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Article (refereed) - postprint Volta, Pietro; Jeppesen, Erik; Leoni, Barbara; Campi, Barbara; Sala, Paolo; Garibaldi, Letizia; Lauridsen, Torben L.; Winfield, Ian J.. 2013 Recent invasion by a non-native cyprinid (common bream Abramis brama) is followed by major changes in the ecological quality of a shallow lake in southern Europe. Biological Invasions, 15 (9). 2065-2079. 10.1007/s10530-013-0433- © Springer Science+Business Media Dordrecht 2013 This version available http://nora.nerc.ac.uk/15239/ NERC has developed NORA to enable users to access research outputs wholly or partially funded by NERC. Copyright and other rights for material on this site are retained by the rights owners. Users should read the terms and conditions of use of this material at http://nora.nerc.ac.uk/policies.html#access This document is the author’s final manuscript version of the journal article, incorporating any revisions agreed during the peer review process. Some differences between this and the publisher’s version remain. You are advised to consult the publisher’s version if you wish to cite from this article. The final publication is available at link.springer.com Contact CEH NORA team at [email protected] The NERC and CEH trademarks and logos (‘the Trademarks’) are registered trademarks of NERC in the UK and other countries, and may not be used without the prior written consent of the Trademark owner. 1 Recent invasion by a non-native cyprinid (common bream Abramis brama) is 2 followed by major changes in the ecological quality of a shallow lake in 3 southern Europe 4 5 Pietro VOLTA1, Erik JEPPESEN2,3,4, Barbara LEONI5, Barbara CAMPI1, Paolo 6 SALA1, Letizia GARIBALDI5, Torben L. LAURIDSEN2,3, Ian J. WINFIELD6 7 8 1CNR - ISE Institute of Ecosystem Study 9 L.go Tonolli 50 - 28922 Verbania Pallanza – Italy 10 11 2 Dept. of Bioscience, Aarhus University, Vejlsøvej 25, 8600 Silkeborg, Denmark 12 3 Greenland Climate Research Centre (GCRC), Greenland Institute of Natural 13 Resources, Kivioq 2, P.O. Box 570 3900, Nuuk, Greenland 14 4 Sino-Danish Centre for Education and Research (SDC), Beijing, China 15 5 Università degli Studi di Milano Bicocca, Milano, Italy 16 6 Centre for Ecology & Hydrology, Lancaster Environment Centre, Library 17 Avenue, Bailrigg, Lancaster LA1 4AP, U.K. 18 *e-mail corresponding author: [email protected] 19 Phone: +39323518335 20 Fax: +39323556513 21 22 Running head: Common bream in Lake Montorfano 23 24 ABSTRACT 25 26 We present an example of how an invasion by a non-native cyprinid (common 27 bream, Abramis brama (Pisces: Cyprinidae), hereafter bream) in a natural shallow 28 lake in southern Europe (Lake Montorfano, northern Italy) may have adversely 29 affected the state of the lake’s ecosystem. In less than two decades, bream became 30 the most abundant species and characterized by a stunted population with 31 asymptotic length 33.5 cm, an estimated mean length at first maturity of 19.6 cm, 32 a total mortality rate of 0.64 y-1 and a diet overwhelmingly dominated by 33 microcrustaceans. Following bream establishment, nutrients and phytoplankton 34 biomass rose, the proportion of Cyanobacteria by numbers increased markedly 35 and water transparency decreased. Total zooplankton abundance increased with a 36 marked increase in small cladocerans and copepods, whereas the abundance of 37 large herbivorous cladocerans did not change. The coverage of submerged 38 macrophytes declined, as did the abundance of native pelagic zooplanktivorous 39 fish. The composition of the fish community shifted towards a higher proportion 40 of zoobenthivorous species, such as bream and pumpkinseed (Lepomis gibbosus). 41 Our results indicate that bream affected water quality through bottom-up 42 mechanisms, while top-down effects were comparatively weak. Selective removal 43 of bream and perhaps stocking of native piscivores might improve the ecological 44 status of the lake. 45 2 46 Key words: invasive alien species IAS, electrofishing, multi-mesh survey gill nets, 47 CPUE, cyprinids, ecosystem functioning 48 3 49 1. INTRODUCTION 50 51 Non-native species, i.e. species outside their natural range which frequently 52 become established and abundant following their introduction (Rejmánek et al. 53 2002; Cambray 2003), are increasingly recognized as constituting one of the main 54 threats to biodiversity and ecosystem functioning (e.g. Ricciardi and McIsaac 55 2011) and are often associated with environmental degradation (Biro 1997; 56 Wilcove et al. 1998; Byers 2002). Furthermore, in the case of freshwater fish 57 faunas such biotic homogenization frequently has high ecological and economic 58 costs (Welcomme 1998; Rahel 2000). 59 60 Successful non-native species are often characterized by high physiological 61 tolerance and functional characteristics different from those of the members of 62 invaded communities (Moyle and Marchetti 2006; Bollache 2008), enabling them 63 to occupy vacant niches and to spread and increase rapidly. Moreover, successful 64 non-native species have been reported to affect the functional diversity of 65 communities with possible strong impacts on food webs and ecosystem 66 functioning (Hooper et al. 2005; Britton et al. 2010; Simberloff 2011). 