Pamela Quiroga - Academia.edu (original) (raw)

Papers by Pamela Quiroga

Research paper thumbnail of Fish and Fisheries of the Patagonian Steppe

Natural and Social Sciences of Patagonia

Research paper thumbnail of Morphological Maturity of the Knobbed Spider Crab, <I>Leurocyclus Tuberculosus</I> (H. Milne Edwards & Lucas, 1842) (Brachyura, Majidae) in the Northern Patagonian Gulfs

Crustaceana, 2009

... 2. Top, allometric discontinuity of ln(ChL) on ln(CW), and regression lines fitted to data fr... more ... 2. Top, allometric discontinuity of ln(ChL) on ln(CW), and regression lines fitted to data from morphologically immature and mature Leurocyclus tuberculosus (H. Milne Edwards &amp;amp;amp;amp; Lucas, 1842 ... This study was supported by projects PIP CONICET 5835 and PICT ANPCyT 14700. ...

Research paper thumbnail of Revalidation of the Argentinian pouched lamprey Geotria macrostoma (Burmeister, 1868) with molecular and morphological evidence

PLOS ONE, 2020

Background The Argentinian pouched lamprey, classified as Petromyzon macrostomus Burmeister, 1868... more Background The Argentinian pouched lamprey, classified as Petromyzon macrostomus Burmeister, 1868 was first described in 1867 in De La Plata River, in Buenos Aires, Argentina, and subsequently recorded in several rivers from Patagonia. Since its original description, the validity of P. macrostomus was questioned by several ichthyologists and 36 years after its original discovery it was considered a junior synonym of Geotria australis Gray, 1851. For a long time, the taxonomic status of G. australis has been uncertain, largely due to the misinterpretations of the morphological alterations that occur during sexual maturation, including the arrangement of teeth, size and position of fins and cloaca, and the development of an exceptionally large gular pouch in males. In this study, the taxonomic status of Geotria from across the "species" range was evaluated using both molecular analysis and examination of morphological characteristics. Methodology/principal findings Phylogenetic and species delimitation analyses based on mitochondrial DNA sequences of Cytochrome b (Cyt b) and Cytochrome C Oxidase Subunit 1 (COI) genes, along with morphological analysis of diagnostic characters reported in the original descriptions of the species were used to assess genetic and morphological variation within Geotria and to determine the specific status of the Argentinian lamprey. These analyses revealed that Geotria from Argentina constitutes a well differentiated lineage from Chilean and Australasian populations. The position of the cloaca and the distance between the second dorsal and caudal fins in sub-adult individuals, and at previous life stages, can be used to distinguish between the two species. In addition, the genetic distance between G. macrostoma and G.

Research paper thumbnail of Spatial Pattern and Habitat Requirements of Galaxias maculatus in the Last Un-Interrupted Large River of Patagonia: A Baseline for Management

Environment and Natural Resources Research, 2014

The relationship between the native Galaxias maculatus and environmental variables was studied in... more The relationship between the native Galaxias maculatus and environmental variables was studied in 52 sites located along 306 km of the main stemof the Santa Cruz River, the second largest river in Argentinean Patagonia. The abundance varied along the river, with three general sections clearly defined: upstream with minimum abundance increasing towards midstream and downstream areas. Distance to the sea and river wet width which were negatively significantly associated with abundance,and maximum depth explained the abundance in a polynomial shape-achieving a total explanation of 41.1%. The best predictive model also combined the river sinuosity.Our results suggested that the construction of two proposed hydroelectric dams will modify these variables, which might generate changes in G. maculatus distribution. The information obtainedduring the present study represents valuable information for conservation management of this species.

Research paper thumbnail of On the invalid resurrection of the lamprey genus Exomegas Gill, 1883

Journal of Fish Biology, 2021

The lamprey genus Exomegas Gill, 1883 was erected on the assumption that it was distinguishable f... more The lamprey genus Exomegas Gill, 1883 was erected on the assumption that it was distinguishable from Geotria Gray, 1851 by possessing three rather than two cusps on the transverse lingual lamina (TLL). Based on literature review and examination of holotypes and new data we reaffirm that the TLL of Geotria possesses two or three cusps in the adult stage. The reduction or disappearance of the middle cusp at the beginning or during the spawning run constitutes a key feature of Geotria. The resurrection of Exomegas by Firpo Lacoste et al. (2021), is therefore unjustified and not supported. This article is protected by copyright. All rights reserved.

