Biogeographia – The Journal of Integrative Biogeography, 2016
We present a data set on the biodiversity of Italian freshwaters, including lakeshores and riverb... more We present a data set on the biodiversity of Italian freshwaters, including lakeshores and riverbanks of natural (N=379: springs, streams and lakes) and artificial (N=11: fountains) sites. The data set belongs partly to the Italian Long Term Ecological Research network (LTER-Italy) and partly to LifeWatch, the European e-Science infrastructure for biodiversity and ecosystem research. The data included cover a time period corresponding to the last fifty years (1962-2014). They span a large number of taxa from prokaryotes and unicellular eukaryotes to vertebrates and plants, including taxa linked to the aquatic habitat in at least part of their life cycles (like immature stages of insects, amphibians, birds and vascular plants). The data set consists of 6463 occurrence data and distribution records for 1738 species. The complete data set is available in csv file format via the LifeWatch Service Centre.
ABSTRACT Invasions by non-native species are increasingly detected all over the World, as a conse... more ABSTRACT Invasions by non-native species are increasingly detected all over the World, as a consequence of globalization. Successful establishment implies the presence of unexploited niches and/or competitive advantage of invader vs. native closely related species. As a consequence, invasion also impacts functional diversity and trophic relationships in ecosystems. Feeding niche is a relevant component of ecological niche; it can be investigated by means of C, N stable isotopes analyses (SIA). Here we present results of a study in which feeding niche of the invader Rutius rutilus is compared with those of Coregone lavaretus and Alosa agone. in a deep, subalpine lake (Lago Maggiore, Italy ). By applying SIA we quantified seasonal shifts in pelagic vs. littoral diet sources and in their percentage contributions for the three species. Feeding plasticity, namely spatial and temporal displacement, allowed for a peaceful coexistence of the invader and the other two potential competitors.
<p>... more <p>Ettore Grimaldi (1934-2015) was one of the brightest and active ichthyologists in Italy. He was a man of great enthusiasm, boundless energy and great curiosity. He was a person with an open mind. He originally visited the Institute of Pallanza in June 1957 as a master student at the Faculty of Veterinary Medicine, University of Milan. He was formally called back by the Director Vittorio Tonolli, as a research assistant in 1962....</p>
Invasions by non-native species are increasingly detected all over the World, as a consequence of... more Invasions by non-native species are increasingly detected all over the World, as a consequence of globalization. Successful establishment implies the presence of unexploited niches and/or competitive advantage of invader vs. native closely related species. As a consequence, invasion also impacts functional diversity and trophic relationships in ecosystems. Feeding niche is a relevant component of ecological niche; it can be investigated by means of C, N stable isotopes analyses (SIA). Here we present results of a study in which feeding niche of the invader Rutius rutilus is compared with those of Coregone lavaretus and Alosa agone. in a deep, subalpine lake (Lago Maggiore, Italy ). By applying SIA we quantified seasonal shifts in pelagic vs. littoral diet sources and in their percentage contributions for the three species. Feeding plasticity, namely spatial and temporal displacement, allowed for a peaceful coexistence of the invader and the other two potential competitors.
