Electrophoretic identification of roach (Rutilus rutilus L.), rudd (Scardinim erythrophthalmus L.), bream (Abramis brama L.) and their natural hybrids

Roach, rudd, bream and their natural hybrids of 2 cm standard length or larger can be definitively identified by their enzyme electrophoretic patterns. Zymograms of lactate dehydrogenase and esterases as produced by vertical starch gel electrophoretic analysis of whole fry or adult eye extracts are the most useful in this respect. The lactate dehydrogenase isozymes, containing B sub-units, migrate more anodally in rudd and bream than in roach. Due to the tetrameric structure of lactate dehydrogenase, in hybrid rudd x roach and roach x bream, eleven isozymes can be observed as compared with six in the parental patterns. Esterases show unique patterns for all species and hybrids. With the exception of one fraction in rudd x bream, the esterase patterns of hybrids show summations of the parental phenotypes.     

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.     

Specific features of expression of aspartate aminotransferase genes in early development of some cyprinid fishes and their intergeneric F1 hybrids

Temporal parameters of expression of the aspartate aminotransferase gene Aat-1 parental alleles were studied in early development of intergeneric reciprocal F1 hybrids of the bream, roach, and blue bream. When the first AaT-1 expression was timed to the early stages (late blastula-gastrula), the gene parental alleles were activated asynchronously according to the maternal types (blue bream x roach hybrids). When the first Aat-1 expression was timed to later stages (yolk sac resorption), the parental alleles were activated synchronously (bream x roach, roach x bream, and roach x blue bream hybrids). The pattern of activation of embryonic genes is determined by the maternal environment and the influence of allele interactions is not excluded: Aat-f/Aat-sl (bream x roach, roach x bream, and roach x blue bream) and Aat-sl/Aat-med (blue bream x roach).     

A molecular approach to detect hybridization between bream Abramis brama, roach Rutlius rutilus and rudd Scardinius erythrophthalmus

Hybridization between roach Rutilus rutilus , bream Abramis brama and rudd Scardinius erythrophthalmus was investigated using morphological and genetic analysis employing both nuclear (ITS1) and mitochondrial (cytochrome b ) markers. Allele-specific amplification (ASA) reactions for both markers were developed and ITS1 sequence data for all three species are presented. Sequencing detected two ITS1 haplotypes within both roach and bream which most likely evolved in isolation and were subsequently brought together as a result of restocking by anglers. Analysis of cloned hybrid nuclear ribosomal DNA revealed evidence of recombination between parental ITS1 sequences. ASA proved to be an effective method for identifying hybrids and detected multiple ITS1 copies in fishes identified as purebred by morphological analysis. In addition this suggests post-F1 hybridization and introgression may be occurring between roach and bream, and rudd and bream, although some barriers appear to be suppressing backcrosses within the hybrid population. Analysis of the hybrid population demonstrated that hybridization has occurred in both directions.     

Description of two hybrids involving silver bream, Blicca bjoerkna (L.), from British waters

This paper describes specimens of naturally occurring hybrids of silver bream x bronze bream and silver bream x roach from Lincolnshire and South Humberside waters.     

三种普通欧洲鲤科鱼类(拟鲤、粗鳞鳊和欧鳊)人工杂交F1代形态学观察

对反交试验获得的18个月的拟鲤、粗鳞鳊和欧鳊F1代进行了鉴定.对不同于拟鲤、粗鳞鳊和欧鳊三种鱼的可量和可数形态特征分析表明,拟鲤×欧鳊和拟鲤×粗鳞鳊杂交种比粗鳞鳊×欧鳊杂交种与它们的双亲更容易区分.拟鲤杂交种间具有很多形态上的相似性,例如,上侧虹膜在拟鲤为红色,杂交种则介于双亲之间.在粗鳞鳊×欧鳊杂交种中也可以观察到居间类型.拟鲤×粗鳞鳊和拟鲤×欧鳊各自的杂交种可以通过眼睛的大小、较少的侧线鳞数和2行咽喉齿等特征相区分.粗鳞鳊×欧鳊杂交种与另外两个杂交种相比,具有更多的臀鳍分支鳍条数和一个中央具一黑线的虹斑.三个种进行杂交再获得的互交种通常不易区分.     

