Effect of boat noise and angling on lake fish behaviour

The effects of disturbances from recreational activities on the swimming speed and habitat use of roach Rutilus rutilus, perch Perca fluviatilis and pike Esox lucius were explored. Disturbances were applied for 4 h as (1) boating in short intervals with a small outboard internal combustion engine or (2) boating in short intervals combined with angling with artificial lures between engine runs. The response of the fish species was evaluated by high‐resolution tracking using an automatic acoustic telemetry system and transmitters with sub‐minute burst rates. Rutilus rutilus swimming speed was significantly higher during disturbances [both (1) and (2)] with an immediate reaction shortly after the engine started. Perca fluviatilis displayed increased swimming activity during the first hour of disturbance but not during the following hours. Swimming activity of E. lucius was not significantly different between disturbance periods and the same periods on days without disturbance (control). Rutilus rutilus increased their use of the central part of the lake during disturbances, whereas no habitat change was observed in P. fluviatilis and E. lucius. No difference in fish response was detected between the two types of disturbances (boating with and without angling), indicating that boating was the primary source of disturbance. This study highlights species‐specific responses to recreational boating and may have implications for management of human recreational activities in lakes.     

Environmental factors regulate the effects of roach Rutilus rutilus and pike Esox lucius on perch Perca fluviatilis populations in small boreal forest lakes

In this study of 18 small boreal forest lakes, the effects of abiotic and biotic factors (roach Rutilus rutilus and pike Esox lucius) on various population variables of perch Perca fluviatilis were examined. As a single variable, the gillnet catch per unit effort (CPUE) of R. rutilus was negatively related to the mean mass of small (< 200 mm) and the growth rate of young (1–2 years) P. fluviatilis. The mean mass of large (≥ 200 mm) P. fluviatilis was the highest at intermediate CPUE of R. rutilus. Redundancy analysis including environmental factors and P. fluviatilis population variables suggested that ‘predation–productivity–humus' gradient affected P. fluviatilis populations by decreasing the CPUE and mean mass of small individuals but increasing these variables of large individuals. The CPUE of R. rutilus and lake area had a negative effect on small and a positive effect on large P. fluviatilis growth rate. In small boreal forest lakes, P. fluviatilis populations are affected by the partially opposite forces of competition by R. rutilus and predation by E. lucius, and the intensity of these interactions is regulated by several environmental factors.     

Feeding efficiency of planktivores under disturbance,the effect of water colour,predation threat and shoal composition

The consumption of phantom midge Chaoborus flavicans larvae by Perca fluviatilis showed clear response to water colour, predation threat and shoal composition with the most significant negative effect for water colour. In the case of Rutilus rutilus, no similar combined response was observed and the total prey consumption was significantly negatively affected by predation threat of Esox lucius. The results suggest that differences in life‐history traits may result in disparity in species‐specific responses to disturbance.     

A field evaluation of long-term effects of PIT tagging

Passive integrated transponder (PIT)-tagging is commonly used in behavioural studies of fish, although long-term evaluations of effects from tagging under natural conditions are scarce. We PIT-tagged common bream Abramis brama, European perch Perca fluviatilis, pike Esox lucius and roach Rutilus rutilus, released them in their lakes of origin and recaptured them after 103–3269 days. Overall, tagged fish did not differ in condition from non-tagged fish, except for small R. rutilus that had a lower length-specific body mass in one lake in 1 year. We conclude that PIT-tagging in general has negligible long-term effects on fish condition.     

Species-specific responses of planktivorous fish to the introduction of a new piscivore: implications for prey fitness

1. Antipredator behaviour by the facultative planktivorous fish species roach (Rutilus rutilus), perch (Perca fluviatilis) and rudd (Scardinius erythrophthalmus) was studied in a multi‐year whole‐lake experiment to evaluate species‐specific behavioural and numerical responses to the stocking of pikeperch (Sander lucioperca), a predator with different foraging behaviour than the resident predators large perch (P. fluviatilis) and pike (Esox lucius). 2. Behavioural responses to pikeperch varied greatly during the night, ranging from reduced activity (roach and small perch) and a shift in habitat (roach), to no change in the habitat use and activity of rudd. The differing responses of the different planktivorous prey species highlight the potential variation in behavioural response to predation risk from species of similar vulnerability. 3. These differences had profound effects on fitness; the density of species that exhibited an antipredator response declined only slightly (roach) or even increased (small perch), whereas the density of the species that did not exhibit an antipredator response (rudd) decreased dramatically (by more than 80%). 4. The maladaptive behaviour of rudd can be explained by a ‘behavioural syndrome’, i.e. the interdependence of behaviours expressed in different contexts (feeding activity, antipredator) across different situations (different densities of predators). 5. Our study extends previous studies, that have typically been limited to more controlled situations, by illustrating the variability in intensity of phenotypic responses to predators, and the consequences for population density, in a large whole‐lake setting.     