Research paper thumbnail of On the invalid resurrection of the lamprey genus Exomegas Gill, 1883

Journal of Fish Biology, 2021

The lamprey genus Exomegas Gill, 1883 was erected on the assumption that it was distinguishable f... more The lamprey genus Exomegas Gill, 1883 was erected on the assumption that it was distinguishable from Geotria Gray, 1851 by possessing three rather than two cusps on the transverse lingual lamina (TLL). Based on literature review and examination of holotypes and new data we reaffirm that the TLL of Geotria possesses two or three cusps in the adult stage. The reduction or disappearance of the middle cusp at the beginning or during the spawning run constitutes a key feature of Geotria. The resurrection of Exomegas by Firpo Lacoste et al. (2021), is therefore unjustified and not supported. This article is protected by copyright. All rights reserved.

Research paper thumbnail of Morphometric and physical characteristics distinguishing adult Patagonian lamprey, Geotria macrostoma from the pouched lamprey, Geotria australis

The pouched lamprey, Geotria australis Gray, 1851, has long been considered monotypic in the Geot... more The pouched lamprey, Geotria australis Gray, 1851, has long been considered monotypic in the Geotriidae family with a wide southern temperate distribution across Australasia and South America. Recent studies have provided molecular and morphological evidence for a second Geotria species in South America; Geotria macrostoma (Burmeister, 1868). The aim of this study was to determine morphometric and physical characteristics of adult G. macrostoma that further differentiate this re-instated species of Geotriidae from G. australis. The diagnostic features discriminating immature adult G. macrostoma from G. australis when entering fresh water, are distinct differences in dentition, oral papillae and fimbriae counts and differences in coloration. In addition, G. macrostoma display greater growth of the prebranchial region and oral disc and has a deeper body depth and higher condition factor. All current ecological knowledge of the genus Geotria is based on Australasian populations, which ...

Research paper thumbnail of Morphometric and physical characteristics distinguishing adult Patagonian lamprey, Geotria macrostoma from the pouched lamprey, Geotria australis

The pouched lamprey, Geotria australis Gray, 1851, has long been considered monotypic in the Geot... more The pouched lamprey, Geotria australis Gray, 1851, has long been considered monotypic in the Geotriidae family with a wide southern temperate distribution across Australasia and South America. Recent studies have provided molecular and morphological evidence for a second Geotria species in South America; Geotria macrostoma (Burmeister, 1868). The aim of this study was to determine morphometric and physical characteristics of adult G. macrostoma that further differentiate this re-instated species of Geotriidae from G. australis. The diagnostic features discriminating immature adult G. macrostoma from G. australis when entering fresh water, are distinct differences in dentition, oral papillae and fimbriae counts and differences in coloration. In addition, G. macrostoma display greater growth of the prebranchial region and oral disc and has a deeper body depth and higher condition factor. All current ecological knowledge of the genus Geotria is based on Australasian populations, which ...

Research paper thumbnail of Revalidation of the Argentinian pouched lamprey Geotria macrostoma (Burmeister, 1868) with molecular and morphological evidence

Research paper thumbnail of Spatial Pattern and Habitat Requirements of Galaxias maculatus in the Last Un-Interrupted Large River of Patagonia: A Baseline for Management

Environment and Natural Resources Research, 2014

The relationship between the native Galaxias maculatus and environmental variables was studied in... more The relationship between the native Galaxias maculatus and environmental variables was studied in 52 sites located along 306 km of the main stemof the Santa Cruz River, the second largest river in Argentinean Patagonia. The abundance varied along the river, with three general sections clearly defined: upstream with minimum abundance increasing towards midstream and downstream areas. Distance to the sea and river wet width which were negatively significantly associated with abundance,and maximum depth explained the abundance in a polynomial shape-achieving a total explanation of 41.1%. The best predictive model also combined the river sinuosity.Our results suggested that the construction of two proposed hydroelectric dams will modify these variables, which might generate changes in G. maculatus distribution. The information obtainedduring the present study represents valuable information for conservation management of this species.

