Fish assemblage changes relative to environmental factors and time in the Warta River, Poland, and its oxbow lakes

Abstract

Four oxbow lakes and two neighbouring sections of their parent Warta River (Odra River system, Poland) were sampled to investigate differences in fish assemblages between habitats in 1999-2000. Additional comparisons were made with 12 other oxbow lakes in this section of the river that were sampled 30-40 years ago. Downstream of a man-made reservoir, higher species number, diversity and evenness were recorded in oxbow lakes than in the river channel. Upstream of the reservoir, differences in these variables from both habitats were insignificant. Fluvial and stagnant water samples were clearly separated in the multivariate space of a detrended correspondence analysis (DCA). For two oxbow lakes and two neighbouring sections of the Warta River, 12 abiotic and biotic environmental variables were available, and only velocity, water temperature and conductivity were significantly correlated with canonical correspondence analysis (CCA) axes. Fish assemblages of four recently investigated oxbow lakes were clearly separated in the multivariate space of DCA from other neighbouring oxbows sampled 30-40 years ago. Species previously subdominant were becoming rare. Oxbow lakes that are continuously or at least periodically connected with the channel are indispensable for maintaining high biodiversity and a sustainable fishery in the river system. # 2004 The Fisheries Society of the British Isles

Restoration of a river backwater and its influence on fish assemblage

“…On the other hand, pike was always abundant in the backwater, which is not always typical (Hohausová and Jurajda, 1996;Penczak et al, 2004) of similar locations. For this phytophilic species preferring lentic and vegetated habitats (Balon, 1975) limited in this reach of the Morava River, sites such as Kurfürst backwaters are important locations.…”

Long-term changes in fish assemblages of the Widawka and Grabia Rivers (Poland): pattern recognition with a Kohonen artificial neural network

“…However, the present low dominance of those species recorded in the Widawka and Grabia is one of the highest in the system of the Warta River and may be compared only with the ichthyofauna of the upper Warta , Kruk 2007) and the systems of certain tributaries of the Noteć River (Fig. 1) (Koszaliński et al 1989, Chełkowski et al 1996, Penczak et al 1998b, A. KRUK (12) Table 4. Dominance [%] of the 31 studied fish species within SOM output subclusters and neurons.…”

“…3, Tables 3, 4). Perch and roach are two first dominants not only in the Widawka and Grabia, but also in other human-impacted parts of the Warta River system (Penczak et al 1999, Kruk 2007) and of other lowland systems in Poland ).…”

“…The NPR are most vulnerable to worsened water quality, simplified channel structure and disrupted connectivity of riverine habitats, and this is why their declines and/or extinction are typical for unbalanced lotic ecosystems (Przybylski 1993, Kirchhofer & Hefti 1996, Oberdorff et al 2001, Kruk & Penczak 2003, Kruk 2004, 2006, 2007. Psammophils (stone loach and gudgeon) often predominate in degraded smaller streams (Bahlo 1991, Witkowski et al 1991, 1992, 2005, while a high dominance of roach and perch is typical for disturbed larger rivers (Przybylski 1993, Penczak et al 1999, Kruk 2006, 2007. Sample symbols contain the first two letters of the river's name, followed by the number of the sampling site (the same as in Fig.…”

Early development and allometric growth patterns of rheophilic cyprinid common dace Leuciscus leuciscus (Cyprinidae: Leuciscinae)

“…In recent years, several populations of this species have declined or disappeared. The main causes of this situation are pollution of the aquatic environment, regulation of river flow and excessive fishing (Penczak et al 2004). Common dace spawns relatively earlier than other cyprinids.…”