http://sedici.unlp.edu.ar:80/handle/10915/68055 2026-07-16T17:32:36Z 2026-07-16T17:32:36Z Instituto de Limnología "Raúl A. Ringuelet" http://sedici.unlp.edu.ar:80/handle/10915/68797 2019-04-05T20:05:29Z 2009-01-01T00:00:00Z

Edicion de revista V Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP), (Luján, 2008); Biología Acuática; no. 26 Tenemos el placer de poner en manos de la comunidad científica las versiones expandidas de una importante parte de las contribuciones presentadas en el V Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP), celebrado en la Sede Central de la Universidad Nacional de Luján, entre el 3 y el 5 de diciembre de 2008; también compartimos con los lectores las Conclusiones finales del Congreso, elaboradas al finalizar el Congreso. Este número reúne 23 artículos originales, que involucran a 67 investigadores y a 19 instituciones. Los textos permiten apreciar una diversidad temática y riqueza de la información generada, que vienen a confirmar que la Biología Acuática en nuestro país es una disciplina definitivamente afianzada en el escenario mayor de las Ciencias Biológicas. Todos los artículos que integran esta entrega han sido revisados en forma independiente por 1-3 lectores-evaluadores, quienes emitieron por escrito su opinión científica sobre diferentes aspectos de los textos, la que luego fue puesta en conocimiento de los autores. Ellos, cuando correspondía, revisaron o corrigieron sus manuscritos hasta la versión que ahora se entrega en este número de "Biología Acuática".

2009-01-01T00:00:00Z Tenemos el placer de poner en manos de la comunidad científica las versiones expandidas de una importante parte de las contribuciones presentadas en el V Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP), celebrado en la Sede Central de la Universidad Nacional de Luján, entre el 3 y el 5 de diciembre de 2008; también compartimos con los lectores las Conclusiones finales del Congreso, elaboradas al finalizar el Congreso. Este número reúne 23 artículos originales, que involucran a 67 investigadores y a 19 instituciones. Los textos permiten apreciar una diversidad temática y riqueza de la información generada, que vienen a confirmar que la Biología Acuática en nuestro país es una disciplina definitivamente afianzada en el escenario mayor de las Ciencias Biológicas. Todos los artículos que integran esta entrega han sido revisados en forma independiente por 1-3 lectores-evaluadores, quienes emitieron por escrito su opinión científica sobre diferentes aspectos de los textos, la que luego fue puesta en conocimiento de los autores. Ellos, cuando correspondía, revisaron o corrigieron sus manuscritos hasta la versión que ahora se entrega en este número de "Biología Acuática". Dippolito, Andrea Ardohain, Diego Martín Claps, María Cristina Gabellone, Néstor Adrián http://sedici.unlp.edu.ar:80/handle/10915/68796 2019-04-05T20:05:32Z 2009-01-01T00:00:00Z

Articulo V Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP), (Luján, 2008); Biología Acuática; no. 26 The objective of this study was to investigate changes occurred in the structure and dynamics of zooplankton community during dredging works made in the lower sector of Salado River (Buenos Aires, Argentina). The samples were taken before and during the extraction of a river restriction and the replacement of a bridge at one site upstream and other downstream of this hydraulic modification. The dredging works were made during low water period. Zooplankton samples were obtained filtering volumes of 10 l extracted at three points of a transect in the river channel (both banks and the middle of the course) during 14 weeks (weekly from March to June). Physical and chemical parameters were measured in situ with a multimeter. The conductivity decreased from 12,000 μS/cm (March-April) to 6,000 μS/cm (April-June). The zooplankton assemblages were correlated with factors such as conductivity, turbidity, water temperature, and phytoplankton density. Tintinids (Tintinnidium fluviatile and Codonella cratera) prevailed with high salinity whereas rotifers (Brachionus plicatilis and Keratella tropica, among others) dominated later. Microcrustaceans were scarce related to the conductivity of the river. The analyzed sites showed similar composition and abundance of zooplankton during all sampling period. We can assume that the effects of dredging works in low water conditions cause minimal downstream perturbations on zooplankton community.

2009-01-01T00:00:00Z The objective of this study was to investigate changes occurred in the structure and dynamics of zooplankton community during dredging works made in the lower sector of Salado River (Buenos Aires, Argentina). The samples were taken before and during the extraction of a river restriction and the replacement of a bridge at one site upstream and other downstream of this hydraulic modification. The dredging works were made during low water period. Zooplankton samples were obtained filtering volumes of 10 l extracted at three points of a transect in the river channel (both banks and the middle of the course) during 14 weeks (weekly from March to June). Physical and chemical parameters were measured in situ with a multimeter. The conductivity decreased from 12,000 μS/cm (March-April) to 6,000 μS/cm (April-June). The zooplankton assemblages were correlated with factors such as conductivity, turbidity, water temperature, and phytoplankton density. Tintinids (Tintinnidium fluviatile and Codonella cratera) prevailed with high salinity whereas rotifers (Brachionus plicatilis and Keratella tropica, among others) dominated later. Microcrustaceans were scarce related to the conductivity of the river. The analyzed sites showed similar composition and abundance of zooplankton during all sampling period. We can assume that the effects of dredging works in low water conditions cause minimal downstream perturbations on zooplankton community. Vignatti, A. Echaniz, Santiago Andrés Ramos, D. Pilati, A. Bazán, Graciela Inés http://sedici.unlp.edu.ar:80/handle/10915/68795 2019-04-05T20:05:40Z 2009-01-01T00:00:00Z

