An individual-based model to predict the spatial distribution of northern pike, European perch and pikeperch from habitat use in a reservoir subject to water level fluctuations

The aim of this study was to examine how the presence of a predator and an interspecific competitor influence the habitat use of adult perch (Perca fluviatilis; size: 15.1 ± 0.5 cm) when given the choice between two adjacent habitats. By conducting aquarium experiments, the habitat occupancy of P. fluviatilis was documented in the presence and absence of a predator (pike Esox lucius; size: 25.4 ± 2.1 cm) and a potential competitor (ruffe Gymnocephalus cernuus; size: 14.1 ± 0.3 cm) fish species. Two P. fluviatilis individuals generally shared the same habitat. In the presence of a conspecific, P. fluviatilis favoured the structurally more-complex, artificial macrophyte habitat over the less-structured rock and sand habitat, which in turn were used equally. In the predator- and competitor treatments, P. fluviatilis seemed to adapt their habitat use to the habitat occupancy of E. lucius and G. cernuus in the Macrophyte vs. Rock and, in the predator treatment, also in the Macrophyte vs. Sand habitat combination, by increasingly occupying a habitat that was used less by the predator or competitor species, respectively. This behaviour suggests that P. fluviatilis tried to avoid the other fish species by choosing a, in some cases less preferred, predator- or competitor-free habitat. This study emphasizes the importance of biological interactions illustrated by the potential of predation risk and competition to structure fish communities by influencing habitat use at small spatial scales.

We investigated experimentally how presence or absence of different piscivores influenced habitat use, diet, and individual growth of two size classes of juvenile perch (Perca fluviatilis) and abundances of juvenile perch resources in different habitats. Pond enclosures encompassed 3 x 6 m of dense vegetation and 9 x 6 m of open habitat, and were stocked with 75 young—of—year and 30 1—yr—old perch and with either three piscivorous perch, three northern pike (Esox lucius), or no piscivores. Northern Pike were both larger and possessed a larger gape than piscivorous perch. To isolate behavioral responses of juvenile perch to piscivores, we replaced consumed young—of—year perch. Prey fish mortality was lowest without piscivores and highest with northern pike. Young—of—year perch increased their use of vegetation in the presence of both piscivores, whereas 1—yr—old perch increased their use of vegetation only with northern pike. For both age classes of prey fish, increased use of the vegetation led to reduced individual growth, owing to two complementary mechanisms. First, the physical complexity of submerged macrophytes likely interfered with the benthic feeding of perch. Second, increased use of the (relatively small) vegetated habitat increased the mean density experienced by prey fish. Piscivore—induced changes of prey fish densities in the two habitats had substantial effects on the biomass of prey fish resources in the open habitat, but only minor effects in the vegetation. Sialis lutaria, the major predatory macroinvertebrate (°50% of total macroinvertebrate biomass in the open habitat), and total predatory macroinvertebrates were positively affected by piscivores in the open habitat, but not in the vegetation. Chironomids (<3% of total macroinvertebrate biomass in the vegetation) and the sizes of nonpredatory macroinvertebrates were negatively affected by piscivores in the vegetation, but not in the open habitat. Biomass of nonpredatory macroinvertebrates, Cladocera, and Copepoda did not differ among treatments in either habitat. From our review of field experiments, vulnerable prey fish always change their habitat use in the presence of piscivores. Behaviorally mediated indirect effects of piscivores on individual growth rates and prey fish resources were just as frequently observed as direct effects of piscivores on prey fish survival.

