Annals of Parasitology 2015, 61(2), 85–92 Copyright© 2015 Polish Parasitological Society Original papers Species richness and diversity of the parasites of two predatory fish species – perch (Perca fluviatilis Linnaeus, 1758) and zander ( Sander lucioperca Linnaeus, 1758) from the Pomeranian Bay Iwona Bielat, Monika Legierko, Ewa Sobecka Division of Hydrobiology, Ichthyology and Biotechnology of Breeding, Faculty of Food Sciences and Fisheries, West Pomeranian University of Technology, Kazimierza Królewicza 4, 71-550 Szczecin, Poland Corresponding author: Ewa Sobecka; e-mail: [email protected] ABSTRACT. Pomeranian Bay as an ecotone is a transition zone between two different biocenoses, which is characterized by an increase in biodiversity and species density. Therefore, Pomeranian Bay is a destination of finding and reproductive migrations of fish from the rivers entered the area. The aim of the study was to compare parasitic fauna of two predatory fish species from the Pomeranian Bay, collected from the same fishing grounds at the same period. A total of 126 fish studied (53 perches and 73 zanders) were collected in the summer 2013. Parasitological examinations included: skin, fins, gills, vitreous humour and lens of the eye, mouth cavity, body cavity and internal organs. Apart from the prevalence and intensity of infection (mean, range) the parasite communities of both fish species were compared. European perch and zander were infected with parasites from five different taxonomic units. The most numerous parasites were Diplostomum spp. in European perch and Bucephalus polymorphus in zander. The prevalence of infection of European perch ranged from 5.7% ( Diphyllobothrium latum ) to 22.3% ( Diplostomum spp.) and for zander from 1.4% ( Ancyrocephalus paradoxus , Hysterothylacium aduncum ) to 12.3% ( Bucephalus polymorphus ). Different composition of the parasitic fauna is likely due to the different biology of both fish species. Key words: parasites, Perca fluviatilis , Sander lucioperca , Pomeranian Bay, Poland Introduction brackish waters [3]. European perch is present in all types of lakes Pome ranian Bay is located in the south-western and brackish waters and belongs to the most Baltic Sea and belongs to the Oder estuary. The depth common fish species in Poland. Adult European does not exceed 20 m, the area covers almost 6000 perch dwells in the lakes in the sublittoral and km 2 [1]. The main tributaries on Polish side are Oder, littoral zones. Research on the biology of this Parsęta and Rega rivers, and Piana and Wkra on the species showed that European perch fry swims and German side. Pomeranian Bay is characterized by feeds in the summer months with the fry of zander, variable hydro-chemical conditions caused by the ruffe and cyprinids [3]. European perch is interaction of marine and inland waters. Mainly characterized by a large increase in the body length caught fish, important for the local economy, are cod, during the first year of life. At the SL (standard herring, sprat, flat fish, brown trout, eel, roach, length) of approx. 15 cm they undergo from bream, European perch and zander [2]. invertebrates to fish diet. European perch and zander (Percidae) are Parasitic fauna of European perch has been studied predatory fish that compete in the Szczecin Lagoon in Poland [e.g. 4–7] and in the world [e.g. 8–10], but with each other for food, and also migrate to feeding these fish from the Szczecin Lagoon and Pomeranian grounds of Pomeranian Bay. The diet of both Bay were investigated only by Pilecka-Rapacz [11] species consists of organisms inhabiting fresh and and Sobecka and Słomińska [12]. 86 I. Bielat et al. Zander inhabits the middle and lower course of The following scale was used to determine large rivers, oligotrophic lakes and brackish waters species dominance: of sea lagoons. It is a species of the pelagic zone. Di>10% – eudominants; 5.01%<D i<10% – do mi - Those living in rivers and lakes, classified as the nants; 2.01% <D i< 5% – subdominants; non-migratory fish. Zander of coastal marine waters 1.01% <D i< 2% – recedents; D i>1% – subrecedents migrate both for food and reproduction, therefore, The following indicators characterizing parasite they are considered the semi-migratory fish [13]. communities were calculated [21]: Parasitic fauna of zander in Poland has been 1. Berger-Parker dominance index: d=n max /N studied in lakes [14], in the Gulf of Gdansk [15] and where: n max – number of parasites of the most Szczecin Lagoon [11]. In Finland, the parasites of abundant species, N – total number of parasites in fry were examined, breed in reservoirs of various the sample natural food resources [16]; in Turkey parasitic 2. Shannon-Weaver species diversity index: Metazoa of adult zander