ABSTRACT Aim Our aim was to document geographical patterns of variation in the body-size structur... more ABSTRACT Aim Our aim was to document geographical patterns of variation in the body-size structure of European lake fish assemblages along abiotic gradients, and any differences in fish assemblage structure. We hypothesized that patterns in the body-size structure of entire lake fish assemblages are primarily tempera-ture driven and consistent with the dominant pattern of the temperature–size rule, which suggests a decrease in adult body size with increasing developmen-tal temperature for many ectothermic species. Location 356 European lakes. Methods Variation in the body-size structure of fish assemblages was explored on a continental scale along gradients of temperature, morphometry, produc-tivity and fish assemblage structure for 356 European lakes. The mean fish assemblage body-size and individual body-size distributions were selected as size metrics. Separate analyses were conducted for lakes located within five eco-region subsets (Borealic Uplands/Tundra, FennoScandian Shield, Central Plains, Western Plains and Western Highlands) and for lakes with different functional fish classifications (cold-, cool-and warmwater fish assemblages). Results Geographical patterns of variation in the body-size structure of Euro-pean lake fish assemblages could be clearly discerned along a temperature gradi-ent for both the continental dataset (356 lakes) and the smaller geographical (ecoregion) subsets. We found systematic changes in fish assemblage body-size structure across temperature gradients in correspondence with the dominant thermal fish guild. The majority of the lakes, mainly located in the warmer Euro-pean lowlands, were dominated by eurythermic cool-and warmwater fish assem-blages, with smaller sized individuals characterized by linear individual body-size distributions. Lakes located in colder regions and dominated by stenothermic coldwater salmonids with larger sized individuals were characterized by unimodal or bimodal size distributions. The mean body size of cold-, cool-and warmwater fish assemblages changed uniformly along the temperature gradient. Main conclusions Patterns of variation in the body-size structure of Euro-pean lake fish assemblages are consistent with the temperature–size rule. Tem-perature modifies fish assemblage size structure uniformly within the thermal fish guilds and in different ecoregions. Furthermore, our results indicate an increasing predictive power of temperature to explain variability in body-size structure when moving from warmer to colder geographical regions.
La valutazione dello stato di conservazione di biodiversità, funzioni e servizi degli ecosistemi ... more La valutazione dello stato di conservazione di biodiversità, funzioni e servizi degli ecosistemi di acque interne e la stima della loro vulnerabilità ai cambiamenti climatici sono affrontate considerando tipologie omogenee di ecosistemi acquatici, alla scala integrata del bacino idrografico e della zona di transizione adiacente. Gli ecosistemi acquatici sono ripartiti, secondo uno schema tradizionale, in: bacini fluviali, laghi, zone umide e acque lentiche di piccole dimensioni, ecosistemi dipendenti dalle acque sotterranee (Groundwater Dependent Ecosystems - GDE) e ambienti di transizione a mare. I bacini fluviali e i laghi sono inoltre analizzati nel contesto della regione geografica cui appartengono, assumendo che vi siano associate diverse pressioni e minacce derivanti dai cambiamenti climatici. I cambiamenti climatici hanno effetti diretti sulla fenologia e sulla distribuzione delle specie che si manifestano in seguito a modificazioni della durata delle fasi di crescita, antici...
ABSTRACT Variations in the size structure of fish communities were explored at European scale alo... more ABSTRACT Variations in the size structure of fish communities were explored at European scale along gradients of climate, morphometry, productivity and fish community structure in more than 1800 lakes. Size metrics used were average fish body size, individual size distributions and size diversity. Analyses were conducted at both continental and regional scale. We found changes in fish community size structure across temperature gradients in correspondence with the dominant thermal fish guild. Lakes located in the warmer European lowlands were dominated by eurythermic cool- and warm-water fish communities with small-sized individuals characterised by linear individual size distributions. Lakes located in cold regions and dominated by stenothermic coldwater salmonids with larger-sized individuals were characterised by unimodal or bimodal size distributions. Our results show that temperature modifies fish community size structure uniformly within the thermal fish guilds and different ecoregions. The importance of temperature in explaining variability in fish size increased when moving from warm to cold regions. After controlling for the natural factors, productivity negatively influenced average fish size. At a macroecological scale, the strong effect of environmental temperature suggests future changes in fish size structure as a consequence of climate change, whereas eutrophication effects become more apparent at a regional scale.
