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Management decisions in conservation of threatened species require trading off social needs against biodiversity values, including the prioritization of conservation locations, i.e. where conservation efforts should take place. To improve conservation decisions for the thick-shelled river mussel, Unio crassus, a highly threatened temporary parasite on fish, we performed a field study on how mussel and host fish density (European bullhead, Cottus gobio, and common minnow, Phoxinus phoxinus) affect reproduction potential of the mussel at different sites along a river. We assumed that the proportions of gravid mussels would be higher at high mussel density, and result in enhanced glochidia (mussel larvae) encapsulation rates on fish. We also expected the highest 'glochidia density'—a proxy for the potential number of recruits per stream area, assessed by multiplying glochidia encapsulation rates on fish by fish density, to occur at high mussel density sites. Such river sites, producing many offspring and conveying important conservation values, may thus be prioritized. However, contrary to our assumptions, higher glochidia density and higher proportions of gravid mussels occurred at lower density mussel sites. We also found that P. phoxinus had higher glochidia encapsulation rates than C. gobio, possibly related to species-specific behavioural and life-history traits. Even so, glochidia density was similar for both fish species, reflecting comparable ecological functions in hosts. The results of this study suggest that mussel and host fish densities should be considered along with glochidia density in conservation prioritization and management trade-offs. [ABSTRACT FROM AUTHOR]

Our understanding on the role of chemical signals in parasite-mediated sexual selection is still limited, and only some existing studies have focused on fish. Furthermore, published studies on the effect of parasite infection on behavioral sexual competition of the male hosts have yielded contradictory results. Here, we examined whether the infection of the body cavity-dwelling parasitic nematode Philometra ovata influences odor-based female choice and behavioral sexual competition (dominance and courtship behavior) between males in the European minnow ( Phoxinus phoxinus), the cyprinid fish host. In contrast to our predictions, we found that naïve females showed no preference between the odors of infected and non-infected males, thus indicating that P. ovata infection may not affect odor-based female choice. Moreover, P. ovata did not impair sexual competitiveness of their hosts either. Our results indicate that despite its relatively large size, P. ovata may not alter sexual cues and the success of the male hosts in sexual selection. [ABSTRACT FROM AUTHOR]

Although high mountain lakes are naturally fishless, there have been numerous trout introductions to such ecosystems in many areas of the world with negative ecological consequences. In recent decades other fishes, such as minnows, have been introduced to some mountain areas, including the Pyrenees. These introductions may cause further ecological problems, since minnows also occupy the top of the food chain, and are difficult to manage since such introductions occur without permission from the authorities. In this study we have analyzed the process of minnow introductions in all high mountain lakes of the southern slope of the Pyrenees to find out which particular factors best explained their present distribution and to evaluate which management measures have been most effective for stopping introductions. We found 27 % of the lakes had minnows ( Phoxinus sp.) present, 52 % had trout and 47 % were fishless. Trout presence was the most significant variable explaining 27 % of deviance of minnow presence data in a generalized additive model. Recreational fishing using minnows as live bait is likely responsible for these introductions. Minnow introductions are therefore mediated by a preceding invasive species and facilitated by human activity. We also compared the number of minnow introductions in non-fishing areas of National Parks with other areas where managed fishing takes place. We found that the number of lakes with minnow introductions was increasing in all areas except those where fishing was prohibited, indicating that prohibiting fishing is an effective management practice for stopping minnow introductions. [ABSTRACT FROM AUTHOR]

The results of a study of common minnow populations in the Ungra River (conservation zone) and the Chulman River (town of Neryungri) in Southern Yakutia are presented. The main biological characteristics of the fish are given. Minnows have proven to be highly adaptive: their lifespan could exceed 10 years in the technogenic zone of the Chulman River in the absence of predators and competition for food. The common minnow was a host to 36 species of parasites, 11 of which were typical for this fish and 9 are detected for the first time in Yakutia. [ABSTRACT FROM AUTHOR]

