Diel vertical and horizontal distribution of crustacean zooplankton and young of the year fish in a sub-alpine lake: an approach based on high frequency sampling

• Published in: Journal of Plankton Research
• Main Authors: Masson, Stéphane, Angeli, Nadine, Guillard, Jean, Pinel-Alloul, Bernadette
• Format: Text
• Language: English
• Published: Oxford University Press 2001
• Subjects: ORIGINAL ARTICLES; Alpine Lake; Longhurst; Salvelinus alpinus
• Online Access: http://plankt.oxfordjournals.org/cgi/content/short/23/10/1041; https://doi.org/10.1093/plankt/23.10.1041

Understanding the spatial dynamics of predators and their prey is one of the most important goals in aquatic ecology. We studied spatial and temporal onshore–offshore distribution patterns in young of the year (YOY) Eurasian perch (Perca fluviatilis) and crustacean zooplankton (Daphnia hyalina, Cyclops prealpinus) along a transect in Lake Annecy (France). Our study represents a first attempt at coupling hydroacoustic fish survey and high frequency zooplankton recording to assess simultaneously the large-scale distribution patterns of YOY fish and their zooplankton prey over a diel cycle (day, dusk and night sampling). We hypothesized that the spatial distribution of zooplankton could be shaped by both anti-predator behaviour (horizontal and vertical migrations) and predation losses. Fish biomass, size structure and diet were assessed from split-beam echosounding and net trawling samples, whereas crustacean abundances were estimated with a small modified Longhurst–Hardy continuous plankton recorder. We evaluated the diel changes in the spatial distribution patterns of fish and zooplankton and determined the overlap between their distributions. Fish biomass was dominated by YOY perch in upper warmer layers and salmonids (Coregonus lavaretus and Salvelinus alpinus) in the colder and oxygenated deep layers. YOY perch were aggregated in dense schools in the epilimnion during the day and dispersed at night. Fish biomass was distributed along a strong increasing onshore–offshore gradient at night, whereas crustacean prey showed a decreasing gradient. This onshore–offshore negative gradient in crustacean distribution, expressed on a shorter scale during the day, shifted toward the surface waters at night. A distinct kinetic of diel vertical migration (DVM) patterns was exhibited by daphnid and cyclopoid populations and resulted in distinct vulnerability to perch predation. Spatio-temporal distribution of crustaceans in Lake Annecy during the diel cycle study was probably shaped both by predation loss to YOY perch and by ...