Research paper thumbnail of Influence of maternal habitat choice, environment and spatial distribution of juveniles on their propensity for anadromy in a partially anadromous population of rainbow trout (Oncorhynchus mykiss)

Ecology of Freshwater Fish, 2014

This study evaluated the importance of the environment and spatial distribution of juvenile fish ... more This study evaluated the importance of the environment and spatial distribution of juvenile fish for the adoption of alternative migratory tactics in a partially anadromous population of rainbow trout (Oncorhynchus mykiss) from the Santa Cruz River. We captured young-of-the-year fish along the river during autumn 2009, 2010 and spring 2010 and determined their maternal origin (anadromous vs. resident) using strontium to calcium ratios in the otolith core. Relative proportion of anadromous offspring, modelled with logistic regression, increased towards headwaters and in areas with deeper channels and larger substrate composition. Body length, modelled with linear multiple regression, varied positively with site depth, water velocity, substrate size and anadromous maternal origin. Based on evidence for limited juvenile movements (<25 km), the spatial extent of this study (240 Rkm) and the identification of large, contrasting reaches along the river, it is likely that the observed spatial distribution of juveniles and their association to sites with coarse substrate composition reflects maternal spawning activity. Results further indicate that anadromous females breed predominantly in middle and upper river sections in areas with coarse substrate. Given that body size in this system has been positively related to propensity for anadromy, we propose that female spawning choice affects their offspring's spatial distribution, providing the adequate physical template for anadromous offspring to reach or maintain larger body sizes and display anadromy themselves. Relevance of this study is also discussed in the context of alterations in response to future dam construction in one of the latest free-flowing rivers sustaining anadromous O. mykiss.

Research paper thumbnail of Influence of maternal habitat choice, environment and spatial distribution of juveniles on their propensity for anadromy in a partially anadromous population of rainbow trout (Oncorhynchus mykiss)

Ecology of Freshwater Fish, 2014

This study evaluated the importance of the environment and spatial distribution of juvenile fish ... more This study evaluated the importance of the environment and spatial distribution of juvenile fish for the adoption of alternative migratory tactics in a partially anadromous population of rainbow trout (Oncorhynchus mykiss) from the Santa Cruz River. We captured young-of-the-year fish along the river during autumn 2009, 2010 and spring 2010 and determined their maternal origin (anadromous vs. resident) using strontium to calcium ratios in the otolith core. Relative proportion of anadromous offspring, modelled with logistic regression, increased towards headwaters and in areas with deeper channels and larger substrate composition. Body length, modelled with linear multiple regression, varied positively with site depth, water velocity, substrate size and anadromous maternal origin. Based on evidence for limited juvenile movements (<25 km), the spatial extent of this study (240 Rkm) and the identification of large, contrasting reaches along the river, it is likely that the observed spatial distribution of juveniles and their association to sites with coarse substrate composition reflects maternal spawning activity. Results further indicate that anadromous females breed predominantly in middle and upper river sections in areas with coarse substrate. Given that body size in this system has been positively related to propensity for anadromy, we propose that female spawning choice affects their offspring's spatial distribution, providing the adequate physical template for anadromous offspring to reach or maintain larger body sizes and display anadromy themselves. Relevance of this study is also discussed in the context of alterations in response to future dam construction in one of the latest free-flowing rivers sustaining anadromous O. mykiss.

Research paper thumbnail of Dams in the last large free-flowing rivers of Patagonia, the Santa Cruz River, environmental features, and macroinvertebrate community

Limnologica, 2013

ABSTRACT Three large rivers have their headwaters in the Patagonian Ice Fields (PIFs) in the Ande... more ABSTRACT Three large rivers have their headwaters in the Patagonian Ice Fields (PIFs) in the Andes Mountains, the largest mid-latitude ice masses on Earth: Santa Cruz, Baker and Pascua. They are the last large free flowing rivers in Patagonia, but plans are advanced for building dams for hydroelectric power generation. The three PIF rivers, with a discharge dominated by ice melt, share a common, unique hydrograph compared to that of the other eight large rivers in the region: a distinct seasonal cycle, and an extremely stable discharge, with much lower variability than other rivers. In this study we present the first extensive survey of habitats and benthic macroinvertebrates in the least studied system, the Santa Cruz River. We assess how much of the natural capital provided and sustained by benthic invertebrates are expected to be lost by flooding and discuss how dams would affect riverine habitat and biota. In the Santa Cruz River, we conducted an intensive field survey during September 2010; a total of 52 sites located at regular 6 km intervals were sampled along the 310 river-km for macroinvertebrates and seventeen habitat variables. Although some habitat structure is apparent at the local scale, the Santa Cruz River could be described as very homogeneous. Macroinvertebrate density and the richness (38 genera) found in the Santa Cruz River resulted to be one of the lowest in comparison with 42 other Patagonian rivers. Albeit weak, the structure of the macroinvertebrates assemblages was successfully described by a reduced set of variables. The reduced flow variation and the lack of bed scouring flows have a direct and negative effect on the heterogeneity of riverbeds and banks. The high turbidity of the Santa Cruz River may also contribute to shorter food webs, by affecting autotrophic production, general trophic structure, and overall macroinvertebrate productivity and diversity. Dams will obliterate 51% of the lotic environment, including the most productive sections of the river according to our macroinvertebrate data. Since Santa Cruz River has a naturally homogeneous flow cycle, dams may provide more variable flows and more diverse habitat. Our data provide critically valuable baseline information to understand the effects of dams on the unique set of glacial driven large rivers of Patagonia.

