Roach Populations Research Articles

Fish migration between a temperate reservoir and its main tributary

Upstream- and downstream-directed migration between the Řimov Reservoir and its only tributary, the Malse River (Czech Republic) was studied using two giant traps, sited at the mouth of the tributary, during the spring and summer periods, 2000–2002. The highest number of fish species was found in the tributary area (26 species and one hybrid). Over 10% of all fish biomass of the reservoir migrated through the tributary zone. The most important migration, in terms of fish numbers and intensity of movement, was the upstream spawning run. The fish species living in the reservoir can be divided into three groups: (1) the obligatory tributary-spawners (asp Aspius aspius(L.), bleak Alburnus alburnus (L.),chub Leuciscus cephalus(L.), and white bream Blicca bjoerkna(L.)); (2) generalists — fish spawning both in the tributary and the reservoir (bream Abramis brama(L.),roach Rutilus rutilus(L.), perch Perca fluviatilisL., pike Esox luciusL., and ruffe Gymnocephalus cernuus(L.)); and (3) fish spawning out of the tributary area (carp Cyprinus carpioL., pikeperch Stizostedion lucioperca(L.), catfish Silurus glanis L. and eel Anquilla anguilla(L.)). Tributary spawning is likely to support the strong roach population in the river upstream. Downstream migration from the river by salmonids appeared to be less important, in terms of relative numbers. Asp, roach and perch migrated as single spawners, bleak, bream and chub as multiple spawners. It was possible to define six periods of migration succession during spring and summer, which differed in species dominance, gonadal status and migration rates. The sequence starts with asp spawning and finishes after local movements of resident fish replace the spawning migrations. The most spectacular period during this sequence is the mass spawning of cyprinids when the roach, bleak, chub and bream migrate upstream and spawn nearly synchronically. During this period the daily migration rate exceeded 1000 individuals, which is over 100 times higher than during the feeding migration period.

The role of phosphorus release by roach [Rutilus rutilus (L.)] in the water quality changes of a biomanipulated lake

SUMMARY 1. Following fish removal, the water quality in biomanipulated lakes often improves concomitant with decreased phosphorus (P) levels. Because the decrease in P concentrations derives most probably either directly or indirectly from fish, which are the main target of biomanipulation, this study examined the P release of 0+, 1+ and 2+ roach [Rutilus rutilus (L.)] and changes in the P release during summer in a shallow eutrophic lake in Finland.2. The P release was separated into P derived from benthic and littoral food items and into recycled P derived from feeding on zooplankton, to estimate the contribution of net P additions to the water column by the fish to the increase in P concentrations of the lake water (75–110 mg P m−3) in summer 1991–96.3. Individual P release of roach by both egestion and excretion was estimated with a bioenergetics model. The size of the roach population was estimated with a depletion method and the proportions of different age groups from catch samples, using a programme separating mixtures of normal distributions. The sensitivity of the release estimates to variation in the growth data was estimated with the jackknife technique.4. The biomass‐specific P release by 0+ roach (0.36–0.54 mg P g−1 day−1) was higher than that by older roach (0.07–0.16 mg P g−1 day−1) throughout the summer. The P release by the whole roach population deriving from benthic and littoral food items (0.7–2.7 mg m−3 during July to August, representing a net addition to the water column) was 5–19 times lower in 1991–96 than the recycled P release deriving from zooplankton (8.9–25.7 mg m−3), and too low to explain the increase in the P concentration of the lake water during the summer. Because the biomass‐specific P release and roach diet composition vary with fish age, it is important to consider the age structure of fish populations to obtain correct estimates of P release and net additions to the water column.5. The removal of roach by fishing diminished the roach stock greatly, but the fish‐mediated P release to the water column changed little. This effect was because of the high compensation capacity of the roach population, leading to high recruitment of young fish with higher biomass‐specific P release rates.6. External loading is very low during summer months and therefore it cannot explain the increase in the P concentration of water during that time. Internal loading from the sediment might be as high as 10.2 mg P m−2 day−1, i.e. 50 times higher than the maximum net P addition by the total roach population.

The differential effects ofLigula intestinalis(L.) plerocercoids on host growth in three natural populations of roach,Rutilus rutilus(L.)