Articulo V Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP) (Luján, 2008); Biología Acuática; no. 26 Primary production (PPr) is the energy fixed by autotrophic organisms. In aquatic ecosystems, it is mostly produced by photosynthetic processes performed by planktonic or benthic algae and macrophytes. In La Pampa, the ecology of shallow lakes has recently begun to be studied, but there is no reference inade to the algal PPr and how it is influenced by zooplankton. Since shallow lakes in La Pampa are different from those widely studied in Buenos Aires province, the objective of this contribution was to determine the phytoplanktonic PPr of an organic turbid shallow lake of the northeast La Pampa, and the influence of zooplankton in its valué. PPr was estimated 6 times along the day with the dissolved oxygen technique, using clear and dark bottles. To test the ef- fect of zooplankton on PPr estimates, we compared PPr with and without zooplankton, which was removed with a 40-micron mesh net. A higher concentration of nutrients was recorded than the typical pampasic shallow lakes of Buenos Aires province, Phytoplank- ton was dominated by Chlorophyta and the zooplankton assemblage was typical of low salinity environments. Zooplankton densities were reduced during noon-afternoon hours, what might indícate an important zooplankton migration process. Net PPr was similar to the detected in lakes at similar latitudinal location, but the máximum PPr per unít chlorophyll was higher than the recorded in organic turbid lakes of Buenos Aires Province. Zooplankton had a weak influence on PPr. Determinations from the two treat- ments did not show significant differences, except at 8 PM when the net PPr without zooplankton was three times higher than the treaíment with zooplankton.

2009-01-01T00:00:00Z Primary production (PPr) is the energy fixed by autotrophic organisms. In aquatic ecosystems, it is mostly produced by photosynthetic processes performed by planktonic or benthic algae and macrophytes. In La Pampa, the ecology of shallow lakes has recently begun to be studied, but there is no reference inade to the algal PPr and how it is influenced by zooplankton. Since shallow lakes in La Pampa are different from those widely studied in Buenos Aires province, the objective of this contribution was to determine the phytoplanktonic PPr of an organic turbid shallow lake of the northeast La Pampa, and the influence of zooplankton in its valué. PPr was estimated 6 times along the day with the dissolved oxygen technique, using clear and dark bottles. To test the ef- fect of zooplankton on PPr estimates, we compared PPr with and without zooplankton, which was removed with a 40-micron mesh net. A higher concentration of nutrients was recorded than the typical pampasic shallow lakes of Buenos Aires province, Phytoplank- ton was dominated by Chlorophyta and the zooplankton assemblage was typical of low salinity environments. Zooplankton densities were reduced during noon-afternoon hours, what might indícate an important zooplankton migration process. Net PPr was similar to the detected in lakes at similar latitudinal location, but the máximum PPr per unít chlorophyll was higher than the recorded in organic turbid lakes of Buenos Aires Province. Zooplankton had a weak influence on PPr. Determinations from the two treat- ments did not show significant differences, except at 8 PM when the net PPr without zooplankton was three times higher than the treaíment with zooplankton. Schwerdt, Marcelo Gabriel López Cazorla, Andrea Cecilia http://sedici.unlp.edu.ar:80/handle/10915/68794 2021-03-24T19:10:02Z 2009-01-01T00:00:00Z

Articulo V Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP) (Luján, 2008); Biología Acuática; no. 26 This study aims at characterizing the seasonal dynamics of the ichtyofauna of Alsina lagoon which belongs to the Encadenadas del Oeste (Province of Buenos Aires, Argentina). Fish sampling was performed on a three-month basis, from April 2007 to March 2008, using gill nets and a trawl net. Diversity (H’) and species richness were calculated for every sampling station and for each season. Differences in H´ values were analyzed via ANOVA. Relative abundance in number was estimated with net mesh capture. Capture per unit effort (CPUE) was calculated considering the fishing night as unit effort and the size structure of the dominant species was described. A total of 8643 individuals belonging to 14 species were captured. Species richness varied from 8 to 11. H´ evidenced no significant differences among places (p=0.15) although differences were recorded all over the year (p=0.001). H´ was highest in autumn (2.23) and lowest in spring (0.96). In autumn, the dominant species were Odontesthes bonariensis (34%), Parapimelodus valenciennis (32%) and Oligosarcus jenynsii (28%). In winter, the dominant species were only O. bonariensis and O. jenynsii, both representing more than 90%. A significant increase in CPUE was observed in pejerrey (O. bonariensis). Dominant size ranges were 15-17 and 20-25 cm Lst in O. bonariensis and 17-23 cm Lst in O. jenynsii. It can thus be concluded that Alsina lagoon has a key role as a biodiversity reservoir of continental waters. The ichthyc community has undergone modifications, of which the most relevant include: disappearance of P. valenciennis and increase of O. bonariensis. The recuperation of O. bonariensis stock therefore guarantees a promissing future for this environment which formerly reached highest productivity in Encadenadas del Oeste system.

2009-01-01T00:00:00Z This study aims at characterizing the seasonal dynamics of the ichtyofauna of Alsina lagoon which belongs to the Encadenadas del Oeste (Province of Buenos Aires, Argentina). Fish sampling was performed on a three-month basis, from April 2007 to March 2008, using gill nets and a trawl net. Diversity (H’) and species richness were calculated for every sampling station and for each season. Differences in H´ values were analyzed via ANOVA. Relative abundance in number was estimated with net mesh capture. Capture per unit effort (CPUE) was calculated considering the fishing night as unit effort and the size structure of the dominant species was described. A total of 8643 individuals belonging to 14 species were captured. Species richness varied from 8 to 11. H´ evidenced no significant differences among places (p=0.15) although differences were recorded all over the year (p=0.001). H´ was highest in autumn (2.23) and lowest in spring (0.96). In autumn, the dominant species were Odontesthes bonariensis (34%), Parapimelodus valenciennis (32%) and Oligosarcus jenynsii (28%). In winter, the dominant species were only O. bonariensis and O. jenynsii, both representing more than 90%. A significant increase in CPUE was observed in pejerrey (O. bonariensis). Dominant size ranges were 15-17 and 20-25 cm Lst in O. bonariensis and 17-23 cm Lst in O. jenynsii. It can thus be concluded that Alsina lagoon has a key role as a biodiversity reservoir of continental waters. The ichthyc community has undergone modifications, of which the most relevant include: disappearance of P. valenciennis and increase of O. bonariensis. The recuperation of O. bonariensis stock therefore guarantees a promissing future for this environment which formerly reached highest productivity in Encadenadas del Oeste system. Rodríguez, Lorena Peluso, Fabio O. González Castelain, José http://sedici.unlp.edu.ar:80/handle/10915/68793 2019-04-05T20:05:46Z 2009-01-01T00:00:00Z