The habitat quality of the littoral zone is of key importance for almost all lentic fish species. In anthropogenically created gravel pit lakes, the littoral zone is often structurally homogenized with limited fish habitats. We supplemented deadwood brush piles in the littoral zone of eight gravel pit lakes and investigated the diurnal and seasonal use of this and other typical microhabitats by six dominant fish species. Shoreline habitats were sampled using point abundance electrofishing during day and night in all four seasons, and patterns of fish abundance were compared amongst unstructured littoral habitats, emerged macrophytes and brush piles. We caught a total of 14,458 specimens from 15 species in the gravel pit lakes. Complex shoreline structures were used by all fish species that we examined, especially during daytime, whilst the use of unstructured habitats was highest during night. The newly added brush piles constituted suitable microhabitats for selected fish species, perch (Perca fluviatilis), roach (Rutilus rutilus) and pike (Esox lucius), particularly during winter. Supplemented deadwood provides suitable fish habitat in gravel pit lakes and may to some degree compensate for the loss of submerged macrophytes in winter by offering refuge and foraging habitat for selected fish species.

Element concentrations in selected fish species from different trophic levels were analyzed. The following fish species were analyzed: common nase (Chondrostoma nasus), roach (Rutilus rutilus), freshwater bream (Abramis brama), barbel (Barbus barbus), Prussian carp (Carassius gibelio),chub (Squalius cephalus), European perch (Perca fluviatilis), wels catfish (Silurus glanis)and northern pike (Esox lucius). Fish were collected from the Medjuvrsje Reservoir (West Morava River Basin, western Serbia) during 2012, and samples of liver, muscle and gills were analyzed for As, B, Ba, Cd, Co, Cr, Cu, Fe, Hg, Li, Mn, Mo, Ni, Pb, Sr, and Zn using inductively coupled plasma optical emission spectrometry (ICP-OES). The liver and gills had the highest measured element concentrations, with Cu, Zn, Fe and Sr being the most prominent. The bioaccumulation of metals was species-specific, with the accumulation exhibiting the following trends: Prussian carp > northern pike > freshwater bream > European perch > chub > common nase > barbell > roach > wels catfish; Li>Pb>Zn>Cu>Fe>Ba>Mn>Sr>Cr>As>Mo>Ni>B, in all examined species; for Co, Cd and Hg, the bioaccumulation factor (BAF) was 0. Results of this study point to the tissue-specific differences in element concentrations, and to distinct differences between fish species regarding the accumulation patterns: common nase, with the highest accumulation observed in the liver, and Prussian carp, with the highest accumulation observed in the gills.

Perch Perca fluviatilis is a widespread predator in European reservoirs, frequent in open waters but also known to spend a lot of time in the littoral zones. To get insight into how adult perch used and selected their habitat in an environment subject to water-level (WL) fluctuations, 21 perch were continuously tracked using acoustic telemetry over 2 years in the Bariousses Reservoir (France). The different available habitats were characterized by depth classes and substrate types, presence of emerging trees and presence of tree stumps in the littoral zone. We showed that perch habitat preferences were strongly dependent on the season, except for substrate type, and in line with their habitat use. Surprisingly we did not find any influence of the WL which, however, reduced the structural complexity of the littoral zone when lowering. In spring and summer, whatever the WL, we observed a strong preference for the littoral zone and complex habitats. In autumn and winter, perch migrated into deeper waters. However, the individual variability of the habitat preferences was quite high. This type of research helps to understand the spatial ecology of fish and provides useful guidance to hydromorphological restoration for fish populations.