Abstract – This study reports the differential effect of the pseudophyllidean cestode,Ligula intestinalis, on the growth rates of three fish populations of the roach,Rutilus rutilus, under field conditions. Here, we show that only one host‐population is affected by parasite‐induced gigantism in the first 2 years of host life. Paradoxically, this increase in fish growth is strongly correlated with the parasitic load in plerocercoid stages, in that only the roach population subjected to the heaviest parasitic pressure shows an enhanced growth of cestode‐parasitized individuals. This host gigantism observed in only one locality is associated with parasite‐induced fish mortality occurring, on average, one year earlier in this fish population when compared to other populations. We discuss the different reasons for this differential parasite effect on growth enhancement across host‐population in natural settings. Whether the growth effects represent an adaptive response by the host or a manipulation byL. intestinalisof the host, remains to be elucidated.

Epizootic cutaneous papillomatosis in roach Rutilus rutilus: sex and size dependence, seasonal occurrence and between-population differences.

Epidemiology of epidermal papillomatosis in roach Rutilus rutilus was studied in 11 roach populations in Finland in 1999 and 2000 during the spawning period. In addition, the seasonal pattern of the disease was described in 1 population. Papilloma tumours were observed on the skin and fins of roach in 8 populations out of 11. Prevalence of papillomatosis varied from 0 to 62%, being higher in populations subject to industrial or sewage effluents. Males and large fish had higher prevalence of papilloma tumours. The disease outbreak peaked during the spawning period and signs of recovered skin on fish were observed later during the year. The gender dependence in the disease prevalence found in the study may indicate differences in stress and immunocompetence between roach males and females during the spawning period.

Reproductive, biochemical, physiological, and population responses in perch (Perca fluviatilis L.) and roach (Rutilus rutilus L.) downstream of two elemental chlorine‐free pulp and paper mills

AbstractPerch (Perca fluviatilis L.) and roach (Rutilus rutilus L.) populations in a state of late vitellogenesis were studied downstream of two pulp and paper mills and at upstream references in southern Lake Saimaa, Finland. The mills used elemental chlorine‐free bleaching and activated sludge effluent treatment technologies. The exposure of fish to pulp mill effluents, as measured by concentrations of chlorophenolics in the bile and liver ethoxyresorufin‐O‐deethylase (EROD) activity, was low and almost similar to the references. Nevertheless, bile resin acid concentrations in exposed perch and roach (260–320 μg/ml) and bile β‐sitosterol concentrations in exposed roach (1.5–3.5 μg/ml) were, respectively, 10 to 30 times and 2 to 5 times higher compared with the references. Reproductive parameters like plasma 17β‐estradiol and testosterone levels were lower in exposed male and female perch but the same in roach. Vitellogenin concentrations in plasma and liver cytosol of roach were similar. Gonad weight and fecundity were lower in exposed female perch but similar in roach. The relative liver weight was higher in exposed roach but not in perch. The body condition and immunologic parameters in fish were the same. The growth and age at maturity of exposed perch and roach were similar to the references. The size and age distribution of perch in the recipient of one of the mills was shifted toward smaller and younger fish. Our results show that several reproductive variables were altered in late vitellogenic perch in the vicinity of the mills, but they were not altered in roach.

Parasite-induced mortality in three host populations of the roachRutilus rutilus(L.) by the tapewormLigula intestinalis(L.)

Patterns of parasite infestation by plerocercoid forms of the tapeworm Ligula intestinalis (Cestoda, Pseudophyllidea) in the second intermediate host, the roach Rutilus rutilus, were analysed in three fish populations of South-Western France during 1998. In all three studied sites, i.e. Pareloup Lake, Lavernose-Lacasse and Muret gravel pits, roach were commonly parasitized with plerocercoids. A strong increase in prevalence, mean number of parasites and parasitic load was observed in the youngest hosts with a maximum peak reached in the medium-age (2+, 3+)roach classes. Such trends as a function of host fish age would indicate the occurrence of parasite-induced host mortality, with the most heavily infected fish specimens being removed from the three roach populations. The three roach populations infected by L. intestinalis exhibit different patterns of parasite-induced mortality which could correspond to different possible ecological and evolutionary responses associated with local variation in host-parasite interactions. The parasite-induced host mortality observed, i.e. direct mortality caused by pathogenic effects and /or enhanced fish predation by piscivorous birds to increase parasitic transmission is discussed within the context of the adaptative parasite-induced manipulation hypothesis. Mortalite induite dans trois populations de gardons hotes Rutilus rutilus (L.) par le parasite Ligula intestina lis (L.)