67 Additionally, as invasions by non-native species in novel environments are often 68 characterized by boom-bust phenomena (Strayer and Malcom 2006; Salonen et al. 69 2007; Volta and Jepsen 2008; Liso et al. 2011) with strong recruitment leading to 70 high densities, the adverse effects on ecosystem processes may be further 71 exacerbated. 4 72 73 Southern European fresh waters, including those of Italy and other countries 74 adjacent to the Mediterranean Sea, are isolated from those of the rest of Europe. 75 Mountain ranges have prevented the migration of aquatic and many other 76 organisms from northern and central Europe, thus favouring isolation and 77 allopatric speciation (Bianco 1998; Hewitt 1999; Rayol et al. 2007). However, the 78 anthropogenic introduction of non-native species, a long-lasting and continuing 79 process, has recently led to homogenization of the fish fauna and coexistence of 80 native and non-native species in several southern European basins (Clavero and 81 Garcia-Berthou 2006; Gherardi et al. 2007; Kottelat and Freyhof 2007). In 82 particular, the Italian peninsula has experienced the introduction of several non- 83 native fish species since the Roman and Middle Ages. During the 1800s, stocking 84 of water bodies with new fish species became a widespread practice with the 85 purpose of enhancing the production of commercially valuable fish species and, 86 later, species of angling interest. This has resulted in a local shift from salmonids 87 and coregonids to centrarchids and, more recently, cyprinids (Bianco 1998; 88 Gherardi et al. 2007). 89 90 Common bream (Abramis brama) (hereafter bream) is native in most European 91 drainages, from parts of the U.K. in the west to the White Sea basin in the east, 92 but it is naturally absent from the Iberian peninsula, the Adriatic basin, Italy, 93 northern and western parts of the British Isles and north of 67°N. However, in 94 recent decades, this cyprinid has been introduced to Spain and Italy (Benejam et 5 95 al. 2005; Kottelat and Freyhof 2007). Although both adaptable and tolerant to 96 different kinds of water bodies (e.g. Jeppesen et al. 2006; Lapirova and Zabotkina 97 2010), this potentially large-bodied fish prefers meso-eutrophic shallow lakes with 98 a dense vegetated area or reed belt around the shoreline (Lammens et al. 2004; 99 Mehner et al. 2005; Kottelat and Freyhof 2007). It is a zoobenthivorous species 100 (Lammens and Hoogenboezem 1991; Persson and Brönmark 2002) and is in some 101 cases known to have a significant negative effect on the water quality in shallow 102 lakes (Tatrai et al. 1990; Breukelaar 1994; Vanni 2002). The potential to exert 103 adverse effects on lake food webs and ecosystem functioning operates through at 104 least two mechanisms: i) through a reduction the abundance of large zooplankton 105 followed by increased phytoplankton abundance (top-down mechanism) (Brooks 106 and Dodson 1965; Shapiro et al. 1975; Carpenter et al. 1985; Benndorf et al. 107 2002) and, ii) through increased nutrient cycling due to an increased excretion rate 108 at the community scale and the disturbance of bottom sediments through 109 ‘bioturbation’ (Meijer et al. 1990; Vanni 2002, Verant et al. 2007) favouring 110 phytoplankton growth (bottom-up mechanism). Furthermore, bream often has a 111 pronounced migratory behaviour (e.g. Schulz and Berg 1987; Borcherding et al. 112 2002; Skov et al. 2011) and may consequently move considerable distances to 113 other lakes within a river system. Finally, although often attaining large individual 114 sizes, this species may also develop stunted high density populations becoming 115 locally abundant, with potential negative consequences both within and beyond 116 the local fish community due to competition for food resources (Van de 117 Wolfshaar et al. 2006; Persson et al. 2007) or hybridization (Hayden et al. 2010). 6 118 In combination, these features make bream a potentially effective and highly 119 undesirable invader of southern European waters. 120 121 The introduction history of bream in Italy began as recently as the 1980s 122 (Delmastro 1983; Marconato et al. 1985). Its distribution is still scattered and in 123 running waters it is currently limited to a few small stretches of slow-flowing 124 rivers and canals in the eastern part of the north-eastern lowlands, and to the main 125 rivers Arno (Tuscany region) and Tevere (Latium region) in central Italy (Mancini 126 et al. 2005). Its presence in lentic waters is known to be confined to only three 127 lakes belonging to different catchments but with similar limnological 128 characteristics: Lake Monticolo Grande (Trentino Alto-Adige Region, Adige river 129 drainage), Lake Fimon (Veneto Region, Tagliamento river Drainage) and Lake 130 Montorfano (Lombardy Region, river Po catchment).