Fish parasites as bioindicators of the pollution of bodies of water]

The paper presents the results of studies on the effect of wastes of the Cherepovets iron-and-steel works containing phenol, naphthaline and oil products on fish parasites of the Sheksna part of the Rybinsk water reservoir (the Volga river system). It has been shown that the number of highly sensitive ectoparasites of Abramis brama (Protozoa, Dactylogyrus monogeneans, Ergasilus sieboldi crustaceans and Caspiobdella fadejewi leeches) considerably decreases in the zone of pollution. It has been first suggested to use Diplozoon paradoxum and Caryophyllaeus laticeps, parasites of bream highly resistant to toxic effect, the number of which considerably increases in the zone of pollution, as indicators of anthropogenic pollution and ecological state of a water body. Among diplozoons there have been first discovered individuals having structural anomalies (reduction of the attachment organs, violation in the symmetry of arrangement and number of valves) that serves as evidence of mutagenic effect of toxic substances of polluted waters on morphogenesis of the parasite.     

First record of Lamproglena pulchella Nordmann 1832 in the Pielach and Melk rivers, Austria

Between April and November 2003, parasitological examinations of the nase Chondrostoma nasus L. and the chub Leuciscus cephalus L. from the neighbouring Melk and Pielach rivers in Lower Austria were conducted. Amongst various gill parasites, Lamproglena pulchella Nordmann 1832 was detected on both fish species, which was the first record of this parasitic crustacean in Austria. Physico‐chemical examinations of water samples of the two rivers were carried out during the same period. The results indicate that general water parameters in the Melk were subjected to more vigorous changes than in the Pielach. Critical temperature levels and ammonia concentration as well as drastic changes in the ionic composition occurred more frequently in the Melk River. The observed distribution of L. pulchella indicates its sensitivity to such stress factors: there was no evidence of the parasite in the Melk River until late November and it only then occurred on the gills of L. cephalus with a prevalence of 20% and a mean intensity of 2. In the Pielach River, infestation on chub had already occurred in June with a prevalence of 40% and a mean intensity of 3, rising to 60% and 7 in November; 45% of the nase was also infested in November at a mean intensity of 3.     

Growth and mortality of introduced fish larvae in a newly restored urban river

The potential of a newly restored river as a nursery for endangered rheophilic fish species was estimated by introducing a population of individually marked larvae of nase Chondrostoma nasus into two river sections differing in river morphology and hydrological conditions. After 12 months, clear differences in fish abundance and fish size were observed: in the braided floodplain section C. nasus were more abundant and larger in size than in the straight river channel section. Total mortality rates over the whole investigation period did not differ between the two sections.     

Influence of rearing method on ide Leuciscus idus L. juvenile survival under pike and pikeperch predation

Nase Chondrostoma nasus L., once one of the most common fish species in the upper reaches of central European rivers, is now considered endangered throughout its natural range. Since 2000 the Department of Ichthyobiology and Fisheries, Warsaw Agricultural University, has co-operated with the Polish Anglers Association in Krosno to study the effects of river restocking with pond‐farmed nase juveniles. The experiment is carried out on Wislok River, where nase was very twenty years ago but has now completely disappeared. Selected parts of the river are stocked with tagged, one‐summer and 1 year‐old juveniles. Changes in nase occurrence, and their growth and foraging behaviour have been analysed.     

Seasonal occurrence of helminths in the anadromous fish Coilia nasus (Engraulidae): parasite indicators of fish migratory movements

To understand the seasonal migration of the anadromous Coilia nasus , we attempted to identify the parasites infecting C. nasus and determine their seasonal occurrence. From June 2007 to July 2008, a survey of 775 C. nasus individuals from the estuary of the Yangtze River and the coast of the East China Sea revealed more than 7,300 parasites associated with the gills and alimentary tracts of C. nasus . The following 6 helminth taxa were identified, i.e., the monogeneans Heteromazocraes lingmueni and Helciferus tenuis, the digenean Elytrophallus coiliae, the acanthocephalan Acanthosentis cheni , and larvae of the nematodes Anisakis simplex and Contracaecum sp., all of which are marine or brackish-water parasites. The absence of freshwater helminths suggested that the parasites acquired in freshwater may have been accidentally, and easily, lost by the time the fish had reached the estuary and coast. Contrary to seasonal occurrence of the parasites' life cycles, the lowest mean abundance and prevalence of H. lingmueni and A. cheni occurred in August, which suggested the immigration of C. nasus from freshwater to the Yangtze estuary, with lower parasite burdens. The highest mean abundance and prevalence of the nematodes A. simplex and Contracaecum sp. in May and June, and the lowest in August, indicated the arrival of the fish from the coast and the Yangtze River, to the estuary, respectively. These findings suggested that a majority of the fish prepared for spawning migration in the estuary in spring and early summer and returned to the estuary after spawning in the lower and middle reaches of the Yangtze River in late summer.     