The roach population in the hypertrophic Bautzen Reservoir: Structure, diet and impact on Daphnia galeata

The structure and diet of the roach ( Rutilus rutilus) population in the hypertrophic Bautzen Reservoir was examined from April to November 1998. Under the long-term impact of high predation pressure by piscivorous fish, a very heterogeneous population structure of roach had developed. Only a few age classes were dominant while other age classes were nearly absent. The proportion of males decreased with increasing age to 4% of the total abundance of one age class, which nevertheless seemed to have no negative effect on reproductive success. Food analysis revealed that the diet consisted of a high proportion of algae and macrophytes. The collapse of the Daphnia galeata population in early summer 1998 forced the roach to switch to benthic food resources [macroinvertebrates and fish: chironomids, molluscs and ruffe ( Gymnocephalus cernuus)] in early June. Total consumption of age-2 and age-4 roach, the two most dominant year classes, was calculated by a bioenergetics model. Additionally, consumption of age-0 roach was estimated by assuming a fixed daily food consumption rate. The results suggest that daily consumption by these age groups, which never exceeded 0.2% of total biomass of the D. galeata population, had a negligible impact on the population of daphnids in Bautzen Reservoir during the period studied.

An individual-based approach to depict the influence of the feeding strategy on the population structure of roach ( Rutilus rutilus L.)

We used an individual-based modelling strategy to simulate the growth of a roach population. Individual growth is based on food utilization, bioenergetics, spatial distribution, and seasonal influences. With this approach, it is possible to connect the animals' activity pattern with the energetic needs required for this activity. This allows investigating the role of spatial heterogeneity and individual variability for the dynamics of fish growth. The parameterisation is based on laboratory measurements and field studies performed at Lake Belau (Schleswig-Holstein, Northern Germany). The interactions of the behavioural repertoire, growth processes, and food preferences emerge in the context of a decreasing proportion of zooplankton in the food composition of simulated roach. Roach feeding on molluscs grow faster. The ontogenetic shift is related to the necessity to switch to larger prey as a consequence of the increase of energetic demands with body size.

Long-term dynamics of Ligula intestinalis and roach Rutilus rutilus: a study of three epizootic cycles over thirty-one years.

Data are presented on 2 full epizootic cycles and the start of a third of Ligula intestinalis in roach Rutilus rutilus in a small lake, and the relationships of these cycles to the densities of rudd, Scardinius erythrophthalmus, and Great Crested Grebes, Podiceps cristatus, over 31 years. The parasite was introduced to the lake by P. cristatus in 1973 at a time when the roach population had increased in response to eutrophication to a level at which individual fish growth was stunted and the hithero dominant rudd population had declined in numbers as a consequence of inter-specific competition with roach. Ligula prevalence peaked at 28% in only 2 years: thereafter parasite-induced host mortality caused a decline in the roach population, releasing fish from stunting and allowing the rudd population to recover. The consequent improved growth of roach individuals and their short life-span reduced Ligula transmission rates and prevalence levels declined to approximately 1% although Ligula nevertheless persisted for a further 10 years. Following a massive winter-kill of the fish populations in 1984-1985, fish and Ligula numbers declined to barely detectable levels and the parasite disappeared from samples. Rudd recovered first, then roach and interspecific competition again led to a decline in rudd numbers. This increase in roach numbers led to a decrease in roach growth rates, which coincided with the re-colonization of the lake by Ligula. This second epizootic of Ligula peaked within 2 years in 1991-1992, when up to 78% of roach were infected with a maximum abundance of 2.2 parasites and intensity of 21 parasites. Heavy parasite-induced mortality of roach led to a decline in numbers, an improvement in individual growth rate and a reduction of Ligula transmission rates such that the epizootic died out in 1996. Similar conditions of roach numbers and growth prevailed at the start of a third cycle in 1998. The course of events over the second cycle was so similar to that of the first that it confirms the interpretations of that cycle. Comparison with other localities shows that epizootics of Ligula always coincide with rapid increases in roach numbers, for whatever cause, and stunted growth, which together attract piscivorous birds. At the start of a cycle Ligula is a major determinant of the population dynamics of the roach, but at the end of the cycle the fish population dynamics determine those of the parasite. The cycles are not regulated and the roach-Ligula system is inherently unstable.