Influence of roundup herbicide on the activities of peptidases in the intestines of various fish species

It has been revealed that, as a rule, Roundup herbicide inhibits activities of peptidases in the intestine mucosa and chyme in various fish species, both benthivorous (common carp Cyprinus carpio, silver bream Blicca bjoerkna, roach Rutilus rutilus, and crucian carp Carassius carassius) and piscivorous (perch Perca fluviatilis, pike Esox lucius, and sander Sander lucioperca). The tolerance of peptidases to the herbicide is species-specific. The magnitude and vector of the effects of Roundup depend on its concentration and localization of an enzyme. In the mucosa, the enzymes of common carp and pike are most tolerant, while the enzymes of common carp, silver bream, and pike are most tolerant in the chyme.     

Dynamics and the state of fishery resources in the Rybinsk Reservoir from 1950–2010

Data on dynamics of the main commercial fish populations in the Rybinsk Reservoir over the period of 1950–2010 have been generalized. Fishing intensity is the main factor that determines the state of fish resources. It affects not only the abundance of commercial fish but also determines changes in population characteristics, i.e., changes in age and size structure and increase in the portion of young individuals. The effect of fishing on populations of some species depends on their commercial value. Commercial fishing affects notably such species as bream Abramis brama, zander Sander lucioperca, and pike Esox lucius. Commercial fishing affects, to a lesser extent, populational characteristics of such mass fish species as roach Rutilus rutilus and blue bream Abramis ballerus whose commercial value is lower.     

Effect of temperature on proteinase activites of enteral microbiota and intestinal mucosa of fish of different ecological groups

Effect of temperature on proteinases activities of enteral microbiota and of intestinal mucosa was studied in five fish species (roach Rutilus rutilus, crucian carp Carassius carassius, common perch Perca fluviatilis, pike-perch Zander lucioperca, and pike Esox lucius) belonging by the nutrition type to different ecological groups. Essential differences of temperature characteristics of proteinases of intestinal mucosa and of enteral microbiota are revealed in fish belonging to different ecological groups. The character of the t-function of proteinases of intestinal mucosa and enteral microbiota for casein and hemoglobin as a rule is different. The values of the apparent E _act proteinases of intestinal mucosa for casein in most cases are higher than those of enteral microbiota, while those for hemoglobin, on the contrary, are lower. The lowest values of relative proteinase activities for casein in the zone of low temperatures (38 and 45.3% of the maximal activity) and the E_act value (less than 2.0 kcal/mol) are found at study of proteinases of enteral microbiota in common perch and crucian carp. The latter indicates a significant adaptability of the enteral microbiota proteinases of common perch and crucian carp to functioning at low temperatures.     

Diet shifts and food selection of perch Perca fluviatilis and roach Rutilus rutilus in humic lakes of varying water colour

The field data from four humic lakes suggested that water colour may have both direct and indirect effects on inter‐ and intra‐specific interactions of perch Perca fluviatilis and roach Rutilus rutilus. The results agree with suggestions that, compared with R. rutilus, P. fluviatilis may be an inferior forager on zooplankton in highly coloured water. As an indirect effect, water colour decreases the coverage of macrophytes and limits suitable littoral habitats, benefiting R. rutilus over P. fluviatilis. Perca fluviatilis benefiting from complex habitats does not have the advantage in macrophyte‐poor highly coloured water.     

Fish–duck interactions in boreal lakes in Finland as reflected by abundance correlations

We studied the hypothesis that fish play an important role in lake use by ducks (pairs and broods) in boreal lakes. The study was based on densities of different duck and fish species in 28 boreal lakes in southern Finland. We focused on the three most common duck species (mallard Anas platyrhynchos, green-winged teal A. crecca and common goldeneye Bucephala clangula) and on the three most common fish species (perch Perca fluviatilis, roach Rutilus rutilus and pike Esox lucius) in the region. We considered both competitive and predatory interactions between ducks and fish, the perch and roach being potential competitors with ducks and the pike a potential predator of ducks. We found a negative association between green-winged teal brood density and total fish density, the other duck species having only a weak association with total fish density. When the three fish species were considered separately, a negative association, suggesting food competition, was found between perch, green-winged teal and goldeneye, whereas the role of roach as a food competitor seemed to be of minor importance. We did not find any clear signs of predatory effects of pike on ducks. Our results suggest that food competition is a more important factor than pike predation in affecting lake use by ducks in oligotrophic boreal environments in southern Finland.     

