Long-term changes in the fish community structure revealed by gillnet monitoring in a shallow, lowland reservoir

Abstract

Kaczkowski Z., Frankiewicz P. 2017. Long-term changes in the fish community structure revealed by gillnet monitoring in a shallow, lowland reservoir. Acta Ichthyol. Piscat. 47 (3): 279-288.Background. Fish communities can support or hinder water quality management. Sulejów Reservoir, which is situated on the Pilica River in Central Poland, serves as a strategic reserve of drinking water for the Łódź Agglomeration. Precise knowledge of the long-term dynamics of the structure of the fish community, what was the aim of this study, is important for proper management to slow the eutrophication of the reservoir and prevent toxic algal blooms. Materials and methods.To determine fish species composition, multimesh gill nets with mesh sizes ranging from 11 to 80 mm were used. From 1993 to 2015, gillnetting was conducted 1-2 times per month from June through November in two representative parts of the reservoir, and principal component analysis (PCA) was applied to explore the temporal variation in fish community structure expressed as the relative contribution of each species to the total fish biomass.Results. Dominance fluctuated among four species in the fish community: common bream, Abramis brama (Linnaeus, 1758); roach, Rutilus rutilus (Linnaeus, 1758); white bream, Blicca bjoerkna (Linnaeus, 1758); and pike-perch, Sander lucioperca (Linnaeus, 1758). PCA revealed three principal components with eigenvalues larger than one that explained 73.3% of the observed variance in the temporal changes in fish community composition. A negative correlation was found between pike-perch biomass and roach biomass (r = 0.82), while a positive correlation was observed between the biomass of pike-perch and that of common bream (r = 0.73). Consequently, there was a highly negative correlation between the biomasses of common bream and roach (r = 0.80). Furthermore, an interesting temporal pattern was observed; from 1993 to 2000, the fish community was dominated by common bream and pike-perch but then shifted towards domination by roach and white bream, despite declining phosphorous and carbon concentrations. Recently, this trend has been reversed, and a more balanced fish community structure has been established. Conclusion. Fish community succession, which is usually reported to be a one-directional process in reservoirs, i.e., from a riverine fish or percid-dominated to a cyprinid (bream)-dominated state, was more ambiguous in Sulejów Reservoir. This was likely a consequence of both restoration issues related to decreasing nutrient loads and the influence of zebra mussel, Dreissena polymorpha invasion on the trophic relations in the reservoir.

Relationship between fish assemblage and angler catch in the Sulejów Reservoir, central Poland, in the context of a warming climate

“…The development of fish fauna in large, shallow reservoirs (Epler, Kuboszek, Łuszczek‐Trojnar, Socha & Drąg‐Kozak, ; Kaczkowski & Frankiewicz, ) seems to differ in many aspects from the results obtained for large, deep and stratified reservoirs, which is based on a majority of available reservoir studies (Benndorf, ; Říha et al., ; Scharf, ). The fish community in Sulejów Reservoir, similar to the majority of fish communities surveyed in reservoirs in Poland (Andrzejewski & Mastyński, ; Epler et al., ; Wiśniewolski, ; Wiśniewolski et al., ), matches the most common cyprinid‐dominated faunal type, with common bream as the primary dominant species and roach and white bream as subdominants (Kubečka, ).…”

“…These species included three cyprinid species, common bream, roach, and white bream Blicca bjoerkna (L.), and a piscivorous percid species, pikeperch. Other fish species important to recreational fisheries that were regularly found in gillnet catches included perch, ide Leuciscus idus (L.), asp Leuciscus aspius (L.), northern pike Esox lucius L. and wels catfish Silurus glanis L. A detailed analysis of the fish community composition and fluctuation in the Sulejów Reservoir over a 20‐year period (1993–2015) was described by Kaczkowski and Frankiewicz ().…”

“…Environmental and biological conditions were described in detail in Gągała et al. (), Wojtal‐Frankiewicz, Kruk, Frankiewicz, Oleksińska and Izydorczyk () and Kaczkowski and Frankiewicz ().…”

“…Due to the high densities of large cyprinids, non‐standardised, benthic multi‐mesh gillnets with mesh sizes from 11 to 80 mm were used to determine fish species composition (Kaczkowski & Frankiewicz, ; Šmejkal et al., ). Identical nets (used in Sulejów Reservoir since 1990s), each 77 m long and 3 m high and consisting of 11 different 7‐m‐long panels (mesh panel sizes from knot to knot in the following order: 11, 24, 50, 60, 30, 70, 35, 80, 40, 20 and 16 mm), were used.…”

“…Identical nets (used in Sulejów Reservoir since 1990s), each 77 m long and 3 m high and consisting of 11 different 7‐m‐long panels (mesh panel sizes from knot to knot in the following order: 11, 24, 50, 60, 30, 70, 35, 80, 40, 20 and 16 mm), were used. The height of the nets allowed sampling of almost the entire water column (Kaczkowski & Frankiewicz, ). Fish aged 1 year and older were considered in this study.…”