Articulo V Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP), (Luján, 2008); Biología Acuática; no. 26 In the basin of the Azul Creek (centre of Buenos Aires Province) different uses are made (agricultural, recreational, the reception of urban effluents). Although there is a physicochemical characterization of its surface, it is necessary to do further studies in order to know the variables that determine the water quality of the resource to be managed more efficiently. This following aims at sectoring the basin according to its water quality and to identify significant parameters to describe the variations. Therefore, multivariate techniques were applied: Cluster (CA) and principal components (PCA) on standardized data. These techniques come from twelve seasonal campaigns where 27 variables were measured at 14 stations located in different sectors of the basin (n = 168). The results from CA show the formation of two groups: one consisting of samples of the upper and middle basin, and the other of some samples of the middle and lower basin. Due to the PCA, 3 factors were obtained that explain 53 % of the total variance, reducing the list of parameters to 13, weighing more than 0.70. To conclude, the results obtained by both techniques are consistent since areas with different water quality were identified and those affected by urban effluents were discriminated allowing the identification of parameters which explain this variability. The physicochemical sectoring of surface water which was obtained is not strictly coincident with that determined by the geomorphology and groundwater hydrochemistry.

2009-01-01T00:00:00Z In the basin of the Azul Creek (centre of Buenos Aires Province) different uses are made (agricultural, recreational, the reception of urban effluents). Although there is a physicochemical characterization of its surface, it is necessary to do further studies in order to know the variables that determine the water quality of the resource to be managed more efficiently. This following aims at sectoring the basin according to its water quality and to identify significant parameters to describe the variations. Therefore, multivariate techniques were applied: Cluster (CA) and principal components (PCA) on standardized data. These techniques come from twelve seasonal campaigns where 27 variables were measured at 14 stations located in different sectors of the basin (n = 168). The results from CA show the formation of two groups: one consisting of samples of the upper and middle basin, and the other of some samples of the middle and lower basin. Due to the PCA, 3 factors were obtained that explain 53 % of the total variance, reducing the list of parameters to 13, weighing more than 0.70. To conclude, the results obtained by both techniques are consistent since areas with different water quality were identified and those affected by urban effluents were discriminated allowing the identification of parameters which explain this variability. The physicochemical sectoring of surface water which was obtained is not strictly coincident with that determined by the geomorphology and groundwater hydrochemistry. Pozzobon, M. V. http://sedici.unlp.edu.ar:80/handle/10915/68791 2019-04-05T20:05:52Z 2009-01-01T00:00:00Z

Articulo V Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP), (Luján, 2008); Biología Acuática; no. 26 Periodic hydrologic and ecological alterations in the Lobos’s shallow lake in the last few years and concern and interest of intitutions and authorities, which both value the preservation of the place as a touristic, recreative and sportive resource, have motivated the implementation of the Program of permamanent surveillance of environmental quality of Lobos’s shallow lake . This programe includes low budget and of concrete implementation initiatives using local resources for evaluating the dynamic together with the shallow lake’s environmental quality and its main afluent, Las Garzas’s stream, in a continuous period of time. This study has been carreid out in a framework which has as a main objective to periodically analyze this shallow lake and its afluent’s most significant limnologic variables and to detect any system’s alteration caused by the conjuction of environmental and/or climatic unfavorable conditions or local or regional environmental impacts of diverse origins (industrial, from sewers, or from farming activity). Seventeen samplings have been developed from January of 2000 until September of 2008 in two different areas of study: First Area: Las Garzas Stream and drainage channels, with 4 stations of sampling next to industrial and cattle areas; Second Area: Lobos’s shallow lake, with 4 stations of sampling of hydrologic interest. In each stage of the sampling, the deep, turbidity, pH, temperature and dissolved oxygen was registered and samples of fytoplankton for its cualitative and quantitative analysis were taken. In the First Area, in March of 2001, February of 2004 and Spetember of 2008 samplings show that the unload of efluents have afected the quality of the water of Las Garzas’s stream. Limonologic characteristics of the Second Area show a close relation whit season variables and, in general, the water presented conditions that can be adapted to recreative use. The death of fishes occurred in March of 2000, January of 2001 and July of 2006 coincide with the low levels of oxygen dissolved in the water, high temperatures in relation with the avareage and the amount of algaes (more than 50000 cells/ml) dominated by cyanophytes. The analysis of hydrologic and biologic variables of this shallow lake and its afluent have allowed to achieve periodic observations of this hydric environment, know its dynamic and detect the causes of ecological alterations in the environment. Besides, it has provided with new tools to fund new decisions taken regarding to the managing of the shallow lake.