Research paper thumbnail of Dams versus habitat: predicting the effects of dams on habitat supply and juvenile rainbow trout along the Santa Cruz River, Patagonia

Hydrobiologia, 2015

Because of their remote location and lack of supporting infrastructure, large glacial rivers of s... more Because of their remote location and lack of supporting infrastructure, large glacial rivers of southern Patagonia have remained free of dams. But this is bound to change: two dams proposed for the Santa Cruz River would supply 16% of Argentina's hydropower and five dams planned for the Pascua and Baker Rivers could supply over 20% of Chile's hydropower. In this paper, we project the losses of habitat and juvenile Oncorhynchus mykiss, a recreationally important species, following the construction of the two dams in the Santa Cruz River. We applied a two-stage fitting approach, using generalized additive models and generalized lineal models (GLMs) sequentially to describe habitat-species relationships based on data collected through an intensive field survey of fish and environmental variables along 310 km of river. A simplified GLM trout model based on wetted width, substrate size, and river kilometer was selected which represents the observed geographic distribution very well and with the lowest predictive error. Based on this model, we estimated that habitat supporting 86% of current juvenile trout production will be lost to flooding by the dams. Our data generate a rare opportunity to perform a dam impact assessment by comparison with potential post-dam conditions. Keywords Oncorhynchus mykiss Á Juvenile fish Á Habitat variables Á Species-habitat models Á Dams Á Patagonia Á Argentina Handling editor: M. Power

Research paper thumbnail of Fish and Fisheries of the Patagonian Steppe

Natural and Social Sciences of Patagonia

Research paper thumbnail of Morphological Maturity of the Knobbed Spider Crab, <I>Leurocyclus Tuberculosus</I> (H. Milne Edwards & Lucas, 1842) (Brachyura, Majidae) in the Northern Patagonian Gulfs

Crustaceana, 2009

... 2. Top, allometric discontinuity of ln(ChL) on ln(CW), and regression lines fitted to data fr... more ... 2. Top, allometric discontinuity of ln(ChL) on ln(CW), and regression lines fitted to data from morphologically immature and mature Leurocyclus tuberculosus (H. Milne Edwards &amp;amp;amp;amp; Lucas, 1842 ... This study was supported by projects PIP CONICET 5835 and PICT ANPCyT 14700. ...

Research paper thumbnail of Revalidation of the Argentinian pouched lamprey Geotria macrostoma (Burmeister, 1868) with molecular and morphological evidence

PLOS ONE, 2020

Background The Argentinian pouched lamprey, classified as Petromyzon macrostomus Burmeister, 1868... more Background The Argentinian pouched lamprey, classified as Petromyzon macrostomus Burmeister, 1868 was first described in 1867 in De La Plata River, in Buenos Aires, Argentina, and subsequently recorded in several rivers from Patagonia. Since its original description, the validity of P. macrostomus was questioned by several ichthyologists and 36 years after its original discovery it was considered a junior synonym of Geotria australis Gray, 1851. For a long time, the taxonomic status of G. australis has been uncertain, largely due to the misinterpretations of the morphological alterations that occur during sexual maturation, including the arrangement of teeth, size and position of fins and cloaca, and the development of an exceptionally large gular pouch in males. In this study, the taxonomic status of Geotria from across the "species" range was evaluated using both molecular analysis and examination of morphological characteristics. Methodology/principal findings Phylogenetic and species delimitation analyses based on mitochondrial DNA sequences of Cytochrome b (Cyt b) and Cytochrome C Oxidase Subunit 1 (COI) genes, along with morphological analysis of diagnostic characters reported in the original descriptions of the species were used to assess genetic and morphological variation within Geotria and to determine the specific status of the Argentinian lamprey. These analyses revealed that Geotria from Argentina constitutes a well differentiated lineage from Chilean and Australasian populations. The position of the cloaca and the distance between the second dorsal and caudal fins in sub-adult individuals, and at previous life stages, can be used to distinguish between the two species. In addition, the genetic distance between G. macrostoma and G.