The apparent inability of cyprinid fish to produce skin-sensitizing antibody

Both egg albumin and horse serum failed to induce systemic anaphylactic shock in cyprinid fish. The production of skin-sensitizing antibody by these fish to either horse serum, egg albumin or antigenic extracts of the cestode, Caryophyllaeus laticeps or the acantho-cephalan, Pomphorhynchus laevis , could not be demonstrated by homologous passive cutaneous anaphylaxis (PCA) or by heterologous PCA reaction in guinea-pigs. It was considered therefore, that fish are unable to produce such antibody, at least in response to these antigens, and that it is unlikely that skin-sensitizing antibody is involved in the rejection of C. laticeps by dace Leuciscus lueciscus (L.). The phylogenetic origins of skin-sensitizing antibody are discussed.     

Divergent reaction of fish metrics to human pressures in fish assemblage types in Europe

Using a large pan-European dataset, we compared least disturbed sites to sites impacted by human pressures across broad river types to assess which aspects of bio-ecological traits of the fish assemblage are most sensitive to alterations of the river ecosystem. To control for variation across river types and large-scale environmental gradients, we began by clustering the least disturbed sites (n = 716) into four homogenous fish assemblage types (FATs) differing by four fish metrics, i.e., lithophilic, rheophilic, omnivorous, and potamodromous fish. We predicted these FATs (headwater streams, medium gradient rivers, lowland rivers, and Mediterranean streams) using environmental variables, i.e., altitude, river slope, temperature, precipitation, latitude, and longitude for impacted sites in our dataset (n = 2,389). Using tests of sensitivity and intensity, 17 fish metrics showed a clear reaction to human pressures. However, 12 metrics responded exclusively within only one of the four FATs. Hence we observed a divergent reaction of fish metrics to human pressures in, e.g., headwater versus lowland rivers. Type-specific reactions are useful in customizing impact assessment for particular river types. It is of primary importance to understand the comparative sensitivity and efficiency of fish-based indicators of water quality for detecting human-induced degradation of river ecosystems.     

Survival, development and food energy partitioning of nase larvae and early juveniles at different temperatures

Survival was generally high, 94–100%, for newly hatched larvae of the nase Chondrostoma nasus held at 10, 13, 16, 19, 22, 25 and 28° C up to day 66 post-fertilization. The developmental rate decreased with age and increased with temperature. Specific growth rates increased with temperature; within one temperature range growth rate decreased with ontogenetic development. Food consumption and respiration increased with temperature and body size. A temperature increase from 25 to 28° C resulted in slightly reduced survival, minor acceleration of developmental growth and respiration rates, and impeded skeleton formation. Growth efficiency of consumed energy decreased throughout the larval period from 55 to 67% at the first larval stage (L1) to 36–48% at the first juvenile stage (J₁). A similar trend for assimilation efficiency and its utilization for growth was observed. The constant temperatures required by larval nase ranged from a minimum 8–10° C to a maximum 25–28° C. A shift of optimum temperatures, 8–12, 13–16, 15–18, 19 and 22° C for nase spawning, embryonic development, yolk feeding larvae, early externally feeding larvae and, late larvae and juveniles, respectively, paralleled the spring rise in the river water temperature. Larval and juvenile nase show high survival, growth and energy conversion efficiencies compared with other fish species. On the other hand, low survival rates and growth can be attributed to external perturbations; thus, young nase may be considered a good indicator of the environmental and ecological integrity of river systems.     