Despite that the existence of animal personalities is widely recognized, no consensus has been reached on the relative importance of different ecological factors behind their expression. Recently, it has been suggested that parasites may have a crucial role in shaping animal personalities, but only a very few studies have experimentally tested the idea. We infected Eurasian minnows ( Phoxinus phoxinus) with the brain-encysted trematode parasite, Diplostomum phoxini, and studied whether infection could modify the personality of their hosts. Our results show that D. phoxini infection did not affect the mean levels of boldness, activity or exploration, but infected minnows showed higher repeatability in boldness and activity, and reduced repeatability in exploration. We also found that D. phoxini may be able to break the associations (behavioral syndromes) between behavioral traits, but that this effect may be dependent on parasite intensity. Furthermore, the effect of D. phoxini infection on personality of the hosts was found to be nonlinearly dependent on infection intensity. Taken together, our results suggest that D. phoxini parasites may shape the personality of their hosts, but that behavioral consequences of ecologically relevant infection levels may be rather subtle and easily remain undetected if only the mean trait expressions are compared. [ABSTRACT FROM AUTHOR]

A total of 68 cyprinid microsatellites were screened for cross-species amplification in order to develop three PCR multiplex kits for the Eurasian minnow ( Phoxinus phoxinus L.) and the gudgeon ( Gobio gobio L.). The multiplex kits cluster 21 and 18 microsatellites for P. phoxinus and G. gobio, respectively. All loci were evaluated using ~80 individuals sampled from three distinct populations. By multiplexing the markers, we aim to decrease genotyping costs and increase time efficiency. These two microsatellite sets represent a valuable tool for ecological, evolutionary, conservation and management issues. [ABSTRACT FROM AUTHOR]

Non-invasive diagnoses for most of the extraintestinal helminth infections among vertebrates are rare. In the present study, we developed and tested a non-invasive visual diagnosis method to detect the infection of the nematode Philometra ovata, which is parasitising in the body cavity of the common minnow Phoxinus phoxinus. By observing the surface of minnow's abdomen, we diagnosed infected minnows with irregular or vermiform-shaped uplifts as a consequence of the presence of P. ovata in the body cavity. We conducted the diagnosis in minnows with or without anaesthetisation, and our results showed the non-invasive method is highly reliable (correct rate of diagnoses > 95 %) in both anaesthetised and non-anaesthetised groups. The correct rate of diagnoses in truly uninfected fish (i.e. specificity) was nearly 100 % in both groups, while the correct rate of diagnoses in truly infected fish (i.e. sensitivity) was 71 and 65 % in anaesthetised and non-anaesthetised fish, respectively. The correct rate in fish diagnosed as infected or uninfected (i.e. positive or negative predictive power) of non-invasive diagnosis was nearly 100 % among the anaesthetised fish, and over 95 % in non-anaesthetised group. The diagnosis also yielded prevalence of P. ovata infection similar to the real prevalence in anaesthetised fish. Diagnoses conducted by an inexperienced observer indicated that the method is repeatable. Taken together, the present non-invasive method seems to be a promising new tool for non-invasive detection of P. ovata infections in minnows and probably can be applied for the detection of other body cavity dwelling metazoan parasites in various host taxa. [ABSTRACT FROM AUTHOR]

Young minnow specimens suffer higher parasite loading than Phoxinus phoxinus adult specimens. [ABSTRACT FROM AUTHOR]

