Showing papers in "Knowledge and Management of Aquatic Ecosystems in 2012"
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TL;DR: The objective of this paper is to make available to the scientific community an important check-list of taxa frequently observed in European rivers with their memberships to metrics, and clearly appears that metrics memberships are determined by taxonomy.
Abstract: Key-words: Bacillariophyta, biomonitoring, check-list, metric, river Diatoms are a very diverse group of microalgae that encompass about 100000 taxa. This makes an excellent bioindicator especially of rivers. The majority of biotic indices based on diatoms are constructed on species pollution-sensitivities. Nevertheless, recent studies showed the interest to use complementary metrics for biomonitoring: life-forms, cell-sizes and ecological guilds. Unfortunately, taxa memberships to such metrics are scattered in numerous floras and papers. Therefore, studies using such metrics often referred to grey literature or home-made checklists. The objective of this paper is to make available to the scientific community an important check-list of taxa frequently observed in European rivers with their memberships to these metrics. After defining these metrics, 1115 taxa were codified using Biofresh and Omnidia codes in an Excel file. Metrics memberships were then explored in a taxonomical framework. It clearly appears that metrics memberships are determined by taxonomy. Lifeforms and cell sizes taxa memberships and their study in the framework of evolutionary history of diatoms is a field that is worth studying for a better understanding of diatoms ecology. Such inputs should be beneficial for the future improvement of diatom-based monitoring tools.
263 citations
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TL;DR: A synthesis, based on more than 300 references, is proposed, which details thermal tolerances for the entire life cycle: reproduction, embryonic, larval, juvenile and adult life stages, which is of great importance to an understanding of the trends observed in fish communities.
Abstract: The effects of industrial cooling water on fish communities were widely debated at the end of the seventies, when large thermal power plants were being developed. This led to numerous research programs on thermal tolerance in fish. The recent warming climatic period and especially the 2003 heat wave have brought thermal biology back to center stage. The work presentedherehasconsistedinanalyzinghistoricalandcontemporaryliterature to update basic knowledge on thermal tolerances of 19 riverine fish species. These data were then validated and completed by European fish specialists. We finally proposed a synthesis, based on more than 300 references, which details thermal tolerances for the entire life cycle: reproduction, embryonic, larval, juvenile and adult life stages. This updated material is of great importance to an understanding of the trends observed in fish communitiesorforforecastingfuturebehaviorinclimatechangescenarios.
68 citations
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TL;DR: In this article, the prevalence of Aphanomyces astaci DNA in the narrow clawed crayfish (Astacus leptodactylus) collected from two Turkish lakes, Lake Iznik and Hirfanli Dam (N = 40 from both sites).
Abstract: Crayfish stocks collapsed in Turkey in mid 1980’s due to crayfish plague epidemics, with up to 25% survival in some cases. The collapsed stocks have then recovered slowly and commercial crayfish fishery was reinitiated gradually within a decade. We examined the prevalence of Aphanomyces astaci DNA in the narrow clawed crayfish (Astacus leptodactylus) collected from two Turkish lakes, Lake Iznik and Hirfanli Dam (N = 40 from both sites). The qPCR results, verified by conventional PCR and sequencing, indicated that nearly all sampled crayfish were A. astaci carries with some of them showing gross symptoms of infection, such as tissue erosion and melanisation, while some did not show any visible symptoms. The prevalence of A. astaci DNA was high in both stocks, being on the average 95% in both Lake Iznik and Hirfanli Dam. Our results show that these stocks are carries of A. astaci , but capable of forming productive stocks which indicates past and contemporary partial resistance adaptation in the host or virulence evolution in the A. astaci .
53 citations
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TL;DR: The taxonomic status of Unio mancus Lamarck, 1819, superficially similar to Unio pictorum (Linnaeus, 1758) and often synonymized with it, is re-evaluated based on a random sample of major French drainages and a systematic sample of historical type localities.