2009-01-01T00:00:00Z Periodic hydrologic and ecological alterations in the Lobos’s shallow lake in the last few years and concern and interest of intitutions and authorities, which both value the preservation of the place as a touristic, recreative and sportive resource, have motivated the implementation of the Program of permamanent surveillance of environmental quality of Lobos’s shallow lake . This programe includes low budget and of concrete implementation initiatives using local resources for evaluating the dynamic together with the shallow lake’s environmental quality and its main afluent, Las Garzas’s stream, in a continuous period of time. This study has been carreid out in a framework which has as a main objective to periodically analyze this shallow lake and its afluent’s most significant limnologic variables and to detect any system’s alteration caused by the conjuction of environmental and/or climatic unfavorable conditions or local or regional environmental impacts of diverse origins (industrial, from sewers, or from farming activity). Seventeen samplings have been developed from January of 2000 until September of 2008 in two different areas of study: First Area: Las Garzas Stream and drainage channels, with 4 stations of sampling next to industrial and cattle areas; Second Area: Lobos’s shallow lake, with 4 stations of sampling of hydrologic interest. In each stage of the sampling, the deep, turbidity, pH, temperature and dissolved oxygen was registered and samples of fytoplankton for its cualitative and quantitative analysis were taken. In the First Area, in March of 2001, February of 2004 and Spetember of 2008 samplings show that the unload of efluents have afected the quality of the water of Las Garzas’s stream. Limonologic characteristics of the Second Area show a close relation whit season variables and, in general, the water presented conditions that can be adapted to recreative use. The death of fishes occurred in March of 2000, January of 2001 and July of 2006 coincide with the low levels of oxygen dissolved in the water, high temperatures in relation with the avareage and the amount of algaes (more than 50000 cells/ml) dominated by cyanophytes. The analysis of hydrologic and biologic variables of this shallow lake and its afluent have allowed to achieve periodic observations of this hydric environment, know its dynamic and detect the causes of ecological alterations in the environment. Besides, it has provided with new tools to fund new decisions taken regarding to the managing of the shallow lake. Pilati, A. Echaniz, Santiago Andrés Vignatti, Alicia Trucco, A. Álvarez, S. B. http://sedici.unlp.edu.ar:80/handle/10915/68609 2019-04-05T20:05:59Z 2009-01-01T00:00:00Z

Articulo V Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP) (Luján, 2008); Biología Acuática; no. 26 Don Tomás is a shallow, hypereutrophic lake that received sewage inputs from the city of Santa Rosa until 1987. In 1993, the main body of water was divided into smaller adjacent ponds. One of these ponds, Canotaje pond (with a small surface area and average depth), receives an important urban runoff from the city. Thus, the high load of nutrients and sediments after a storm should result in a higher trophic state than Don Tomás. The objective of this research was to compare the limnological characteristics of both water bodies to verify their trophic status. We did not find any significant statistical differences among the measured variables in the two systems, except for water conductivity and suspended organic solids, which were higher in Don Tomás, and for dissolved phosphorus, which was higher in Canotaje. Laboratory experiments determined that the phytoplankton community of both systems was limited by nitrogen, which is consistent with the observed low Redfield ratio of dissolved N and P (1.32). Algal diversity in both systems was represented by 66 taxa, 1/3 of which belonged to the phylum Cyanophyta. In addition, a Planktothrix agardhii bloom was observed in both water bodies. From the present study, we determined that Don Tomás and Canotaje have the same trophic state (i.e. hypereutrophic). In spite of the high urban runoff loaded with nutrients and sediments into Canotaje, the high amounts of P present in this system sediments would make both ponds highly resilient to changes in trophic state.

2009-01-01T00:00:00Z Don Tomás is a shallow, hypereutrophic lake that received sewage inputs from the city of Santa Rosa until 1987. In 1993, the main body of water was divided into smaller adjacent ponds. One of these ponds, Canotaje pond (with a small surface area and average depth), receives an important urban runoff from the city. Thus, the high load of nutrients and sediments after a storm should result in a higher trophic state than Don Tomás. The objective of this research was to compare the limnological characteristics of both water bodies to verify their trophic status. We did not find any significant statistical differences among the measured variables in the two systems, except for water conductivity and suspended organic solids, which were higher in Don Tomás, and for dissolved phosphorus, which was higher in Canotaje. Laboratory experiments determined that the phytoplankton community of both systems was limited by nitrogen, which is consistent with the observed low Redfield ratio of dissolved N and P (1.32). Algal diversity in both systems was represented by 66 taxa, 1/3 of which belonged to the phylum Cyanophyta. In addition, a Planktothrix agardhii bloom was observed in both water bodies. From the present study, we determined that Don Tomás and Canotaje have the same trophic state (i.e. hypereutrophic). In spite of the high urban runoff loaded with nutrients and sediments into Canotaje, the high amounts of P present in this system sediments would make both ponds highly resilient to changes in trophic state. Peluso, Fabio O. González Castelain, José Rodríguez, L. Othax, N. http://sedici.unlp.edu.ar:80/handle/10915/68608 2019-04-05T20:06:02Z 2009-01-01T00:00:00Z

Articulo V Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP), (Luján, 2008); Biología Acuática; no. 26 Surveys for water quality in Tres Arroyos County show the presence of heavy metals in several locations. Considering that water of Tres Arroyos and Claromecó streams is used for recreational purposes during summer, the aim of this paper is to analyze if heavy metals contents (Al, As, Cr, Cu, Hg Mn, Pb y Zn) cause a risk for swimmers. The analysis was made by a recreational health risk assessment (HRA) based on the USEPA probabilistic model including accidental intake and direct skin contact with water in nine points of the basin. The HRA was aggregated (simultaneous exposure to both contact ways) and cumulative (simultaneous exposure to all metals), for non carcinogenic effects, and was made using an additive model. The theoretical individual exposed was a ten years old child (32 kg), that, on average, takes 20 baths/year, 1 hour long each, during 7 years. The results show that the higher value of aggregated and cumulative risk was very low, 7.82E-02, at the Claromecó stream location. So, bathing use of the streams does not represent an adverse health risk considering the assumed conditions of exposure for both types of exposure and all substances simultaneously.