ABSTRACT The systematic is still unresolved for the genus Squalius (Cyprinidae, Leuciscinae), a r... more ABSTRACT The systematic is still unresolved for the genus Squalius (Cyprinidae, Leuciscinae), a rich group of small to large fishes widely distributed throughout Europe. The distinction of one of the Italian narrowly endemic species, Squalius albus ( Bonaparte, 1838), described for the area surrounding lake Trasimeno, from the more common and widespread Squalius squalus (Bonaparte, 1837) is doubtful. The application of integrative taxonomy, with DNA taxonomy and quantitative morphometric, using both living and preserved individuals collected from lake Trasimeno before Squalius sp. restocking, allowed us to explicitly test for the identity of the two species in the complex. COI barcoding data, used for phylogenetic reconstructions, underlined that two clades may exist in the complex; nevertheless, DNA taxonomy (ABGD and GMYC) and morphometrics show no statistical support for their identity as separate species. Moreover, during our survey of the genetic diversity of the Italian Squalius, we provided further support for the species status of Squalius lucumonis, and found evidence of the occurrence in Southern Italy of another chub species, Squalius vardarensis (Karaman, 1928), previously known only from the Southern part of the Balkan Peninsula.
In 1990, in order to celebrate the 50 th anniversary of the former Italian Institute of Hydrobiol... more In 1990, in order to celebrate the 50 th anniversary of the former Italian Institute of Hydrobiology, now Institute of Ecosystem Study, a special issue summarising the advances in limnology was published by Memorie dell'Istituto Italiano di Idrobiologia, now Journal of Limnology. After 25 years, it is time again for a synthesis of what limnology did in the past, but mostly for suggestions on widening the horizon of the discipline, by including new tools and techniques. We hope that limnology will live long, and we celebrate the 75 th anniversary of the Institute with this special issue, containing manuscripts on the advances in the field and introducing recent and new lines of research in lentic waters studies.
Freshwater ecosystems and their biodiversity are presently seriously threatened by global develop... more Freshwater ecosystems and their biodiversity are presently seriously threatened by global development and population growth, leading to increases in nutrient inputs and intensification of eutrophication-induced problems in receiving fresh waters, particularly in lakes. Climate change constitutes another threat exacerbating the symptoms of eutrophication and species migration and loss. Unequivocal evidence of climate change impacts is still highly fragmented despite the intensive research, in part due to the variety and uncertainty of climate models and underlying emission scenarios but also due to the different approaches applied to study its effects. We first describe the strengths and weaknesses of the multi-faceted approaches that are presently available for elucidating the effects of climate change in lakes, including space-for-time substitution, time series, experiments, palaeoecology and modelling. Reviewing combined results from studies based on the various approaches, we describe the likely effects of climate changes on biological communities, trophic dynamics and the ecological state of lakes. We further discuss potential mitigation and adaptation measures to counteract the effects of climate change on lakes and, finally, we highlight some of the future challenges that we face to improve our capacity for successful prediction.
A point source of DDT pollution of industrial origin, discovered in 1996 in Lago Maggiore, the se... more A point source of DDT pollution of industrial origin, discovered in 1996 in Lago Maggiore, the second largest (212 km 2 ) and deepest (373 m) lake in Italy, created concern for wildlife and human health because contamination in some fish species exceeded the threshold for human consumption, even though the concentrations measured in the water were much lower than the legal requirements for drinking purposes. Some precautionary measures were undertaken to prevent DDT runoff from the industrial site to the lake but soil restoration had not yet been carried out. The first study to quantify land based sources of DDT homologue pollution was performed in 1998 by sampling all the main tributaries monthly in order to evaluate the annual load to the lake. From May 2001 to May 2002, the study was repeated in order to evaluate the degree of recovery. In this work we compared the results of that survey with those of a more recent campaign carried out from May 2001 to May 2002, concluding that land based sources are still relevant for pp'DDE, the most stable metabolite of pp'DDT, while they are negligible for the parent compound. Furthermore, the Toce River, receiving the soil runoff of the industrial area, was found to give the greatest contribution of DDT and DDE load to the lake in the past campaign, while its load drastically decreased in 2001-2002 in the case of pp'DDT, being comparable to that of Ticino River(the second biggest river of the Lago Maggiore basin, which rises in the St. Gotthard Massif of the Swiss Alpes). Air transport and cold condensation are very likely responsible for trapping DDT and DDE in high mountain glaciers, which represent a secondary pollution source.
