Acetylcholinesterase and butyrylcholinesterase activities in brain and plasma of freshwater teleosts: cross-species and cross-family differences

Brain and plasma acetylcholinesterase (AChE; EC 3.1.1.7) and plasma butyrylcholinesterase (BChE; EC 3.1.1.8) specific activities were assayed in 16 freshwater teleosts belonging to four families: Cyprinidae, Percidae, Esocidae and Lotidae. Brain AChE activity varied among fish species approximately 15-fold, ranging from 138 to 2011 micromol/g per h. All cyprinids had higher brain AChE activity than other fish families. Plasma AChE activity was on average 100-fold lower than that in brain, varying from 1.2 to 18.6 micromol/ml per h. Plasma BChE activity was found only in cyprinids with the exception of the common and crucian carp, and sabrefish. It varied from 26 to 1083 micromol/ml per h. In bream (Abramis brama) only 30% of specimens studied had BChE activity. The correlation coefficient values between activities of brain and plasma AChE, brain AChE and plasma BChE, plasma AChE and BChE were 0.67, 0.68 and 0.84, respectively. Cross-species and also cross-family differences in AChE and BChE activities among fish were demonstrated. Possible reasons for the differences are discussed.     

Organophosphorus Compound O,O-Dimethyl-O-(2,2-dichlorovynyl)-Phosphate as Selective Inhibitor for Separate Determination of Acetylcholinesterase and Butyrylcholinesterase Activities in the Roach Rutilus rutilus

A comparative study is carried out on dependence of degree of activity inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) of a freshwater bony fish, the roach Rutilus rutilus L., on concentration of organophosphates: O,O-dimethyl-O-(2,2-dichlorovynyl)phosphate (DDVP) and tetraisopropylamidopyrophosphate (iso-OMPA). It has been shown that both in roach and in horse the both inhibitors are selective for BChE in comparison with AChE. Their selectivity degree was 2000-fold and 80-fold, respectively. The ranges of effective DDVP concentrations are overlapped for horse AChE and BChE, while they do not for the roach enzymes. A similar regularity is revealed at action of iso-OMPA. It is established that DDVP has a higher inhibitory potency and selectivity in relation to roach BChE, than iso-OMPA. It is suggested to use DDVP as a new selective inhibitor for separate evaluation of AChE and BChE activities in fish tissues.     

Development of fish communities in lakes after biomanipulation

Biomanipulation measures in the Netherlands are usually a combination of a drastic fish stock reduction and an introduction of pike fingerlings. In three small shallow lakes (Noorddiep, Bleiswijkse Zoom and Zwemlust) these measures resulted in a clear water state and the development of macrophytes. After the measures the fish community developed differently because of the new physical and biological conditions. Results of lake Noorddiep and lake Bleiswijkse Zoom showed that the fish community became more divers. Bream and carp became less dominant and were partly replaced by roach and perch. The importance of the main predator pike-perch was strongly reduced and replaced by pike and perch. The share of piscivorous fish in the total fish stock increased at all sites. The recruitment of young-of-the-year was similar or even higher in the clear overgrown areas than in the turbid water before the measures, but the recruitment of young-of-the-year to older fish differed between the species. Predation by pike and perch could not control the young-of-the-year cyprinids, but their predation may have contributed to the shift from bream to roach, because of selective predation on bream in the open water, while roach was hiding in the vegetation. The macrophytes provide new refugia and feeding conditions that favour roach and perch, but offer relatively poor survival conditions for bream and carp.     