Jůza T, Blabolil P, Čech M, Draštík V, Kubečka J, Muškaa M, Prchalováa M, Sajdlováa Z, Tušera M, Vašeka M, Vejříka L, Peterkaa J. 2024. Fish predation on newly stocked juvenile predatory fish in a biomanipulated reservoir. Lake Reserv Manag. 40:325–337. Juveniles of pikeperch, asp, and northern pike were stocked into the Římov Reservoir. Subsequently, potential fish predators were monitored by gillnets at the stocking sites and their diet was analyzed for presence of stocked fish. Asp and European perch were predominant predators, while pikeperch and northern pike were less abundant in gillnet catches. Digestive tract analysis revealed the highest percentage of ingested fish in northern pike, followed by pikeperch, asp, and European perch. The amount of stocked fish did not correlate with the number of predatory fish caught in gillnets. When asp was stocked, this species was strongly preferred by northern pike and partly by pikeperch and 0.3 individual of stocked asp was eaten per 1 kg of predatory fish captured by gillnets. During the northern pike stocking, this species was mainly preyed upon by asp and occasionally by northern pike, and 0.8 individual of stocked northern pike was eaten per 1 kg of predatory fish. When pikeperch was stocked, it was strongly preferred by pikeperch, northern pike, and European perch, it was almost absent in the diet of asp, and 1.1 individual of stocked pikeperch was eaten per 1 kg of predators. Our results indicate that pikeperch juveniles had the highest mortality rate due to predation after stocking, mainly due to sedentary behavior and the high proportion of cannibalism. In northern pike, cannibalism was found in only one case, and was never found in asp, which was under the lowest predation pressure.

Habitat use and preference of adult pike (Esox lucius L.) in an anthropogenically impacted lowland river

Thepaper is presenting some aspects regarding the influence of environmentalfactors on fish communities structure from Danube, between Siret River and PrutRiver mouth. Fish were collected from March to December 2010 in four fishingareas. During the year, 12064.23 kg, respectively 14692 fish of 29 species werecollected. Cyprinidae, the dominant family, 55.17% in term of number of species, was represented by 16 species (Cyprinus carpio, Carassius gibelio, Barbusbarbus, Abramis brama, Abramis sapa, Blicca bjoerkna, Leuciscus idus, Vimba vimba, Aspius aspius, Pelecus cultratus,Chondrostoma nasus, Ctenopharingodon idella, Hypophthalmichthys molitrix,Hypophthalmichthys nobilis, Scardinius erythrophthalmus, Rutilus rutilus).Other families had the following structure: Percidae (17.24%) with 5 species (Sanderlucioperca, Zingel zingel, Zingel streber, Perca fluviatilis, Gymnocephalusschraetzer), Acipenseridae (13.79%) with 4 species (Huso huso,Acipenser stellatus, Acipenser ruthenus, Acipenser gueldenstaedtii), Clupeidae (6.90%) with two species (Alosa immaculata, Alosa tanaica), Siluridae (3.45%) with one species (Silurus glanis) and Esocidae (3.45%) with one species (Esox lucius). The highest capture was 8217.62 kg (68.12%), duringthe spring season (March-May), followed by autumn season (September–November), with 1437.56 kg (11.92%). The water level and water flow showed highcorrelation with both number and total catch, respectively.

Brent geese Branta bernicla spring fattening around Agerø, Denmark, alternate between feeding on saltmarshes and submerged Zostera beds in Limfjorden. It appeared from field observations that these alternations depended on the water level in Limfjorden. A model was developed to assess the impact of water level fluctuations on the habitat use. A second model was developed to estimate the impact of water level on Zostera availability. The first model was successful in demonstrating that fluctuations in water levels had considerable influence on habitat use by the brent geese, i.e. they fed on Zostera at low water levels and on saltmarshes during high water levels, particularly so in early spring, and that the switch between habitats occurred within a narrow water level span of ca 30 cm. The second model demonstrated that the switch between habitats could be explained by lowered availability of Zostera as water levels increased. By combining the output from the two models, differences between years could partly be explained by differences in Zostera availability in the early spring period (21 March ‐ 25 April), whereas a more complicated situation was detected later in spring (26 April ‐ 31 May). The models presented may be considered as tools in investigations of habitat use and carrying capacity of seagrass beds in non‐tidal areas, where birds' access to feeding areas regularly may be hindered by high water levels.