Very recently, a common cyprinid fish species at northern latitude, the roach (Rutilus rutilus L.... more Very recently, a common cyprinid fish species at northern latitude, the roach (Rutilus rutilus L.) has been observed in the large south-alpine Lago Maggiore for the first time. The colonization of the lake has the characteristics of an invasion. In order to investigate this new fish population, benthic multi-mesh and commercial gill nets were used to sample fish in a wide gulf in the central part of the lake (Golfo Borromeo) from February to October 2006. In total 779 roach (TL: 5.5 -38.8 cm) were caught, aged, sexed and stomach analyzed. Fecundity was assessed by counting the eggs in ripe gonads of females of age 3 and 4. The roach have become clearly the dominant species in the catches, constituting over 70% of the biomass and 70% of the numbers caught. None of the roach exceeded 8 years in age. They grow very fast (Φ' = 2.55) and have high fecundity (F abs = 13740 ±4700 S.D. at age 3 and F abs = 14768 ±5642 S.D. at age 4). The diet spectrum is wide and characterized by a strong seasonality. In early spring algae (benthic and planktonic algae), benthos and detritus prevail, whereas in summer zooplankton is the most frequent food item. In autumn roach switch back to benthos and detritus. Algae occur more frequently in young specimens while zooplankton, benthos and detritus in adults. The roach population is practically unimpacted by fishing. The minimum legal mesh size (25 mm) of gillnets, used by commercial fishermen, selects roach at the mean L T of 21.2 cm, which is over its length at maturity. The results suggest that roach established a viable population in Lago Maggiore less than a decade ago and rapidly became one of the dominant (if not the dominant) fish species. The possible consequence for the fish fauna in general and for the ecological status of the whole lake is briefly discussed.
Biogeographia – The Journal of Integrative Biogeography, 2016
We present a data set on the biodiversity of Italian freshwaters, including lakeshores and riverb... more We present a data set on the biodiversity of Italian freshwaters, including lakeshores and riverbanks of natural (N=379: springs, streams and lakes) and artificial (N=11: fountains) sites. The data set belongs partly to the Italian Long Term Ecological Research network (LTER-Italy) and partly to LifeWatch, the European e-Science infrastructure for biodiversity and ecosystem research. The data included cover a time period corresponding to the last fifty years (1962-2014). They span a large number of taxa from prokaryotes and unicellular eukaryotes to vertebrates and plants, including taxa linked to the aquatic habitat in at least part of their life cycles (like immature stages of insects, amphibians, birds and vascular plants). The data set consists of 6463 occurrence data and distribution records for 1738 species. The complete data set is available in csv file format via the LifeWatch Service Centre.
ABSTRACT Invasions by non-native species are increasingly detected all over the World, as a conse... more ABSTRACT Invasions by non-native species are increasingly detected all over the World, as a consequence of globalization. Successful establishment implies the presence of unexploited niches and/or competitive advantage of invader vs. native closely related species. As a consequence, invasion also impacts functional diversity and trophic relationships in ecosystems. Feeding niche is a relevant component of ecological niche; it can be investigated by means of C, N stable isotopes analyses (SIA). Here we present results of a study in which feeding niche of the invader Rutius rutilus is compared with those of Coregone lavaretus and Alosa agone. in a deep, subalpine lake (Lago Maggiore, Italy ). By applying SIA we quantified seasonal shifts in pelagic vs. littoral diet sources and in their percentage contributions for the three species. Feeding plasticity, namely spatial and temporal displacement, allowed for a peaceful coexistence of the invader and the other two potential competitors.