Modelling the habitat preferences of preadult and adult fishes on the shoreline of the large, lowland Elbe River

From the years 1997 to 2000, fish assemblages from 15 groyne fields and training walls (a current guiding dyke, protecting the groyne field) of the Middle Elbe River (Germany) were examined by electrofishing. The aim of the study was to detect abiotic environmental key variables which determine preadult and adult fish assemblage in typical riverbank structures using multivariate ordination techniques (canonical correspondence analysis) and univariate methods (logistic regression analysis). Habitat preferences of preadult and adult stages of selected fish species were also estimated. Fish sampling was carried out at 190 river stretches; a further 1615 samples were taken by the point‐abundance sampling method. In total, 21 732 preadult and adult individuals belonging to 30 fish species were caught; perch, eel, ide, roach, chub, gudgeon, bleak and white bream were the most frequent. Eurytopic species clearly dominated the fish assemblage with 72% total abundance, followed by rheophilic species (26%). Limnophilic fish species (rudd, crucian carp, stickleback and tench) were relatively rare (2% of total abundance), with frequencies of occurrence between 1 and 10%. The highest species diversities were estimated in structurally diverse training walls and groyne fields with defective groynes, whereas low species diversity was found to occur in poorly structured, strongly silted groyne fields with intact groynes. Additionally, typical seasonal and annual changes of the fish assemblage were observed. From the mesoscalic point of view, the structure of the preadult and adult fish assemblage was affected by both spatial (type of groyne field, river stretch) and temporal factors (year, season). Regarding the microhabitat, hydromorphological parameters (slope, current velocity, water level, predominant and secondary substrate) followed by physicochemical water values [dissolved oxygen (DO), temperature and pH‐value] are of significance for the structure of the fish community. Furthermore, hiding places (shelter) are of subordinate but significant importance for the fish assemblage in the poorly structured main channel of the Elbe River. Importance of hydromorphological factors on the microhabitat scale was confirmed by multiple logistic regression in 12 of 14 preference models, conducted for different ontogenetic stages of roach, bream, white bream, bleak, ide, chub, gudgeon, asp, perch and eel. Habitat preferences of adult bleak and preadult roach were first determined by physicochemical water values and seasonal influences. Univariate models were generated to describe specific habitat preferences of different species and age‐stages regarding the most important environmental variables (depth, velocity, predominant substrate, slope and shelter). Intraspecific differences were noticed between preadult and adult chub regarding preferences for water velocity, or between preadult and adult perch concerning slope of shore. Interspecific differences were observed, e.g. between adult roach and white bream, with regard to the use of shelters.     

Fish drift in a Danube sidearm‐system: I. Site‐, inter‐ and intraspecific patterns

A total of 10 649 larval and juvenile fishes of 24 species were caught in the drift at Marchfeldkanal, a man‐made side branch of the Danube River near Vienna, Austria, with tubenose goby Proterorhinus marmoratus being the dominant species. Distinct differences in inter‐ and intraspecific drift patterns among different sampling stations along the course of the channel were found. The percentage of the rheophilic and rheoparous ecological guild was highest at the inlet of the channel, where it is directly fed with water from the Danube. For individual species, significant differences in drift densities among sites were found for tubenose goby, barbel Barbus barbus , ide Leuciscus idus , roach Rutilus rutilus and for the two most abundant percids, the pike‐perch Sander lucioperca and zingel Zingel zingel combined. The occurrence of larval and juvenile fishes in the drift was related to certain developmental stages and differed between species and sites. Most species (common bream Abramis brama , bleak Alburnus alburnus , gudgeon species Gobio spp., chub Leuciscus cephalus , ide and roach) occurred with highest densities at the earliest developmental larval stage, but some species ( e.g . common bream and roach) were also found abundantly in drift at later developmental stages. Application of Ivlev's index of electivity as a drift index describing the propensity of the different species to drift, yielded the highest indices for the gudgeon species, common bream and bleak and the lowest for perch Perca fluviatilis , Prussian carp Carassius auratus gibelio and rudd Scardinius erythrophthalmus .     

Growth and production of O+ bream (Abramis brama), O+ roach (Rutilus rutilus) and O+ carp (Cyprinus carpio) in 10 drainable 0.1 Ha ponds

In ten 0.1 ha drainable ponds O⁺ cyprinids were stocked to assess their impact on the aquatic community. Bream and roach were stocked in early June, 1986, and carp in early July, 1986. The ponds were drained mid November, 1986. The relationship between the fish community and its food resource was estimated in terms of production and consumption with use of the data on growth and mortality of the fish. The average gross production of the fish species in the ten ponds (48.4 kg during the experiment) was dominated by the carp (58.5%). A minimum estimate of the food consumption of the O⁺ cyprinids is 760 kJ.m^–2. The average production of bream and roach was much lower than that of carp due to a higher mortality and a more specialized feeding pattern. The gross productions of carp, bream and roach in the ten ponds were not significantly related, although stomach analysis showed diet overlap between the carp and the bream.     