2009-01-01T00:00:00Z Surveys for water quality in Tres Arroyos County show the presence of heavy metals in several locations. Considering that water of Tres Arroyos and Claromecó streams is used for recreational purposes during summer, the aim of this paper is to analyze if heavy metals contents (Al, As, Cr, Cu, Hg Mn, Pb y Zn) cause a risk for swimmers. The analysis was made by a recreational health risk assessment (HRA) based on the USEPA probabilistic model including accidental intake and direct skin contact with water in nine points of the basin. The HRA was aggregated (simultaneous exposure to both contact ways) and cumulative (simultaneous exposure to all metals), for non carcinogenic effects, and was made using an additive model. The theoretical individual exposed was a ten years old child (32 kg), that, on average, takes 20 baths/year, 1 hour long each, during 7 years. The results show that the higher value of aggregated and cumulative risk was very low, 7.82E-02, at the Claromecó stream location. So, bathing use of the streams does not represent an adverse health risk considering the assumed conditions of exposure for both types of exposure and all substances simultaneously. Mancini, M. Salinas, V. Haro, José Gustavo http://sedici.unlp.edu.ar:80/handle/10915/68607 2021-03-24T18:30:46Z 2009-01-01T00:00:00Z

Articulo V Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP) (Luján, 2008); Biología Acuática; no. 26 South of the Villa Mercedes city (San Luis province, Argentina), there are over one hundred shallow lakes of different surface. Many of these lakes are exploited as recreational fishery resources. However, the information available about the ecology and fishes is very limited. In october 2007, the main ichthyofauna characteristics and different ecological aspects of six shallow lakes (34º00’S, 65º24’’W) were studied with special focus on the pejerrey Odontesthes bonariensis population. The average area of shallow lakes was 17.8 (±9.9) ha. Turbid (green) and clear shallow lakes were observed with great abundance of Potamogeton berteroanus and Secchi disk values of were up to 2.30 m. All the lakes showed a reed belt of Schoenoplectus americanus with a different degree of development. The abundance of zooplankton was variable with a maximum of 338167 org/m3. The water was classified as oligohaline and very hard. In total, 7 species of fishes were caught distributed in 4 orders and 5 families: O. bonariensis, Astyanax eigenmanniorum, Cheirodon interruptus, Oligosarcus jenynsii, Corydoras paleatus, Cnesterodon decemmaculatus y Jenynsia multidentata. The Shannon-Wiener diversity index was low to medium (0.91-1.55 bits). The largest capture per unit effort of O. bonariensis (CPUEp) was 28.6 kg/20hs/net with a proportional stock density (PSD) of 60.7.

2009-01-01T00:00:00Z South of the Villa Mercedes city (San Luis province, Argentina), there are over one hundred shallow lakes of different surface. Many of these lakes are exploited as recreational fishery resources. However, the information available about the ecology and fishes is very limited. In october 2007, the main ichthyofauna characteristics and different ecological aspects of six shallow lakes (34º00’S, 65º24’’W) were studied with special focus on the pejerrey Odontesthes bonariensis population. The average area of shallow lakes was 17.8 (±9.9) ha. Turbid (green) and clear shallow lakes were observed with great abundance of Potamogeton berteroanus and Secchi disk values of were up to 2.30 m. All the lakes showed a reed belt of Schoenoplectus americanus with a different degree of development. The abundance of zooplankton was variable with a maximum of 338167 org/m3. The water was classified as oligohaline and very hard. In total, 7 species of fishes were caught distributed in 4 orders and 5 families: O. bonariensis, Astyanax eigenmanniorum, Cheirodon interruptus, Oligosarcus jenynsii, Corydoras paleatus, Cnesterodon decemmaculatus y Jenynsia multidentata. The Shannon-Wiener diversity index was low to medium (0.91-1.55 bits). The largest capture per unit effort of O. bonariensis (CPUEp) was 28.6 kg/20hs/net with a proportional stock density (PSD) of 60.7. Maiztegui, Tomás Campanella, Daniela Colautti, Darío César http://sedici.unlp.edu.ar:80/handle/10915/68375 2020-05-07T00:31:38Z 2009-01-01T00:00:00Z

Articulo V Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP), (Luján, 2008); Biología Acuática; no. 26 The use of Cheirodon interruptus as a sport fishing bait puts under serious pressure the pampean shallow lakes ecosystems, because it is mostly obtained from natural environments. This project aims to evaluate the possibility of developing the technological and biological know-how for a production system in captivity for sustainable use of the resource. We used a system with a low daily water renovation rate and a 150 % daily recirculation rate through a biofilter. Fishes in every ontogenetic stage in the system showed good health conditions and high acceptance to artificial diet formulations. Two spawning events were registered during spring season and the development of larvae through its juvenile stage went by with no further requirements than isolation from adults and granulometry variation of food. Although the character of this trial is just preliminar, we may conclude that a massive production system is possible, in order to make this bait market a sustainable activity not only in the commercial aspect but in its ecological as well.

2009-01-01T00:00:00Z The use of Cheirodon interruptus as a sport fishing bait puts under serious pressure the pampean shallow lakes ecosystems, because it is mostly obtained from natural environments. This project aims to evaluate the possibility of developing the technological and biological know-how for a production system in captivity for sustainable use of the resource. We used a system with a low daily water renovation rate and a 150 % daily recirculation rate through a biofilter. Fishes in every ontogenetic stage in the system showed good health conditions and high acceptance to artificial diet formulations. Two spawning events were registered during spring season and the development of larvae through its juvenile stage went by with no further requirements than isolation from adults and granulometry variation of food. Although the character of this trial is just preliminar, we may conclude that a massive production system is possible, in order to make this bait market a sustainable activity not only in the commercial aspect but in its ecological as well. Mac Donagh, María Elicia Casco, María Adela Cano, María Gabriela Solari, Lía Cristina Claps, María Cristina Gabellone, Néstor Adrián http://sedici.unlp.edu.ar:80/handle/10915/68373 2019-12-17T18:46:03Z 2009-01-01T00:00:00Z

Articulo V Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP), (Luján, 2008); Biología Acuática; no. 26 The Alternative Stable States Hypothesis has been revised over the last years, owing to the differences found between shallow lakes from temperate zones and those from other latitudes and climates. Studies performed in shallow lakes of the Pampean region showed that the temporal and spatial changes and the interactions between algal communities are very complex. In these shallow lakes the epiphyton and epipelon may play significant roles that can be as or ever more important as the roles described for phytoplankton. In Lacombe Lake, three different phases of equilibrium were defined, one of them with intermediate characteristics between clear and turbid phases. The aim of this paper was to analyze the individual fit of some estimators of system dynamics of infrequently used application in the equilibrium state definition to this conceptual scheme. The differences between phases were mainly identified in water variables, whereas sediment variables did not show great variations although changes in system’s state were being recorded. Chlorophyll a, phytoplankton density and water organic matter were the best indicators of the phases. With respect to sediment variables, the three phases were only differentiated on the basis of variations in the settled planktonic algae.

