**1. Introduction**

The topmouth gudgeon, *Pseudorasbora parva* (Temminck and Schlegel, 1846) (sub fam. Gobioninae) is a small cyprinid fish distributed in Japan, China, Korea, Hungary, Germany, Serbia, Austria, Greece, Poland, North Africa, Romania, Czech Republic, United Kingdom, Azerbaijan and Ukraine [1–10]. It usually occupies a range of lotic and lentic habitats, including rivers, reservoirs, canals, ponds, shallow lakes and oxbows [11–13]. This species is one of the most effective invasive species to have been introduced into inland waters in Turkey for the past 30 years [14–23]. Generally, the topmouth gudgeon is considered as an important predator on crustaceans, zooplankton, ostracods, molluscs, chironomid larvae, rotifers and benthic organisms. It also feeds on phytoplankton (diatoms and other algae), zooplankton (cladocerans, copepods), the larvae and eggs of native fish species, insects and detritus [7, 24–26]. Although there are some data available on its age, growth, reproduction and habitat [27–33], published information on the diet of topmouth gudgeon is still scarce.

underground water source, surface springs, runoff water, rain and small streams. Evaporation and water flow into Lake Kovada through a channel are main outflows of the lake [41]. The lake is an important source of drinking water as well as tourism and agricultural irrigation. The previous fauna and flora studies carried out in the lake yielded a rich biodiversity. According to the QB/T [42], the Rotifera index showed that the lake has mesotrophic features in terms of zooplankton. Carlson's trophic state index also supports that the lake shows both mesotrophic and eutrophic characteristics. Annual mean concentration of chlorophyll-a (3.0 ± 0.2 mg/

Prey Selection of *Pseudorasbora parva* (Temminck and Schlegel, 1846) in a Freshwater Ecosystem (Lake Eğirdir/Turkey)

) also supported the proposed trophic status of the lake [43]. Zooplanktonic organisms, which is significant part of the lakes, consisted of Rotifera (40 species), Cladocera (22 species) and Copepoda (3 species). Rotifers, *Poyarthra dolichoptera* and *Keratella cochlearis* known as indicator of mesotrophic conditions, were reported to occur predominantly in the lake [43]. A total of 129 algal taxa belonging to six groups Ochrophyta (65 species), Chlorophyta (30 species), Charophyta (13 species), Cyanophyta (12 species), Euglenophyta (6 species) and Myzozoa (3 species) were determined [44]. The average abundance of 24 zoobenthic spe-

53.4% relative density. The proportions of Insecta, Bryozoa and Malacostraca were reported

In the first and most comprehensive study on lake, it was reported that the lake fish fauna consisted of 10 different (*Cyprinus carpio, Schizothorax prophylax, Varicorhinus pestai, Acanthorutilus handlirschi, Vimba vimba, Thylognathus klatti, Aphanius chantrei, Cobitis taenia, Nemachilus angorae, Pararhodeus niger*) species [46]. In fact nine species occurs in the lake since *S. prophylax* and *V. pestai* are synonyms of each other. Perch (*Sander lucioperca*) was the first fish introduced into the lake in 1955. A total of nine different non-native species were reported at different times over a period of about 70 years. Today, there are totally 14 fish species (2 native, 6 endemic, 7 non-native) belonging to 8 families in the lake. These species are listed as *Cyprinus carpio, Vimba vimba* (native), *Oxynoemacheilus mediterraneus*, *Seminemacheilus ispartensis, Cobitis turcica, Capoeta pestai, Pseudophoxinus egridiri, Aphanius anatoliae* (endemic), *Atherina boyeri, Carassius gibelio, Pseudorasbora parva, Knipowitschia caucasica, Gambusia holbrooki* and *Sander* 

Fish samples were collected between April and August in the years of 2010 and 2011. All fish caught by the gill nets and purse seine were evaluated in the diet study. Fishing nets with mesh size 10, 16, 45 and 0.9 mm were used. Sampling was performed at two different sites (**Figure 1**), one in the southern of the lake (St 1, 5–7 m of depth) and the other in the southeast (St 2, with 2–5 m depth). Fish specimens were measured to the nearest 0.1 mm fork length (FL) and weighed to the nearest 0.001 g. The contents of the stomach were removed and the empty stomach was reweighed to the nearest 0.001 g. A total of 88 topmouth gudgeon were analyzed. Each prey item was determined to the lowest possible taxonomic level and counted. Proportion of full and empty stomachs was also determined. Volume calculation was used in Malacostraca, Annelida and Insecta. In addition, average volume was estimated [50] for *Disparalona rostrata, Chydorus* 

μ<sup>3</sup>

), *Graptoleberis testudinaria, Alona* 

. Dominant species were Oligochaeta with

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cies was recorded recently as 4.195 individuals/m2

as 17.6%, 11.7% and 10.6%, respectively [45].

*lucioperca* (non-native) [41, 47–49].

**2.2. Specimen sampling and data analysis**

*sphaericus* and *Nitocra hibernica, Mesocyclops leuckarti* (1.0 × 107

m<sup>3</sup>

Feeding habits and feeding ecology of topmouth gudgeon were studied by Wolfram-Wais et al. [4] in Neusiedler See (Austria) and Xie et al. [34] in the Biandangtang Lake of China. Hliwa et al. [35] studied the diet of the species in the Kis-Balaton Reservoir, whereas Nikolova et al. [36] investigated seasonal variation in the diet of topmouth gudgeon from shallow eutrophic lakes along River Vit in Bulgaria. Yalçin-Özdilek et al. [37] carried out research on the feeding ecology of the species from Gelingüllü Reservoir and Karakuş [22] studied dietary interactions between non-native species topmouth gudgeon and some native fish species in Sarıçay Stream in Turkey. Didenko and Kruzhylina [10] investigated trophic interaction between topmouth gudgeon and the co-occurring species during summer in the Dniprodzerzhynsk Reservoir in Ukraine.

Asian cyprinid, *Pseudorasbora parva*, causes increased mortality and totally inhibiting spawning of endangered native fish, the European cyprinid *Leucaspius delineatus*. This threat is caused by an infectious pathogen, a rosette-like intracellular eukaryotic parasite that is a deadly, non-specific agent. It is probably carried a vector of an emergent infectious disease and could decrease fish biodiversity in Europe [38].

The topmouth gudgeon is successfully inhabited invasive fish in Lake Eğirdir. However, its feeding properties have not been sufficiently studied yet. The aim of the present study was to determine the diet composition of *Pseudorasbora parva* and its prey selectivity in the Lake Eğirdir, Turkey.