Abstract: Key-words: COI gene, conservation genetics, freshwater mussel, molecular systematics, species delimitation The conservation status of European unionid species rests on the scientific knowledge of the 1980s, before the current revival of taxonomic reappraisals based on molecular characters. The taxonomic status of Unio mancus Lamarck, 1819, superficially similar to Unio pictorum (Linnaeus, 1758) and often synonymized with it, is re-evaluated based on a random sample of major French drainages and a systematic sample of historical type localities. We confirm the validity of U. mancus as a distinct species occurring in France and Spain, where it is structured into three geographical units here ranked as subspecies: U. m. mancus [Atlantic drainages, eastern Pyrenees, Spanish Mediterranean drainages], U. m. turtonii Payraudeau, 1826 [coastal drainages East of the Rhone and Corsica] and U. m. requienii Michaud, 1831 [Seine, Saone-Rhone, and coastal drainages West of the Rhone]. Many populations of Unio mancus have been extirpated during the 20th century and the remaining populations continue to be under pressure; U. mancus satisfies the criteria to be listed as “Endangered” in the IUCN Red List.
46 citations
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TL;DR: Evidence is provided that O. immunis exhibits a strongly r-selected life history and omnivorous feeding habits and the ability to prey on a wide array of invertebrate taxa presumably supports the sustained high growth rate of O. Immunis.
Abstract: In the present study, the life history and diet of the highly successful North American invader Orconectes immunis was assessed for the first time in its introduced European range. In 2007, O. immunis population dynamics were monitored in a typical backwater habitat using unbaited funnel traps, and its life history was analysed using Von Bertalanffy’s growth function. Juveniles hatched as early as March and may attain sexual maturity at the end of their first summer. The adult population moulted up to four times during the summer months, with the non-breeding form (II) lasting for a remarkably short time period. The high growth rate of O. immunis was combined with a short longevity, which was estimated at 2.5 years. The fecundity ranged from 119 to 495 pleopodal eggs. The stomach contents were dominated by detritus, followed by macroinvertebrates and macrophytes, and no ontogenetic shift in diet was observed. The ability to prey on a wide array of invertebrate taxa presumably supports the sustained high growth rate of O. immunis . The presented data provide evidence that O. immunis exhibits a strongly r-selected life history and omnivorous feeding habits. These ecological properties have often been linked to successful invaders and enhance the invasiveness of O. immunis .
36 citations
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TL;DR: Assessment of elemental accumulation patterns in a number of economically important fish species from the Danube River in Serbia found distribution of elements among different tissues had a consistent pattern among the species.
Abstract: The Danube River in the vicinity of the city of Belgrade receives large amounts of untreated or poorly treated communal and industrial waste waters. The aim of this study was to assess elemental accumulation patterns in a number of economically important fish species in this area that belong to different trophic levels. Concentrations of 17 elements (Al, As, B, Ba, Cd, Co, Cr, Cu, Fe, Li, Mn, Mo, Ni, Pb, Se, Sr and Zn) were assessed in liver, muscle, gills and gonads of silver carp (Hypophthalmichthys molitrix ), freshwater bream (Abramis brama ), white bream (Blicca bjoerkna ), common carp (Cyprinus carpio ) and wels catfish (Silurus glanis ) from the Danube River in Serbia by the use of ICP-OES. Silver carp specimens were differentiated from the other four species by high concentrations of Al and Fe in the liver. Common carp specimens were differentiated by high concentrations of Zn in gills, muscle and liver. Distribution of elements among different tissues had a consistent pattern among the species. Concentrations of Pb, Cd, As, Zn, Cu and Fe in muscle were at acceptable levels for human consumption, while concentrations of Fe and Zn were above maximum acceptable concentrations in liver and gonads.
32 citations
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TL;DR: In this paper, the authors used relative weight (W r ), a condition index which allows evaluation of fish well-being, as a tool to investigate the impact of the presence of non-native species (NNS) on the condition of the key native species (NS) of the Tiber River basin (Italy): Barbus tyberinus Bonaparte, Leuciscus cephalus (Linnaeus), Leucisus lucumonis Bianco, Rutilus rubilio (Bonaparte) and Telestes muticellus (Bon
Abstract: The aim of the research was to test relative weight (W r ), a condition index which allows evaluation of fish well-being, as a tool to investigate the impact of the presence of non native species (NNS) on the condition of the key native species (NS) of the Tiber River basin (Italy): Barbus tyberinus Bonaparte, Leuciscus cephalus (Linnaeus), Leuciscus lucumonis Bianco, Rutilus rubilio (Bonaparte) and Telestes muticellus (Bonaparte). By means of Canonical Correlation Analysis, data from 130 sampling sites, distributed throughout Tiber River basin, were examined. W r of NS was related to densities of NNS and to environmental variables. Moreover, the correlation between W r of NS and density of NNS was investigated through linear regression analysis and covariance analysis. Preliminary results encourage the use of W r as a tool to assess the relationship between NS and ecological factors (such as the presence of NNS) and to explain the changes that occur along the longitudinal gradient of a river.
