species that spawn during the winter-mixing period in the Mediterranean are described from 22 vertically stratified plankton tows. Diel differences in the vertical distribution patterns in relation to physical data and potential prey abundance throughout the water column were examined. Even in absence of stratification, the larvae of the various fish species showed different patterns of vertical distribution and diel changes. The larvae of shelf-dwelling species were found in the surface layers, mainly above 50-m depth, and with some exceptions, with very little diel variation in depth distribution. Therefore, the vertical distribution of the larvae of these species coincided with the maximum concentrations of their potential food, nauplii and copepodite stages of copepods. The larvae of mesopelagic fishes showed deeper distributions in the water column and most of these species were located closer to the surface during the day than at night. Given the homogeneity of the physical characteristics throughout the water column, except for light, this behaviour may be determined not only by the higher concentration of prey in the surface layers but also by adequate light levels for feeding.
Keywords: fish larvae, Northwestern Mediterranean, vertical distribution
Received 17 February 2004; accepted 18 July 2004.