Long-term development of fish populations in the Římov Reservoir

Abstract  The inshore fish community of the Římov Reservoir in the Czech Republic was evaluated over 21 years using shore seining at night. The development of the fish community was divided into two separate phases: a highly dynamic and unstable phase dominated by perch, Perca fluviatilis L., was replaced by an extremely stable cyprinid phase dominated by roach, Rutilus rutilus (L.), and bream, Abramis brama (L.). The abundance of both these species oscillated during the cyprinid phase, but with decreasing amplitude. The proportion of piscivorous fish species such as asp, Aspius aspius (L.), pike, Esox lucius L., and pikeperch, Sander lucioperca (L.), increased slightly with time but remained low. The biomass of large Cladocera was negatively correlated with fish biomass only during the perch phase. The Shannon–Weaver index of diversity increased during the fish community succession, mainly because of greater evenness amongst the species.     

The effect of depth, distance from dam and habitat on spatial distribution of fish in an artificial reservoir

Abstract –  Spatial distribution of the fish community in the deep canyon-shaped Římov Reservoir, Czech Republic, was studied using overnight gillnetting fishing in 1999–2007. Effects of depth, distance from the dam to the tributary and habitat type (benthic and pelagic) on fish community structure, catch per unit of effort (CPUE), biomass per unit of effort (BPUE) and average weight were tested. Fish were recorded in all sampled depths and parts of the reservoir. Redundancy analysis revealed that effects of three environmental variables were significant and most variability was explained by depth, then by distance from the dam and habitat type. CPUE and BPUE of all species decreased with depth and responses of individual species to depth were similar for juvenile and adult fish. Number of species, CPUE and BPUE of all species except perch increased heading towards the tributary and peaked close to or at the tributary part of the reservoir. Responses of juvenile fish to distance from the dam differed from that of adult fish. Structure of fish community differed in benthic and pelagic habitats with species preferably occupying epipelagic (bleak, asp, rudd and juvenile bleak, roach and bream) or littoral waters (perch, pikeperch, ruffe, roach, bream and juvenile percids). This study showed that fish distribution in the reservoir followed distinct patterns, which were probably shaped by a combination of physiological constraints plus trade-off between food resources and competition.     

Long-term effects of human influence on fish community structure and fisheries in Berlin waters: an urban water system

Commercial catch and fisheries monitoring data were compared with hydrological and water course characteristics conditions to identify the cause of changes in fisheries production in Berlin water courses since the 1950s. The urban parts of Berlin are densely populated, and the waters are under pressure from shipping, hydraulic engineering, pollution and recreation use. Most Berlin waters are polytrophic or hypertrophic, with an annual nutrient input of 595 t of total phosphorous and 8640 t of total nitrogen. A total of 34 fish species were recorded, eight of which were introduced. According to historical records, seven native fish species are extinct or missing. At present, the fish community is dominated by a few eurytopic species, i.e. roach, Rutilus rutilus (L.), common bream, Abramis brama (L.), silver bream, Blicca bjoerkna (L.), and perch, Perca fluviatilis L., which contribute 85% of all individuals caught. Two 'faunal breaks' were identified. The first was the changing of river character from a barbel to bream zone caused by damming and river regulation. This started in the thirteenth century and ended at the beginning of the twentieth century with the extinction of anadromous fishes. The second break was during the 1960s and 1970s, with the eutrophication of Berlin waters and the near total loss of submerged macrophytes. All phytophilic fish species declined greatly and a mass development of eurytopic species started. The catch of pike, Esox lucius L., common carp, Cyprinus carpio L., and tench, Tinca tinca (L.), became negligible, and at present, eel, Anguilla anguilla (L.), and pikeperch, Stizostedion lucioperca (L.), are the main commercial fish species. Concomitantly, the profitability of the fisheries declined and was linked to a decrease in the number of people employed in fisheries by more than 75% compared with 1950.     

Voluntary angler logbooks reveal long‐term changes in a lentic pike,Esox lucius,population

Sixty‐two years of voluntarily collected angling logbook data from a large natural Danish lake were used to study variation in pike, Esox lucius L., CPUE (catch per unit effort), expressed as no. of captured pike per boat trip, as an index of stock size. Pike CPUE was positively related to pike release rate by anglers and negatively affected by certain commercial fishers. The stocking of young‐of‐the‐year pike and a fishery‐dependent index of perch, Perca fluviatilis L., abundance (which may be pike prey or predator depending on size) did not correlate with pike CPUE. Analyses of the size distribution of pike, based on sizes of annual record trophy pike captured by anglers, confirmed the negative impact of commercial pike fishing and revealed a positive influence of air temperature. It is concluded that high‐quality angler logbooks that record effort and catch can be a cost‐effective tool to inform lake fisheries management by revealing long‐term population trends. Further, state space modelling, a statistical technique not yet seen in recreational fisheries science, is recommended as a tool to model proxies for population dynamics from angler logbook data.     