Reproductive, biochemical, physiological, and population responses in perch (Perca fluviatilis L.) and roach (Rutilus rutilus L.) downstream of two elemental chlorine-free pulp and paper mills.

Perch (Perca fluviatilis L.) and roach (Rutilus rutilus L.) populations in a state of late vitellogenesis were studied downstream of two pulp and paper mills and at upstream references in southern Lake Saimaa, Finland. The mills used elemental chlorine-free bleaching and activated sludge effluent treatment technologies. The exposure of fish to pulp mill effluents, as measured by concentrations of chlorophenolics in the bile and liver ethoxyresorufin-O-deethylase (EROD) activity, was low and almost similar to the references. Nevertheless, bile resin acid concentrations in exposed perch and roach (260-320 micrograms/ml) and bile beta-sitosterol concentrations in exposed roach (1.5-3.5 micrograms/ml) were, respectively, 10 to 30 times and 2 to 5 times higher compared with the references. Reproductive parameters like plasma 17 beta-estradiol and testosterone levels were lower in exposed male and female perch but the same in roach. Vitellogenin concentrations in plasma and liver cytosol of roach were similar. Gonad weight and fecundity were lower in exposed female perch but similar in roach. The relative liver weight was higher in exposed roach but not in perch. The body condition and immunologic parameters in fish were the same. The growth and age at maturity of exposed perch and roach were similar to the references. The size and age distribution of perch in the recipient of one of the mills was shifted toward smaller and younger fish. Our results show that several reproductive variables were altered in late vitellogenic perch in the vicinity of the mills, but they were not altered in roach.

Sex-change chemicals and their influence on the brain.

The potential for man-made chemicals to mimic or antagonise natural hormones is a controversial issue, but one for which increasing amounts of evidence are being gathered worldwide. The controversy surrounds not so much the matter of whether these chemicals can mimic hormones in vitro — this phenomenon has been widely accepted in the scientific world — but more whether, as a result, they can disrupt reproduction in a wildlife situation. It has, nevertheless, been acknowledged that many wildlife populations are exhibiting reproductive and/or developmental abnormalities such as intersex gonads in wild roach populations in the U.K.[1] and various reproductive disorders in alligators in Lake Apopka, Florida[2]. However, the causative agents for many of these effects are difficult to specify, due to the extensive mixtures of chemicals — each of which may act via different pathways — to which wild populations are exposed, together with the wide variability observed even in natural (uncontaminated) habitats. As a result, any information detailing fundamental mechanism of action of the so-called endocrine disrupting chemicals (EDCs) is of use in determining whether or not these chemicals, as they are present in the environment, may in fact be capable of causing some of the effects observed in wildlife over recent years.

Growth of roach Rutilus rutilus (L.) In the River Odra estuary

The back-calculation method was applied to determining growth rate of roach caught in the Międzyodrze, Lake Dąbie, Szczecin Lagoon, and the Pomeranian Bay. Samples were collected from April 1995 to October 1997. The Pomeranian Bay and Międzyodrze individuals showed a faster growth rate than that attributed to other stocks. In each of the areas studied, older females grew faster than males. The Odra estuary roach population can be regarded as one of to the fastest growing populations of the species.

The effects of thermal effluent exposure on the gametogenesis of female fish

High temperature in Swedish and Lithuanian thermal effluent areas influenced gametogenesis of female perch Perca fluviatilis, roach Rutilus rutilus and pike Esox lucius negatively, indicating reduced reproductive capacity. Oocyte atresia started during vitellogenesis in autumn, and was often followed by asynchronous egg cell development. Among other anomalies, multi‐nucleus oocytes and hermaphroditism were observed. No significant impact was seen in silver bream Blicca bjoerkna. Ruffe Gymnocephalus cernuus reacted by a tendency to produce an additional mature oocyte generation during the spawning period. Ovaries in roach from coastal areas were often infected by a microsporidian parasite Pleistophora mirandellae, causing severe damage to the gonad. Parasites were also detected in pike, but neither in perch nor in lake populations of roach. Fish living in open coastal environments did not avoid impact by moving out of the heated areas. There seems to be a conflict in some temperate fish between temperature preference behaviour and safeguarding normal reproduction.

