Cristina García-Fresca | Universidad de Navarra (original) (raw)

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Papers by Cristina García-Fresca

En este estudio se elabora un marco general descriptivo de los rios Erro y Urederra, se aportan d... more En este estudio se elabora un marco general descriptivo de los rios Erro y Urederra, se aportan datos sobre la biologia de salmonidos y ciprinidos y se evaluan los principales errores cometidos con la utilizacion de la metodologia empleada. El periodo de muestreo abarco los anos, 1995, 1996 y 1997. Los rios estudiados presentaron caracteristicas de montana y tuvieron aguas frescas con concentraciones de oxigeno relativamente elevadas. El habitat predominante fue somero o con profundidad media, con sustrato de cantos y velocidades del agua medias o bjas. Ambos resultaron ser salmonicolas en la cabecera dandose una evolucion aguas abajo hacia comunidades ciprinicolas. Las densidades de las poblaciones de peces sufrieron cambios posiblemente debidos a alteraciones humanas y modificaciones del habitat, al comportamiento de los peces y a variaciones en la eficiencia de captura. El estudio de las poblaciones de cada especie aporto datos sobre su distribucion de tallas, edad, fecundidad absoluta y relativa, indice gonadosomatico y habitat. El metodo de caracterizacion del medio empleado reflejo fielmente las condiciones de cada tramo; sin embargo, se propusieron mejoras del mismo. La estimacion de las abundancias, densidades y distribuciones de peces dependieron de la fecha de realizacion del muestreo, de las caracteristicas del tramo muestreado y del comportamiento de las especies. La estimacion de la edad mediante la lectura de escamas y otolitos presento unos resultados buenos aunque el balance esfuerzo-beneficio resulto poco satisfactorio. La estimacion de la fecundidad mediante el metodo gravimetrico presento errores absolutos bajos que mejoraron con el recuento de una gonada completa.

Hydrobiologia, 2005

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

Annales de Limnologie - International Journal of Limnology, 2005

Rainbow trout, Oncorhynchus mykiss (Walbaum, 1792), occur naturally in the eastern Pacific Ocean,... more Rainbow trout, Oncorhynchus mykiss (Walbaum, 1792), occur naturally in the eastern Pacific Ocean, and in fresh water they exist mainly in the west of the Rocky Mountains from northwest Mexico to the Kuskokwim River, Alaska (Jonsson et al. 1993). The species was first introduced in Spain in the late 19 th century (Elvira 1995) and it is still present in all Spanish basins (Doadrio 2001), especially in areas close to fish farms, from where specimens frequently escape (Carss 1990). The introduction of rainbow trout can alter native fish populations through predation, competition for food or territorial space, acting as carriers of different diseases and through destruction of earlier trout spawning beds (Landergren 1999). Knowledge of the interaction between exotic and native species is necessary for adequate aquatic management. In this way, diet studies constitute an important tool (Neveu 1979), because trophic interaction between species (competition and predation) is an important mechanism in determining the distribution of aquatic communities (Lammens et al. 1992, Declerck et al. 2002). The aim of this study is to describe the diet composition of rainbow trout in the Urederra River, as a first step in evaluating the interaction between rainbow trout and native fishes. The possible interaction will be discussed in comparison with previous works describing the feeding preferences of brown trout,

Annales de Limnologie - International Journal of Limnology

In 1996, a compound gauging weir was built in Villaveta Township (Navarra, North of Spain) in the... more In 1996, a compound gauging weir was built in Villaveta Township (Navarra, North of Spain) in the river Erro (Ebro River Basin). Before and after its construction, fish and physical and chemical variables were examined to determine weir’s impact on the reach. Fish captured by electrofishing were measured (total length), and population density and length distribution of the species were estimated. Species diversity (Shannon’s diversity index), dominance (Simpson’s dominance index) and evenness were also calculated. The results revealed an increase in fish population density, especially in smaller specimens, but a decrease in the larger fishes. Substrate and shelter alterations could explain the observed variations in the fish community. In order to improve the consolidation of well-developed fish populations, the placement of great boulders and the restoration of the riparian vegetation are suggested.

mammalia, 2000

An Error Occurred Setting Your User Cookie. This site uses cookies to improve performance. If you... more An Error Occurred Setting Your User Cookie. This site uses cookies to improve performance. If your browser does not accept cookies, you cannot view this site. Setting Your Browser to Accept Cookies. There are many reasons why a cookie could not be set correctly. ...