Density and temperature dependence of gill net catch per unit effort for perch, Perca fluviatilis, and roach, Rutilus rutilus

Abstract  The densities of perch, Perca fluviatilis L., and roach, Rutilus rutilus (L.), were estimated in six and three lakes, respectively, using mark–recapture and ranged from 25–1064 perch ha⁻¹ and 865–2749 roach ha⁻¹. Effects of fish density, net type and water temperature on catch-per-unit-effort (CPUE) were analysed by generalised linear models (GLM) and generalised additive models (GAM). GAMs were fitted to estimate the simultaneous linear and nonlinear effects of temperature and density on CPUE. These models showed significant nonlinear effects of density on CPUE – mostly for perch, and also for both species at high densities. The models also revealed that both species had distinct density–temperature criteria of expected maximum CPUE and zero CPUE values. Because of the nonlinear relationship between CPUE and density, it was concluded that CPUE should be used with caution as a proxy of density.     

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

The Pilica River has warmed at a rate of 0.06°C per year since 1969, threatening the ecological services provided by the Sulejów Reservoir. Gillnet sampling revealed that the reservoir is inhabited by a cyprinid‐dominated fish assemblage with roach, Rutilus rutilus (L.) (42% of the total biomass), the dominant species. However, the interest of the anglers was primarily focused on common bream, Abramis brama (L.) (almost 65% of the catch), as revealed by the catch statistics (2004–2014). No direct evidence was found that the temperature increase had an influence on the recreational fishery or fish assemblage structure. On the other hand, changes in the fish assemblage that were reflected in angler catch composition were observed. A decrease in the catch of common bream in gillnets was accompanied by a shift in angler choices towards roach and other fish species. The sustainability of recreational fisheries is more likely to be influenced by changes in the economic status of society, water quality (toxic cyanobacteria blooms) and water management practices in Poland. The question arises about which species will dominate in the impoundment in the future if the warming trend continues and common carp, Cyprinus carpio L., stocking is maintained.     

Inter- and size-specific patterns of fish seasonal migration between a shallow lake and its streams

Abstract –  This study used passive telemetry (passive integrated transponders) to evaluate winter migration in three species of cyprinids (roach ( Rutilus rutilus (L.)), white bream ( Blicca bjoerkna (L.)) and rudd ( Scardinius erythrophthalmus (L.))) and their potential predators (pike ( Esox lucius (L.)) and perch ( Perca fluviatilis (L.))) between a shallow lake and its streams. Migration patterns were investigated from October to June, and a substantial part of the roach (40%) and white bream (55%) populations tagged in the lake during autumn migrated during winter into the streams, whereas only very few piscivores (<2%) migrated. In contrast to roach and white bream, only few rudd (<6%) migrated, which is likely a consequence of different overwintering strategies, e.g., rudd overwintering in shallow highly structured habitats. Small rudd migrated more than larger rudd, whereas there were no size-differentiated migration patterns for roach or white bream. Migration of the cyprinid fishes was generally initiated in late October and ended in May, and specific synchronised bursts of migration were observed in December, January and April, suggesting that migration is triggered by one or more proximate environmental cues. The cyprinid fishes generally entered the streams in late afternoon or in the morning, depending on season, but overall migration patterns varied between the three streams. We suggest and discuss that our results have great implications for lake management as well as for the interpretation of seasonal trophic dynamics in shallow lakes.     

Mark-recapture experiments with noble crayfish, Astacus astacus L., in a Norwegian lake

Abstract. In July and August 1980–1987, mark-recapture experiments with noble crayfish, Astacus astacus L., were performed to estimate density in Lake Steinsfjorden, south-east Norway. Recapture rates were examined for variation according to sex, length, sampling method or length of recovery period, i.e. the time between release and recapture. Lake Steinsfjorden supports a dense, heavily exploited population of noble crayfish with few large individuals.
Recapture rates did not vary with sex, but were significantly lower among crayfish smaller than 90mm total length than for larger crayfish. Different sampling methods (baited traps and scuba) prior to marking did not influence the rate of recapture (in baited traps). When the recovery period was increased from 2 to 4 days, the recapture rate increased two- to threefold, but a further increase in the recovery period to 4–6 days did not increase the recapture rate.
The estimated density of noble crayfish varied between 013 and 036 individuals 5 70 mm total length per m² (95% CL. varied from 84 to 280%).     