Odonates as indicators of the ecological integrity of the river corridor: Development and application of the Odonate River Index (ORI) in northern Italy

The assessment of the ecological conditions of rivers is crucial for their appropriate management and restoration. Bioindicators commonly used to evaluate the river status (i.e. diatoms, aquatic macrophytes, benthic macroinvertebrates and fish) detect alterations of water quality, but are not particularly sensitive to hydromorphological degradation, which is another relevant pressure in river systems. Furthermore, those bioindicators are usually applied only to flowing channels. We developed a new multimetric index, the Odonate River Index (ORI), to assess the conditions of the whole corridor in alluvial rivers. The ORI is a development of an evaluation system proposed in Austria, and based on the Odonate Habitat Index (OHI). Odonates were chosen as bioindicators for the ecological integrity of the river corridor, since this taxon provides information on the conditions of their aquatic breeding sites, as well as on the surrounding terrestrial areas, due to its amphibiotic life cycle. We used a case study of 18 reaches from six Italian Alpine rivers, characterized by different morphological conditions and level of human impact. Within each study reach, we selected four sites, both lotic and lentic sites. Dragonfly surveys consisted in field observation of adults, and collection of larvae and exuviae. To define the best sampling strategy, we compared the results of the ORI metrics obtained varying the input data by combining different sampling methods: the best compromise between effort and exhaustiveness was obtained coupling the observation of adults with the collection of exuviae. We found the ORI to be a robust and reliable tool to assess the status of the river corridor in a wide range of environmental conditions and river morphology, being particularly suitable to detect hydromorphological degradation and alterations of the structure of aquatic and riparian vegetation. We identified two limiting factors for the applicability of this index: low water temperatures of the main channel (i.e. mean annual value below 10 °C) and river reaches with no or scarce aquatic and riparian vegetation. In addition to the assessment of river conditions, the ORI could also be applied for monitoring the effects of river restoration actions.     

长江安庆段刀鲚寄生线虫群落结构及感染特征

为理清刀鲚(Coilia nasus)洄游时间与体内寄生线虫的关系,于2018年4—7月在长江安庆段调查了刀鲚寄生线虫的感染情况及群落结构。结果显示,刀鲚线虫感染率为96.0%,平均感染强度为8.06±7.26,平均感染丰度为7.74±7.29。经ITS分子标记共鉴定出7种线虫,其中异尖属2种,宫脂属4种,针晶蛔属1种,均为海水性寄生虫,可作为刀鲚有海水生活经历的生物标记。其中派氏异尖线虫(Anisakis pegreffii)的感染率最高,为84.5%,其次为内弯宫脂线虫(Hysterothylacium aduncum)(31.0%),二者的感染强度和感染丰度也较高,其中平均感染强度分别为6.40±6.08和2.81±2.49,平均感染丰度分别为5.41±6.05和0.87±1.90;派氏异尖线虫感染丰度和感染强度在洄游早期呈上升趋势,到6月下旬稍有降低但不显著(P>0.05),内弯宫脂线虫感染丰度和强度则均表现为下降趋势。刀鲚寄生线虫的群落结构在不同洄游时间也有所差异,其中刀鲚感染线虫的平均物种丰富度和Brillouin多样性指数均呈下降趋势,但优势物种一直是派氏异尖线虫,...     

Occurrence of the caryophyllid cestode Lytocestus parvulus Furtado, 1963 in Clarias batrachus (L.) in a tropical environment, Kedah, Malaysia

Clarias batrachus (L.) and C. macrocephalus Gunther were collected monthly between October 1982 and September 1984 from Pendang, Kedah, Malaysia. The caryophyllid cestode Lytocestus parvulus Furtado, 1963 was found in 37.7% of C. batrachus examined, with a mean intensity of 11.3. Infection of the cestode in C. macrocephalus was minimal, so detailed study was not attempted. In C. batrachus , no seasonal cycles of prevalence, mean intensity or maturation of the cestode were detected. The prevalence and mean intensity of L. parvulus decreased with increasing size of the fish. The first segment of the intestine was the preferred site where larger numbers of the cestodes and the greatest numbers of mature parasites were found. The number and maturation decreased towards the posterior end of the intestine.     

Helminth communities of the barbel Barbus barbus from large river systems in Austria

The composition and diversity of the total and intestinal component endohelminth communities were determined in the cyprinid barbel from three study areas in two large river systems in Austria. Two sample sites in the Danube and one site in the River Drau are the only free flowing stretches of these rivers in Austria. Nine helminth species were identified, with the acanthocephalan Pomphorhynchus laevis being dominant in the Danube, with up to 100% prevalence. In the Drau, where the dominant species was the cestode Bathybothrium rectangulum, species diversity was higher than in the Danube.     