Studies of the brown trout ( Salmo trutta) population in the Norwegian subalpine lake, Øvre Heimdalsvatn, over a 50-year period have revealed major changes in population dynamics. In 1958, the population density was high, with individuals stagnating in growth at lengths below 30 cm. After heavy exploitation during the years 1958–1969, the number of older fish declined substantially, and growth rates increased significantly. Since 1969, the European minnow ( Phoxinus phoxinus) have been observed in the lake, with increasing densities from 1977–1978 to 1999–2000. The age structure of the brown trout population has changed markedly from the 1960s to the period 1993–2006. Annual recruitment significantly declined, from an average number of 3746 individuals in age-class 4 during the period 1958–1966 to an average of 1668 during the period 1993–2006. However, due to lower exploitation rates, the number of old fish was significantly higher in the latter period. The summer diet of brown trout has changed substantially from a dominance of the large crustaceans Lepidurus arcticus and Gammarus lacustris to a high occurrence of European minnows, while L. arcticus has become practically absent from the diet. There was a negative relationship between brown trout biomass and annual length increment. However, despite a brown trout biomass at the same level during the years 1993–2006 as in the 1960s, annual individual growth rates have significantly declined. The reduced recruitment and reduced annual growth rates of the brown trout, as well as changes in the diet, are most likely related to the introduction and establishment of the invasive species, the European minnow. [ABSTRACT FROM AUTHOR]

A study of the diet of native brown trout ( Salmo trutta) parr and introduced European minnow ( Phoxinus phoxinus) in the subalpine lake, Øvre Heimdalsvatn, showed that the two species had considerable dietary overlap, both in the littoral zone and in the outlet of the lake. Chironomidae constituted a substantial proportion of the diet of the two species in both habitats. The results indicated that both zooplankton (Cladocera) and large macroinvertebrates (EPT-species) made up a higher proportion of the minnow diet in the early phase of the minnow establishment (1975–1977) than later, and that the significance of small macroinvertebrates (Chironomidae) as prey has increased during the same period. Dietary analysis of the sympatric brown trout and minnow population in Øvre Heimdalsvatn does not provide a definitive conclusion about the degree of competition between the two species. However, together with the findings in other studies in Øvre Heimdalsvatn that have documented reduced recruitment and individual growth of brown trout, decreased individual growth of minnows and a marked decline in the density of large crustaceans ( Lepidurus arcticus and Gammarus lacustris) in the shallow littoral of the lake during the last decades indicates that competitive interactions between the two species are likely. This is probably an example of the competition between two fish species with a high degree of dietary overlap when living in sympatry, most likely caused by absence of alternative prey and alternative habitats due to the high predation risk for both brown trout parr and minnows in deeper parts and in the open waters of the lake. [ABSTRACT FROM AUTHOR]

The littoral benthos of the subalpine lake, Øvre Heimdalsvatn, has been documented in a series of investigations carried out in 1972, 1976, 1985 and 2000. During this 28-year period there have been major changes in the benthos of the lake following the introduction of European minnow ( Phoxinus phoxinus) into the lake where brown trout ( Salmo trutta) was formerly the sole species. In 1972 Ephemeroptera, Trichoptera, Plecoptera and Gammarus lacustris dominated the macrobenthos, constituting 85% of faunal numbers, while Chironomidae and Oligochaeta made up only c. 6%. However, by 1976, chironomids and oligochaetes had increased in relative abundance, while G. lacustris declined. This trend towards a dominance of chironomids and oligochaetes was confirmed in 1985 and 2000, although absolute numbers of Ephemeroptera, Plecoptera and Trichoptera increased in 2000 relative to 1972 values. Gammarus lacustris had a 2-year life cycle in Øvre Heimdalsvatn. In 1972 there were significantly more females than males, but by 1976 and through to 2000 there were greater numbers of males. Despite this reduction in females, numbers of juveniles increased, although mortality, probably due to increased predation from minnows, was higher than earlier. The introduction of the alien species, the European minnow, into Øvre Heimdalsvatn has clearly changed the composition and structure of the littoral macroinvertebrate benthos. [ABSTRACT FROM AUTHOR]