30 citations
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TL;DR: Preliminary results encourage the use of W r as a tool to assess the relationship between NS and ecological factors and to explain the changes that occur along the longitudinal gradient of a river.
30 citations
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TL;DR: It is suggested that human population density and economic growth are positively related to increased number of non-indigenous freshwater crayfish species and this pattern is evident in countries with higher overall footprint.
Abstract: Non-indigenous freshwater crayfish species (NICS) outnumber the indigenous ones in many European countries, representing a major threat to biodiversity via the spread of crayfish ‘plague’ and aggressive invasion andantagonismperformance.Althoughthebiologicalbasisofthissituation is well studied, the possible role of social, economic and demographic factors on this situation has been ignored. In an attempt to explore such relationships, we suggest that human population density and economic growth (measured as gross domestic product (GDP) per capita) are positivelyrelatedtotheincreasednumberofNICSintheEUarea.Moreover, this pattern is evident in countries with higher overall footprint (i.e. the human demand of biologically productive land and sea in global hectares required to provide resources and services on waste assimilation) compared to biocapacity. Within the above context, actions are urgently needed to restore/balance existing and projected metabolic rifts (i.e. rupturesinthenormalmetabolicprocessesinnaturalsystems)created by the presence of NICS.
28 citations
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TL;DR: Behavioural differences among the sexes and life stages were suggested to cause differences in food selection and the size of the food items also influences food preference.
Abstract: The giant mudskipper (Periophthalmodon schlosseri ) is one of the commonly found mudskipper species living and it makes a significant biomass value in the mangrove ecosystem. Samples of this mudskipper species were collected and analysed for stomach content and stable isotope ratios (δ 13 C and δ 15 N) to determine their food preference. The stomach content analysis showed four groups of food items: fiddler crabs (Uca sp.), medaka fish (Oryzias sp.), juveniles of indeterminate fish species and indeterminate remains of prey items. P. schlosseri females prefer to prey on Oryzias sp. (57.8%), Uca sp. (26.7%) and juveniles of indeterminate fish species (6.7%), while the males prefer to prey on Uca sp. (84.6%) and Oryzias sp. (7.7%). The indeterminate remaining prey items were 8.9% and 7.7% for respective sexes. The stable isotope analysis showed Uca sp. and Oryzias sp. being the main food items for P. schlosseri . The values of δ 13 C and δ 15 N ratios also showed differences in food preference among sexes, where females of all life stages prefer to prey more on Oryzias sp. and little Uca sp. In contrast, the male P. schlosseri prefer to prey only on Uca sp. throughout their life, with the exception of juvenile male P. schlosseri, which suggested they also consume a small amount of Oryzias sp. Behavioural differences among the sexes and life stages were suggested to cause differences in food selection. The size of the food items also influences food preference.
27 citations
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TL;DR: In this paper, the authors investigated macroinvertebrate communities in a small reservoir, Malilangwe reservoir over seven months (April to October) by active sweep netting and searching soil sediments.
Abstract: Key-words: Macroinvertebrates, diversity, Malilangwe reservoir, macrophyte cover, conductivity, water level The aim of our study was to investigate macroinvertebrate communities so as to understand factors and processes structuring macroinvertebrate communities in a small reservoir, Malilangwe reservoir over seven months (April to October). Sampling was performed by active sweep netting and searching soil sediments. Water temperature, conductivity, dissolved oxygen, pH, ammonia, nitrogen, phosphorus, chemical oxygen demand and macrophyte cover were determined. In total, forty-two macroinvertebrate families belonging to 10 orders were identified amongst 13 macrophyte species and sediments. Thiaridae and Physidae (Mollusca) were the dominant and most abundant taxa (57.71%) and there were followed by the Hemiptera (27.31%). High indices for sites 1 to 3 for the Simpsons index, the Shannon-Weaver index and evenness were recorded, while low indices were observed for sites 4 to 5, with significant differences being observed among the study site using the Kruskal-Wallis ANOVA test (p < 0.05). Redundancy Analysis revealed that among environmental factors, hydrologically linked parameters such as conductivity, water level and macrophyte cover had the strongest influence on macroinvertebrate distribution.
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TL;DR: Evidence is presented that invasive signal crayfish create a new link in energy transfer from littoral areas to profundal areas and thereby increase connectivity between these spatially distinct habitats.