The distribution and growth of coarse fish in gravel-pit lakes in south-east England

SUMMARY. Age and growth rates of the coarse fish of thirty-nine gravel-pit lakes in south-east England are compared. Species composition was very variable, the commonest species being roach ( Rutilus rutilus ), bream ( Abramis brama ), tench ( Tinca tinca ), perch ( Perca fluviatilis ) and pike ( Esox lucius ). Two main kinds of fish community were identifiable from the survey: (1) those consisting of a mixture of cyprinids, usually roach and bream; and (2) those in which cyprinids were rare or absent and the fish community was composed of perch and pike. The majority of the lakes fell into the first category. Comparison of growth curves derived by back-calculation showed that, in all species, variation occurred from lake to lake and from year to year. The majority of gravel-pit lake fishes had 'medium' growth rates when compared with published data by other workers on different waters. Seasonal growth of roach infected with plerocercoids of Ligula intestinalis was observed at monthly intervals. Annulus formation on the scales of these fish occurred at the onset of growth in May. The heavy Ligula burden in 89% of these fish had not caused the formation of any additional or false rings.     

Polymorphism and heterogeneity of transferrins in some species of the fish family Cyprinidae

In fish of the family Cyprinidae extensive polymorphism and heterogeneity of serum transferrins were found. Ten variants of transferrins were detected in barbel, 9 in dace and bleak, 7 in chub and bream, 6 in rudd, 5 in roach, white bream, silver carp, big head and crucian carp, 3 in tench, and 2 variants in nase, ide and goldfish. All the variants observed bound radioactive iron. The phenotype patterns indicated a simple genetic determination, by a set of codominant alleles at one locus, and this even in tetraploid species. Transferrins of some species were partly isolated. The transferrins of all 22 species analysed were heterogeneous and homozygous pheno-types had 1 to 6 zones of various intensities, binding ⁵⁹Fe. In barbel both single-zone and two-zone variants were present and transferrins of roach had variable heterogeneity. Sialic acid was found only in transferrins of silver carp, big head and in the two-zone variants of barbel. The occurrence of phenotypes with single and double zones of transferrins in barbel indicates the possibility of genetic determination of the inability of single-zone variants to bind sialic acid.     

Food searching decisions in four cyprinid species

Synopsis Four species of cyprinids (vimba, bream, Danubian bleak and roach) which had been incubated and reared under identical conditions differed qualitatively as well as quantitatively in the use of prey search strategies during comparative experiments. While bream and vimba prefer to use sampling techniques under conditions of reduced visibility of benthic prey, roach favor almost exclusively directed search methods. Vimba and Danubian bleak, in contrast to bream and roach, rapidly increase their total search activity in response to successive presentations of novel prey. These results have several ecological implications which are confirmed by field data. It is concluded that food searching cyprinids follow decision rules which are species specific both in the amount of sampling and in the responsiveness to rapidly changing conditions.     

Occurrence of cyprinids in fish ladders in relation to flow

To analyse the relationship between spawning migrations and flow, cyprinids from ten fish ladders of the Elbe River (Czech Republic) were collected during the period of spawning migrations (April–June) in 1996, 2000 and 2001. Number of species and individuals in the fish ladders increased with increasing flow up to medium values, followed by further decrease during high flows, whilst length of individuals increased with increasing flow. Moreover, occurrence of four the most numerous species (bleak, roach, silver bream and barbel) showed species specific differences in response to flow variability. In early spring, the highest number of bleak in fish ladders occurred during the low flow, whilst later increased with increasing flow. Occurrence of roach and silver bream achieved the maximum during the medium flow values across the whole studied period. In opposite, occurrence of barbel increased with increasing flows during the whole period. Furthermore, it can be assumed that occurrence of fish in ladders was associated not only with spawning migrations but also reflected shifts in local fish distribution in response to flow variability in the main channel.     