<p>... more <p>Ettore Grimaldi (1934-2015) was one of the brightest and active ichthyologists in Italy. He was a man of great enthusiasm, boundless energy and great curiosity. He was a person with an open mind. He originally visited the Institute of Pallanza in June 1957 as a master student at the Faculty of Veterinary Medicine, University of Milan. He was formally called back by the Director Vittorio Tonolli, as a research assistant in 1962....</p>
Invasions by non-native species are increasingly detected all over the World, as a consequence of... more Invasions by non-native species are increasingly detected all over the World, as a consequence of globalization. Successful establishment implies the presence of unexploited niches and/or competitive advantage of invader vs. native closely related species. As a consequence, invasion also impacts functional diversity and trophic relationships in ecosystems. Feeding niche is a relevant component of ecological niche; it can be investigated by means of C, N stable isotopes analyses (SIA). Here we present results of a study in which feeding niche of the invader Rutius rutilus is compared with those of Coregone lavaretus and Alosa agone. in a deep, subalpine lake (Lago Maggiore, Italy ). By applying SIA we quantified seasonal shifts in pelagic vs. littoral diet sources and in their percentage contributions for the three species. Feeding plasticity, namely spatial and temporal displacement, allowed for a peaceful coexistence of the invader and the other two potential competitors.
ABSTRACT Aim Our aim was to document geographical patterns of variation in the body-size structur... more ABSTRACT Aim Our aim was to document geographical patterns of variation in the body-size structure of European lake fish assemblages along abiotic gradients, and any differences in fish assemblage structure. We hypothesized that patterns in the body-size structure of entire lake fish assemblages are primarily tempera-ture driven and consistent with the dominant pattern of the temperature–size rule, which suggests a decrease in adult body size with increasing developmen-tal temperature for many ectothermic species. Location 356 European lakes. Methods Variation in the body-size structure of fish assemblages was explored on a continental scale along gradients of temperature, morphometry, produc-tivity and fish assemblage structure for 356 European lakes. The mean fish assemblage body-size and individual body-size distributions were selected as size metrics. Separate analyses were conducted for lakes located within five eco-region subsets (Borealic Uplands/Tundra, FennoScandian Shield, Central Plains, Western Plains and Western Highlands) and for lakes with different functional fish classifications (cold-, cool-and warmwater fish assemblages). Results Geographical patterns of variation in the body-size structure of Euro-pean lake fish assemblages could be clearly discerned along a temperature gradi-ent for both the continental dataset (356 lakes) and the smaller geographical (ecoregion) subsets. We found systematic changes in fish assemblage body-size structure across temperature gradients in correspondence with the dominant thermal fish guild. The majority of the lakes, mainly located in the warmer Euro-pean lowlands, were dominated by eurythermic cool-and warmwater fish assem-blages, with smaller sized individuals characterized by linear individual body-size distributions. Lakes located in colder regions and dominated by stenothermic coldwater salmonids with larger sized individuals were characterized by unimodal or bimodal size distributions. The mean body size of cold-, cool-and warmwater fish assemblages changed uniformly along the temperature gradient. Main conclusions Patterns of variation in the body-size structure of Euro-pean lake fish assemblages are consistent with the temperature–size rule. Tem-perature modifies fish assemblage size structure uniformly within the thermal fish guilds and in different ecoregions. Furthermore, our results indicate an increasing predictive power of temperature to explain variability in body-size structure when moving from warmer to colder geographical regions.
La valutazione dello stato di conservazione di biodiversità, funzioni e servizi degli ecosistemi ... more La valutazione dello stato di conservazione di biodiversità, funzioni e servizi degli ecosistemi di acque interne e la stima della loro vulnerabilità ai cambiamenti climatici sono affrontate considerando tipologie omogenee di ecosistemi acquatici, alla scala integrata del bacino idrografico e della zona di transizione adiacente. Gli ecosistemi acquatici sono ripartiti, secondo uno schema tradizionale, in: bacini fluviali, laghi, zone umide e acque lentiche di piccole dimensioni, ecosistemi dipendenti dalle acque sotterranee (Groundwater Dependent Ecosystems - GDE) e ambienti di transizione a mare. I bacini fluviali e i laghi sono inoltre analizzati nel contesto della regione geografica cui appartengono, assumendo che vi siano associate diverse pressioni e minacce derivanti dai cambiamenti climatici. I cambiamenti climatici hanno effetti diretti sulla fenologia e sulla distribuzione delle specie che si manifestano in seguito a modificazioni della durata delle fasi di crescita, antici...
