The parasite fauna of the fish of the Shropshire Union Canal, Cheshire

A survey was made of the parasites of 603 roach Rutilus rutilus (L.), 15 bream Abramis brama (L.), 201 perch Perca fluviatilis L., 30 pike Esox lucius L. and four eels Anguilla anguilla (L.) caught in the Shropshire Union Canal at Backford, Cheshire from December 1964 to August 1966. Twenty-seven species of parasites were found, 17 in roach, seven in bream, ten in perch, ten in pike and two in the eel. Two species of Protozoa, seven species of Monogenea, five species of Digenea, six species of Cestoda, two species of Nematoda, one species of Acanthocephala, two species of Hirudinea, one species of Crustacea and mollusc glochidia were recorded. The following parasites are believed to be new records for the British Isles: Henneguya oviperda (Cohn, 1895), Dactylogyrus suecicus Nybelin, 1936, D. wunderi Bykhovskii, 1931, Asymphylodora kubanicum (Isaichikov, 1923), and Philometra rischta Skryabin, 1917.
One table shows the species of parasites found, together with data on the site of occurrence in the host, and the percentage and intensity of infection of the fish. A second table compares the occurrence of the parasites in four other localities in the British Isles, Loch Lomond Scotland, Llyn Tegid (Bala Lake), Merionethshire, Rostherne Mere, Cheshire and the River Lugg, Herefordshire. A further column gives the normal hosts in the U.S.S.R.
A limited comparison is made of the numerical occurrence of six species of parasites in the canal, Llyn Tegid and Druzno Lake, Poland. It is concluded that unless relatively large samples of fish of all length groups are collected on a regular basis throughout the year such comparisons will have little meaning.
The concept of the characterization of parasite faunas is briefly noted. It is suggested that the high degree of host specificity shown by many of the species of parasites is evidence in support of the concept.     

Studies on grayling, Thymallus thymallus L., in Llyn Tegid and the upper River Dee, North Wales.

Scale and length/weight data from 2071 Llyn Tegid grayling and 1803 River Dee grayling were used for age and growth determinations. The time of scale annulus formation varied from autumn in some years to spring in other years. Seasonal changes in length, weight and the condition factor were described. The main growth period was from spring to autumn with very little growth occurring during the winter. Annual growth in length was back-calculated from scale measurements, and von Bertalanffy's model was fitted to the resulting length for age data. Comparisons were made between the specific growth rates and ultimate lengths ( L_x ) of Llyn Tegid and River Dee grayling, and between the growth of male and female grayling. Males grew faster than females after the onset of sexual maturity. Calculated lengths were converted to weights using a combined length/weight relationship for Llyn Tegid and River Dec grayling. Changes were evident in this relationship throughout the life of the fish.     

A technique for determining the distribution of pelagic fish larvae

A technique is described for studying small scale distributional patterns of fish larvae in the pelagic region. A plankton net is mounted beneath the bows of a small boat, the contents of the net are emptied continually by a suction pump. This system has advantages over previous techniques as it allows a large number of small discrete samples to be taken over a wide area in a short space of time. Preliminary results showed the population of perch larvae in Llyn Tegid is extremely clumped and the overall abundance of the larvae decreases as samples are taken progressively further away from the south-west end of the lake.     

Some observations on the food of the gwyniad Coregonus clupeoides pennantii Valenciennes of Llyn Tegid (Lake Bala), North Wales

The seasonal variations in the diet of adult gwyniad Coregonus clupeoides pennantii=C. lavaretus from Llyn Tegid, North Wales were studied. Stomachs were examined to determine fullness, volume and identity of contents.
A clear seasonal cycle in food intake was found. Feeding rates were low from January to April but increased during the summer (May-June) and remained at a high level until December. The period of low feeding intensity coincided with the time of spawning and the time of annulus formation of both scales and otoliths. The diet showed seasonal changes and two main periods were distinguished : December to July, when the fish fed mainly on bottom fauna, and August to November, when the diet included both bottom fauna and midwater and surface foods.
The gwyniad were shown to be opportunistic in feeding, the composition of the diet reflecting availability of food items rather than selective feeding on the part of the fish.     