Abstract: Several studies have shown that distinct compartments of lake ecosystems are coupled via transportation of organic matter, nutrients and energy across habitat boundaries. Here we evaluate the potential of the invasive signal crayfish (Pacifastacus leniusculus (Dana)) to modify energy pathways in large boreal lakes. Using a stable isotope mixing model and calculation of the isotopic niches we estimated the contribution of different food sources to the diets of crayfish captured from different habitats, and from that inferred their potential to transport energy across the littoral-profundal gradient. The crayfish caught from the littoral area utilized mainly littoral food sources, whereas the importance of profundal sources increased consistently with depth. We also found crayfish in deeper habitats with littoral δ13 C label, which indicates significant use of littoral sources. These results presents evidence that invasive signal crayfish create a new link in energy transfer from littoral areas to profundal areas and thereby increase connectivity between these spatially distinct habitats. Our results highlight a need for better understanding of the role of crayfish in lake energy dynamics and habitat connectivity.
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TL;DR: In this article, the effects of land use changes on flow regime and water chemistry of headwater streams in the highlands of Chiapas, a region in southern Mexico that has experienced high rates of deforestation in the last decades.
Abstract: We studied the effects of land use changes on flow regime and water chemistry of headwater streams in the highlands of Chiapas, a region in southern Mexico that has experienced high rates of deforestation in the last decades. Samples for water chemistry were collected and discharge was measured between September 2007 and August 2008 at eight streams that differed in the land uses of their riparian and catchment areas, including streams draining protected forested areas. Streams with high forest cover (>70%) in their catchments maintained flow through the year. Streams draining more disturbed catchments exhibited reduced or no flow for 4 − 6 months during the dry season. Nitrate concentrations were lower at streams draining forested catchments while highest concentrations were measured where conventional agriculture covered a high proportion of the catchment and riparian zone. Highest phosphorus concentrations occurred at the catchment where poultry manure was applied as fertilizer. Differences between forest streams and those draining disturbed areas were correlated with the proportion of forest and agriculture in the riparian zone. Variation in stream variables among sampling dates was lower at the forest sites than at the more disturbed study streams. Conversion of forest into agriculture and urban areas is affecting flow regime and increasing nutrient concentrations, although the magnitude of the impacts are influenced by the type of agricultural practices and the alteration of the riparian zone.
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TL;DR: Preliminary evidence of marine-derived nutrients from introduced Chinook salmon in stream food webs of Laguna Los Patos, NW Patagonia is presented to elucidate the mechanisms and consequences of nutrients subsidies from salmon carcasses in those invaded ecosystems.
Abstract: Using stable isotope analyses of N and C we present preliminary evidence of marine-derived nutrients from introduced Chinook salmon (Oncorhynchus tshawytscha Walbaum) in stream food webs of Laguna Los Patos, NW Patagonia. Similar to values reported within Chinook salmon's native distributional range periphyton and aquatic insects are the trophic levels that show the greatest enrichment of δ 15 N (5–6‰). Since there is a rapid expansion of Chinook salmon in South America future effort is needed to elucidate the mechanisms and consequences of nutrients subsidies from salmon carcasses in those invaded ecosystems.
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TL;DR: Wang et al. as mentioned in this paper investigated how upstream fish assemblage has responded to successive impoundments of the Three Gorges Reservoir (TGR) during the period from 1997 to 2011.
Abstract: The construction of the Three Gorges Reservoir (TGR) has seriously affected the fish assemblage in the impounded reaches. However, fish assemblage changes in the riverine zone remain poorly documented. In order to explore how upstream fish assemblage has responded to the successive impoundments of the TGR, fish investigations were conducted biannually in Hejiang, a protected reach of the upper Yangtze River, during the period from 1997 to 2011. Multivariate analysis revealed significant temporal differences in fish assemblage following the impoundments of the TGR. Prior to the impoundments, the fish assemblage appeared to be very diversified and very even. Immediately after the first and the second impoundment, the lotic species, such as Coreius guichenoti, Rhinogobio ventralis, Rhinogobio cylindricus and Coreius heterodon, became evidently dominant, due to their upstream migrations from the reservoir. However, two years after the third impoundment, the lotic species decreased dramatically, while lentic Hypophthalmichthys molitrix and Pelteobagrus vachelli became the new dominant species. Based on this and other studies, we can see the habitats of the riverine fish in the upper Yangtze River have been shrunk seriously because of the impoundments of the TGR. The cascade hydropower development in the lower Jinsha River will pose an accumulative effect on the aquatic environment in the mainstream of the upper Yangtze River. Free-flowing tributaries, such as the Chishui River, will play more important roles in fish conservation.