Polymorphism of A, B and C loci of lactate dehydrogenase in European fish species of the Cyprinidae family

In 24 fish species of the Cyprinidae family, belonging to 21 genera, isoenzyme patterns of lactate dehydrogenase (LDH) were determined, which could be classified in the majority of cases into 3 main groups. Isoenzyme patterns in natural hybrids of roach and rudd, roach and bream, roach and bleak were also analysed. In bitterling, polymorphism was observed in B locus of LDH. In white bream polymorphism exists in the A locus. In bream, rudd, silver carp and barbel polymorphism was found in C loci. Isoenzyme patterns indicate that in each case the polymorphism is genetically controlled by two alleles at a single locus. The populations investigated were in Hardy-Weinberg equilibrium. No significant differences were found in the activity of liver LDH in various polymorphic types of C loci of bream and rudd.     

Proteolytic activity and electrophoretic profiles of proteases from seminal plasma of teleosts

Using gelatin-SDS-PAGE, proteolytic activity was found in the seminal plasma of 10 teleosts: common carp Cyprinus carpio , bream Abramis brama , ide Leuciscus idus , chub Leuciscus cephalus , rainbow trout Oncorhynchus mykiss , grayling Thymallus thymallus , perch Perca fluviatilis , pike Esox lucius , goldfish Carassius carassius and pikeperch Stizostendion lucioperca . This activity was also measured, using azoalbumin as a substrate, in the seminal plasma of these species, with exception of pikeperch and goldfish. When azoalbumin-hydrolysing activity was expressed per volume, it was highest in common carp. Otherwise, as expressed per g of protein, the activity was highest in pike. The lowest proteolytic activity (expressed per g and volume) was observed in perch seminal plasma. Using gelatin containing polyacrylamide gels for detecting gelatinolytic activity, species-specific electrophoretic profiles were found. For all cyprinids two similar bands with a molecular mass of 68 and 74 kDa were found. The seminal plasma of grayling and rainbow trout showed similarities in the 41 kDa band. Perch and pikeperch had one similar main band with a molecular mass of 61 kDa. Proteolytic enzymes of seminal plasma from pike showed high individual variability. These results suggest that multiple forms of proteolytic enzymes exist in seminal plasma of teleosts and they differ among fish families and species.     

To migrate, or not to migrate: partial diel horizontal migration of fish in a temperate freshwater reservoir

The diel horizontal migration (DHM) of fish between the inshore and offshore zones of the ?ímov Reservoir (Czech Republic, deep, stratified, meso-eutrophic) was investigated by a combination of horizontal and vertical hydroacoustic surveys at 3-h intervals over 48 h and day/night purse seining in August 2007. An overwhelming majority of fish were aggregated within the epilimnetic layer. Considering only the horizontal surveys, cyclic diel fish movements between inshore and offshore habitats were apparent, while the total fish biomass remained constant between day and night. A higher fish biomass was detected in the offshore zone during daytime by both hydroacoustics and purse seining. In contrast, a higher fish biomass was recorded at night in the inshore zone. Bream Abramis brama, roach Rutilus rutilus, and perch Perca fluviatilis dominated the daytime offshore fish assemblage whereas bleak Alburnus alburnus prevailed at night. Bream and roach decreased in abundance at night while perch completely disappeared from the offshore habitat. The diel differences in size distributions and direct catches suggested the population-wide horizontal offshore migration of bleak and inshore migration of all perch during dusk. On the other hand, partial inshore migration of bream and roach adults was observed during dusk (52 and 80%, respectively). The different proportions of offshore residents among species and size classes suggested that differences in size, and, therefore, predation vulnerability, contributed to the observed migration patterns.     

