Ecology of Freshwater Fish 2009: 18: 15–23 Ó 2008 The Authors Printed in Malaysia Æ All rights reserved Journal compilation Ó 2008 Blackwell Munksgaard ECOLOGY OF FRESHWATER FISH Feeding tactics and body condition of two introduced populations of pumpkinseed Lepomis gibbosus: taking advantages of human disturbances? Almeida D, Almodo´var A, Nicola GG, Elvira B. Feeding tactics and body D. Almeida1, A. Almodo´var1, condition of two introduced populations of pumpkinseed Lepomis G. G. Nicola2, B. Elvira1 gibbosus: taking advantages of human disturbances? 1Department of Zoology and Physical Anthropol- Ecology of Freshwater Fish 2009: 18: 15–23. Ó 2008 The Authors. ogy, Faculty of Biology, Complutense University Journal compilation Ó 2008 Blackwell Munksgaard of Madrid, Madrid, Spain, 2Department of Environmental Sciences, University of Castilla-La Mancha, Toledo, Spain Abstract – Feeding tactics, body condition and size structure of two populations of pumpkinseed Lepomis gibbosus from Caban˜eros National Park (Guadiana River basin, central Spain) were compared to provide insight into the ecological requirements favouring levels of success ⁄ failure in relation to human intervention. Habitat, benthic macroinvertebrates and pumpkinseed were quantified in Bullaque (regulated flow, affected by agricultural activities) and Estena (natural conditions) rivers, from May to September of 2005 and 2006. Significant differences were found in the limnological characteristics between the two rivers. Spatial and temporal Key words: invasive species; feeding tactics; prey variations in diet composition were likely related to opportunistic feeding selection; freshwater fishes and high foraging plasticity. Diet diversity was higher in Bullaque River. B. Elvira, Department of Zoology and Physical Electivity of benthic prey showed variation between sized individuals and Anthropology, Faculty of Biology, Complutense populations. The body condition of pumpkinseed was better in Bullaque University of Madrid, E-28040 Madrid, Spain; River. Current results show that this invasive species is favoured by human e-mail: [email protected] intervention in Bullaque River. Accepted for publication May 9, 2008 In Spain, more than 25 fish species have been Introduction introduced (Elvira 1995a; Elvira & Almodo´var 2001; Biological invasions induced by human activities have Ribeiro et al. 2008). Available studies indicate that the resulted in serious disturbances and deleterious effects impact of invaders upon native fish assemblages are of natural ecosystems all around the world (Money & due to habitat alteration (Garcı´a-Berthou 2001), pre- Hobbs 2000). Actually, such invasions are one of the dation (Elvira et al. 1996; Nicola et al. 1996), trophic most important causes of biodiversity loss, particularly competition (Garcı´a-Berthou 1999; Alcaraz & Garcı´a- in aquatic ecosystems (Welcomme 1992). The grow- Berthou 2007) and hybridisation with native species ing concern about the impacts of non-native fish has (Elvira 1995b, 2001; Almodo´var et al. 2001, 2006). led to the study of these species outside of their native The pumpkinseed Lepomis gibbosus (L.), a centrar- ranges to improve our ability to predict their impact chid fish native to eastern North America, was first and to control the expansion of existing ones (March- introduced into the Iberian Peninsula (first time in etti et al. 2004; Garcı´a-Berthou 2007; Ribeiro et al. Lake Banyoles, northeastern Spain) in 1910–1913 2008). Nevertheless, despite intensive research, there (Elvira & Almodo´var 2001) and was first recorded in is still an urgent need to increase our knowledge on the the 1970s in the Guadiana River basin (Almac¸a 1995). life history of non-native fish species (Wootton et al. The pumpkinseed is now widespread, particularly in 2000). reservoirs, and has been related to changes in native doi: 10.1111/j.1600-0633.2008.00317.x 15 Almeida et al. fish assemblages (Zapata & Granado-Lorencio 1993; promoting losses of water quality. In contrast, more Godinho & Ferreira 1998a; Garcı´a-Berthou & Moreno- natural conditions prevail in Estena River, i.e., higher Amich 2000). Within its natural distributional range, water velocity and well developed riparian vegetation. pumpkinseed inhabits lentic environments such as lakes During the study period, the limnological characteris- and ponds (Fox 1994; Robinson et al. 2000), where it tics differed substantially between the two rivers chiefly feeds on zooplankton and benthic inverte- (Table 1 and Fig. 2). Whilst the regulated water brates (Scott & Crossman 1979; Deacon & Keast course of Bullaque River ensures a continuous flow 1987). during the rainless summer, isolated pools typify The objective of this study was to compare auto- Estena River, a drought condition typical of small ecological features between two