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TL;DR: In this paper, a non-metric multidimensional scaling for macroinvertebrate taxa and a principal component analysis for environmental variables strongly separated upstream sites (e.g. Vacas Heladas and Malo Rivers), which presented low pH and high dissolved metal concentrations, from other sites.
Abstract: Catchments in the semiarid regions are especially susceptible to environmental perturbation associated with water scarcity, hydrological variations and overuse by anthropogenic activities. Using multivariate analysis to relate environmental and biological data, and diversity and biotic indices (ChBMWP, ChIBF), we analyzed the macroinvertebrate composition of 12 rivers of the semiarid region of northern Chile. A non-metric multidimensional scaling for macroinvertebrate taxa and a principal component analysis for environmental variables strongly separated upstream sites (e.g. Vacas Heladas and Malo Rivers), which presented low pH and high dissolved metal concentrations, from other sites. Effectively, CCA showed that metals and low pH, associated with the altitudinal gradient, determined the distributional patterns of macroinvertebrates in the Elqui catchment. The causes of these particular conditions could be related to geological processes and human impact. The biotic indices applied to the sampling sites corroborated and reflected these characteristics, with La Laguna and Turbio Rivers showing a diverse macroinvertebrate community and moderate to good water quality, and the Claro River showing favorable conditions for the development of aquatic biota, indicating its better quality relative to other stations. To the middle and low part of the basin, a change in the composition of the community was observed, with species that suggest an impact by an increase in organic matter, due to agricultural activities and urban settlements concentrated in this area. Our results suggest that macroinvertebrate taxa in northern Chile may be exceptional species, adapted to unfavorable geochemical conditions, and emphasize the need for protection of the semiarid basins of the region.
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TL;DR: The hypothesis that young stream living trout only feed during the day to the extent needed to sustain growth is supported, with a significant difference in diel shelter use between day and night and a significant increase in shelter use during daytime conditions.
Abstract: The diel partitioning of juvenile brown trout Salmo trutta foraging behaviour is controlled by a number of factors including predation risk, competition, temperature and food availability. The present study uses PIT-tagging and visual observation to asses the use of shelter and foraging behaviour of Danish wild juvenile brown trout (13.5–15.6 cm). The experiment was conducted in a fluvarium and the fish were fed to satiation. It was hypothesised that food satiation would promote nocturnal foraging and increase daytime shelter use. Our results showed a significant difference in diel shelter use between day and night with a significant increase in shelter use during daytime conditions. Visual observations showed a significant preference for nocturnal feeding. Together with the significantly reduced shelter use during the night, our results support the hypothesis that young stream living trout only feed during the day to the extent needed to sustain growth.
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TL;DR: It is concluded that P. clarkii is likely to spread from Regents Canal into the nearby Brent, Crane, Colne, Lee and Thames catchments within 50 years and therefore tighter enforcement is needed to slow the spread of this species.
Abstract: The Louisiana red swamp crayfish Procambarus clarkii is highly invasive. It is now common in Europe where it is causing problems to native wildlife and structural damage to habitats. Procambarus clarkii was first recorded in Britain in 1991 and is currently found in the Hampstead Heath ponds and Regents Canal in London, as well as a small lake 15 km outside of Greater London. This paper considers how conditions in Britain affect the life cycle, breeding habits and potential range expansion of P. clarkii . Results of trapping surveys are presented in an effort to map the current distribution of P. clarkii and predict which areas it could colonise in the future. The ecological impact of potential colonisation is discussed by considering the impact P. clarkii has in mainland Europe. It is concluded that P. clarkii is likely to spread from Regents Canal into the nearby Brent, Crane, Colne, Lee and Thames catchments within 50 years. This time would be reduced significantly if further deliberate or accidental introductions by humans occur since this is deemed a far greater risk than natural expansion. P. clarkii is expected to have a negative impact on aquatic ecosystems in Britain and therefore tighter enforcement is needed to slow the spread of this species.
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TL;DR: T trapping effort was not efficient enough to obtain an accurate estimate of the population size of this species in a fish-pond larger than 2 − 3 ha, and the adopted protocol appeared useful to assess the effect of intensive trapping and other control methods on P. clarkii populations.