Seasonal variations of mercury (Hg) concentration in muscle tissue of northern pike - Esox lucius L, European whitefish - Coregonus lavaretus L and European perch - Perca fluviatilis L have been investigated in Lake Heddalsvatn, southern Norway. Our data confirmed seasonal differences in the Hg concentrations in fish, but the causes for that may vary depending on fish species. Length (pike and perch) and age (perch and whitefish) were the strongest explanatory factors for the Hg fluctuations. Fish caught in December (pike and whitefish) had the highest Hg concentrations, while the concentrations in May were higher than in September for all 3 species, statistically significant for perch (P<0.0001) and close to significant for pike (P=0.07). Higher δ 15 N signatures were found in December and May compared with September, but these differences might be related to fish body size variations. There was a large range of δ 13 C signatures in the investigated fish, but no significant differences between seasons neither within nor between species.

Metals (Mn, Fe, Cu, Zn, Cd, Co, Hg, Pb) contents in organs (muscle, liver, gills) of fishes (Acipenser ruthenus, Esox lucius, Abramis brama, Leuciscus idus, Perca fluviatilis and Sander lucioperca) of the middle Ob river by the method of atomic absorbtion was studied. For the investigation fish were caught in June of the year 2018 in 15 km higher village Novonikolskoe. Chemical analysis of the samples was carried out in the laboratory of isotope-geochemical analysis of the Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences with using plasma and connection of atomization. It was releaved complicated character of distribution of metals in fish organs, as in samples of each species, as in the same organs of various fish species. Effect of Hg magnification in muscles was detected in some variants of comparison and not detected in other. Content Hg in fish muscle no exceed standards for fresh fish products in Russia.

Baikal has passed through different climatic epochs in its evolution. This is reflected in the structure of its ichthyofauna, which includes species of different faunistic complexes. Of significant interest is the comparison of ichthyofaunas in the northern rivers and especially between the Angara River and Lake Baikal, which have been connected for a long time. Studies of fish bone remains from the archeological sites with Mesolithic layers (6–8 Ky) at the upper parts of the Angara River (the Belaya River, Verholenskaya Mountain) has been carried out in most detail by Tzepkin (1976), based on large specimens of: Acipeser baeri, Hucho taimen, Esox lucius, Lota lota, and also Perca fluviatilis and Cyprinidae. At lower parts of the river (Pashino Settlement) Aciperser ruthenus and Stenodus leucichthys nelma were also studied. Coregonus lavaretus are observed in the upper reaches of the river, but Tzepkin’s review (1995) does not include them, or Thymallus arcticus, among the ancient commercial ichthyofauna of the Angara River. In 1996, N.A. Savel’ev and E.S. Igumnova found a great deal of archeological material (Savel’ev et al., 2001) at Ust’-Haita site (high flood-lands on the right bank of the Haita River, a tributary of the Belaya River) near Mishelevka Settlement. Scales of one fish species predominated in fish remains in layers 5a and 6; in layers 7 and 8 skeleton fragments were chiefly of large fish heads. The material included fragments of Cyprinidae skeletons and perch, Perca fluviatilis only rarely. In total, ten fish species and a Cyprinidae group were identified, among which Thymallus arcticus, Coregonus lavaretus, Esox lucius, Lota lota and Hucho taimen predominated. Good preservation of the material allowed the authors to define fish age and their catching terms. Quantitative ratios of scales to skeletons (more than 95%) at the archeological sites on the Belaya River, as well as in all archeological sites on territory of the former USSR, were demonstrated for the first time.