A search for introgressive hybridization in the rudd, Scardinius erythrophthalmus (L.), and the roach, Rutilus rutilus (L.)

Rudd, roach and their hybrids from an interbreeding population at Norwich were examined electrophoretically for seven enzymes; an examination of pharyngeal teeth supplemented the data. The rudd were compared to rudd from Lake Trawsfynydd, Wales, a lake free from roach. No differences were observed between the rudd from the two localities and no evidence was found of introgression within the fish from Norwich.     

Specific features of expression of aspartate aminotransferase genes in early development of some cyprinid fishes and their intergeneric F1 hybrids

Temporal parameters of expression of the aspartate aminotransferase gene Aat-1 parental alleles were studied in early development of intergeneric reciprocal F1 hybrids of the bream, roach, and blue bream. When the first Aat-1 expression was timed to the early stages (late blastula-gastrula), the gene parental alleles were activated asynchronously according to the maternal types (blue bream × roach hybrids). When the first Aat-1 expression was timed to later stages (yolk sac resorption), the parental alleles were activated synchronously (bream × roach, roach × bream, and roach × blue bream hybrids). The pattern of activation of embryonic genes is determined by the maternal environment and the influence of allele interactions is not excluded: Aatf/Aat-sl (bream × roach, roach × bream, and roach × blue bream) and Aat-sl/Aat-med (blue bream × roach).     

On the populations of roach (Rutilus rutilus), rudd (Scardinius erythrophthalmus), and their hybriin Esthwaite Water, with notes on the distinctions between them

Samples of cyprinid fishes from Esthwaite Water, Westmorland, have been examined and identified as roach ( Rutilus rutilus ), rudd ( Scardinius erythrophthalmus ), with a high degree (37%) of hybridization between these species. The distinguishing features of roach and rudd are discussed in the light of the difficulty of distinguishing the roach x rudd hybrid from the roach. It is concluded that the only reliable characters are the number and external morphology of the pharyngeal teeth.     

The biology of bream, Abramis brama (L), and its natural hybrid with roach, Rutilus rutilus (L), in the River Exe

Hybrids between bream, Abramis brama , and roach, Rutilus rutilus , occur in the lower reaches of the River Exe and were positively identified by their meristic features and shape of the pharyngeal bone. The growth of bream and hybrids was determined by back-calculation from scales. Annual checks were laid down in early June. The mean length for age of female bream was significantly larger than that of males for fish 6 years of age and older. This divergence in growth rate was associated with the sexual maturation of the fish. Data for the sexes were combined and compared with the growth rate of hybrids and roach from the same region. Hybrid growth was similar to that of bream for the first 6 years of life but was intermediate between that of the two parent species in the older age groups. Some hybrids with developing gonads were found. A change in the diet of bream from planktonic feeding to a benthophagic habit with age was noted. Detritus, substrate and chironomid larvae formed the bulk of the diet of hybrids.     

An ecomorphological framework for the coexistence of two cyprinid fish and their hybrids in a novel environment

Niche variation between hybrid taxa and their parental species has been deemed imperative to the persistence of hybrid populations in nature. However, the ecological factors promoting hybrid establishment remain poorly understood. Through the application of a multidisciplinary approach integrating genetics, morphometry, life‐history, and trophic ecology, we studied the hybrids of roach (Rutilus rutilus L.) and bream (Abramis brama L.), and their parental species inhabiting an Irish lake. The roach × bream hybrid exhibited a body shape intermediate of that of the parental species. Diet analyses depicted the hybrid as a generalist, feeding on all prey items consumed by either parental species. Stable isotope data confirm the trophic niche breadth of hybrids. A significant correlation between body shape and diet was detected, suggesting that the intermediate phenotype of hybrids might play a role in their feeding abilities, resulting in the utilization of a broader trophic spectrum than the parental species. Growth and age class structure analyses also yielded a scenario that is consistent with the ecological success of hybrids. Genetic analyses suggest that the majority of hybrids result from first‐generation crosses between the parental species; however, a potentially significant proportion of back‐crosses with bream were also detected. The recent introduction of roach and bream into Irish waters, as well as the climatic and ecological features of the colonized habitats, can explain the remarkable success of the roach × bream hybrid in Ireland. The adaptive significance of hybridization and its demographic consequences for the parental species are discussed. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99 , 768–783.     