Abstract: The red swamp crayfish, Procambarus clarkii , was discovered in 2007 in the “Parc naturel regional (PNR) de la Brenne” (France). Ten colonized sites have been identified in the park to date, including two new sites discovered in 2011. The present study aims at establishing a protocol suitable for estimating the population size of P. clarkii by the use of a Capture-Mark-Recapture (CMR) technique in a chain of five connected fish-ponds. Results show different cohorts of individuals among seasons and fish-ponds. However, trapping effort was not efficient enough to obtain an accurate estimate of the population size of this species in a fish-pond larger than 2 − 3 ha. On the other hand, the adopted protocol appeared useful to assess, in smaller fish-ponds, the effect of intensive trapping and other control methods on P. clarkii populations.
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TL;DR: This study is the first contribution showing the role of water transparency in controlling the depth distribution of perch egg strands in lakes and reservoirs.
Abstract: The roles of wind protected bays, presence of littoral vegetation and light attenuation in the water column on spawning site selection and depth of egg strands deposition by perch Perca fluviatilis was studied in Řimov Reservoir, Czech Republic, in the years 2007 and 2011 using boat observation and SCUBA divers. The data were compared with results from Chabařovice Lake, Czech Republic, where similar monitoring took place in 2007–2010 and 2012. In shallow water of Řimov Reservoir, the density of egg strands was significantly higher in grass bays compared to both rocky bays and the main reservoir body. Most egg strands were deposited in water less than 0.5 m deep on reed canarygrass Phalaris arudinacea . In year when the littoral vegetation was absent perch were forced to spawn significantly deeper on various types of woody structures. In Řimov Reservoir, which is less vulnerable to wind, 91.1% of egg strands were spawned in water ≤3 m deep. In contrast, in the wind exposed Chabařovice Lake, even in the presence of littoral vegetation, 90.5% of egg strands were found at depths greater than 3 m. In Chabařovice Lake, the light penetrated to three times greater depth compared to Řimov Reservoir and, similarly, the depth limit to which 95% of egg strands were spawned was three times greater in this lake compared to Řimov Reservoir. This study is the first contribution showing the role of water transparency in controlling the depth distribution of perch egg strands in lakes and reservoirs.
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TL;DR: Though it is one of the most widespread and interested species in fishing in Italian waters, tench has not been widely studied; this research deepens some biological characteristics of this species that is strongly shrinking in Italy.
Abstract: Growth and some reproductive properties of native Tinca tinca Linnaeus, 1758 from Trasimeno Lake were investigated during 2009 and 2010. The total sample of fish (510) was composed by 126 males, 221 females and 163 immature specimens. Total length (TL ± 0.1 cm) and weight (W ± 0.1 g) were recorded; age estimation was based on scalimetry and sex was determined by microscopic observation of the gonads. Age composition varied from 1+ to 11+ . The TL -W relationship was log 10 W = −2.235 + 3.248log 10 TL . Previous growth was determined with back-calculation from scale measurements using the Fraser-Lee method. Theoretical length growth was estimated with von Bertalanffy’s model. Analysis of the gonadosomatic index (GSI) suggests that the reproductive period of the population took place from May to July. Sexual maturation occurred in both sexes at the second year of life. The mean diameter of eggs was 0.075 mm. The mean number of eggs produced by each female was 233 930 and increased with the size of the specimens. Though it is one of the most widespread and interested species in fishing in Italian waters, tench has not been widely studied; this research deepens some biological characteristics of this species that is strongly shrinking in Italy.
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TL;DR: The impact of Lernaea cyprinacea on fish populations ten years after its first outbreak in the Malilangwe reservoir is currently showing no sign of declining in the reservoir, and there was a significant relationship between parasite intensity and environmental factors.
Abstract: Key-words: Lernaea cyprinacea, Clinostomoides brieni, parasite, cichlids, intensity, Malilangwe An assessment was carried out on the impact of Lernaea cyprinacea on fish populations ten years after its first outbreak in the Malilangwe reservoir, and Lernaea cyprinacea is currently showing no sign of declining in the reservoir. Eight fish species were examined for ectoparasite prevalence and intensity. The possible relationship between L. cyprinacea infestation and environmental factors were investigated. Two parasite species, L. cyprinacea in Oreochromis mossambiccus, Oreochromis placidus, Oreochromis macrochir, Labeo altivelis and Tilapia rendalli and trematode cysts (Clinostomoides brieni) in Clarias gariepinus were found. Lernaea cyprinacea prevalence was 100% amongst all cichlids but varied for L. altivelis. Parasite intensity increased during the cool, dry season (May to July), with the greatest mean intensity being observed amongst the cichlids. There was a significant relationship between parasite intensity and environmental factors; dissolved oxygen (p < 0.05), temperature (p < 0.001) and pH (p < 0.001).