Research paper thumbnail of Spatial Pattern and Habitat Requirements of Galaxias maculatus in the Last Un-Interrupted Large River of Patagonia: A Baseline for Management

Environment and Natural Resources Research, 2014

The relationship between the native Galaxias maculatus and environmental variables was studied in... more The relationship between the native Galaxias maculatus and environmental variables was studied in 52 sites located along 306 km of the main stemof the Santa Cruz River, the second largest river in Argentinean Patagonia. The abundance varied along the river, with three general sections clearly defined: upstream with minimum abundance increasing towards midstream and downstream areas. Distance to the sea and river wet width which were negatively significantly associated with abundance,and maximum depth explained the abundance in a polynomial shape-achieving a total explanation of 41.1%. The best predictive model also combined the river sinuosity.Our results suggested that the construction of two proposed hydroelectric dams will modify these variables, which might generate changes in G. maculatus distribution. The information obtainedduring the present study represents valuable information for conservation management of this species.

Research paper thumbnail of On the invalid resurrection of the lamprey genus Exomegas Gill, 1883

Journal of Fish Biology, 2021

The lamprey genus Exomegas Gill, 1883 was erected on the assumption that it was distinguishable f... more The lamprey genus Exomegas Gill, 1883 was erected on the assumption that it was distinguishable from Geotria Gray, 1851 by possessing three rather than two cusps on the transverse lingual lamina (TLL). Based on literature review and examination of holotypes and new data we reaffirm that the TLL of Geotria possesses two or three cusps in the adult stage. The reduction or disappearance of the middle cusp at the beginning or during the spawning run constitutes a key feature of Geotria. The resurrection of Exomegas by Firpo Lacoste et al. (2021), is therefore unjustified and not supported. This article is protected by copyright. All rights reserved.

Research paper thumbnail of On the invalid resurrection of the lamprey genus Exomegas Gill, 1883

Journal of Fish Biology, 2021

The lamprey genus Exomegas Gill, 1883 was erected on the assumption that it was distinguishable f... more The lamprey genus Exomegas Gill, 1883 was erected on the assumption that it was distinguishable from Geotria Gray, 1851 by possessing three rather than two cusps on the transverse lingual lamina (TLL). Based on literature review and examination of holotypes and new data we reaffirm that the TLL of Geotria possesses two or three cusps in the adult stage. The reduction or disappearance of the middle cusp at the beginning or during the spawning run constitutes a key feature of Geotria. The resurrection of Exomegas by Firpo Lacoste et al. (2021), is therefore unjustified and not supported. This article is protected by copyright. All rights reserved.

Research paper thumbnail of Morphometric and physical characteristics distinguishing adult Patagonian lamprey, Geotria macrostoma from the pouched lamprey, Geotria australis

The pouched lamprey, Geotria australis Gray, 1851, has long been considered monotypic in the Geot... more The pouched lamprey, Geotria australis Gray, 1851, has long been considered monotypic in the Geotriidae family with a wide southern temperate distribution across Australasia and South America. Recent studies have provided molecular and morphological evidence for a second Geotria species in South America; Geotria macrostoma (Burmeister, 1868). The aim of this study was to determine morphometric and physical characteristics of adult G. macrostoma that further differentiate this re-instated species of Geotriidae from G. australis. The diagnostic features discriminating immature adult G. macrostoma from G. australis when entering fresh water, are distinct differences in dentition, oral papillae and fimbriae counts and differences in coloration. In addition, G. macrostoma display greater growth of the prebranchial region and oral disc and has a deeper body depth and higher condition factor. All current ecological knowledge of the genus Geotria is based on Australasian populations, which ...