Effects of Pulp and Paper Mill Effluents on Reproduction, Bile Conjugates and Liver MFO (Mixed Function Oxygenase) Activity in Fish at Southern Lake Saimaa, Finland

Reproductive indices like gonad size, fecundity, egg size and sex steroid levels of estradiol-17β and testosterone, vitellogenin in the blood as well as bile conjugates and liver 7-ethoxyresorufin O-deethylase (EROD) activity were studied in populations of perch (Perca fluviatilis L.) and roach (Rutilus rutilus L.) and experimentally exposed juvenile whitefish (Coregonus lavaretus L. s.l.) at the Southern Lake Saimaa (S.E. Finland). Our studies showed that the introduction of elemental chlorine free (ECF) bleaching and secondary treatment of effluents in a modern activated sludge plant at the mill in 1992 have substantially reduced the exposure of feral and caged fish to organochlorines. The liver EROD activity was noticeably lower in feral and caged fish near the mill indicating lesser impacts on the liver mixed function oxygenase (MFO) system. However, at the mill site, liver EROD activies in feral and caged fish still tend to be one to four times higher than at the reference sites. Significantly decreased plasma estradiol-17β and testosterone concentrations in perch and roach in the period of development of the gonads (autumn and winter) indicate that there were endocrine disrupting compounds present in the lake receiving ECF pulp and paper mill effluents. Cause-effect relationships, however, are difficult to establish.

The growth of whitefish in relation to water quality and fish species composition

Water quality in 16 Finnish lakes did not affect directly densely gill‐rakered whitefish growth, except possibly in an acid (pH 4·9) lake, Iso Lehmaälampi, where acidity may have retarded the growth of whitefish. The density of roach affected whitefish growth in the second year of life: highest growth rates were in lakes without a roach population and lowest growth rates in lakes having strong roach populations. Competition by vendace also retarded the growth of young whitefish. The efficient mass removal of roach from a eutrophic lake was considered to have increased the growth rate of young whitefish. It is suggested that an examination of the fish species composition and relative abundance, as well as the growth of whitefish, can be used as an aid in predicting the success of stocking with whitefish.

Changes in roach ( Rutilus rutilus L.) population structure induced on draining a large reservoir

The influence of draining a large reservoir (Pareloup, South of France) on the population structure and the growth of roach is studied in this work. This reservoir, with an area of 13 km 2, drained in June 1993, was refilled 2 months later. Fish were sampled monthly before draining (1981) and after refilling (1997) by nylon monofilament gill nets used at the same catching effort for both periods. This permitted a comparison to be made between the density of roach and length distribution before and after refilling. Changes in growth were determined by scalimetry. The observed difference in population structure and growth underlined that the differences are mainly due to a greater growth rate after refilling during the first 2 years of roach life. These growth changes are explained by the decrease in roach density and the increase in 1993 of the biomass of Zooplankton, which constitute the main feeding resource for 0 + and 1 + roach. The study led us to propose hypotheses on the ecological significance of growth changes induced by refilling, which can be considered as a rejuvenation of the aquatic ecosystem.

Effects of pulp and paper mille effluents on reproduction, bile conjugates and liver MFO (mixed function oxygenase) activity in fish at Southern Lake Saimaa, Finland