The morphometric characteristics of the most common commercial fish were studied: carp – Cyprinus carpio L., pike – Esox lucius L., crucian carp– Carassius auratus gibelio Bloch. and perch – Perca fluviatilis L., two years old, with an average mass of 290–330 g., 300–350 g., 150–230 g. and 170–230 g. respectively, caught from the small rivers of the Western Podillia (Strypa, Seret, Zolota Lypa). It was found, that the indicators of full length, standard length, head length, head height at the back of the head, the largest and smallest body height in carp, crucian carp and perch decreased linearly in a number of rivers Strypa – Seret – Zolota Lypa. It is noted, that the values of the liver index in the investigated fish species differ significantly from the representatives of the rivers Seret and Zolota Lypa compared to the species from the Strip River. This indicator increases in the Strypa – Seret – Zolota Lypa range, except for the pike index, which is of the lowest importance in the representatives of the Seret River. All the fish species studied saw an increase in the gills index in a number of Strypa – Seret – Zolota Lypa rivers.&#x0D; The study demonstrated that the values of the Fulton and Clark fattening coefficients in carp, crucian carp and perch decreased in a number of Strypa – Seret – Zolota Lypa rivers. In pike the highest values of fattening coefficients were noted for fish from the river Seret. Considering the same age of the fish and relatively the same trophic conditions in the studied rivers, it can be assumed, that the differences in morphometric indices are due to different anthropogenic influence on the watercourses. In this case, the least favorable environmental conditions are in the Zolota Lypa river, which is obviously due to its complex pollution.

The aim of this study is to summarise the determination of concentrations of microcystins (MCs) in muscle and liver of freshwater fish species caught in stagnant waters of the Czech Republic. Within the years 2007-2009, 351 muscle samples and 291 liver samples of 16 freshwater fish species derived from four fishponds, and four water reservoirs were analysed. MCs were detected in 53 liver samples. The highest concentrations of microcystins were determined in liver samples of carnivorous fish species; 50.3 ng/g of fresh weight (FW) in perch (Perca fluviatilis) and 22.7 ng/g FW in pikeperch (Sander lucioperca). MCs in liver were detected in other five fish species; asp (Aspius aspius), pike (Esox lucius), common carp (Cyprinus carpio), grass carp (Ctenopharyngodon idella) and European eel (Anguilla anguilla). Concentrations of MCs in liver of nine fish species (European bream, whitefish, tench, silver carp, European catfish, roach, chub, crucian carp and rudd) were below the detection limit of 1.2-5.4 ng/g FW for different MC congeners. However, the concentrations of MCs in all muscle samples were below the detection limit. The assessment of MCs concentrations might be influenced by the detection method used. Due to the concentrations of MCs being below the detection limit in muscle samples of all fish species analysed, it seems that there might be a low potential threat for human health in case of fish muscle consumption.

Water level (WL) fluctuations substantially alter the fauna, flora, and microbial community of nearshore aquatic ecosystems. Water level management therefore has the potential to strongly influence a wide variety of ecosystem processes. Many northern temperate lake food webs experience substantial methylmercury contamination, which is partially mediated by the action of sulfate‐reducing bacteria occurring in sediments that are periodically inundated. For lakes with elevated methylmercury, WL management could be designed to reduce methylmercury contamination. At the lake scale, this concept is supported by studies that identified statistical associations between fish mercury content and water level (WL) fluctuations. Here, we compiled a long‐term dataset (1997–2015) of mercury content in young‐of‐year Yellow Perch (Perca flavescens) from six lakes on the border of the United States and Canada and examined whether mercury content was associated with WL fluctuation. Many WL metrics covary and appear to have strong associations with Yellow Perch mercury. However, these associations appear to vary by lake, and lake‐specific models are needed to identify relationships between WL fluctuation and Yellow Perch mercury content. We used partial least‐squares regression (PLSR) to identify the associations between Yellow Perch mercury content and WL metrics, temperature, and annual deposition data for lakes in northern Minnesota. These PLSR models not only showed some variation among lakes, but also supported strong associations between WL fluctuations and annual variation in Yellow Perch mercury content. The study lakes underwent a change in WL management in 2000, when winter WL minimums were increased by about 1 m in five of the six study lakes, which reduced annual WL fluctuation on those lakes. Using the PLSR models, we estimated how this change in WL management would have affected Yellow Perch mercury content. In four of the five study lakes in which annual WL fluctuation was reduced in 2000, the change in WL management likely reduced Yellow Perch mercury content, relative to the previous WL management regime.