Research paper thumbnail of Morphometric and physical characteristics distinguishing adult Patagonian lamprey, Geotria macrostoma from the pouched lamprey, Geotria australis

The pouched lamprey, Geotria australis Gray, 1851, has long been considered monotypic in the Geot... more The pouched lamprey, Geotria australis Gray, 1851, has long been considered monotypic in the Geotriidae family with a wide southern temperate distribution across Australasia and South America. Recent studies have provided molecular and morphological evidence for a second Geotria species in South America; Geotria macrostoma (Burmeister, 1868). The aim of this study was to determine morphometric and physical characteristics of adult G. macrostoma that further differentiate this re-instated species of Geotriidae from G. australis. The diagnostic features discriminating immature adult G. macrostoma from G. australis when entering fresh water, are distinct differences in dentition, oral papillae and fimbriae counts and differences in coloration. In addition, G. macrostoma display greater growth of the prebranchial region and oral disc and has a deeper body depth and higher condition factor. All current ecological knowledge of the genus Geotria is based on Australasian populations, which ...

Research paper thumbnail of Revalidation of the Argentinian pouched lamprey Geotria macrostoma (Burmeister, 1868) with molecular and morphological evidence

Research paper thumbnail of Spatial Pattern and Habitat Requirements of Galaxias maculatus in the Last Un-Interrupted Large River of Patagonia: A Baseline for Management

Environment and Natural Resources Research, 2014

The relationship between the native Galaxias maculatus and environmental variables was studied in... more The relationship between the native Galaxias maculatus and environmental variables was studied in 52 sites located along 306 km of the main stemof the Santa Cruz River, the second largest river in Argentinean Patagonia. The abundance varied along the river, with three general sections clearly defined: upstream with minimum abundance increasing towards midstream and downstream areas. Distance to the sea and river wet width which were negatively significantly associated with abundance,and maximum depth explained the abundance in a polynomial shape-achieving a total explanation of 41.1%. The best predictive model also combined the river sinuosity.Our results suggested that the construction of two proposed hydroelectric dams will modify these variables, which might generate changes in G. maculatus distribution. The information obtainedduring the present study represents valuable information for conservation management of this species.

Research paper thumbnail of Influence of maternal habitat choice, environment and spatial distribution of juveniles on their propensity for anadromy in a partially anadromous population of rainbow trout (Oncorhynchus mykiss)

Ecology of Freshwater Fish, 2014

This study evaluated the importance of the environment and spatial distribution of juvenile fish ... more This study evaluated the importance of the environment and spatial distribution of juvenile fish for the adoption of alternative migratory tactics in a partially anadromous population of rainbow trout (Oncorhynchus mykiss) from the Santa Cruz River. We captured young-of-the-year fish along the river during autumn 2009, 2010 and spring 2010 and determined their maternal origin (anadromous vs. resident) using strontium to calcium ratios in the otolith core. Relative proportion of anadromous offspring, modelled with logistic regression, increased towards headwaters and in areas with deeper channels and larger substrate composition. Body length, modelled with linear multiple regression, varied positively with site depth, water velocity, substrate size and anadromous maternal origin. Based on evidence for limited juvenile movements (<25 km), the spatial extent of this study (240 Rkm) and the identification of large, contrasting reaches along the river, it is likely that the observed spatial distribution of juveniles and their association to sites with coarse substrate composition reflects maternal spawning activity. Results further indicate that anadromous females breed predominantly in middle and upper river sections in areas with coarse substrate. Given that body size in this system has been positively related to propensity for anadromy, we propose that female spawning choice affects their offspring's spatial distribution, providing the adequate physical template for anadromous offspring to reach or maintain larger body sizes and display anadromy themselves. Relevance of this study is also discussed in the context of alterations in response to future dam construction in one of the latest free-flowing rivers sustaining anadromous O. mykiss.

Research paper thumbnail of Influence of maternal habitat choice, environment and spatial distribution of juveniles on their propensity for anadromy in a partially anadromous population of rainbow trout (Oncorhynchus mykiss)