Data from the International Biological Programme (IBP) and subsequent studies have been re-analysed to test the two hypotheses which previously have been suggested concerning the zooplankton in the mountain lake, Øvre Heimdalsvatn: (1) the average temperature in June, more than other summer months, is affecting the growth rate and population densities of zooplankton in the lake, (2) the invasion of the European minnow ( Phoxinus phoxinus) has caused changes in the zooplankton community. The analyses have demonstrated that the June temperature strongly affects the growth rate of all the zooplankton species, but that there is no relationship with the population maxima. The species composition in the crustacean zooplankton has not changed between 1969 and 1999, and any direct impact of the minnows on the zooplankton community could not be detected. Indirectly, the minnows may have reduced the density of invertebrate predators, and thus caused an increase in juvenile survival and increased summer maximum density of Bosmina longispina. The variation in density of the copepod, Cyclops scutifer, was correlated with the density of Heterocope saliens, most likely the result of predator–prey interactions. [ABSTRACT FROM AUTHOR]

The alien fish species, European minnow ( Phoxinus phoxinus), was recorded in the mountain lake, Øvre Heimdalsvatn, southern Norway, for the first time in 1969. After some years minnows were observed in the diet of brown trout ( Salmo trutta). In 2006, brown trout had significantly higher δ15N values than European minnow, indicating that brown trout holds the top trophic position in the lake food web. The δ15N signatures of brown trout were significantly correlated to fish size, age and mercury concentration, while δ15N signatures in minnows did not show any change with fish size, age and mercury concentrations, indicating that European minnow remain at the same trophic level throughout the life history. The mercury concentrations (mg kg−1 w.w.) in brown trout and minnows were in the range 0.014–0.093 and 0.014–0.16, respectively. For both species, positive relationships between total mercury concentrations and fish length, weight and age were found. Although European minnow was found as prey in brown trout stomachs, minnow had significantly higher mercury concentrations than brown trout. It is most likely that the higher mercury concentrations in the European minnow are due to the high metabolic rate, with more energy spent on maintenance than on growth as a consequence of its small size and very low annual growth rate compared to brown trout. Changes in population densities of both brown trout and European minnow may influence their habitat use, feeding preferences and metabolism, and may thus potentially lead to changes in the mercury loads of both species. [ABSTRACT FROM AUTHOR]

The cephalic lateral line systems of seven Far Eastern Phoxinus species (P. phoxinus, P. kumgangensis, P. semotilus, P. lagowskii, P. oxycephalus, P. perenurus, and P. czekanowskii) were investigated. In this genus, the infraorbital canal is not connected with either the supraorbital canal or the preoperculomandibular canal. Phoxinus phoxinus is unique for having an underdeveloped condition, such as canal formation or remaining as uncovered. A unified supraorbital canal was observed in all species, but the infraorbital canal of both P. perenurus and P. czekanowskii was not unified into a single canal throughout their development. Unification between both sides of the supratemporal canal occurred in larger individuals of P. lagowskii, P. oxycephalus, and P. czekanowskii. The preoperculomandibular canal of P. kumgangensis, large P. lagowskii, and large P. oxycephalus was unified. The pore number of each part of the canal system also varied depending on the species. Intraspecific variations were observed between Korean and Japanese specimens of P. lagowskii in the unification of the supratemporal canal and the preoperculomandibular canal, and the number of pores of the supratemporal canal. It was inferred that the specific characteristic patterns of their cephalic lateral line systems reflected the following two factors: different environmental requirement for their microhabitat and different maximum body size. [ABSTRACT FROM AUTHOR]

As a consequence of the construction of the A-15 highway between 1991 and 1995, some modifications affecting the Larraun River (Navarra, North of Spain) were made. One of the most important effects was the channelization of a section of the river in the middle zone. Fish were caught by electrofishing in August of 1996 in the channelized reach, as well as in non-modified stretches upstream and downstream. Physical and chemical variables and shelter availability were also analyzed. The captured fish were measured (total length) and released into the river. We calculated the density, biomass, length distribution and diversity, comparing the obtained results from the different stretches. The number of species was higher in the lower zones of the river and diversity increased progressively downstream. The fish density in the channelized section was slightly lower than in the other two points. Also biomass in the channelized section was about a factor of 10 smaller than the calculated biomass in unaltered points. Moreover, in comparison with the unaltered sections of the river, in the channelized area a major decrease in the presence of fish larger than 150 mm was detected. The low shelter availability in the channelized section, lack of bank vegetation and alterations in the substratum could explain the observed variations in the length distribution, biomass and the lower value of the density of European minnow, Phoxinus phoxinus (Linnaeus, 1758). [ABSTRACT FROM AUTHOR]