The population biology of two species of eyefluke, Diplostomum spathaceum and Tylodelphys clavata, in roach and rudd

Infections of roach ( Rutilis rutilus ), and rudd ( Scardinius erythrophthalmus ), by the eyeflukes Diplostomun spathaceum and Tylodelphys clavata were studied in a lake over a three year period. T. clavata first appeared at the beginning of the study. Roach were heavily infected by both parasites, whereas the rudd contained very few specimens of either species. A small number of roach-rudd hybrids were also examined, and appeared to have a susceptibility intermediate between the parental types.
Levels of T. clavata in roach increased throughout the study. This parasite had a life span of a year or less in the fish, and was continuously lost from the population. This loss was balanced by a minor infection period in April/May and a major one extending from August until January. The fish continued to accumulate infections until they reached a size of about 130 mm, but thereafter intensity fluctuated about the level reached.
D. spathaceum infections similarly increased throughout the period of study, and there was a suggestion of a wave of infection in the spring. This parasite has a much longer life span, and levels of infection increased with fish size, only falling in the largest, and therefore oldest, hosts.
The major changes in the parasite populations in the roach were reflected, to a lesser extent, in the rudd. Both species were over-dispersed, but the data from roach was too heterogeneous to fit to any theoretical models, whereas that from the rudd was found to conform to a Negative Binomial distribution.     

Interspecific dominance amongst three species of coarse fish in Slapton Ley, Devon

Marked changes in the relative numbers of roach Rutilus rulilus (L.), rudd Scardinius erylhroplhalmus (L.) and perch Perca fIuviatilis L. , in Slapton Ley, Devon, have been observed over the period 1967–1978. Historically, the lake had been dominated by rudd and perch; significant numbers of roach were not thought to be present until 1967. From then onwards the roach population exhibited a considerable expansion, apparently replacing the rudd, which had virtually disappeared by 1974. In 1975 extensive mortalities of roach were caused by the pseudophyllidean cestode Ligula intestinalis L. During 1976 and 1977 larger number of rudd, belonging to the 1975 and 1976 year classes, were present, suggesting that the roach mortalities might be giving the rudd a chance to recover. However, very few rudd were present during 1978, possibly because lower incidences of ligulosis during 1976–1978 had allowed the roach to recover from the main outbreak of the disease in 1975, and to replace the rudd for the second time. Evidence from trap catches indicated that the perch population had shown a consistent decline between 1970 and 1977. The major phase of this decrease occurred between 1971 and 1973, when the roach population was increasing the most rapidly. Comparisons were made with changes in fish populations in other localities. The major reason for the changes observed was thought to be a competitive relationship between the plankton feeding younger stages, with roach being the dominant species, although other factors may also have been involved.     

Controlled breeding studies to verify the identity of roach and common bream hybrids from a natural population

The occurrence of post-F1 generation hybrids between common bream and roach in natural populations has still to be qualified. To do this, common bream, roach, F1 and F2 hybrid progeny were produced under controlled conditions. All progeny groups exhibited overlaps in the ranges of their meristic characters. Discriminant analysis of meristic data combined with allozymes allowed identification of post-Fl hybrids. Enzyme electrophoresis showed Fl progeny to be heterozygous at diagnostic loci. Back-crossed F2 progeny had a mixture of homozygosity and heterozygosity at diagnostic loci. Meristic and genetic analysis of fish from a natural population indicated that they were all F1 hybrids. Post-Fl hybridization cannot be ruled out from natural populations because Fl hybrids are known to be fertile. It is suggested that post-Fl hybrids were not detected either because of their low incidence of occurrence or due to biological phenomenon Such as inferior fitness.     