Ecology of Freshwater Fish, 2014

This study evaluated the importance of the environment and spatial distribution of juvenile fish ... more This study evaluated the importance of the environment and spatial distribution of juvenile fish for the adoption of alternative migratory tactics in a partially anadromous population of rainbow trout (Oncorhynchus mykiss) from the Santa Cruz River. We captured young-of-the-year fish along the river during autumn 2009, 2010 and spring 2010 and determined their maternal origin (anadromous vs. resident) using strontium to calcium ratios in the otolith core. Relative proportion of anadromous offspring, modelled with logistic regression, increased towards headwaters and in areas with deeper channels and larger substrate composition. Body length, modelled with linear multiple regression, varied positively with site depth, water velocity, substrate size and anadromous maternal origin. Based on evidence for limited juvenile movements (<25 km), the spatial extent of this study (240 Rkm) and the identification of large, contrasting reaches along the river, it is likely that the observed spatial distribution of juveniles and their association to sites with coarse substrate composition reflects maternal spawning activity. Results further indicate that anadromous females breed predominantly in middle and upper river sections in areas with coarse substrate. Given that body size in this system has been positively related to propensity for anadromy, we propose that female spawning choice affects their offspring's spatial distribution, providing the adequate physical template for anadromous offspring to reach or maintain larger body sizes and display anadromy themselves. Relevance of this study is also discussed in the context of alterations in response to future dam construction in one of the latest free-flowing rivers sustaining anadromous O. mykiss.

Research paper thumbnail of Dams in the last large free-flowing rivers of Patagonia, the Santa Cruz River, environmental features, and macroinvertebrate community

Limnologica, 2013

ABSTRACT Three large rivers have their headwaters in the Patagonian Ice Fields (PIFs) in the Ande... more ABSTRACT Three large rivers have their headwaters in the Patagonian Ice Fields (PIFs) in the Andes Mountains, the largest mid-latitude ice masses on Earth: Santa Cruz, Baker and Pascua. They are the last large free flowing rivers in Patagonia, but plans are advanced for building dams for hydroelectric power generation. The three PIF rivers, with a discharge dominated by ice melt, share a common, unique hydrograph compared to that of the other eight large rivers in the region: a distinct seasonal cycle, and an extremely stable discharge, with much lower variability than other rivers. In this study we present the first extensive survey of habitats and benthic macroinvertebrates in the least studied system, the Santa Cruz River. We assess how much of the natural capital provided and sustained by benthic invertebrates are expected to be lost by flooding and discuss how dams would affect riverine habitat and biota. In the Santa Cruz River, we conducted an intensive field survey during September 2010; a total of 52 sites located at regular 6 km intervals were sampled along the 310 river-km for macroinvertebrates and seventeen habitat variables. Although some habitat structure is apparent at the local scale, the Santa Cruz River could be described as very homogeneous. Macroinvertebrate density and the richness (38 genera) found in the Santa Cruz River resulted to be one of the lowest in comparison with 42 other Patagonian rivers. Albeit weak, the structure of the macroinvertebrates assemblages was successfully described by a reduced set of variables. The reduced flow variation and the lack of bed scouring flows have a direct and negative effect on the heterogeneity of riverbeds and banks. The high turbidity of the Santa Cruz River may also contribute to shorter food webs, by affecting autotrophic production, general trophic structure, and overall macroinvertebrate productivity and diversity. Dams will obliterate 51% of the lotic environment, including the most productive sections of the river according to our macroinvertebrate data. Since Santa Cruz River has a naturally homogeneous flow cycle, dams may provide more variable flows and more diverse habitat. Our data provide critically valuable baseline information to understand the effects of dams on the unique set of glacial driven large rivers of Patagonia.

Research paper thumbnail of Dams versus habitat: predicting the effects of dams on habitat supply and juvenile rainbow trout along the Santa Cruz River, Patagonia

Hydrobiologia, 2015

Because of their remote location and lack of supporting infrastructure, large glacial rivers of s... more Because of their remote location and lack of supporting infrastructure, large glacial rivers of southern Patagonia have remained free of dams. But this is bound to change: two dams proposed for the Santa Cruz River would supply 16% of Argentina's hydropower and five dams planned for the Pascua and Baker Rivers could supply over 20% of Chile's hydropower. In this paper, we project the losses of habitat and juvenile Oncorhynchus mykiss, a recreationally important species, following the construction of the two dams in the Santa Cruz River. We applied a two-stage fitting approach, using generalized additive models and generalized lineal models (GLMs) sequentially to describe habitat-species relationships based on data collected through an intensive field survey of fish and environmental variables along 310 km of river. A simplified GLM trout model based on wetted width, substrate size, and river kilometer was selected which represents the observed geographic distribution very well and with the lowest predictive error. Based on this model, we estimated that habitat supporting 86% of current juvenile trout production will be lost to flooding by the dams. Our data generate a rare opportunity to perform a dam impact assessment by comparison with potential post-dam conditions. Keywords Oncorhynchus mykiss Á Juvenile fish Á Habitat variables Á Species-habitat models Á Dams Á Patagonia Á Argentina Handling editor: M. Power