Reproductive indices like gonad size, fecundity, egg size and sex steroid levels of estradiol-17β and testosterone, vitellogenin in the blood as well as bile conjugates and liver 7-ethoxyresorufin O-deethylase (EROD) activity were studied in populations of perch ( Perca fluviatilis L.) and roach ( Rutilus rutilus L.) and experimentally exposed juvenile whitefish ( Coregonus lavaretus L. s.l.) at the Southern Lake Saimaa (S.E. Finland). Our studies showed that the introduction of elemental chlorine free (ECF) bleaching and secondary treatment of effluents in a modern activated sludge plant at the mill in 1992 have substantially reduced the exposure of feral and caged fish to organochlorines. The liver EROD activity was noticeably lower in feral and caged fish near the mill indicating lesser impacts on the liver mixed function oxygenase (MFO) system. However, at the mill site, liver EROD activies in feral and caged fish still tend to be one to four times higher than at the reference sites. Significantly decreased plasma estradiol-17β and testosterone concentrations in perch and roach in the period of development of the gonads (autumn and winter) indicate that there were endocrine disrupting compounds present in the lake receiving ECF pulp and paper mill effluents. Cause-effect relationships, however, are difficult to establish.

Susceptibility of carp, roach and goldfish to a Dermocystidium‐like organism

A visceral form of a Dermocystidium‐like organism was found at 13% prevalence in a carp and in 7·4% in a roach population from Greece. Successful experimental transmission was recorded only in carp. Pathology of the parasite in experimental fish and naturally infected fish was similar. ©1998 The Fisheries Society of the British Isles

Effects of ECF-Bleached Kraft Mill Effluent on Reproductive Steroids and Liver MFO Activity in Populations of Perch and Roach

Samples of perch (Perca fluviatilis L.) and roach (Rutilus rutilus L.) populations were collected in Lake Saimaa in September-October, after the onset of vitellogenesis and deposition of yolk in the eggs. The study area received elemental chlorine-free (ECF)-bleached kraft mill effluent (BKME). The pulp and paper mill studied used chlorine dioxide for bleaching and its effluents were treated in a modern activated sludge plant. The amounts of chlorophenolics in the bile of perch and roach at the mill site, 1 km from the discharge point, were two to four times higher than in fish from the upstream reference site. In the roach population near the mill liver the 7-ethoxyresorufin 0-deethylase (EROD) activity was four times that measured in the reference areas. However, the EROD activity in the perch remained unchanged. The liver 7-pentoxyresorufin 0-dealkylase (PROD) activity was induced to twice the amount only in male roach near the mill, whereas the relative liver size (LSI) was increased in female and male roach and female perch. The plasma concentrations of oestradiol-17β were decreased in female perch and female roach, but increased in male roach at the mill site. Near the mill, vitellogenin gene expression was also reduced in female perch. In addition, the plasma testosterone concentrations were reduced in female and male perch near the mill. No differences were noted in the plasma immunoglobulin concentrations in roach and in the relative gonad size (GSI) in the perch and roach populations. The condition factor was significantly lower only in female roach near the mill.

Comparative study of reproductive biology in single- and multiple-spawner cyprinid fish. I. Morphological and histological features

To clarify the dynamics and regulation of oogenesis in single- and multiple-spawning cyprinid fish with group-synchronous oocyte development, a multidisciplinary approach to their reproduction was undertaken using three species from the River Meuse (Belgium): the roach Rutilus rutilus as a single spawner, and the bleak Alburnus alburnus and the white bream Blicca bjoerkna as multiple spawners. The gonadosomatic index (GSI) and histomorphometric changes (distribution of oocyte size, relative proportion of the various oocyte stages) in the ovary are compared. Different patterns of GSI and oocyte growth were observed both between the single- and multiple-spawner fish and between the two multiple spawners. Maximum GSIs were higher in roach (21%) than in bleak and white bream (17.7 and 14.5%, respectively), and compared to the rapid decline of GSI in the roach population, the GSI of multiple spawners decreased progressively during the spawning season. In roach, a short gonadal quiescent period and an early onset of vitellogenesis was recorded from late summer onwards whereas, in bleak and white bream, exogenous vitellogenesis was not systematically observed before winter. A protracted spawning season and/or a low water temperature in autumn are hypothesized to explain this long period of gonadal quiescence. In bleak, during the spawning season, the oocytes recruited arose from the stock of endogenous vitellogenesis and attained the final maturation stage very rapidly. This recruitment occurred during the whole spawning season. In white bream, the differentiation of vitellogenic oocytes from smaller oocytes was completed before the onset of the spawning season. During the spawning period, the proportion of vitellogenic oocytes decreased progressively whereas the percentage of oocytes in the final maturation stage remained approximately constant.