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TL;DR: In this article, post fishing mortality of the glass eel was monitored in 2007 in the Vilaine estuary and the mortality was significantly correlated with body injuries, but not to other environmental factors.
Abstract: Post fishing mortality of the glass eel was monitored in 2007 in the Vilaine estuary. The mortality of the glass eels varied from 2 to 82% (mean 42%) in the two days following the fishing. The mortality of samples collected by handnetsorfromthetrappingladderwasnull.Alterationsoftheskinmucus were analyzed by the use of Indigo carmine. The mortality was significantly correlated with body injuries, but not to other environmental factors. The presence of a large injury on the body systematically led to the death of theglasseels,andamongthesedeadglasseels,only3.5%hadnoexternal injury. These results are discussed, along with the results from other estuaries, with a view to transport glass eels across Europe, with the objective of restoring the eel stock.
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TL;DR: In this paper, the authors examined whether gillnetting and hydroacoustics provide comparable relative fish density and fish size distribution estimates in the uppermost water layer of a shallow turbid lake and whether the inclusion of environmental and stock parameters could improve comparability of data between different gears.
Abstract: We examined whether gillnetting and hydroacoustics provide comparable relative fish density and fish size distribution estimates in the uppermost water layer of a shallow turbid lake and whether the inclusion of environmental and stock parameters could improve comparability of data between different gears. According to gillnetting, most fish shorter than 14 cm in total length were Alburnus alburnus , and most fish longer than 14 cm were Pelecus cultratus . Size distributions and median sizes obtained from gillnetting and acoustics differed. Pure acoustics-derived density estimates accounted for only <8.8% of the variation in the gillnet catch by number and no correlation was found in biomass indices. Most variances observed in the gillnet catch-per-unit-effort data were associated with water transparency, none of the other investigated variables had significant explanatory power. We conclude that the feasibility of establishing a powerful model describing the relationship between fish density estimates of gillnetting and acoustics is low in shallow and turbid habitats, and it might be successful only if the crucial sampling and environmental parameters affecting catch efficiency of gillnets and post-processing of acoustic data are considered. This study cautions again that gillnetting should be used carefully to analyse trends of fish abundance.
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TL;DR: Six congener pattern distributions were identified, which mainly differed in the respective proportions of congeners potentially biotransformed by fish, and could be used for setting remediation priorities.
Abstract: The 2006 european directive on polychlorodibenzodioxins and related compounds in foodstuffs prompted in France a nationwide monitoring study of freshwater fish contamination by these compounds. A database covering about 300 sites (2848 samples of 36 fish species) was obtained from this study. This database was used to explore congener pattern distributions, in order to identify typical sources and the impact of biotransformation on these sources. Fish ecological traits and fish size are the main factors explaining the overall PCB contamination in the two pre-identified categories of species (high or low propensity to accumulate hydrophobic compounds). Lipid content is also an influencing factor, but its relationship to other factors remains uncertain. Species show distinct congener patterns, related more to their physiology than to ecological traits. Spatial patterns were studied on selected sites having more than five individuals analysed – either chub (Squalius cephalus ) or barbel (Barbus barbus ), the most widespread species in the database –. We identified six patterns, which mainly differed in the respective proportions of congeners potentially biotransformed by fish. No connection to typical sources, e.g. technical mixtures, was identified. These patterns instead represent an ageing path of the initial mixtures; they could be used for setting remediation priorities.
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TL;DR: This multimetric index of fish assemblage integrity could serve as a practical technical reference for conducting cost-effective biological assessments of lotic systems.
Abstract: The aim of this study was to develop effective tools based on fish assemblages, allowing the development of an effective assessment approach for the ecological status of running waters. Fish samples were collected using gill-nets with mesh sizes of 8, 10, 12, 14, 15, 18, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75 and 80 mm. Forty sites were visited from October 2008 to September 2009 in the Bandama River. A large part of the data set on fish descriptors associated with environmental parameters was compiled from regional databases. For each of the fish assemblage descriptors, stepwise multiple linear regressions with habitat variables were carried out. The residuals of the models obtained were used as candidate metrics independent of natural environmental factors. Student t-tests used to compare each metric in reference and disturbed samples indicated significant difference (P < 0.05) for six metrics. The standard residuals of metrics selected were added to constitute the final index. This multimetric index of fish assemblage integrity could serve as a practical technical reference for conducting cost-effective biological assessments of lotic systems.
