|Diel spatial distribution and feeding activity of herring (Clupea harengus) and sprat (Sprattus sprattus) in the Baltic Sea|
Cardinale, M.; Casini, M.; Arrhenius, F.; Håkansson, N. (2003). Diel spatial distribution and feeding activity of herring (Clupea harengus) and sprat (Sprattus sprattus) in the Baltic Sea. Aquat. Living Resour. 16(3): 283-292
In: Aquatic Living Resources = Ressources vivantes aquatiques. Elsevier: Montrouge. ISSN 0990-7440, more
|Authors|| || Top |
- Cardinale, M.
- Casini, M.
- Arrhenius, F.
- Håkansson, N.
We analysed Baltic Sea pelagic fish (herring and sprat) spatial and temporal distribution, size distribution at different depths and time of theday and diel feeding pattern. In 1995 the study area was investigated by acoustic survey for 3 d, 3, 4 and 11 October, to investigate spatial andtemporal distribution of pelagic fish. The areawas divided in four different transects forming a survey quadrate of 15 nautical miles of side. Thesurvey quadrate was ensonified each day four times in the 24 h. In 1997 the acoustic survey was conducted in the same area and in the sameweek of the year to analyse the diel feeding cycle of herring and sprat and their size distribution by depth and time of the day using pelagictrawls. Fish abundance, from 1995 survey, was statistically different among days and survey quadrates. However, from our data it is not clearwhether the variation stems from random dispersion or directed movements occurring at the temporal small-scale. Pelagic fish were dispersedduring the night at the surface and aggregated during the day at the bottom. They aggregated at dawn and dispersed at dusk at the surface. Forherring this distribution pattern coincided with peaks of stomach fullness analysed in the 1997 survey, while sprat seemed to continue feedingduring the whole day time. Larger herring were deeper in thewater column than smaller individuals. Diel vertical migrations (DVM) of pelagicfish likely mirrored zooplankton diel vertical movements and it was reasonably in response to optimal predation conditions in the sea andpossibly intertwined with predation avoidance and bioenergetic optimisation.