Associations between water chemistry and fish community composition: a comparison between isolated and connected lakes in northern Sweden

1. The correlation between water chemistry, physical variables and fish community composition was examined in 40 small (≤30 ha) coastal lakes in northern Sweden. Twenty of the 40 lakes were isolated from other water bodies and 20 were connected to the Baltic Sea. Lakes were fished in summer, using three different methods. Water chemistry was sampled in late winter prior to ice‐out and pH was measured additionally in summer. 2. Our central question was whether water chemistry plays a greater role in the composition of fish communities in isolated lakes than in connected lakes, as isolated lakes cannot be recolonised once a species has become extinct. 3. Results indicate that winter anoxia affects community composition only in isolated lakes, whereas acidity is of importance in both connected and isolated lakes. Methane (indicating anoxia), was significantly correlated with variation in fish community composition in isolated lakes, and a group of variables that indicate anoxia (CH₄, pCO₂, inorganic carbon and dissolved oxygen) explained 24–34% of the variation. pH alone explained 12% of the variation in community composition for connected lakes and a group of variables indicating acidity (summer and winter pH and ANC) explained 10–20% of the variation in isolated lakes. Lake area was the most important physical variable, being significantly correlated with the variation in fish community composition in connected lakes. 4. In isolated lakes, the presence of pike (Esox lucius), perch (Perca fluviatilis) and roach (Rutilus rutilus) was associated with low CH₄. The occurrence of crucian carp (Carassius carassius) and roach was positively correlated with pH, and the crucian carp was apparently also affected by predation by pike and perch. In connected lakes the effect of anoxia was low, probably due to the possibility of recolonisation and pockets of oxygenated water, allowing pike and perch to persist and thereby limiting the distribution of crucian carp.     

Feeding efficiency of planktivorous perch Perca fluviatilis and roach Rutilus rutilus in varying turbidity: an individual‐based approach

The feeding rate of perch Perca fluviatilis showed high individual variation at low and moderate turbidities, when one individual had consumed more Daphnia pulex than any other fish, whereas no such variation in feeding efficiency was observed with roach Rutilus rutilus. There was a significant decrease in total consumption of D. pulex by P. fluviatilis with increasing turbidity, but no correlation was observed in the case of R. rutilus. The results suggest that the difference in the ontogeny of P. fluviatilis and R. rutilus may be detectable as behaviour‐related species‐specific trait differences in the early planktivorous feeding stage of the two common species.     

Trophic flexibility and opportunism in pike Esox lucius

The first comprehensive investigation of pike Esox lucius trophic ecology in a region (Ireland) where they have long been thought to be a non‐native species is presented. Diet was investigated across habitat types (lake, river and canal) through the combined methods of stable‐isotope and stomach content analyses. Variations in niche size, specialization and the timing of the ontogenetic dietary switch were examined, revealing pronounced opportunism and feeding plasticity in E. lucius, along with a high occurrence of invertivory (up to 60 cm fork length, L_F) and a concomitant delayed switch to piscivory. Furthermore, E. lucius were found to primarily prey upon the highly available non‐native roach Rutilus rutilus, which may alleviate predation pressure on brown trout Salmo trutta, highlighting the complexity of dynamic systems and the essential role of research in informing effective management.     

Ichthyofauna of the Lena River (Laptev Sea Basin): Modern composition and historical formation

The modern ichthyofauna of the Lena River includes 46 species and subspecies: 45 bony fishes and one lamprey. In the upper reaches, 24 species have been recorded, 38 in the middle reaches, 36 in the lower reaches, and 24 in the delta. Four of the seven species intentionally introduced into water bodies of the Lena River basin have successfully naturalized; the presence of the others is unconfirmed. All areas of the river are dominated by fishes of the orders Salmoniformes and Cypriniformes. The ranges of the Amur carp Cyprinus rubrofuscus, common bream Abramis brama, ide Leuciscus idus, roach Rutilus rutilus, pike Esox lucius, and perch Perca fluviatilis have expanded over the last few years. The causes and possible ways of the historical formation of the Lena River fish population are discussed in the light of data on the Pleistocene paleogeographical events and patterns of the distribution of species in the river and in adjacent basins.     

Piscivorous fishes diet dominated by the Asian cyprinid invader,topmouth gudgeon (<Emphasis Type="Italic">Pseudorasbora parva</Emphasis>)

Predation on the non-native cyprinid, Pseudorasbora parva, was reported during an annual study in a small connecting canal about 40 km south of Brno, Czech Republic. Two cyprinid fish species (Pseudorasbora parva, Rutilus rutilus) were identified in the diet of 23 piscivores belonging to three native fishes (Perca fluviatilis, Sander lucioperca, Esox lucius). The relative abundance of prey fishes changed seasonally and was dominated by the topmouth gudgeon in spring. Thereafter roach incidence continuously increased. In contrast, topmouth gudgeon was found to be a more sized-available prey and was the most dominant prey species in the diet of all piscivorous fishes during the whole season. Strong piscivory towards this alien might be beneficial for its eradication or control to support ecological integrity in natural and modified seminatural habitats.     