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TL;DR: The Volta River stock of G. paradoxa is overfished and requires immediate action to conserve it by implementing a minimum landing size restriction and intensifying the culture of smaller clams which is a traditional activity at the estuary.
Abstract: Population parameters such as asymptotic (L ∞ ), growth coefficient (K ), mortality rates (Z,F and M ), exploitation level (E ) and recruitment pattern of the freshwater clam Galatea paradoxa were estimated using length-frequency data from the Volta River estuary, Ghana. The L ∞ for G. paradoxa at the Volta estuary was 105.7 mm, the growth coefficient (K ) and the growth performance index (Ǿ) ranged between 0.14–0.18 year-1 and 3.108–3.192, respectively. Total mortality (Z ) was 0.65–0.82 year-1 , while natural mortality (M ) and fishing mortality (F ) were 0.35–0.44 year-1 and 0.21–0.47 year-1 , respectively, with an exploitation level of 0.32–0.57. The recruitment pattern suggested that G. paradoxa has year-round recruitment with a single pulse over an extended period (October–March) in the Volta River. The Volta River stock of G. paradoxa is overfished and requires immediate action to conserve it. This can be achieved by implementing a minimum landing size restriction and intensifying the culture of smaller clams which is a traditional activity at the estuary.
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TL;DR: In this article, the sensitivity of a novel acute bioassay based on the feeding activity of Daphnia magna was assessed, using 2 and 4 h of exposure, using potassium dichromate as the reference chemical.
Abstract: In this study, sensitivity of a novel acute bioassay based on the feeding activity of Daphnia magna was assessed, using 2 and 4 h of exposure. For calibration purposes, results were compared with those of the standard immobility test as described by the ISO 6341:1996 standard. Using potassium dichromate as the reference chemical, after 4 h of exposure the proposed protocol showed similar sensitivity in comparison with the standard, as the EC 50 of the immobility test was 1.093 ± 0.098 mg·L–1 , whereas the EC 50 of the feeding inhibition bioassay was 1.742 ± 0.133 mg·L–1 . In order to test the sensitivity of the bioassay, toxicity of two other contaminants, copper and wastewater, was estimated and the results were compared with those of the standard immobility test. For both cases, the feeding inhibition test showed higher sensitivity, as in the case of copper the EC 50s were 0.0952 ± 0.0087 and 0.0753 ± 0.0152 mg·L–1 , whilst the EC 50 recorded for the 24-h immobility test was 0.2407 ± 0.0159 mg·L–1 . In the case of the effluent, EC 50 values after 2 and 4 h of exposure were 15.698 ± 2.681 and 12.557 ± 2.358 expressed as % of the wastewater, respectively, whereas the EC 50 of the immobility test was calculated to be 36.4688 ± 5.4887.
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TL;DR: In this article, the eco-physiological requirements of caddisflies assemblages in Jiu River (south-west Romania) were analyzed and the output revealed that the communities are driven by a synergic combination of natural factors and pollutants.
Abstract: This survey analyzed the eco-physiological requirements of caddisflies assemblages in Jiu River (south- west Romania). The output revealed that the communities are driven by a synergic combination of natural factors and pollutants. Their ecological profiles are diverse and the degree of tolerance is related to a decrease of water quality over a longitudinal gradient, overlapped with natural variation of physic-chemical factors. The assemblage is dominated by hydropsychids, very tolerant to anthropogenic disturbances, and two other communities separated by large distances (characteristic of headwaters and of lowland areas, respectively) that do rather reveal stronger affinities to the microhabitat requirements then to water pollution. Polyhedral diagrams were employed in order to reveal caddisflies larvae tolerances/intolerances to environmental parameters, in order to test their usefulness for local areas and less numerous samples, as frequently encountered in routine surveys.
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TL;DR: This work examined the prevalence of Aphanomyces astaci DNA in the narrow clawed crayfish collected from two Turkish lakes, Lake Iznik and Hirfanli Dam, and showed that these stocks are carries of A. astaci, but capable of forming productive stocks which indicates past and contemporary partial resistance adaptation in the host or virulence evolution in the A. Astaci.