Dietary Traits of Invasive Bleak Alburnus Alburnus (Actinopterygii, Cyprinidae) Between Contrasting Habitats in Iberian Fresh Waters
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Hydrobiologia (2017) 795:23–33 DOI 10.1007/s10750-016-3052-8 PRIMARY RESEARCH PAPER Dietary traits of invasive bleak Alburnus alburnus (Actinopterygii, Cyprinidae) between contrasting habitats in Iberian fresh waters David Almeida . David H. Fletcher . Carlos Rangel . Emili Garcı´a-Berthou . Eduardo da Silva Received: 16 February 2016 / Revised: 14 October 2016 / Accepted: 9 November 2016 / Published online: 17 November 2016 Ó Springer International Publishing Switzerland 2016 Abstract The bleak Alburnus alburnus (L., 1758) is detritus were more consumed in the river, especially a limnophilic fish native to most of Europe. This benthos and detritus during spring, whereas plant cyprinid species is a successful invader in the Iberian intake decreased during this season. Shannon index, as Peninsula, where it threatens the highly endemic fish a measure of trophic diversity, was higher in the fauna. However, studies on bleak autoecology are reservoir, except for spring. Overall results suggest scarce in this region, with few data on foraging that this wide trophic plasticity will facilitate the bleak strategies. The aim of this work was to compare the invasion process throughout Mediterranean Europe, dietary traits of bleak populations between contrasting which poses a serious risk to its highly valuable native habitats in Iberian fresh waters. For this purpose, bleak fish fauna. were seasonally collected from the small River Ge´vora and the Sierra Brava Reservoir (Guadiana River Basin, Keywords Gut content analysis Á Mediterranean southwestern Spain). As percentages of occurrence river Á Non-native fish Á Reservoir Á Trophic diversity and ingested mass, plant material and planktonic Crustacea were the most important food categories in the river and the reservoir, respectively. The intake of pelagic prey was higher in the reservoir, especially Introduction during summer. Benthic prey, plant material and Biological invasions are a major driver of biodiversity loss at the global scale (Mooney & Hobbs, 2000; Handling editor: Alison King Butchart et al., 2010). Multiple native fish species have been introduced globally, with adverse effects reported D. Almeida (&) Á E. Garcı´a-Berthou GRECO, Institute of Aquatic Ecology, University of on freshwater ecosystems (Cowx, 1998;Rahel,2002). Girona, 17003 Girona, Spain Ecological research has highlighted a variety of serious e-mail: [email protected] impacts on native communities by invasive fish via the mechanisms of hybridization, competition, predation D. H. Fletcher Department of Life and Environmental Sciences, Faculty and acting as disease vectors (e.g. Leunda, 2010; of Science and Technology, Bournemouth University, Ribeiro & Leunda, 2012).Thedisruptiveeffectoffish Poole BH12 5BB, UK invasions is of particular conservation concern in the Iberian Peninsula, where endemism is high in freshwa- C. Rangel Á E. da Silva Department of Anatomy, Cell Biology and Zoology, ter ecosystems. Indeed, [50% of the native fish species University of Extremadura, 06006 Badajoz, Spain are unique to this region, many of them being threatened 123 24 Hydrobiologia (2017) 795:23–33 (Reyjol et al., 2007; Almeida et al., 2013a). Yet, the its spread. In particular, dietary traits of non-native proportion of the ichthyofauna that non-native fishes fishes commonly show wide plasticity under contrast- represent ([30%) continues to increase (Leunda, 2010), ing environmental conditions (Almeida et al., 2009; and this is the reason why the Iberian region is Godard et al., 2013) and their assessment can be of considered a hotspot for fish invasions (Ribeiro et al., particular interest to reveal how non-native species 2008; Clavero, 2011). thrive in recipient ecosystems (Sakai et al., 2001). This The bleak Alburnus alburnus (L., 1758) is a has implications from a conservation perspective, as cyprinid species native to most of Europe, from the this information can be used by policy-makers and Pyrenees to the Ural Mountains. In their native range, environmental managers to assess the potential impact bleak inhabit lakes or still waters in medium-large of bleak on native ecosystems. Indeed, a better rivers, where they chiefly feed on invertebrates from understanding of trophic ecology can also assist the water-column or the surface (Freyhof & Kottelat, monitoring programmes in identifying which other 2008). In the Iberian Peninsula, reservoirs are key areas are most likely to be colonised by invasive locations for the introduction of non-native fish species (e.g. Almeida & Grossman, 2014). However, (Clavero & Hermoso, 2011; Clavero et al., 2013), few data on the diet of invasive bleak exist for the which is true of the bleak (Vinyoles