ABSTRACT Variations in the size structure of fish communities were explored at European scale alo... more ABSTRACT Variations in the size structure of fish communities were explored at European scale along gradients of climate, morphometry, productivity and fish community structure in more than 1800 lakes. Size metrics used were average fish body size, individual size distributions and size diversity. Analyses were conducted at both continental and regional scale. We found changes in fish community size structure across temperature gradients in correspondence with the dominant thermal fish guild. Lakes located in the warmer European lowlands were dominated by eurythermic cool- and warm-water fish communities with small-sized individuals characterised by linear individual size distributions. Lakes located in cold regions and dominated by stenothermic coldwater salmonids with larger-sized individuals were characterised by unimodal or bimodal size distributions. Our results show that temperature modifies fish community size structure uniformly within the thermal fish guilds and different ecoregions. The importance of temperature in explaining variability in fish size increased when moving from warm to cold regions. After controlling for the natural factors, productivity negatively influenced average fish size. At a macroecological scale, the strong effect of environmental temperature suggests future changes in fish size structure as a consequence of climate change, whereas eutrophication effects become more apparent at a regional scale.
ABSTRACT The systematic is still unresolved for the genus Squalius (Cyprinidae, Leuciscinae), a r... more ABSTRACT The systematic is still unresolved for the genus Squalius (Cyprinidae, Leuciscinae), a rich group of small to large fishes widely distributed throughout Europe. The distinction of one of the Italian narrowly endemic species, Squalius albus ( Bonaparte, 1838), described for the area surrounding lake Trasimeno, from the more common and widespread Squalius squalus (Bonaparte, 1837) is doubtful. The application of integrative taxonomy, with DNA taxonomy and quantitative morphometric, using both living and preserved individuals collected from lake Trasimeno before Squalius sp. restocking, allowed us to explicitly test for the identity of the two species in the complex. COI barcoding data, used for phylogenetic reconstructions, underlined that two clades may exist in the complex; nevertheless, DNA taxonomy (ABGD and GMYC) and morphometrics show no statistical support for their identity as separate species. Moreover, during our survey of the genetic diversity of the Italian Squalius, we provided further support for the species status of Squalius lucumonis, and found evidence of the occurrence in Southern Italy of another chub species, Squalius vardarensis (Karaman, 1928), previously known only from the Southern part of the Balkan Peninsula.
In 1990, in order to celebrate the 50 th anniversary of the former Italian Institute of Hydrobiol... more In 1990, in order to celebrate the 50 th anniversary of the former Italian Institute of Hydrobiology, now Institute of Ecosystem Study, a special issue summarising the advances in limnology was published by Memorie dell'Istituto Italiano di Idrobiologia, now Journal of Limnology. After 25 years, it is time again for a synthesis of what limnology did in the past, but mostly for suggestions on widening the horizon of the discipline, by including new tools and techniques. We hope that limnology will live long, and we celebrate the 75 th anniversary of the Institute with this special issue, containing manuscripts on the advances in the field and introducing recent and new lines of research in lentic waters studies.
