Hydroacoustic assessment of young‐of‐year perch, Perca fluviatilis, population dynamics in an oligotrophic lake (Lake Annecy, France)

Abstract

A cohort of perch, Perca fluviatilis (L.) was monitored from hatching to first winter in the oligotrophic Lake Annecy, France, by combining hydroacoustic and direct capture methods (fish plankton net and pelagic trawl). The total stock of pelagic fish increased by a factor of 10 during the season, reaching a maximum in August and decreasing in autumn. Juvenile perch were mainly pelagic, being aggregated into schools in the daytime and dispersed at night. Migration of young-of-year (Y-O-Y) perch to the pelagic zone of Lake Annecy in late spring did not significantly affect zooplankton population abundance. It did, however, result in changes in zooplankton vertical distribution, with Daphnia remaining deeper in the water column. The increase in Y-O-Y biomass during summer was possibly associated with collapse of the Daphnia population by late July, and copepods one month later. K E Y W O R D S :food web, hydroacoustic, Perca fluviatilis, zooplankton.Correspondence: J.

Assessment of the pelagic fish populations using CEN multi-mesh gillnets: consequences for the characterization of the fish communities

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Is the fishery of the introduced Tanganyika sardine (Limnothrissa miodon) in Lake Kivu (East Africa) sustainable?

“…The use of hydroacoustic methods to estimate fish abundance in aquatic ecosystems is well accepted (Simmonds and MacLennan, 2005), particularly for the pelagic zones of lakes (Dunlop et al, 2010;Guillard et al, 2006;Johnson et al, 2004). By contrast, the use of gillnets for assessing fish stocks is likely to provide a biased picture of species composition and size-structure because of known issues with capturing small (b10 cm) fishes using this equipment (Kurkilahti et al, 2002;Prachalováa et al, 2009).…”

Evaluation of food web and fish dietary niches in oligotrophic Lake Annecy by gut content and stable isotope analysis

“…A shift to piscivory among fish depends on the abundance of small-sized prey fish (Vehanen et al 1998). YoY perch could have a dense population in Lake Annecy during some years, and they eat zooplankton in the pelagic zone during summer (Masson et al 2001, Guillard et al 2006). However, if we consider 10 years of SIA data, which showed no major shift, these GCA changes should not be considered a major shift in feeding habits but rather a shift due to different sampling periods.…”