Contents lists available at ScienceDirect Fisheries Research journal homepage: www.elsevier.com/locate/ fishres Short communication Comparison of two passive methods for sampling invasive round goby (Neogobius melanostomus) populations at different depths in artificial lakes Tomáš Jůza a, ⁎ , Petr Blabolil a , Roman Baran a , Vladislav Draštík a , Michaela Holubová a , Luboš Kočvara a , Milan Muška a , Milan Říha a , Zuzana Sajdlová a , Marek Šmejkal a , Michal Tušer a , Mojmír Vašek a , Lukáš Vejřík a , Ivana Vejříková a , Arco J. Wagenvoort c , Jakub Žák a , Henk A.M. Ketelaars b a Biology Centre of the Czech Academy of Sciences, Institute of Hydrobiology, Na Sádkách 7, 37005, České Budějovice, Czech Republic b Evides Water Company, PO Box 4472, 3006, AL Rotterdam, The Netherlands c AqWa, Voorstad 45, 4461 KL Goes, The Netherlands ARTICLE INFO Handled by B. Morales-Nin Keywords: CPUE Depth distribution Size distribution Fyke nets Gillnets ABSTRACT Sampling of benthic fish is complicated, especially in deep inland water bodies with a structured bottom. The catches were compared of rapidly spreading round goby (Neogobius melanostomus) using small fykes nets and benthic gillnets in three artificial lakes in The Netherlands over a two year period. Round gobies were captured at all depth layers in each sampled lake. Significantly larger individuals were captured in gillnets compared to fyke nets. Reference sampling in littoral areas captured a wide range in size of round gobies with beach seines. With fyke nets, the highest catches were usually achieved in the shallowest and deepest depth strata. Gillnets catch decreased at deeper layers. Both methods are passive sampling tools and did not provide the absolute catch per bottom area, however relative density estimates of round gobies at different depths or habitats are possible. Round gobies showed a significant size bias associated with capture method. Because it is important to un- derstand the biology and ecology of invasive species like round goby, the combination of small fyke nets and gillnets appears to be a good solution to sample a variety of ranges in deep or/and structured benthic habitats. 1. Introduction Round goby (Neogobius melanostomus), of the family Gobiidae, is a benthic euryhaline species that is native to central Eurasia including the Black, Azov and Caspian Seas (Verreycken et al., 2011). The species was transported via ballast water to different parts of Europe and North America (Corkum et al., 2004). In newly colonized regions, round goby spread rapidly and reach densities of over 100 individuals per m 2 in some habitats (Cooper et al., 2009). Round goby invasion have had detrimental effects on native fish species such as mottled sculpin (Cottus bairdi, Janssen and Jude, 2001), logperch (Percina caprodes, Balshine et al., 2005), river bullhead (Cottus perifretum, van Kessel et al., 2011, 2016) and ruffe(Gymnocephalus cernua, Jůza et al., 2018) and it is in- cluded in the list of 100 worst European invasive species (www.europe- aliens.org). Similar to many other European and North American water bodies, the River Rhine and, subsequently the River Meuse have been invaded by many Ponto-Caspian species (van Kessel et al., 2016). The first occurrence of round goby in The Netherlands was observed in 2004 (van Beek, 2006). By 2012 round goby were found in three lakes of the Biesbosch lake system (Kruitwagen, 2013). A detailed understanding of biology and ecology is an important prerequisite to prevent future ex- pansions and therefore, an unbiased sampling strategy is absolutely necessary to fulfill it. Methods used to sample and monitor round goby populations in- clude electrofishing (van Kessel et al., 2011; Janáč et al., 2016), seining (van Kessel et al., 2011; Žák et al., 2018), angling (Chotkovski and Marsden, 1999), fyke netting (Sapota and Skóra, 2005), gillnetting (Sapota and Skóra, 2005; Shemonaev and Kirilenko, 2009), bottom trawling, SCUBA diving (Sapota and Skóra, 2005) and video recording (Taraborelli et al., 2010). Because round gobies utilize the pelagic zone during larval and early juvenile stages, fry trawling is an efficient sampling tool in these phases (Jůza et al., 2016). For sampling of round https://doi.org/10.1016/j.fishres.2018.06.002 Received 20 March 2018; Received in revised form 29 May 2018; Accepted 4 June 2018 ⁎ Corresponding author. E-mail addresses: tomas.juza@seznam.cz (T. Jůza), blabolil.petr@seznam.cz (P. Blabolil), r.baran@centrum.cz (R. Baran), v.drastik@gmail.com (V. Draštík), miki_h@seznam.cz (M. Holubová), l.kocvara@seznam.cz (L. Kočvara), muskamilan@seznam.cz (M. Muška), mriha00@gmail.com (M. Říha), zuzana@sajdl.info (Z. Sajdlová), mareks1@centrum.cz (M. Šmejkal), michal.tuser@gmail.com (M. Tušer), mojmir.vasek@seznam.cz (M. Vašek), vejrik.lukas@seznam.cz (L. Vejřík), ivana.vejrikova@gmail.com (I. Vejříková), aqwa@zeelandnet.nl (A.J. Wagenvoort), jakub.zak@natur.cuni.cz (J. Žák), h.ketelaars@evides.nl (H.A.M. Ketelaars). Fisheries Research xxx (xxxx) xxx–xxx 0165-7836/ © 2018 Elsevier B.V. All rights reserved. Please cite this article as: Juza, T., Fisheries Research (2018), https://doi.org/10.1016/j.fishres.2018.06.002