2009-01-01T00:00:00Z The Alternative Stable States Hypothesis has been revised over the last years, owing to the differences found between shallow lakes from temperate zones and those from other latitudes and climates. Studies performed in shallow lakes of the Pampean region showed that the temporal and spatial changes and the interactions between algal communities are very complex. In these shallow lakes the epiphyton and epipelon may play significant roles that can be as or ever more important as the roles described for phytoplankton. In Lacombe Lake, three different phases of equilibrium were defined, one of them with intermediate characteristics between clear and turbid phases. The aim of this paper was to analyze the individual fit of some estimators of system dynamics of infrequently used application in the equilibrium state definition to this conceptual scheme. The differences between phases were mainly identified in water variables, whereas sediment variables did not show great variations although changes in system’s state were being recorded. Chlorophyll a, phytoplankton density and water organic matter were the best indicators of the phases. With respect to sediment variables, the three phases were only differentiated on the basis of variations in the settled planktonic algae. Grosman, Fabián Sanzano, Pablo Colasurdo, Viviana Díaz, O. http://sedici.unlp.edu.ar:80/handle/10915/68199 2019-04-06T04:03:02Z 2009-01-01T00:00:00Z

Articulo V Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP), (Luján, 2008); Biología Acuática; no. 26 A 7 ha shallow water body is located in an urban park in the city of 9 de Julio, Province of Buenos Aires, Argentina. Pluvial water drainage maintains its hydrometric level which is regulated by a spillway. Since 2004, fishing and swimming have been forbidden. In 2008, the government of the city requested the University (UNCPBA) to make a rapid diagnosis of the state of the shallow lake. The objective was to present management alternatives taking into account the structure and functioning of the shallow lake, through sampling as well as from existing information. The water is characterized by low ionic charge. The system is eutrophic. Phytoplankton is co-dominated by chlorophyte and euglenophyte algae. Macrophytes are irrelevant. Macrozooplankton exhibited very high densities. Five fish species were captured, all of which have zooplankton and detritus as primary resources. Sediments tend to accumulate, since nutrients and organic matter cause the saturation of the basin. The main proposals (including alternative, complementary, or sequential actions) are intended to revaluate the public space through its use, introducing local identity and a sense of belonging. Some of the proposed activities are: to regulate the flow, widen the waterbed, sow macrophytes and redirect pluvial discharges; to vacate the place for the extraction of sediment; to allow the practice of recreational fishing; to introduce fishes of sporting interest; to gather leaves and keep clean the surrounding of the shallow lake and neighboring streets; to install a geyser; to monitor the microbial flora; to make analysis of lead and hydrocarbon contents; to establish footpaths and points of reflection and observation of Nature.

2009-01-01T00:00:00Z A 7 ha shallow water body is located in an urban park in the city of 9 de Julio, Province of Buenos Aires, Argentina. Pluvial water drainage maintains its hydrometric level which is regulated by a spillway. Since 2004, fishing and swimming have been forbidden. In 2008, the government of the city requested the University (UNCPBA) to make a rapid diagnosis of the state of the shallow lake. The objective was to present management alternatives taking into account the structure and functioning of the shallow lake, through sampling as well as from existing information. The water is characterized by low ionic charge. The system is eutrophic. Phytoplankton is co-dominated by chlorophyte and euglenophyte algae. Macrophytes are irrelevant. Macrozooplankton exhibited very high densities. Five fish species were captured, all of which have zooplankton and detritus as primary resources. Sediments tend to accumulate, since nutrients and organic matter cause the saturation of the basin. The main proposals (including alternative, complementary, or sequential actions) are intended to revaluate the public space through its use, introducing local identity and a sense of belonging. Some of the proposed activities are: to regulate the flow, widen the waterbed, sow macrophytes and redirect pluvial discharges; to vacate the place for the extraction of sediment; to allow the practice of recreational fishing; to introduce fishes of sporting interest; to gather leaves and keep clean the surrounding of the shallow lake and neighboring streets; to install a geyser; to monitor the microbial flora; to make analysis of lead and hydrocarbon contents; to establish footpaths and points of reflection and observation of Nature. García, M. E. Rodrigues Capítulo, Alberto Ferrari, Lucrecia http://sedici.unlp.edu.ar:80/handle/10915/68198 2019-04-06T04:03:09Z 2009-01-01T00:00:00Z

Articulo V Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP), (Luján, 2008); Biología Acuática; no. 26 The use of benthic invertebrates is considerate and recognized at present as one of the better methodological alternative to detect early modifications or contamination from diffuse origin. The objective of this work was to evaluate the biological quality of two regional pampean plain streams by means of taxonomic and functional indicators of the whole of invertebrates assemblages and to compare the utility of the different applied indicators. The selected streams belong to the Rio de La Plata basin, with different anthropogenic impact. Over a period of two years, the physicochemical parameters and the benthic invertebrates and those present in the vegetation, of these lotic systems were assessed in samplings sites located upstream and downstream. Taxonomic and functional feeding groups, of the invertebrate assemblages were analyzed. The estimated taxonomic indicators reflected seasonal differences and the valuation of the quality of the sites were different and variable depending on the parameter and the taxonomical level used. Even so, the density of the most abundant family, the abundance of Ephemeroptera-Trichoptera (ET), the ET/total and ET/Oligochaeta relations resulted useful to establish differences between sites and streams. The collectors appeared as the dominant functional feeding group in all the sites. No significant differences were observed in the composition of the functional feeding groups of the invertebrate assemblages from headwaters to the mouth of both streams. Then these indicators would not be efficient to evaluate the environmental quality of these systems.