The effect of LED lights on trap catches in Finnish inland fisheries

Trap fisheries can provide catches of high quality, and unwanted bycatch can be released with high survival. Light attraction could be an effective way of increasing trap catches, but research results are largely lacking. Experiments to test the effect of LED lights in trap-net fishing were conducted in two Finnish lakes where fishing targeted Eurasian perch Perca fluviatilis L. and roach Rutilus rutilus (L.). LED lights (white, green, red, blue and combinations) were attached inside the traps. The use of LED lights did not increase fish CPUE. Contrary to expectation, Eurasian perch catches were higher in traps without LED lights. Significant variation in CPUEs was observed, but without interaction with light treatments. The LED lights tested in this study do not increase the effectiveness of trap fishery targeting Eurasian perch and roach in Finnish lakes in the ice-free season.     

Influence of pH upon the activity of glycosidases and proteinases of intestinal mucosa,chyme and microbiota in fish

It is shown that amylolytic and proteolytic activity of the intestinal mucosa, the chyme and the intestinal flora in the fishes, zander Zander lucioperca (L.), perch Perca fluviatilis L., bream Abramis brama (L.) and roach Rutilus rutilus (L.), belonging according to their feeding habits to different ecological groups at the same pH values as well as in the pH range from 5.0 to 10.0 considerably varies. The glycosidase pH optimum of the mucosa and intestinal microbiota is 7.0, whereas that of the chyme varies from 6.0 (in roach) to 8.0 (in bream). pH optimum of the mucosa proteinases in all fish species is 10.0, whereas that of the chyme and the bacterial flora can be observed in all the range of pH values.     

Models for comparing average first-year growth in length of freshwater fish

Abstract  Logistic curves of the average growth in length were elaborated for young-of-the-year perch, Perca fluviatilis L., zander. Stizostedion lucioperca (L.), ruffe, Gymnocephalus cernua (L.), bream, Abramis brama (L.), and roach, Rutilus rutilus (L.), using data from 62 localities. Mean relative deviation from this average growth (MRDAG) is proposed as a simple and reliable indicator of growth rate. The MRDAG for perch, zander, bream and roach showed a significant negative linear relationship with the geographical latitude.     

Annual and seasonal dynamics of fish in the brackish-water Matsalu Bay, Estonia

Abstract –  Matsalu Bay in the Väinameri (West-Estonian Archipelago Sea) is a relatively shallow but large bay. It is the only real delta estuary in the northern Baltic Sea. The fish fauna is strongly dominated by freshwater species such as perch Perca fluviatilis , roach Rutilus rutilus , white bream Blicca bjoerkna and rudd Scardinius erythrophthalmus . The study presents CPUE data describing annual and seasonal variations in the species composition, abundance and spatial distribution, based on 1 year of monthly samplings from August 2001 to August 2002 and routine coastal monitoring (in late July–early August) between 1994 and 2003. The bay can be divided into three rather distinct parts. The fish fauna of the inner part (salinity 0–2 p.p.t.) is different from two open parts and resembles that of freshwater lakes. In the openmost part (salinity usually 4–6 p.p.t.) some marine species, such as herring Clupea harengus membras , flounder Platichthys flesus and eelpout Zoarces viviparus may seasonally be abundant. Species composition and abundance of most species varies seasonally and interannually. Only the abundance of few species such as pike Esox lucius and pikeperch Stizostedion lucioperca was not impacted by seasonality. The most dynamic period in the bay is spring, when several species (some of them very rare in summer, such as herring and smelt Osmerus eperlanus ) enter the bay for spawning.     