The effect of water level fluctuations on a littoral fauna

The littoral fauna of Llyn Tegid, North Wales, in 1968/9 is compared with the results of similar faunal investigations made by Rothwell(née Dunn) in 1951/2 (Dunn, 1953) and Hynes in 1957 and 1959 (Hynes, 1961). The results show the long term effects upon the littoral fauna of the change in mean water level and the increased water level fluctuations produced for a time by the controlled outflow scheme, which came into operation in 1955. In 1961 Hynes recorded big reductions in numbers and variety of invertebrates living in the littoral zone. The reduced water level fluctuations in recent years has resulted in a re-establishment of some of the fauna.     

Genetics of whitefish and vendace in England and Wales

Proportion of loci polymorphic ( P ) and mean heterozygosity per locus ( H _exp) were P = 0.130 and H _exp= 0.096 for C. albula from the English Lake District and P = 0.217 and H _exp= 0.046 for C. lavaretus from the English Lake District and Llyn Tegid, Wales in 1991–2. Significant deviation from the Hardy-Weinberg model was observed at the superoxide dismutase ( sSOD* ) locus in C. albula from Bassenthwaite Lake. This could have been due to chance, to the Wahlund effect or to selection. Genetic distances between the two species were consistent with their taxonomy and genetic differentiation was much greater for the C. lavaretus populations than for the two geographically close C. albula stocks. Llyn Tegid C. lavaretus showed unique alleles at two loci and conservation of fish in this lake is therefore of great importance. Red Tarn C. lavaretus differed most from other Lake District populations probably due to founder effects from early stocking events and/or from selection due to the high altitude of this lake.     

Parasite recruitment by stocked walleye, Stizostedion vitreum vitreum (Mitchill), fry in a small boreal lake in central Canada

Six species of parasites were recovered 4 mo after walleye fry were stocked in Heming Lake, Manitoba. The species of parasites acquired most rapidly were those that were non-host-specific and common to the indigenous populations of both walleye and yellow perch (Perca flavescens). Parasite species overlap (Jaccard's indices) was greatest within age groups of walleye and yellow perch, but was also high between older walleye and yellow perch. The higher numbers of parasites recruited by stocked walleye, particularly ones known to induce pathology, raises questions on the success of walleye introductions to aquatic systems with a diverse indigenous parasite fauna and a fish population with a large proportion of yellow perch.     

The life cycle of myxosporidians in fish of the Kola Peninsula

Monthly studies on the seasonal parasite fauna dynamics of pike, minnow and perch were carried out from May, 1974 to September, 1977. It was found out that the myxosporidian Henneguya creplini has a one-year life cycle. The infection of perch with this parasite takes place at a water temperature not exceeding 13 degrees. In other species (Chloromyxum esocinum, Ch. mitenevi, Myxobolus cybinae) the life cycle is shorter, in consequence of which fishes can be infected with these parasites several times a year and in different seasons. The nature of seasonal changes in abundance of myxosporidians depends to a great extent on weather conditions of each concrete year.     

A PRELIMINARY TAXONOMIC REVISION OF THE BRITISH WHITEFISH WITH ESPECIAL REFERENCE TO THE GWYNIAD OF LLYN TEGID (BALA)

The paper deals with a biometrical analysis of forty-one specimens of the Gwyniad, Coregonus clupeoides pennantii (Cuv. et Val.) of Bala Lake, (Llyn Tegid) North Wales. Tho Gwyniad shows the greatest relationship to the continental coregonids Coregonus lavaretus . It is proposed that the taxonomy of the British whitefishes be revised and that the Gwyniad be classified as Coregonus lavaretus pennantii (Cuv. et Val.). Similarly, it is proposed that the Powan of Loch Lomond be classified as Coregonus lavaretus clupeoides Lacépède. The classification of the Schelly from the English Lake District needs further investigation.     

The comparative feeding behaviour of brown trout, Salmo trutta L. and Atlantic salmon, Salmo salar L. in Llyn Dwythwch, Wales.

A detailed comparative study of the diets of natural brown trout and stocked Atlantic salmon in Llyn Dwythwch, North Wales, was carried out over a period of 13 months. The annual and seasonal composition of both diets was calculated by number, volume and occurrence methods. Food in relation to fish size was compared by Spearman rank correlation. Interspecific competition was only significant during the summer months when food was abundant. The bottom fauna was classified according to accessibility, and utilization of the fauna and electivity is discussed for each species. The similarity of diet between the salmon stocked into Llyn Dwythwch and those in Welsh rivers implies that the former is the result of inheritance rather than from interactive segregation with the lake trout.     