Mating patterns of first-generation hybrids of the roach, <Emphasis Type="Italic">Rutilus rutilus</Emphasis> (L.), and the silver bream, <Emphasis Type="Italic">Blicca bjoerkna</Emphasis> (L.)

Mating patterns among first-generation hybrids of the roach, Rutilus rutilus, and the silver bream, Blicca bjoerkna, between hybrids or with parent-species males, have been investigated under experimental reproduction conditions. The results reveal that the level of sexual activity of these hybrids is high. Hybrid females mated simultaneously and successively with all types of male, resulting in fertilised eggs. Individual participation of roach males in mating was never observed, however.     

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.     

The influence of simulated aquatic macrophytes on the zooplankton consumption rate of juvenile roach, Rutilus rutilus, rudd, Scardinius erythrophthalmus, and perch, Perca fluviatilis

Laboratory experiments showed that, of zooplanktivorous roach, rudd and perch, in the absence of any environmental structure roach were the most efficient feeders, but high densities of simulated submerged marcrophytes elevated perch to this position; rudd matched the performances of perch and roach only at intermediate structure densities. These changes in efficiency rankings with increased structure were the result of overall decreases in the performances of roach and rudd. Simulated water lilies and emergent reeds had their own influences on consumption rate. These effects were largely mediated through relationships between structure density and swimming speed; roach and rudd, not perch, showed reduced swimming speeds in the more structured environments. Observations of the routine behaviour of the fish suggest that their assessment of predation risk may be an important factor in determining their activity level and hence foraging strategy.     

Fertility of roach × bream hybrids, Rutilus rutilus (L.) ×Abramis brama (L.), and their identification

Adult roach, bream and their presumed F₁ hybrid from an Anglian Water reservoir were identified on the basis of morphological and meristic characteristics. The hybrid was clearly intermediate. Four hybrid breeding crosses were induced to spawn by hypophysis. A bream × roach cross (female named first) failed to produce fertile eggs, whereas F₁ hybrid × roach, roach × F₁ hybrid and F₁ hybrid × F₁ hybrid all produced fry. Fertility (defined as survival of eggs to hatching) was high for the F₁ hybrid × roach back-cross (56%) but low for the others (<2%), in comparison to the pure species controls (roach 69%, bream 76%). Progeny from these crosses were reared until anal fin rays could be counted. These counts indicated intermediacy between the parents and back-crossed individuals, and similarity between F₁ hybrids and their F₂ progeny.     

State of the reproductive system of Cyprinidae from the Teterev River and Kiev Reservoir after the Chernobyl accident

The state of the reproductive system in four species of Cyprinidae from the Teterev River and Kiev Reservoir (Ukraine)—descendants of F₃–F₆ generations of individuals subjected to the radiation impact because of accident at the Chernobyl Nuclear Power Plant—has been studied. It was shown that 20 years after the accident, there is a wide range of morphofunctional anomalies of this system in fish. The most significant of them are asymmetry and abnormal morphology of gonads; proliferation of connective tissue-sterilization; and mass destruction of sexual cells of different stages of development. Disturbances of reproductive gonads among the studied species are expressed most strongly in bream Abramis brama and rudd Scardinius erythrophthalmus. In the series of studied generations, maximum frequency of occurrence of gonad anomalies in bream and silver bream Blicca bjoerkna was recorded in F₃–F₄ and that in roach Rutilus rutilus and rudd was recorded in F₄–F₅, which is determined by the phenomenon of prolonged mutagenesis.     

Effects of magnetic fields on fyke net performance

The effects of magnetic fields generated by ferritic magnets and mounted in entrances to fyke nets were studied in 1999–2002. With respect to all fish species trapped (perch, pike, roach, rudd, bleak, bream, ruffe) except eel, the catch potential of magnet‐rigged fyke nets was found to be significantly higher (almost 50% on average) when compared with controls. Differences in magnet placement (N or S poles inside the traps) proved to have no significant importance on the number of fish that chose to enter the fyke nets. Specific behavioural mechanisms in adult fish towards magnetic fields as well as application of fishing gear magnet rigging in fisheries practice in inland waters are discussed.