Piscivory in larval perch (Perca fluviatilis): mechanisms structuring larval roach (Rutilus rutilus) cohorts

Abstract – Perch ( Perca fluviatilis ) can act as a piscivore from larval stage VI (body size 10.3 mm) on newly hatched larval roach ( Rutilus rutilus ), bream ( Abramis brama ) and smaller siblings of its own cohort. Consumption rates at this stage were approx. 0.5 prey/perch*h at 21°C. Larval perch predation was strongly gap-limited, and the maximum size of roach consumed by perch (perch length interval 10.3–62.0 mm) under experimental conditions followed the linear regression, P_prey-max.=0.478*L_Pred.+1.829 ( r ²=0.99, P <0.001, n =12). Under experimental conditions, predatory 0⁺ perch substantially affected the size distributions of 0⁺ roach prey cohorts, since smaller prey individuals were predated more frequently than larger ones. In both unimodal and bimodal size distributions of prey roach, the distributions changed according to the maximum prey size consumed by the added predatory perch. Unimodal prey distributions were positively skewed when piscivorous perch were added compared with controls without predators. According to the size distributions of lake-living 0⁺ roach and 0⁺ perch and the relative size difference between prey and predator, the vulnerability of 0⁺ roach cohort to 0⁺ perch predation changed from June to September. Prey vulnerability was extremely sensitive to the relative size difference between predator and prey. Therefore differences in hatching time and growth rates between the two species will strongly influence the potential for predator-prey interactions. ^Note     

The relationship between stock and catch and the effect of bait on catch as determined for a UK recreational catch and release fishery

Abstract Twelve anglers fishing in a UK navigation canal for a total of 42 h caught 567 fish, mainly gudgeon, Gobio gobio (L.) ( n =306) and roach, Rutilus rutilus (L.) ( n =253) at an average catch rate of 13.4 fish angler-h⁻¹ or 128.5 g angler-h⁻¹. The species and size of fish caught were compared with the numbers determined by depletion estimates at six sections of canal using micromesh seine netting. Fifty four percent of fish caught in the net were < 60 mm FL. Gudgeon (60–99 mm) were over-represented in the anglers' catches whilst roach (60–99 mm) were under-represented. The size distribution of roach and gudgeon caught by anglers using two types of bait (small maggots and chironomid larvae) was examined and smaller fish were found to be caught using the latter.     

The effects of perch, Perca fluviatilis L., and bronze bream, Abramis brama (L.), on insect emergence and benthic invertebrate abundance in experimental ponds

Abstract The effects of perch, Perca fluviatilis L., and bronze bream, Abramis brama (L.), predation on the production of insects emerging at the water surface and the autumn biomass of benthic macro-invertebrates were assessed in a series of experimental ponds. The study attempted to discover whether fish affect food availability for diving and dabbling ducks in freshwater habitats. Ten ponds (bisected by fine netting) were used for the study: one was left totally fish-free, whilst one half of each of three groups of three ponds was stocked with either perch, bream or perch plus bream. The relative abundance of emerging insects (mainly Chironomidae) was significantly reduced in two perch ponds, two perch + bream ponds and two bream ponds. The autumn standing crops of benthic macroinvertebrates were significantly reduced in one perch pond, three bream ponds and one perch plus bream pond. These results support findings of a contemporaneous large bio-manipulation experiment carried out in two adjacent lakes. During the biomanipulation studies, aquatic invertebrate standing stocks greatly increased after the removal of fish and decreased following restocking.     

A 6-year study of Thelohania contejeani parasitism of the noble crayfish, Astacus astacus L., in Lake Steinsfjorden, S. E. Norway

Abstract. During 1981-1986, the mean prevalence of Thelohania contejeani parasitism of the noble crayfish, Astacus astacus L., in Lake Steinsfjorden, S. E. Norway, was 0.29%. The crayfish population is heavily exploited. Thelohania contejeani infection levels increased significantly during the fishing season, and variations between years were more pronounced in catches after the fishing season (0.38-2.11%) compared to catches before the fishing season (0.05-0-19%). Sixty-eight per cent of the variation between years could be explained from variations in trap effort. Scuba-diving yielded significantly higher T. contejeani infection levels than simultaneous trapping with baited traps. Thus, in years with heavy exploitation, a larger fraction of non-infected crayfish are removed from the population as these are more susceptible to capture. The findings do not support the hypothesis that density and cannibalism influence T. contejeani infection.     