et al., 2007). This Iberian Peninsula (e.g. Latorre et al., 2016). Therefore, limnophilic species was first introduced in Spanish information in the present paper would be highly reservoirs from France during the 1990s as a ‘forage relevant to better understand the invasive capacity of fish’ for non-native piscivorous fishes. Some examples this fish species in the Mediterranean region of Europe. of these species are northern pike Esox lucius L., 1758, In light ofthe dearth of research on the autoecology of largemouth bass Micropterus salmoides (Lace´pe`de, this invasive fish in the Iberian Peninsula, the aim of this 1802) or pikeperch Sander lucioperca (L., 1758), work was to compare bleak dietary traits between which are target fishes for recreational angling (Viny- contrasting habitats within this region. Specifically, we oles et al., 2007). Since its introduction, the bleak has analysed diet composition, seasonal variation of food displayed a strong invasive character throughout intake, trophic diversity and ontogenetic shift in bleak Iberian fresh waters, and is now a typical species in populations from a river and a reservoir located in the the fish assemblages of this region (Maceda-Veiga Guadiana River Basin (southwestern Spain). We et al., 2010). The bleak threatens a wide range of hypothesised that (i) bleak will display wide plasticity native fish fauna, mainly via trophic competition and in dietary traits according to the particular environmen- aggression, as Iberian fishes are poorly adapted to such tal conditions of each habitat type, with more intake of invaders, which usually displace them from ecological benthos in the river and pelagic prey in the reservoir resources (Leunda, 2010). For example, direct obser- (Almeida & Grossman, 2014); (ii) diet will be more vations have shown that bleak can disturb the foraging diverse in the river because of a higher habitat behaviour of the endemic Ebro nase Parachondros- complexity (Morley et al., 2008; Almeida & Grossman, toma miegii (Steindachner, 1866) (Almeida & Gross- 2014) and iii) ontogenetic shift will also reflect man, 2012). Moreover, the bleak also threatens the environmental conditions of each habitat type, showing genetic integrity of Iberian fishes through hybridiza- opposite patterns of variation between the river and the tion with the endemic calandino Squalius alburnoides reservoir (Almeida et al., 2009;Godardetal.,2013). (Steindachner, 1866) complex and Southern Iberian chub Squalius pyrenaicus (Gu¨nther, 1868) (Almodo´- var et al., 2012). Materials and methods Despite this ecological risk, the available informa- tion on bleak in the Iberian Peninsula mainly addresses Study areas spatial distribution (Vinyoles et al., 2007) and popu- lation traits (Almeida et al., 2014; Maso´ et al., 2016), The River Ge´vora (length: 74 km; catchment area: but little on ecological interactions or role. Conse- 983 km2; altitude: 170–1027 m.a.s.l.) is a small right- quently, there is a need for more research that yields margin tributary (wetted width: 3–10 m; water depth: accurate insights into bleak invasiveness throughout 0.5–2.0 m; annual discharge: 0.5–0.9 m3 s-1)ofthe Spain and Portugal, which would contribute to control River Guadiana (southwestern Spain). Bleak were 123 Hydrobiologia (2017) 795:23–33 25 Table 1 Diet composition of bleak Alburnus alburnus between habitat types. Percentages of occurrences (Oc., %) and ingested masses (Mass, %) are presented Habitat type River Reservoir Food category Oc. Mass Oc. Mass Algae and vegetation debris 73 59 39 19 Rotifera – – 1 \1 Planktonic Crustaceaa 11 4 80 64 Ephemeroptera and Plecoptera nymphs 17 \11\1 Odonata nymphs 6 \1–– Diptera larvae 23 4 7 \1 Trichoptera larvae 17 2 1 \1 Other benthic invertebratesb 51 1\1 Nektonic and neustonic insectsc 1 \1283 Flying insectsd 18 3 21 3 Terrestrial arthropodse 52 41 Detritus 42 24 27 8 a Cladocera, Copepoda and Ostracoda b e.g. Oligochaeta and Coleoptera larvae c e.g. Corixidae and Gerridae adults d e.g. Hymenoptera, Diptera and Lepidoptera e e.g. Araneae and Formicidae collected from a 10 km section of the River Ge´vora: the river section and the reservoir (around 100 km), all 3885902300N–0685600200Wand3885501400N– these above advantages justified the selection of the two 0685702900W for the upstream and downstream bound- study areas. Furthermore, the assessment of dietary aries of the section, respectively. The Sierra Brava traits between selected contrasting habitats has been Reservoir (area: 1650 ha; volume: 232 hm3; water previously shown as appropriate to reveal wide ranges depth: 10–20 m; altitude: 303–352 m.a.s.l.) is located of phenotypic plasticity in other invasive fishes, on the River Ruecas (3981303600N–0583800600W), a although the study areas were not spatially close (e.g. right-margin tributary of the Guadiana River. The Sierra Almeida et al., 2009,