Fish parasite communities in tropical reservoirs along the Perak River, Malaysia

The parasite communities of fish in three reservoirs (Temengor, Kenering and Cenderuh) along the Perak River, as well as in the lower Perak, are compared. A total of 36 species, 51 species, 61 species and 58 species of metazoan parasites from six types of fishes common in all studied locations, were obtained in Temengor, Kenering, Cenderuh Reservoirs, and downstream Perak River, respectively. The various criteria (prevalence, mean intensity, diversity index, similarity index and evenness) of the parasite community were highest at the Cenderuh Reservoir, followed by the downstream river, Kenering, and Temengor Reservoirs. Monogeneans were the most common parasites in all species of fish examined from all study sites. Fish of the same species showed a high degree of similarity of its parasite fauna regardless of study site, but different hosts had a low similarity of their parasite fauna, even within the same study site. This revised version was published online in August 2006 with corrections to the Cover Date.     

Risk of inter-river transmission of Gyrodactylus salaris by migrating Atlantic salmon smolts, estimated by Monte Carlo simulation

The possibility of Gyrodactylus salaris infection of wild North Atlantic salmon Salmo salar spreading to new rivers poses a major threat in Norway. This freshwater parasite can survive for some time in brackish water, and it has been suggested that smolts leaving infected rivers could transport vital parasites to new rivers. A Monte Carlo simulation model was used to estimate the risk that infected smolts would ascend a new river. Data from an infected watercourse in Norway, where the salmon population is maintained constant by cultivation, were used. The model included information on prevalence of infection, hydrographical conditions, survival of G. salaris in brackish water, fish population characteristics, and smolt behaviour during seaward migration. The annual risk was estimated for 3 neighbouring rivers situated at different distances from the index river. For the nearest river, which shares the same brackish water zone with the index river, the model estimated an annual risk of 31% that at least 1 infected smolt would ascend this river. The results of the simulation were highly sensitive to the water salinity along the migration route. For the other rivers, the annual risk was lower than 0.5%. Risk was positively correlated with the number of fish leaving the index river, indicating control of this number as a possible tool in risk management.     

Study on Centrocestus armatus in Korea. I. Infection status of Zacco platypus and Z. temminckii with the metacercariae of C. armatus

This study was performed to observe the infection rate and infection intensity of fresh water fish such as pale chub (Z. platypus) and dark chub (Z. temminckii) with the metacercariae of C. armatus. The fish were caught in several rivers and streams from June to September, 1988 and examined by artificial digestion technique. Total 370 fish were caught at 19 rivers. The metacercarial (C. armatus) infection rate and average burden in Z. platypus were 86.8% and 224, and those in Z. temminckii were 78.5% and 131. The infection rate and burden per fish were 73.4% and 32 in the fish caught from the Han river, and 88.0% and 44 from the Youngsan river. All fish caught from the Keum and the Tamjin river were infected and their mean metacercarial density was 45 and 59 respectively. The infection rate and density in fish caught from the Seomjin and Nagdong rivers were 100% and 119, and 81.0% and 348 respectively. From this study, it is confirmed that C. armatus is widely distributed along 5 major rivers in Korea.     

Cystidicola farionis as a swimbladder parasite of the whitefish in the Bothnian Bay

Material comprising 3167 specimens of the parasite Cystidicola farionis was assembled from 1741 individuals of the sea-spawning whitefish, Coregonus nasus in the shallow northeastern and deeper central areas of the Bothnian Bay. Occasional parasites were found in the immature fish (≦ 175 mm), but infection increased in the two larger classes as the fish aged, reaching 27% in the northeastern area, and as much as 67% in the southern area. This difference is explained partly by the more frequent feeding on Pontoporeia affinis , the intermediate host for the parasite, the deeper waters extending nearer the coast in the majority of the central and southern Bothnian Bay. The increased intensity of infection with age does not vary significantly between the areas studied. No clear seasonal fluctuations in the prevalence or intensity of infection could be found.     

Changes of nase Chondrostoma nasus L. occurrence in the Wislok River,southern Poland,after stocking with pond reared juveniles

Nase Chondrostoma nasus L., once one of the most common fish species in the upper reaches of central European rivers, is now considered endangered throughout its natural range. Since 2000 the Department of Ichthyobiology and Fisheries, Warsaw Agricultural University, has co‐operated with the Polish Anglers Association in Krosno to study the effects of river restocking with pond‐farmed nase juveniles. The experiment is carried out on Wislok River, where nase was very twenty years ago but has now completely disappeared. Selected parts of the river are stocked with tagged, one‐summer and 1 year‐old juveniles. Changes in nase occurrence, and their growth and foraging behaviour have been analysed.     