Feeding of fish in Lake Glubokoe

Lake Glubokoe is inhabited by 13 species of fish. The commonest are roach, bream, perch and ruff. Comparison of seine catches for 1950 and 1984 revealed a considerable decrease in the share of perch (from 31% to 2%) and ruff (from 18.5 to less than 0.1%) in 1984. The richest food resource in the lake is crustacean plankton. In summer, it is mostly consumed by roach. Estimation of the electivity shows that, unlike perch, roach selectively consumes small crustaceans (Bosmina and Polyphemus). Poor growth rate of all common species of fish points to their food limitation. In summer the diets of common species of fish are differentiated to a considerable extent. Of 36 pairs of combinations a high food overlap was found only in 2 cases: 1) O + perch and Leucaspius delineatus, 2) yearlings and adult roach. Low diet overlap in fish during intensive feeding in summer probably reflects a feedback between the volume and intensity of food competition. The populations of bream and ruff probably compete for chironomid larvae which inhabit the sublittoral, as perch, roach and Leucaspius delineatus probably do for large littoral insects. However, intraspecific competition appears to be more important than interspecific for the roach and bream populations (the two most numerous species in the lake).     

Measurement of vitellogenin,a biomarker for exposure to oestrogenic chemicals,in a wide variety of cyprinid fish

There is increasing concern about man-made chemicals in the aquatic environment that mimic oestrogens because they may disrupt reproductive function. Vitellogenin, a precursor of egg-yolk in fish and other oviparous animals, may be used as a biomarker for “oestrogen” exposure. This study investigated the use of a radioimmunoassay developed to carp (Cyprinus carpio) vitellogenin to measure vitellogenin in other species of fish, especially cyprinids that would be of value for field and laboratory studies on oestrogenic xenobiotics. Of the nine families of fish studied, only vitellogenin from cyprinids (to which the carp belongs) showed good cross-reactivity in the carp vitellogenin radioimmunoassay. Vitellogenin from cyprinids native to Europe that cross reacted in the carp vitellogenin radioimmunoassay included: bream (Abramis brama), roach (Rutilus rutilus), rudd (Scardinius erythropthalmus), gudgeon (Gobio gobio) and minnow (Phoxinus phoxinus). Vitellogenin from cyprinids used widely in ecotoxicology that cross reacted in the carp vitellogenin radioimmunoassay included: fathead minnow (Pimephales promelas), zebrafish (Brachydanio rerio) and goldfish (Carassius auratus). In the cyprinids studies, the concentrations of vitellogenin in mature females were between a few hundred and a thousand microgram per millilitre. Concentrations of plasma vitellogenin in immature females were always greater than 200 ng·m^-1, whereas in males (with the exception of the fathead minnow) plasma vitellogenin concentrations were less than 20 ng·ml^-1 (and generally, much lower). The results suggest that the structure of vitellogenin is highly conserved within the cyprinid family and that the carp vitellogenin radioimmunoassay may be used to measure the concentrations of vitellogenin in plasma from a wide variety of cyprinids.     

The food, growth and abundance of five co-existing cyprinids in lake basins of different morphometry and water quality

The food, growth and abundance of five co-existing cyprinid fish species in the eutrophic Lake Hiidenvesi were studied. The diet overlaps within the cyprinid community in shallow lake basins were compared with those in a deep basin, where littoral resources are less available. Roach, bleak and white bream inhabited both the shallow and the deep parts of the lake. Their growth rate was slow, probably due to the low availability of animal food, indicated by the increasing proportion of detritus and plant material in the diets towards the end of the summer. In the deep basin, roach and bleak, contrary to white bream, did not forage on the very abundant invertebrate Chaoborus flavicans, explained by the migration behaviour of C. flavicans. Blue bream, unlike other cyprinids, utilized copepods and had a relatively fast growth rate, but was mostly restricted to the shallow areas. The condition of the bream stock was weak both in terms of growth and abundance. The availability of zoobenthos was low and bream was not able to compete for zooplankton with the more specialized planktivores.     