Annales de Limnologie - International Journal of Limnology, 2005

Hydrobiologia, 2005

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

En este estudio se elabora un marco general descriptivo de los rios Erro y Urederra, se aportan d... more En este estudio se elabora un marco general descriptivo de los rios Erro y Urederra, se aportan datos sobre la biologia de salmonidos y ciprinidos y se evaluan los principales errores cometidos con la utilizacion de la metodologia empleada. El periodo de muestreo abarco los anos, 1995, 1996 y 1997. Los rios estudiados presentaron caracteristicas de montana y tuvieron aguas frescas con concentraciones de oxigeno relativamente elevadas. El habitat predominante fue somero o con profundidad media, con sustrato de cantos y velocidades del agua medias o bjas. Ambos resultaron ser salmonicolas en la cabecera dandose una evolucion aguas abajo hacia comunidades ciprinicolas. Las densidades de las poblaciones de peces sufrieron cambios posiblemente debidos a alteraciones humanas y modificaciones del habitat, al comportamiento de los peces y a variaciones en la eficiencia de captura. El estudio de las poblaciones de cada especie aporto datos sobre su distribucion de tallas, edad, fecundidad absoluta y relativa, indice gonadosomatico y habitat. El metodo de caracterizacion del medio empleado reflejo fielmente las condiciones de cada tramo; sin embargo, se propusieron mejoras del mismo. La estimacion de las abundancias, densidades y distribuciones de peces dependieron de la fecha de realizacion del muestreo, de las caracteristicas del tramo muestreado y del comportamiento de las especies. La estimacion de la edad mediante la lectura de escamas y otolitos presento unos resultados buenos aunque el balance esfuerzo-beneficio resulto poco satisfactorio. La estimacion de la fecundidad mediante el metodo gravimetrico presento errores absolutos bajos que mejoraron con el recuento de una gonada completa.

Hydrobiologia, 2005

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

Annales de Limnologie - International Journal of Limnology, 2005

Rainbow trout, Oncorhynchus mykiss (Walbaum, 1792), occur naturally in the eastern Pacific Ocean,... more Rainbow trout, Oncorhynchus mykiss (Walbaum, 1792), occur naturally in the eastern Pacific Ocean, and in fresh water they exist mainly in the west of the Rocky Mountains from northwest Mexico to the Kuskokwim River, Alaska (Jonsson et al. 1993). The species was first introduced in Spain in the late 19 th century (Elvira 1995) and it is still present in all Spanish basins (Doadrio 2001), especially in areas close to fish farms, from where specimens frequently escape (Carss 1990). The introduction of rainbow trout can alter native fish populations through predation, competition for food or territorial space, acting as carriers of different diseases and through destruction of earlier trout spawning beds (Landergren 1999). Knowledge of the interaction between exotic and native species is necessary for adequate aquatic management. In this way, diet studies constitute an important tool (Neveu 1979), because trophic interaction between species (competition and predation) is an important mechanism in determining the distribution of aquatic communities (Lammens et al. 1992, Declerck et al. 2002). The aim of this study is to describe the diet composition of rainbow trout in the Urederra River, as a first step in evaluating the interaction between rainbow trout and native fishes. The possible interaction will be discussed in comparison with previous works describing the feeding preferences of brown trout,

Annales de Limnologie - International Journal of Limnology

In 1996, a compound gauging weir was built in Villaveta Township (Navarra, North of Spain) in the... more In 1996, a compound gauging weir was built in Villaveta Township (Navarra, North of Spain) in the river Erro (Ebro River Basin). Before and after its construction, fish and physical and chemical variables were examined to determine weir’s impact on the reach. Fish captured by electrofishing were measured (total length), and population density and length distribution of the species were estimated. Species diversity (Shannon’s diversity index), dominance (Simpson’s dominance index) and evenness were also calculated. The results revealed an increase in fish population density, especially in smaller specimens, but a decrease in the larger fishes. Substrate and shelter alterations could explain the observed variations in the fish community. In order to improve the consolidation of well-developed fish populations, the placement of great boulders and the restoration of the riparian vegetation are suggested.

mammalia, 2000

An Error Occurred Setting Your User Cookie. This site uses cookies to improve performance. If you... more An Error Occurred Setting Your User Cookie. This site uses cookies to improve performance. If your browser does not accept cookies, you cannot view this site. Setting Your Browser to Accept Cookies. There are many reasons why a cookie could not be set correctly. ...

Annales de Limnologie - International Journal of Limnology, 2005

Hydrobiologia, 2005

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