Host length,age, diet,parasites and stable isotopes as predictors of yellow perch (<Emphasis Type="Italic">Perca flavescens</Emphasis>Mitchill), trophic status in nutrient poor Canadian Shield lakes

We used data from parasites and stable isotopes of yellow perch, Perca flavescens, to determine trophic status in four small Canadian Shield lakes as parasites allow the identification of both prey and non-prey dietary components in the host's community. Stable C isotope ratios for all perch ranged from –34 to –19 while stable N isotope ratios ranged from 4.5 to 12.5. These ranges are larger than those observed in many other fish species. Perch age was the most significant predictor of stable C isotope ratio and perch parasite fauna was the most significant predictor of stable N ratios. In particular, parasite fauna indicative of zooplanktivorous or piscivorous perch were most accurate for predicting fish trophic position and thus stable isotope ratio. Fish length and age showed fewer significant relationships with isotope ratios than parasite infracommunity or diet and suggests that trophic category for perch cannot always be predicted based on size.     

The temperature of two welsh lakes and its effect on the distribution of two freshwater insects

Temperature data are presented from the littoral zones of two lakes in North Wales, Llyn Coron and Llyn Dinas. Recording, mainly on a continuous basis, was over a two year period. Despite their different situations, the lakes had similar temperature regimes. Regional weather factors were of greater importance than local variations. However, some differences were present, especially during the summer months. Laboratory experiments were conducted to determine the temperature relationships of Nemoura avicularis Morton (Plecoptera) and Leptophlebia vespertina (L.) (Ephemeroptera), common species in Llyn Dinas but absent from Llyn Coron. Aspects considered included nymphal temperature tolerance and the effect of temperature on egg development and emergence. From the background of the results, it was concluded that the differences in temperature regime between the two lakes were insufficient to explain the absence of the two species from Llyn Coron.     

Parasite fauna of the perch fishes Percidae in waterbodies of the Kola Region

Results of the parasitological investigation of two species of perch fisches (perch Perca fluviatilis and ruff Gymnocephalus cernuus) from Kola Region are given. 63 species of parasites were found on perch in 16 waterbodies belonging to the White Sea and Barents Sea basins (Myxosporea--3, Pleurostomata--1, Suctoria--2, Peritricha--21, Protozoa incertae sedis--1, Monogenea--2, Cestoda--6, Trematoda--10, Nemadota--8, Acanthocephala--4, Hirudinea--1, Bivalvia--1, Crustacea--3). 33 species of parasites were found on ruff in 5 waterbodies belonging to the White Sea basin (Cyrtostomata--1, Hymenostomata--1, Peritricha--8, Monogenea--2, Cestoda--6, Trematoda--9, Nematoda--2, Acanthospehala--2, Bivalvia--1, Crustacea--1). Data on the infestation of perch and ruff by different parasite species are obtained, occurrence of the parasites in the examined waterbodies is shown.     

The food of brown trout in Llyn Alaw, Anglesey, North Wales

The results of the analysis of the contents of 274 brown trout stomachs taken over a period of one year from Llyn Alaw, in Anglesey, North Wales, are described. The annual composition and seasonal changes of the diet were determined using number, volume and occurrence methods. The bottom fauna is classified according to accessibility to the trout as food and the utilization and apparent selection of the fauna by the trout is discussed. Food in relation to trout size is considered in detail.     

Overwinter feeding in rainbow trout

The contents of the stomachs of 38 rainbow trout stocked in Llyn Alaw, Anglesey, in August 1969 and caught between October 1969 and February 1970 were analysed. The fish were actively feeding on the bottom fauna throughout the winter and 21 of the stomachs were full or distended. The mean volume of the contents of the stomachs was 2–8 times greater than that of the contents of stomachs of similarly sized brown trout caught at the same time.     