from Lake S ığı rc ı was H΄=- ∑(p i×ln p i) studied [17]. where: p i – number of parasites of the particular The aim of the study was to compare parasitic species/total number of parasites in the sample fauna of European perch and zander from the 3. Margalef index, specifying the relative species Pomeranian Bay, obtained from the same fishing richness: M=S-1/lnN grounds, at the same time. where: S – number of species, N – total number of parasites in the sample Materials and Methods 4. Simpson index, which is a measure of species diversity in the community: D= ∑ni(n i-1)/N(N-1) The study material (126 fishes: 53 perches, 73 where: n i – total number of parasites of a particular zanders) was collected from the professional species, N – total number of parasites in the sample fishermen in the summer 2013, from the Pomeranian Two coefficients were also calculated to indicate Bay (53 °58 ’–53 °72 ’N; 14 °18 ’ –14 °23 ’E). Fish were the condition of the fish [22]: caught using a bottom trawl at a depth of about 10 1. Fulton coefficient according to the formula: m. The smallest European perches and zanders were K=100×M/L 3 a by-catch during fishing of other fish species. where: M – total weight of fish (g), L – total length Fish were placed in styrofoam containers filled of fish (cm) with ice and transported under such conditions to 2. Clark coefficient according to the formula: the laboratory. The average total length of European C=100 W/L 3 perch was 22.7 cm (10–34 cm), and zander 20.5 cm where: W – gutted fish weight (g), L – SL body (7–58 cm); mean body weight was 208.2 g (10–560 length (cm) g) and 374.2 g (3.2–1938 g), respectively. Age of fish was determined on the scale-reading and it Results amounted to an average of six years for European perch (2–12) and one year for zander (0–5). From the European perch examined, 165 Parasitological examinations included: skin, parasites were collected, belonging to 5 species of 3 fins, gills, vitreous humour and lens of the eye, higher taxa: Digenea, Cestoda and Acanthocephala. mouth cavity, body cavity and internal organs The largest group were the digenean larvae, (stomach, intestine, liver, gall bladder, heart, constituting a community of eye parasites (123 kidneys, gonads and swim bladder). Parasitic specimens), including: 109 Diplostomum spp. communities were determined based on the location metacercariae (in the eye lens) and 14 Tylodelphys of the parasite in the fish, parasites were also clavata metacercariae (Nordmann, 1832) (in the divided into allogeneic and autogenous species. vitreous humour). The second group was the The prevalence, mean intensity, and the range of parasites community of the gastrointestinal tract, intensity of infection were calculated according to consisting of three species of helminths. Acantho - Pojmańska [18] and Bush et al. [19]. cephalans Echinorhynhus gadi (Müller, 1776), (22 Dominance index was calculated according to the specimens) was observed in the midgut (18 following formula [20]: Di=n i×100/N [%] helminths) and hindgut (4 specimens). Among the where: n i – total number of parasites of a particular cestodes (20 parasites), 17 encysted Triaenophorus species, N – total number of all parasites nodulosus (Pallas, 1781) was found in the liver and Species richness and diversity 87 Table 1. Infection parameters of Perca fluviatilis and Sander lucioperca from Pomeranian Bay Prevalence Intensity Number of Host Parasites [%] mean range SD parasites Diplostomum spp. (met.) 22.6 9.1 0-71 9.9 109 Tylodelphys clavata 11.3 2.3 0-5 0.9 14 Perca fluviatilis Triaenophorus nodulosus 15.1 1.3 0-6 1.0 17 p. – 51.0 Diphyllobothrium latum 5.7 1.0 0-1 0.2 3 Echinorhynhus gadi 7.5 6.0 0-14 2.0 22 Ancyrocephalus paradoxus 1.4 5.0 0-3 0.6 5 Sander Bucephalus polymorphus 12.3 19.5 0-30 3.6 67 lucioperca Bunodera luciopercae 2.7 7.4 0-25 3.5 39 p. – 20.5 Hysterothylacium aduncum 1.4 1.0 0-1 0.1 1 Achtheres percarum 2.7 1.0 0-1 0.2 2 Abbreviations: SD – standard deviation; met. – metacercariae; p. – prevalence of all parasite species (%) 3 larvae of Diphyllobothrium latum (Linnaeus, complex of the genus Diplostomum , and the lowest 1758) in stomach. In total, 51% of the fish was for D. latum (Table 2). The most common class of infected. domination was eudominants (Table 2). Diplostomum spp. occurred with the highest In the zanders studied, 114 parasites representing prevalence, while D. latum with the lowest (Table 5 species, including two belonging to Digenea (106 1). Diplostomum spp. also occurred with the highest specimens), one to Monogenea (5 specimens), one intensity and mean intensity of infection. The lowest to Nematoda (4 specimens) and one belonging to values of the above parameters was observed in the Crustacea (2 specimens) were detected.