| Abstract | 1. Sampling of lake fish assemblages is a challenging task in fish science, and the information obtained strongly depends on the choice of sampling gear. The use of more than one sampling technique is generally preferred in order to achieve a comprehensive view on fish assemblage structure. Therefore, the knowledge of whether catches between fishing gears are comparable is crucial. 2. We compared catches in benthic multi-mesh gillnets with fish biomass estimates obtained by vertical hydroacoustics in 18 European lakes strongly varying in morphometry and trophic status. Separate analyses were conducted for different depth strata and for several fish length thresholds to account for depth- and size-selective gillnet catches. 3. Gillnet catches and hydroacoustically obtained fish biomass estimates were significantly correlated. The strength of correlations was independent of the fish length thresholds applied, but varied across different depth strata of the lakes, with the strongest correlations occurring in the shallow strata. 4. The results support the applicability of vertical hydroacoustics for the quantification of fish biomass in stratified lakes. Survey designs combining hydroacoustics with limited gillnetting at sampling dates shortly one after the other, the latter for the purpose of inventory sampling only, are a cost-effective strategy for sampling fish assemblages in lakes. However, gillnet sampling does not provide reliable fish density estimates in very deep lakes with separate, pelagic-dwelling fish assemblages. |
| Text | 328141 2012 10.1111/fwb.12022 Biomass estimates Fish sampling Gillnets Lakes Vertical hydroacoustics Strong correspondence between gillnet cathc per unit effort and hydroacoustically derived fish biomass in stratified lakes Matthias Emmrich; Ian J. Winfield; Jean Guillard; Atle Rustadbakken; Charlotte Verges; Pietro Volta; Erik Jeppesen; Torben Lauridsen; Sandra Brucet; Kerstin Holmgren; Christine Argillier; Thomas Mehner Matthias Emmrich Leibniz Institute of Freshwater Ecology and Inland Fisheries, Berlin, Germany; Ian J. Winfield Centre for Ecology and Hydrology, Lancaster Environment Centre, Lancaster, U.K.; Jean Guillard Institut National de la Recherche Agronomique, UMR CARRTEL, Thonon les bains, France; Atle Rustadbakken Norwegian Institute for Water Research, Oslo, Norway; Charlotte Verges ASCONIT Consultants, ZI Champigny, Ducos, France; Pietro Volta CNR ISE, Pallanza Verbania; Erik Jeppesen Department of Bioscience, Aarhus University, Silkeborg, Denmark; Torben Lauridsen Sino Danish Centre for Education and Research, Beijing, China; Sandra Brucet European Commission, Joint Research Centre, Institute for Environment and Sustainability, Ispra, Italy; Kerstin Holmgren Swedish University of Agricultural Sciences, Department of Aquatic Resources, Institute of Freshwater Research, Drottningholm, Sweden; Christine Argillier Irstea, UR HYAX, Route de Ce´zanne, Aix en Provence Cedex, France; Thomas Mehner Leibniz Institute of Freshwater Ecology and Inland Fisheries, Berlin, Germany 1. Sampling of lake fish assemblages is a challenging task in fish science, and the information obtained strongly depends on the choice of sampling gear. The use of more than one sampling technique is generally preferred in order to achieve a comprehensive view on fish assemblage structure. Therefore, the knowledge of whether catches between fishing gears are comparable is crucial. 2. We compared catches in benthic multi mesh gillnets with fish biomass estimates obtained by vertical hydroacoustics in 18 European lakes strongly varying in morphometry and trophic status. Separate analyses were conducted for different depth strata and for several fish length thresholds to account for depth and size selective gillnet catches. 3. Gillnet catches and hydroacoustically obtained fish biomass estimates were significantly correlated. The strength of correlations was independent of the fish length thresholds applied, but varied across different depth strata of the lakes, with the strongest correlations occurring in the shallow strata. 4. The results support the applicability of vertical hydroacoustics for the quantification of fish biomass in stratified lakes. Survey designs combining hydroacoustics with limited gillnetting at sampling dates shortly one after the other, the latter for the purpose of inventory sampling only, are a cost effective strategy for sampling fish assemblages in lakes. However, gillnet sampling does not provide reliable fish density estimates in very deep lakes with separate, pelagic dwelling fish assemblages. 57 Published version Articolo 2012_Freshwater_Biology_57_2436_2448.pdf Articolo in rivista Blackwell Scientific Publications. 0046 5070 Freshwater biology Print Freshwater biology Print Freshw. biol. Print pietro.volta VOLTA PIETRO TA.P04.016.004 Ecologia teorica e applicata degli ecosistemi acquatici |