2009-01-01T00:00:00Z The use of benthic invertebrates is considerate and recognized at present as one of the better methodological alternative to detect early modifications or contamination from diffuse origin. The objective of this work was to evaluate the biological quality of two regional pampean plain streams by means of taxonomic and functional indicators of the whole of invertebrates assemblages and to compare the utility of the different applied indicators. The selected streams belong to the Rio de La Plata basin, with different anthropogenic impact. Over a period of two years, the physicochemical parameters and the benthic invertebrates and those present in the vegetation, of these lotic systems were assessed in samplings sites located upstream and downstream. Taxonomic and functional feeding groups, of the invertebrate assemblages were analyzed. The estimated taxonomic indicators reflected seasonal differences and the valuation of the quality of the sites were different and variable depending on the parameter and the taxonomical level used. Even so, the density of the most abundant family, the abundance of Ephemeroptera-Trichoptera (ET), the ET/total and ET/Oligochaeta relations resulted useful to establish differences between sites and streams. The collectors appeared as the dominant functional feeding group in all the sites. No significant differences were observed in the composition of the functional feeding groups of the invertebrate assemblages from headwaters to the mouth of both streams. Then these indicators would not be efficient to evaluate the environmental quality of these systems. Fuchs, D. V. Volpedo, Alejandra V. http://sedici.unlp.edu.ar:80/handle/10915/68197 2019-04-06T04:03:19Z 2009-01-01T00:00:00Z

Articulo V Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP), (Luján, 2008); Biología Acuática; no. 26 The otoliths of fishes are complex polycrystalline, composed mainly by calcium carbonate. The lapillus is usually the most conspicuous otolith in Siluriform fishes. Studies of siluriforms’ otoliths are scarce at world level. In this paper are studied the lapilli of Ageneiosus inermis, Auchenipterus nuchalis, Callichthys callichthys, Corydoras paleatus, Pterodoras granulosus, Rhinodoras dorbignyi, Pimelodella gracilis, Pimelodella laticeps, Rhamdia quelen, Hypostomus commersoni, Loricariichthys anus, Paraloricaria vetula, Iheringichthys labrosus, Luciopimelodus pati, Parapimelodus valenciennis, Pimelodus albicans, Pimelodus argenteus, Pimelodus maculatus and Sorubim lima. Fish standard length was registered in millimeters. The otoliths were extracted, described and photographed, and a dichotomical key was made. The results showed that lapilli otoliths of the studied species have a great morphological variability; this could be associated to the diversity and ecological plasticity of the siluriforms group. The morphological features that can be used to differentiate the lapilli of the studied species are: otolith shape, sulcus features, cisure, internal face depression and lapillus edges. The values of index EL (AOL/LOL)x100 were different in each family of siluriforms. The species of Loricariidae present the highest values of EL (>80%), the species of Doradidae present the lowest values (53-55%) and the other species present intermediate values.

2009-01-01T00:00:00Z The otoliths of fishes are complex polycrystalline, composed mainly by calcium carbonate. The lapillus is usually the most conspicuous otolith in Siluriform fishes. Studies of siluriforms’ otoliths are scarce at world level. In this paper are studied the lapilli of Ageneiosus inermis, Auchenipterus nuchalis, Callichthys callichthys, Corydoras paleatus, Pterodoras granulosus, Rhinodoras dorbignyi, Pimelodella gracilis, Pimelodella laticeps, Rhamdia quelen, Hypostomus commersoni, Loricariichthys anus, Paraloricaria vetula, Iheringichthys labrosus, Luciopimelodus pati, Parapimelodus valenciennis, Pimelodus albicans, Pimelodus argenteus, Pimelodus maculatus and Sorubim lima. Fish standard length was registered in millimeters. The otoliths were extracted, described and photographed, and a dichotomical key was made. The results showed that lapilli otoliths of the studied species have a great morphological variability; this could be associated to the diversity and ecological plasticity of the siluriforms group. The morphological features that can be used to differentiate the lapilli of the studied species are: otolith shape, sulcus features, cisure, internal face depression and lapillus edges. The values of index EL (AOL/LOL)x100 were different in each family of siluriforms. The species of Loricariidae present the highest values of EL (>80%), the species of Doradidae present the lowest values (53-55%) and the other species present intermediate values. Elías, F. G. Cervellini, P. M. Garibotti. E. Piccolo, C. http://sedici.unlp.edu.ar:80/handle/10915/68196 2019-04-06T04:03:24Z 2009-01-01T00:00:00Z

Articulo V Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP), (Luján, 2008); Biología Acuática; no. 26 Moina eugeniae is one of the most abundant zooplankton species found in ponds and lakes in Buenos Aires Province. Its importance is due to the common use of cladocerans as food fish. The aim of the present study was to investigate the reproductive structures through histological techniques. Samples were taken with a plankton net (150 μm) from the Calderón lake (Buenos Aires) during Spring 2006. The specimens were anesthetized with CO2 “in situ” and fixed with formaldehyde 4%. Parthenogenetic females in different reproductive stages were selected to perform with them routine histological techniques. No males were identified during our study. The ovaries are pair, secular and disposed dorsally in the body. The oocytes are polyedric with three different stages of maturation: previtellogenic (dense nuclear cromatine), vitellogenic (abundant yolk in cytoplasm and large granules of cromatine in the nucleous) and mature (abundant lipidic drops in cytoplasm). Many of the morphological features observed are similar to those of Daphnia genus. Further investigation is needed to elucidate the reproductive cycle of this species.