Parasite prevalence and intensity in Mugil cephalus (Pisces: Mugilidae), from Colorado River, Baja California, Mexico

The parasitic prevalence and mean intensity in the striped mullet, Mugil cephalus, was seasonally determined during an annual cycle (February 1994 to February 1995) in the confluence of the Colorado and Hardy rivers, Baja California, México. Two species of parasites were identified, a nematode, Contracaecum multipapillatum (von Drasche, 1882) (Ascaridida: Anisakidae), and a copepod, Ergasilus versicolor Wilson, 1911 (Poecilostomatoida: Ergasilidae). The larvae of C. multipapillatum, which were represented by two size classes (A and B stages), had prevalences of 30% and 14.5%, respectively; while A. versicolor had a prevalence of 72.7%. The mean intensity of C. multipapillatum was 6.18 and 2.37 individuals per infected fish for A and B stages, respectively; and for A. versicolor, it was of 4.01. The number of parasites (taxa combined) increased with the size of fish (r = 0.22, p = 0.02), but it was independent of the host's condition factor (KSL).     

Can the risk of parasite infection in fish cause the ecological differentiation in the population of roach Rutilus rutilus (Cyprinidae)?

Population characteristics of macroparasite infection (prevalence and intensity) in juvenile roach Rutilus rutilus have been studied in one of the tributaries of the Rybinsk Reservoir. The level of infection and parasite diversity is higher in the mouth part than in the upper reaches of the river. Habitats in the upper reaches are characterized by a high degree of irregularity of the risk of infection. The intensity of parasitic infection varies from the absence of parasites to 100% infection. Our data confirm the hypothesis about adaptaive value of the spawning migration to habitats with lower risk for the infection of offspring with parasites. Heterogeneous conditions in the upper reaches of the river make it possible for juvenile fish from a migrating part of the population to grow in relatively safe conditions. Differences in the strategy of the spawning migration can be based on the ecological differentiation as a result of which the groups oriented either at the local adaptation or at migration to the other habitat are formed in the population.     

洄游型、淡水型和陆封型刀鲚的寄生蠕虫群落结构

由于对淡水环境的适应和江湖阻隔,部分洄游型刀鲚(Coilia nasus)分化成淡水型和陆封型,为寻找区分洄游型、淡水型和陆封型这3种生态型刀鲚的寄生虫标志,并分析其寄生蠕虫群落结构特征,本文调查了3种生态型刀鲚鳃部、胃、肠和幽门盲囊中寄生蠕虫的种类和感染情况。共发现10种寄生虫,包括鳃上3种单殖吸虫:林氏异钩铗虫(Heteromazocraes lingmueni)、细长嗜鳀虫(Helciferus tenuis)和长江中华钩铗虫(Sinomazocraes changjiangensis);胃部1种复殖吸虫:鲚套茎吸虫(Elytrophallus coiliae);肠道3种线虫:简单异尖线虫(Anisakis simplex)、对盲囊线虫(Contracaecum sp.)和胃瘤线虫(Eustrongylides sp.),以及肠和幽门盲囊的3种棘头虫:陈氏刺棘虫(Acanthosentis cheni)、鲇异吻钩棘头虫(Arhythmacanthus parasiluri)、长江傲刺棘头虫(Brentisentis yangtzensis)。林氏异钩铗虫和陈氏刺棘虫在3种生态型的刀鲚中都有较高的感染率和平均丰度;海水性寄生虫细长嗜鳀虫、鲚套茎吸虫和对盲囊线虫只感染洄游型刀鲚,可作为区分洄游型刀鲚的寄生虫标志;淡水性寄生虫长江中华钩铗虫、鲇异吻钩棘头虫和长江傲刺棘头虫只在淡水型刀鲚中发现,可作为淡水型刀鲚的寄生虫标志。洄游型刀鲚的物种丰富度和Brillouin多样性最高,分别在1.25和0.19以上,淡水型刀鲚的较低,分别为0.79~1.12和0.10~0.12,陆封型刀鲚的最低,分别在0.66和0.02以下,这主要是由于淡水型和陆封型刀鲚中海水性寄生虫大部分丢失,以及淡水性寄生虫感染率和平均丰度都较低造成的。盐度降低和中间宿主缺乏是导致淡水型和陆封型刀鲚中海水性寄生虫丢失的主要原因;而淡水性寄生虫较低的感染水平可能是由于其对新宿主的适应时间较短;地理隔离可能是陆封型刀鲚中寄生虫群落多样性最低的另一重要原因。