Invasive fish species in the largest lakes of Scotland,Northern Ireland,Wales and England: the collective UK experience

An invasive species is defined as an alien (or introduced or non-native) species whose establishment and spread threaten ecosystems, habitats or species with harm. Such threats to UK lake fish communities have long been appreciated and this review assembles case histories, including new data, from the largest lakes of Scotland, Northern Ireland, Wales and England to examine the hypothesis that at least some of these introductions have become invasive. Loch Lomond in Scotland has experienced six introductions [chub (Leuciscus cephalus), common bream (Abramis brama), crucian carp (Carassius carassius), dace (Leuciscus leuciscus), gudgeon (Gobio gobio) and ruffe (Gymnocephalus cernuus)], of which the most significant has been that of the percid ruffe, which has been implicated in a recent decline of the native coregonid whitefish (Coregonus lavaretus). In Northern Ireland, the introduction of the cyprinid roach (Rutilus rutilus) to Lough Neagh has apparently had a negative impact on some overwintering waterfowl, although the native coregonid pollan (Coregonus autumnalis) remains abundant. Llyn Tegid in Wales has received three introductions [rudd (Scardinius erythrophthalmus), ruffe and silver bream (Blicca bjoerkna)], although no impacts on the native whitefish or other fish populations have been observed. In England, individuals of at least 12 native and non-native fish species have been brought to Windermere for the purpose of live-baiting, although only those of the cyprinids roach and common bream have established abundant populations. At the same time, the native salmonid Arctic charr (Salvelinus alpinus) has declined markedly while the native esocid pike (Esox lucius) has shown changes in abundance, distribution and individual condition, although these developments have not been shown to be causally linked. None of these introductions were sanctioned by appropriate fisheries or other regulatory bodies and almost all of them probably arose from the release or escape of live-bait used by pike anglers. Of the 10 species introductions documented here, four (common bream, gudgeon, roach and ruffe) have established abundant populations and two of these (roach and ruffe) have apparently caused or currently threaten harm, supporting the hypothesis that at least some of these introductions have become invasive.     

Top-down effects of underyearling fish on a phytoplankton community

1. The influence of underyearling (0+) fish on planktonic algal biomass and composition was examined during June–August in eight large enclosures (40 m³). Averaged for the entire period, Daphnia densities, transparency and phosphate concentrations were significantly higher ( P < 0.05) and chlorophyll a values significantly lower in fishless controls than in enclosures with fish (bleak ( Alburnus alburnus ), roach ( Rutilus rutilus ) or perch ( Perca fluviatilis )).
2. Enclosures without fish demonstrated a more heterogeneous algal community structure than enclosures with fish. Desmidiales and dinoflagellates were more abundant in controls, whereas green algae dominated the phytoplankton community in enclosures with fish. Larger grazing-resistant algae occurred most frequently in enclosures without fish.
3. The importance of cascading trophic interactions was demonstrated even under strong eutrophic conditions. The strongest effects on Daphnia densities, phytoplankton biomass and nutrients were observed in enclosures with perch, with weaker effects in enclosures with cyprinids. Differences in initial fish size and species accounted for the top-down effects observed. The results of this study emphasize the importance of 0+ perch as a key predator in structuring the plankton community in lakes.     

Top-down effects of underyearling fish on a phytoplankton community

1. The influence of underyearling (0+) fish on planktonic algal biomass and composition was examined during June–August in eight large enclosures (40 m³). Averaged for the entire period, Daphnia densities, transparency and phosphate concentrations were significantly higher ( P < 0.05) and chlorophyll a values significantly lower in fishless controls than in enclosures with fish (bleak ( Alburnus alburnus ), roach ( Rutilus rutilus ) or perch ( Perca fluviatilis )).
2. Enclosures without fish demonstrated a more heterogeneous algal community structure than enclosures with fish. Desmidiales and dinoflagellates were more abundant in controls, whereas green algae dominated the phytoplankton community in enclosures with fish. Larger grazing-resistant algae occurred most frequently in enclosures without fish.
3. The importance of cascading trophic interactions was demonstrated even under strong eutrophic conditions. The strongest effects on Daphnia densities, phytoplankton biomass and nutrients were observed in enclosures with perch, with weaker effects in enclosures with cyprinids. Differences in initial fish size and species accounted for the top-down effects observed. The results of this study emphasize the importance of 0+ perch as a key predator in structuring the plankton community in lakes.