Freshwater ecosystems and their biodiversity are presently seriously threatened by global develop... more Freshwater ecosystems and their biodiversity are presently seriously threatened by global development and population growth, leading to increases in nutrient inputs and intensification of eutrophication-induced problems in receiving fresh waters, particularly in lakes. Climate change constitutes another threat exacerbating the symptoms of eutrophication and species migration and loss. Unequivocal evidence of climate change impacts is still highly fragmented despite the intensive research, in part due to the variety and uncertainty of climate models and underlying emission scenarios but also due to the different approaches applied to study its effects. We first describe the strengths and weaknesses of the multi-faceted approaches that are presently available for elucidating the effects of climate change in lakes, including space-for-time substitution, time series, experiments, palaeoecology and modelling. Reviewing combined results from studies based on the various approaches, we describe the likely effects of climate changes on biological communities, trophic dynamics and the ecological state of lakes. We further discuss potential mitigation and adaptation measures to counteract the effects of climate change on lakes and, finally, we highlight some of the future challenges that we face to improve our capacity for successful prediction.
A point source of DDT pollution of industrial origin, discovered in 1996 in Lago Maggiore, the se... more A point source of DDT pollution of industrial origin, discovered in 1996 in Lago Maggiore, the second largest (212 km 2 ) and deepest (373 m) lake in Italy, created concern for wildlife and human health because contamination in some fish species exceeded the threshold for human consumption, even though the concentrations measured in the water were much lower than the legal requirements for drinking purposes. Some precautionary measures were undertaken to prevent DDT runoff from the industrial site to the lake but soil restoration had not yet been carried out. The first study to quantify land based sources of DDT homologue pollution was performed in 1998 by sampling all the main tributaries monthly in order to evaluate the annual load to the lake. From May 2001 to May 2002, the study was repeated in order to evaluate the degree of recovery. In this work we compared the results of that survey with those of a more recent campaign carried out from May 2001 to May 2002, concluding that land based sources are still relevant for pp'DDE, the most stable metabolite of pp'DDT, while they are negligible for the parent compound. Furthermore, the Toce River, receiving the soil runoff of the industrial area, was found to give the greatest contribution of DDT and DDE load to the lake in the past campaign, while its load drastically decreased in 2001-2002 in the case of pp'DDT, being comparable to that of Ticino River(the second biggest river of the Lago Maggiore basin, which rises in the St. Gotthard Massif of the Swiss Alpes). Air transport and cold condensation are very likely responsible for trapping DDT and DDE in high mountain glaciers, which represent a secondary pollution source.
Very recently, a common cyprinid fish species at northern latitude, the roach (Rutilus rutilus L.... more Very recently, a common cyprinid fish species at northern latitude, the roach (Rutilus rutilus L.) has been observed in the large south-alpine Lago Maggiore for the first time. The colonization of the lake has the characteristics of an invasion. In order to investigate this new fish population, benthic multi-mesh and commercial gill nets were used to sample fish in a wide gulf in the central part of the lake (Golfo Borromeo) from February to October 2006. In total 779 roach (TL: 5.5 -38.8 cm) were caught, aged, sexed and stomach analyzed. Fecundity was assessed by counting the eggs in ripe gonads of females of age 3 and 4. The roach have become clearly the dominant species in the catches, constituting over 70% of the biomass and 70% of the numbers caught. None of the roach exceeded 8 years in age. They grow very fast (Φ' = 2.55) and have high fecundity (F abs = 13740 ±4700 S.D. at age 3 and F abs = 14768 ±5642 S.D. at age 4). The diet spectrum is wide and characterized by a strong seasonality. In early spring algae (benthic and planktonic algae), benthos and detritus prevail, whereas in summer zooplankton is the most frequent food item. In autumn roach switch back to benthos and detritus. Algae occur more frequently in young specimens while zooplankton, benthos and detritus in adults. The roach population is practically unimpacted by fishing. The minimum legal mesh size (25 mm) of gillnets, used by commercial fishermen, selects roach at the mean L T of 21.2 cm, which is over its length at maturity. The results suggest that roach established a viable population in Lago Maggiore less than a decade ago and rapidly became one of the dominant (if not the dominant) fish species. The possible consequence for the fish fauna in general and for the ecological status of the whole lake is briefly discussed.
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