The destruction of an endemic species flock: quantitative data on the decline of the haplochromine cichlids of Lake Victoria

Synopsis The Lake Victoria fish fauna included an endemic cichlid flock of more than 300 species. To boost fisheries, Nile perch (Lates sp.) was introduced into the lake in the 1950s. In the early 1980s an explosive increase of this predator was observed. Simultaneously, catches of haplochromines decreased. This paper describes the species composition of haplochromines in a research area in the Mwanza Gulf of Lake Victoria prior to the Nile perch upsurge. The decline of the haplochromines as a group and the decline of the number of species in various habitats in the Mwanza Gulf was monitored between 1979 and 1990. Of the 123+ species originally caught at a series of sampling stations ca. 80 had disappeared from the catches after 1986. In deepwater regions and in sub-littoral regions haplochromine catches decreased to virtually zero after the Nile perch boom. Haplochromines were still caught in the littoral regions where Nile perch densities were lower. However, a considerable decrease of species occurred in these regions too. It is expected that a remnant of the original haplochromine fauna will survive in the littoral region of the lake. Extrapolation of the data of the Mwanza Gulf to the entire lake would imply that approximately 200 of the 300+ endemic haplochromine species have already disappeared, or are threatened with extinction. Although fishing had an impact on the haplochromine stocks, the main cause of their decline was predation by Nile perch. The speed of decline differed between species and appeared to depend on their abundance and size, and on the degree of habitat overlap with Nile perch. Since the Nile perch upsurge, the food web of Lake Victoria has changed considerably and the total yield of the fishery has increased three to four times. Dramatic declines of native species have also been observed in other lakes as a result of the introduction of alien predators. However, such data concern less speciose communities and, in most cases, the actual process of extinction has not been monitored.     

Evidence for negative impact of plerocercoid infection of Triaenophorus nodulosus on Perca fluviatilis L. stock in Upper Lake Constance, a water body undergoing rapid reoligotrophication

The macro-pathological impact of plerocercoid infection of perch Perca fluviatilis livers was quantitatively determined by an index of liver lesion ( I _LL) in fish from Upper Lake Constance (ULC). These results were compared to the I _LL values of perch from two other lakes. From February to November 1999, 2071 perch were examined from the three sites. Prevalence of infection in ULC was 13% in actively growing first year (0+ year) perch and 94% in older fish, whereas in the two lakes used for comparison the figures for 0+ year perch were 12 and 20%, and in older fish 62 and 60%, respectively. Infected livers from perch caught in ULC revealed significantly higher I _LL values than those of fish from the other two lakes. Perch livers from ULC containing more than three Triaenophorus nodulosus larvae also showed significantly more serious pathological alterations than uninfected livers or those with normal infection levels of one to three T. nodulosus . In all three lakes, excluding heavily infected perch from ULC, 0+ year perch livers revealed little or no damage, whereas in livers of older perch pathological alterations were apparent. In addition, analysis of age and total length data showed that perch infected with one to three parasites in ULC grew significantly slower than uninfected ones, and severely infected perch (greater than three parasites) grew significantly slower than those with a normal parasite load. With respect to mass, growth of ULC fish suffering normal infection (49% of all adults) was reduced by 9% and in those with severe infections (45% of all adults) growth was 16% below expected at normal harvesting age.     

Characteristics of the parasite fauna of the perch Perca fluviatilis L. from the Bolshaya Lindalamba Lake in comparison with other small lakes in Karelia

Parasite fauna of the perch Perca fluviatilis L. is investigated in the Bolshaya Lindalamba Lake, Republic of Karelia. It is shown, that formation of fish parasite fauna in small lakes depends mainly on the type of the lake ecosystem.     

A preliminary study of parasites and diseases of perch in an intensive culture system

The recent development of intensive rearing of European perch Perca fluviatilis in warm water effluents revealed important pathological problems. This study gives a preliminary overview of parasites and diseases encountered in experimental perch farming. No virus has been recorded since the beginning of the experiments in 1993. By contrast, mass mortality caused by bacterial disease alone or associated with other pathogens were frequently observed. The main identified bacterial species were: Aeromonas sp., A. veronii, A. hydrophila, Streptococcus sp., Staphylococcus sp., Vibrio fluviatilis and Enterobacter agglomerans. Protozoans were the most common parasites observed on cultured P. fluviatilis. High mortality rate due to Ichthyobodo necator and Trichodina sp. may take place at different stages of perch rearing. In contrast, the infestation by Ambiphrya sp. and Heteropolaria sp. was size- or age-related; these two ciliates infested perch weighing < 1 g and > 20 g, respectively. In spite of the presence of other parasites such as Ichthyophthirius multifiliis, Hexamita spp., Gyrodactylus sp. and Argulus sp. in the rearing system P. fluviatilis does not appear to be affected. Further abnormalities or diseases inherent to intensive culture systems are also described.