The mechanisms and functions of mixed-species shoaling were investigated in two sympatric species of cyprinids, the chub and the European minnow, from the river Wharfe where they comprised approximately 70% of all year 0+ fish over a 20-year survey. Chub preferred conspecific shoals over heterospecific ones with olfactory cues being more important than visual ones for shoal choice. This preference was consistent with measurements of length:flank area ratios and length:weight ratios which suggest that both species are similar in appearance. When presented with mixed-species shoals, chub increased the percentage time spent with stimulus shoals with increasing proportions of conspecifics. Feeding experiments suggest that the preference for conspecific shoals is driven by interspecific competition (with minnows out-competing similar-sized chub) and the oddity effect. The importance of this work in the context of species assortment in free-ranging shoals is discussed. [ABSTRACT FROM AUTHOR]

In 1990, a monitoring programme was initiated to survey the status of benthic invertebrate communities and fish populations over a wide range of subarctic rivers in northernmost Finnish Lapland (68°15′–70°N). A special emphasis was placed on detecting possible effects of acidification through sulfur emissions from Russian Kola Peninsula. Sampling in 13 rivers within four major river systems covered watercourses from small brooks to large 7th order rivers, and watersheds with different distances from the emission sources. The community structure of zoobenthos and the occurrence of acid-sensitive indicator species were assessed in 90 sampling sites. Sensitive fluvial fish species, including Atlantic salmon (Salmo salar), brown trout (Salmo trutta), European minnow (Phoxinus phoxinus) and burbot (Lota lota), were monitored by studying their occurrence, abundance and juvenile recruitment. No signs of acid-induced failure in juvenile recruitment were detected in salmonid populations. The occurrence of minnow and burbot covered all the systems studied. In parallell, the structure of benthic communities with relatively high species diversity and wide distribution of a highly acid-sensitive caddisfly indicated no effects of acidification. [ABSTRACT FROM AUTHOR]

Southern populations of the European minnow from remote oligotrophic mountain lakes along an Alpine north-south transect accumulated more p,p′ DDE and PCBs than northern populations. As these semi-volatile organochlorines predominantly evaporate in warm countries, higher rates of condensation (deposition) are assumed to occur in the southern slopes of the Alps. The higher accumulation of lead and cadmium in southern population is rather attributed to geogenic and specific environmental impacts than to atmospheric deposition. Increasing liver ratios of [glutathione disulfide]/[glutathione], a potential indicator for oxidative stress, from north to south reflect the generally higher toxic load at remote sites at the southern edge of the Alps. However, histopathological changes in the liver did not correlate with accumulated toxicants indicating that deposition does not lead to severe lesions but induces specific mechanisms for detoxification. [ABSTRACT FROM AUTHOR]

As with many rivers of the Pyrenees Mountains, reservoirs on the River Ariège (SW Francc) are used for hydroelectricity generation, irrigation and to maintain summer flows in the River Garonne. Two river reservoirs on the River Ariège were simultaneously emptied in April 1991 to remove accumulated sediment. Fish and ten environmental variables were sampled using Point Abundance Sampling by electrofishing before (February 1991) and one year later (February 1992) at three study sites downstream of the dams. We examined the short-term impact of reservoir cleaning on the relative abundance, habitat availability and habitat use of three species of small fish: minnow Phoxinus phoxinus (L.), gudgeon Gobio gobio (L.) and stone loach Barbatula barbatula (L.).¶After the reservoir cleaning, areas covered by gravel, sand and mud increased significantly as the result of the sediment release. The three species did not react in the same manner to these environmental changes. Stone loach appeared to be the most sensitive species, with its relative abundance decreasing at all sites. Conversely, minnow seemed to be the most resistant species and as such is a leading pioneer species for colonizing new or impacted stretches of rivers channels. Finally, the number of gudgeon decreased particularly at the most downstream site where large deposits of mud were recorded. [ABSTRACT FROM AUTHOR]