nearby pumpkinseed Mediterranean rivers. populations. More specifically this study compares The fish assemblage of Caban˜eros National Park diet, prey selection, body condition and size structure encompasses 14 species (Doadrio 1997, 2002, and of pumpkinseed in two Spanish streams; namely in authors’ personal data). Eight species are endemic: Bullaque and Estena rivers, within the Caban˜eros Anaecypris hispanica (Steindachner), Iberochondros- National Park, central Spain, differing in the degree of toma lemmingii (Steindachner), Luciobarbus comizo human intervention. (Steindachner), Luciobarbus microcephalus (Almac¸a), Pseudochondrostoma willkommii (Steindachner), Squalius alburnoides (Steindachner), Squalius pyrenai- Study area and fish fauna cus (Gu¨nther), and Cobitis paludica (De Buen). Other Caban˜eros National Park is a protected area of six accompanying species were introduced in nearby 408.56 km2. Altitude ranges from 560 to 1448 m. reservoirs, and have spread throughout. These species This is characterised by a Mediterranean climate and include: Carassius auratus (L.), Cyprinus carpio L., comprises two main streams: Bullaque and Estena Esox lucius L., Gambusia holbrooki Girard, Lepomis rivers (Guadiana River basin, central Spain), which gibbosus (L.) and Micropterus salmoides (Lace´pe`de). run 84 and 61 km in length, respectively. Flow regime of Bullaque River is regulated by the Torre de Materials and methods Abraham reservoir, located nearby Caban˜eros National Park (Fig. 1). This river runs next to the east Sampling and laboratory methods borderline of the Park, where farming activities take place. Therefore, agricultural runoff (nutrients and Monthly samples of pumpkinseeds were conducted organic matter resulting from cattle and farming from May to September of 2005 and 2006 with activities) increases turbidity and organic pollutants electrofishing (2000 W DC generator at 200 V, N Guadiana River Estena River Torre de Abraham Reservoir Cabañeros National Park Bullaque River Fig. 1. Map of the study area. Dotted line marks the boundary of Caban˜eros National 0 5 km Park. Sampling sites surveyed are marked as bold circles. 16 Feeding habits of introduced pumpkinseed Table 1. Limnological features and macroinverte- brate abundances in the studied rivers for each 2005 2006 sampling year. Bullaque River Estena River Bullaque River Estena River Limnological features Water velocity (mÆs)1) 0.27 ± 0.07 0.06 ± 0.03 0.21 ± 0.06 0.05 ± 0.03 Depth (cm) 53.33 ± 2.12 27.08 ± 2.70 48.17 ± 3.03 31.83 ± 2.14 Aquatic vegetation (%) 27.41 ± 1.96 48.67 ± 2.38 30.63 ± 1.33 50.83 ± 2.77 Silt (<0.01 cm) (%) 26.84 ± 1.69 17.00 ± 2.86 29.37 ± 1.12 18.83 ± 2.92 Sand (0.01–0.5 cm) (%) 10.06 ± 1.50 8.07 ± 1.03 11.10 ± 2.35 10.25 ± 1.59 Gravel (0.5–7.6 cm) (%) 35.08 ± 5.33 34.92 ± 3.63 33.60 ± 3.24 36.57 ± 4.15 Pebble (7.6–30.5 cm) (%) 24.67 ± 5.17 33.77 ± 3.31 22.75 ± 5.04 29.75 ± 3.99 Block (>30.5 cm) (%) 3.34 ± 5.52 6.25 ± 3.31 3.18 ± 6.28 4.61 ± 2.47 Macroinvertebrates Density (1000 ind.gÆm)2) 27.41 ± 4.68 5.90 ± 0.54 24.70 ± 3.41 7.29 ± 0.67 Biomass (gÆm)2) 5.18 ± 0.33 1.12 ± 0.16 4.96 ± 0.54 1.09 ± 0.27 Results are means ± SE. Particle size classification is according to Platts et al. (1983). F1,116 = 4.31 F1,168 = 7.07 F1,116 = 4.87 F1,168 = 10.74 P < 0.05 P < 0.01 P < 0.05 P < 0.001 40 10 ) –2 ) 8 30 –2 m · 6 20 4 10 Biomass (g 2 Density (1000 ind. m 0 0 F1,26 = 3.01 F1,40 = 12.95 F1,26 = 4.48 F1,40 = 8.78 P = 0.10 P < 0.001 P < 0.05 P < 0.01 0.30 60 ) –1 s 0.25 · 50 0.20 40 0.15 30 0.10 20 Depth (cm) 0.05 10 Water velocity (m 0.00 0 F1,26 = 0.66 F1,40 = 11.22 F1,26 = 6.65 F1,40 = 0.95 P = 0.43 P < 0.01 P < 0.05 P = 0.34 70 40 ) % 60 35 30 50 ) 25 40 % 20 30 15 Silt ( 20 10 10 5 Aquatic vegetation ( 0 0 Spring Summer Spring Summer Bullaque River Estena River Fig. 2. Significant differences found in macroinvertebrates abundances (densities and biomasses) and habitat characteristics between rivers for each sampling season. Results are means ± SE. F-values and significance levels after anova are indicated. 17 Almeida et al. 1–2 A). Sampling sites were located along 4 km in Assumptions of normality of distributions and Bullaque River and 10 km in Estena River (Fig. 1). homogeneity of variance were verified through These sites (one site per two kilometres, 25–30 m Shapiro-Wilk and Levene’s tests, respectively. Com- long, sampling time 30–40 min) comprised different parisons among macroinvertebrate abundance, habitat mesohabitats (run, riffle, pool) to include the existing characteristics, and pumpkinseed abundance, fork environmental variability. Benthic macroinvertebrates length and body condition between populations were were sampled on the same sites and dates (3–5 three- examined by standard analysis of the variance (anova, minute replicates) and mesohabitats using a cylinder Zar 1996).