Self-Organizing Maps in Revealing Variation in Non-obligatory Riverine Fish in Long-term Data

Sensitiveness to the overall influence of the river channel regulation, impoundment and pollution was studied for 12 non-obligatory riverine (NOR) fish species in the Warta River, Poland, over the period of 1963–1998. Their total abundance has not considerably changed unlike the structure of their aggregation, which was revealed by a self-organizing map (SOM, Kohonen unsupervised artificial neural network) almost perfectly separating 1960s samples from 1990s ones. The greatest changes in proportion were recorded for the dominant roach Rutilus rutilus (from 28.6 to 60.0%), perch Perca fluviatilis (1.9 to 9.5%), pike Esox lucius (2.9 to 4.9%), and the former codominant bleak Alburbus alburnus (22.9 to 1.8%). They resulted from highly significant (p < 0.001), reaching even one order of magnitude, differences in the abundance of these species. Such remarkable alternations in dominant NOR ichthyofauna obviously influenced the whole fish assemblage structure, which was best illustrated by a clear vertical gradient over SOM in Simpson and Shannon indices. Thus, NOR species, both studied together and separately, can supply valuable information on the fish assemblage dynamics and should not be neglected in temporal analyses, often focused only on vulnerable obligatory riverine, migratory and/or endemic species.     

Growth,Reproduction and Condition of Roach (Rutilus rutilus (L.)), Perch (Perca fluviatilis,L.) and Ruffe (Gymnocephalus cernuus (L.)) in Eutrophic Lake Aydat (France)

The growth, reproduction and condition of adults of the three dominant fish species (roach, Rutilus rutilus, (L.); perch, Perca fluviatilis, L. and ruffe, Gymnocephalus cernuus, (L.)) in the eutrophic Lake Aydat were studied over one year cycle. Compared to published data, the growth of R. rutilus and G. cernuus was about average, while that of P. fluviatilis was below average. Comparing to literature, the fecundity of R. rutilus and G. cernuus was low but their oocytes were large. In contrast, P. fluviatilis had a high fecundity but small oocytes. At the end of summer, an abrupt decrease in the condition was recorded only for perch, probably due to stress as a result of environmental conditions. The sex-ratio was in favour of females for the three studied species but, in contrast to G. cernuus, the sex-ratio of R. rutilus and P. fluviatilis increased significantly also with age. It is concluded that Lake Aydat is a more favourable environment for R. rutilus and G. cernuus than for P. fluviatilis.     

Studies on bucephalid digeneans parasitising molluscs and fishes in Finland. II. The description of Rhipidocotyle fennica n. sp. and its discrimination by principal components analysis

Rhipidocotyle fennica n. sp. (= Rhipidocotyle Type A of Taskinen et al., 1991) from the intestine of Esox lucius in central Finland is described and compared by means of a principal components analysis (PCA) with R. campanula (= Rhipidocotyle Type B of Taskinen et al., 1991). Its cercaria develops in the bivalve Anodonta anatina and the metacercaria occurs in the skin and fins of Rutilus rutilus. The metacercaria is discriminated from that of R. campanula by PCA and is described along with aspects of the chaetotaxy of the cercaria. The new species is distinguished from R. campanula, R. kovalae, R. papillosa and R. septpapillata.     

Length‐weight relationships of Rutilus species from fifteen Greek lakes

The length–weight relationships of three endemic species (Rutilus prespensis, Rutilus panosi and Rutilus ylikiensis) and one cosmopolitan (Rutilus rutilus) species are presented for 15 Greek lakes.     

Food web manipulation in a small,eutrophic Lake Wirbel,Poland: effect of stocking with juvenile pike on planktivorous fish

In a four year experiment (1988–1991) carried out in a shallow, eutrophic lake, an increase in young-of-the-year pike (Esox lucius) density was used to control planktivorous fish assemblages consisting mainly of small-sized cyprinids: roach (Rutilus rutilus), Leucaspius delineatus, and white bream (Blicca bjoerkna). Stocking with pike fry of ca 30 mm in three successive springs resulted in large-scale mortality among prey of vulnerable sizes. Rotenone treatment at the end of the fourth year showed that roach and white bream populations contained few 0+ to 2+ fish, but very high numbers of 3+ to 6+ fish. By this time, short-lived, slow-growing L. delineatus, with no size refuge from predators, had been driven almost to extinction.