The morphology of minnows Phoxinus phoxinus from two rivers at the south-east of England was analysed on mensural characters and qualitative traits (occurrence of appendages, pattern of pigmentation and scalation). Eight developmental intervals were identified from the qualitative traits, and bivariate and multivariate analysis revealed that allometric growth occurs occasionally during ontogeny, mainly in earlier developmental periods. Body shape is under the influence of rapid increase during development, mainly due to the quick growth in early developmental intervals. The exclusion of 'general size', remarkable in early developmental intervals, revealed several 'shape' characters that mainly determine minnow morphology by changing the mode of variability during development (e.g. caudal characters, maximum body height, belly length and ventral head length). The tail certainly undergoes the most consistent and most durable change, its characters being the most variable and the most discriminative for developmental periods from larvae to adults. The most prominent alteration in the overall shape development occurs at the transition from larva to juvenile, both regarding the number of characters involved into the change and their variability. This transition takes place at about 28 mm SL, which corresponds to a significant change in microhabitat use in both the rivers Lee and Frome, characterized by shifts by 0+ juveniles to significantly deeper waters than those occupied by larvae, with increased amounts of either submerged filamentous algae (Lee) or vegetation (Frome). [ABSTRACT FROM AUTHOR]

The article presents a study which examines the tissue distribution of selenium and mercury toxicity in minnow Phoxinus phoxinus. The study uses adult minnows in which radioactivity was identified using a Packard Nal gamma scintillation counter. The study has found that the modification of tissue distribution pattern of mercury was one of the observed effects of selenium treatment.

The influence of parasites on the breeding biology of the European minnow ( Phoxinus phoxinus) was studied by examining 268 adult and 59 young-of-the-year minnows from an artificial Swiss Alpine lake for parasites during the breeding seasons in 1990 and 1991. Two trematode parasites; Diplostomum phoxini, in their brains, and Macrolecithus papilliger, in their guts, were found. The prevalence of D. phoxini was 100% in both years. The mean abundance was 231 in 1990 and 448 in 1991; the difference was significant. Prevalence (and abundance) of M. papilliger was 37.5% (1.04±0.39) in 1990 and 59.5% (2.68±0.55) in 1991; also significantly higher in 1991 than in 1990. No differences in prevalence or abundance between males and females were found. Numbers of both parasites were significantly correlated with fish length. There was seasonal variation in the abundance of D. phoxini metacercariae, with a peak in June/July in both years. The prevalence of M. papiller decreased after July in both years. Distribution of the two trematodes was overdispersed as indicated by the variance to mean (abundance) ratio. The observed seasonal variation in D. phoxini abundance also suggests that sublethal parasites could influence the population dynamics of their hosts. [ABSTRACT FROM AUTHOR]

The behaviour of individual minnows (Phoxinus phoxinus) and goldfish (Carassius auratus) foraging on an artificial food patch was recorded for single species shoals of 2, 4, 6, 12 and 20 fish. In both species shoal size accounted for most variation in behaviour in the experiments. The behaviour of individual goldfish differed more than that of individual minnows, a result that can be explained by the weaker shoaling tendency of goldfish. 'Timid' behaviour, for example lurking in the weeds or rapid darting and turning, predominated in small shoals. It was only in large shoals that fish made frequent and lengthy visits to the patch. [ABSTRACT FROM AUTHOR]