Winter distribution and habitat use by fish in a regulated lowland river system of south-east England

The macrohabitat preferences of 1+ fish (10 cm FL) and the microhabitat use of 0+ juvenile fishes in the River Lee catchment (UK) were examined from data collected over a 3-year period between late autumn and early spring using depletion sampling and point abundance sampling, respectively. Canonical correspondence analysis and habitat profiles revealed preferences in the more rheophilous fish species (e.g. brown trout, Salmo trutta L . , barbel, Barbus barbus (L.)) for features characteristic of upstream natural channels and meander sections of the by-passed old river, with the more ubiquitous (e.g. perch, Perca fluviatilis L.) and limnophilous fishes [e.g. pike, Esox lucius L . , tench, Tinca tinca (L.)] preferring habitats mainly in downstream channelised stretches. The microhabitat of 0+ juvenile fishes in the River Lee was similar to that reported elsewhere for the same species, influenced mainly by channel width, depth, and distance from the bank, though microhabitat overlap in 0+ roach, Rutilus rutilus (L.), and gudgeon, Gobio gobio (L.), was greater in the Lee than observed in larger, more open river systems.     

Associations of fish with various types of littoral habitats in reservoirs

Fish associations with different types of littoral habitats were studied in four canyon‐shaped reservoirs in the Czech Republic in years 2010 and 2011 by gillnets. Two to three habitats per reservoir–beaches (former meadows), stump fields (former forest) and rubble slopes–were defined and sampled along the longitudinal axis of reservoirs. Effects of reservoir, habitat and locality (position along longitudinal axis) on fish biomass, abundance and species structure were tested for juvenile and adult fish separately. Hierarchical analysis of variance revealed that habitats differed significantly in fish biomass and abundance. Redundancy analysis showed that analysed environmental variables had significant influence on fish community structure. Most variability in community structure was explained by reservoir and then by combination of habitat and slope steepness. Locality position had the smallest influence on community structure. For both adult and juvenile fish total abundance and biomass, the most inhabited habitat was beaches; rubble slopes were the least inhabited. Habitat associations differed among species. Among adults, bream Abramis brama, white bream Blicca bjoerkna and roach Rutilus rutilus were associated with beaches and stump fields, whereas perch Perca fluviatilis, ruffe Gymnocephalus cernuus, asp Aspius aspius and pike Esox lucius were associated with rubble slopes. Bream, white bream, bleak Alburnus alburnus, roach, ruffe and pikeperch Sander lucioperca were associated with beaches among juveniles, whereas the only juvenile associated with rubble slopes was perch. We showed that most common species are associated with distinct habitats and also that utilisation of various littoral habitats differs in general.     

Habitat distribution of fish in late summer: changes along a nutrient gradient in Danish lakes

Abstract – The horizontal distribution of fish in lakes varies with species, age, predation risk, vegetation coverage and water clarity. Although sporadic data are available for specific lakes, little is known about how habitat distribution generally changes along a gradient in nutrients and clarity. Here we analyse littoral and pelagic fish catch data for 34 Danish lakes (covering 94 lake years) with contrasting total phosphorus (TP) concentrations and mean depth levels (but mainly eutrophic and shallow). Electrofishing was conducted during day along the shore or along the edge of the reed belt if such existed. Gill nets were set overnight for 18 h in open water. We calculated a littoral proportion as: LITPRO = (100 × number caught by electrofishing in the near‐shore area)/(number caught by electrofishing in the near‐shore area and nets in the open water). At all summer TP concentrations LITPRO was high for several ‘littoral’ species such as gudgeon (Gobio gobio), rudd (Scardinius erythrophtalmus) and pike (Esox lucius) and low for more typical pelagic species like pikeperch (Sander lucioperca), ruffe (Gymnocephalus cernuus) and smelt (Osmerus eperlanus). However, for many of these species including the dominant roach (Rutilus rutilus) and perch (Perca fluviatilis) LITPRO increased with TP or lake water chlorophyll a (CHLA) for fish >10 cm, suggesting a more littoral distribution with increasing turbidity. Exceptions are pikeperch and bream (Abramis brama). For bream, LITPRO increased significantly with mean lake depth only. For fish ≤10 cm LITPRO showed only a weak relationship to TP, CHLA or depth. In accordance with the TP‐dependent distribution, major changes occurred in the fish community structure during the monitoring period following nutrient loading reduction. A comparison of LITPRO from the first part of the monitoring period (1989–1993) with a subsequent period (1997–2003) for four abundant species showed a significant decline in LITPRO over time for large‐ and small‐sized roach and perch and large rudd. This suggests a fast response in fish distribution to improved water quality. It further demonstrates that fish monitoring in lakes should cover both littoral and pelagic habitats to describe the recovery process.