2009-01-01T00:00:00Z Moina eugeniae is one of the most abundant zooplankton species found in ponds and lakes in Buenos Aires Province. Its importance is due to the common use of cladocerans as food fish. The aim of the present study was to investigate the reproductive structures through histological techniques. Samples were taken with a plankton net (150 μm) from the Calderón lake (Buenos Aires) during Spring 2006. The specimens were anesthetized with CO2 “in situ” and fixed with formaldehyde 4%. Parthenogenetic females in different reproductive stages were selected to perform with them routine histological techniques. No males were identified during our study. The ovaries are pair, secular and disposed dorsally in the body. The oocytes are polyedric with three different stages of maturation: previtellogenic (dense nuclear cromatine), vitellogenic (abundant yolk in cytoplasm and large granules of cromatine in the nucleous) and mature (abundant lipidic drops in cytoplasm). Many of the morphological features observed are similar to those of Daphnia genus. Further investigation is needed to elucidate the reproductive cycle of this species. Eissa, B. L. Ossana, Natalia A. Salibian, Alfredo Ferrari, Lucrecia Pérez, R. H http://sedici.unlp.edu.ar:80/handle/10915/68195 2019-04-06T04:03:28Z 2009-01-01T00:00:00Z

Articulo V Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP), (Luján, 2008); Biología Acuática; no. 26 Numerous studies have shown that the swimming performance parameters of fish may be useful indicators of their environmental stress. The swimming speed was evaluated in two Pampean species and its alteration as a result of their exposure to sublethal Cadmium concentrations. The swimming speed was calculated from a daily registry of the distance and the time of displacement of fish by means of special software. Juveniles specimens of Astyanax fasciatus and Australoheros facetum were used in the assays; fish were acclimated during 7 days in aereated fresh-water (FW), at constant temperature (20 ± 1ºC) and photoperiod (12D:12N). The experimental design contemplated three successive periods: Control (4 days in FW), Exposure (4 days in FW + 0.3 and 0.5 mg Cd L-1) and Recovery (7 days in FW); simultaneously the speed of individuals maintained in FW during 15 days (CoP) was determined. The swimming speed in both species increased in the Exposure period. After transfer to clean media (Recovery period), the altered values in A. facetum, exhibited a slight tendency to recovery (but without reaching the basal values registered in the Control period). In A. fasciatus a clear cut recovery response was registered in fish exposed to 0.3 mg. L-1 while in animals exposed to the highest concentration of Cd no recovery was registered. These differences were interpreted as evidences of dissimilar uptake and depuration rates of the toxic.

2009-01-01T00:00:00Z Numerous studies have shown that the swimming performance parameters of fish may be useful indicators of their environmental stress. The swimming speed was evaluated in two Pampean species and its alteration as a result of their exposure to sublethal Cadmium concentrations. The swimming speed was calculated from a daily registry of the distance and the time of displacement of fish by means of special software. Juveniles specimens of Astyanax fasciatus and Australoheros facetum were used in the assays; fish were acclimated during 7 days in aereated fresh-water (FW), at constant temperature (20 ± 1ºC) and photoperiod (12D:12N). The experimental design contemplated three successive periods: Control (4 days in FW), Exposure (4 days in FW + 0.3 and 0.5 mg Cd L-1) and Recovery (7 days in FW); simultaneously the speed of individuals maintained in FW during 15 days (CoP) was determined. The swimming speed in both species increased in the Exposure period. After transfer to clean media (Recovery period), the altered values in A. facetum, exhibited a slight tendency to recovery (but without reaching the basal values registered in the Control period). In A. fasciatus a clear cut recovery response was registered in fish exposed to 0.3 mg. L-1 while in animals exposed to the highest concentration of Cd no recovery was registered. These differences were interpreted as evidences of dissimilar uptake and depuration rates of the toxic. Echaniz, Santiago Andrés Vignatti, Alicia Cabrera, Gabriela Cecilia http://sedici.unlp.edu.ar:80/handle/10915/68194 2019-04-06T04:03:34Z 2009-01-01T00:00:00Z

Articulo V Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP) (Luján, 2008); Biología Acuática; no. 26 In La Pampa province, shallow lakes (water bodies of low depth, generally polimictic and with high trophic level) are abundant and broadly distributed. Although previous contributions on these shallow lakes are about their ecology and zooplankton, only recently studies have shed light about nutrient concentrations, chlorophyll a and their influence on the zooplankton biomass. It has also been determined that phosphorus and nitrogen concentrations are higher than other shallow lakes of similar characteristics from other regions. The objectives of this contribution are to perform a limnological characterization of an extensive shallow seepage lake with medium salinity and high trophic level of the east-central region of La Pampa province, strongly influenced by human activity. We also present information on the taxonomic composition and abundance and biomass variations of the zooplankton. We took monthly samples from December 2005 to December 2006. In the past, this lake was a temporary lake, but recently it receives water from sewage treatment plants of Santa Rosa city and its pluvial drainages. This lake has now an important tourist and recreational value related to its condition of permanent lake and the presence of silversides (Odontesthes bonariensis). The zooplankton specific richness (15 taxa) was lower than other organic turbid shallow lakes of La Pampa, but closer to the observed in other high salinity shallow lakes. Another common feature with shallow saline lakes of La Pampa was the prevalence, among the microcrustaceans, of the halophilic calanoid Boeckella poopoensis. Cladocerans, on the other hand, were rarely registered; they had very low abundances and they were small-sized, since they could not prosper related to the predatory pressure by the planktivorous fish that inhabit this lake

2009-01-01T00:00:00Z In La Pampa province, shallow lakes (water bodies of low depth, generally polimictic and with high trophic level) are abundant and broadly distributed. Although previous contributions on these shallow lakes are about their ecology and zooplankton, only recently studies have shed light about nutrient concentrations, chlorophyll a and their influence on the zooplankton biomass. It has also been determined that phosphorus and nitrogen concentrations are higher than other shallow lakes of similar characteristics from other regions. The objectives of this contribution are to perform a limnological characterization of an extensive shallow seepage lake with medium salinity and high trophic level of the east-central region of La Pampa province, strongly influenced by human activity. We also present information on the taxonomic composition and abundance and biomass variations of the zooplankton. We took monthly samples from December 2005 to December 2006. In the past, this lake was a temporary lake, but recently it receives water from sewage treatment plants of Santa Rosa city and its pluvial drainages. This lake has now an important tourist and recreational value related to its condition of permanent lake and the presence of silversides (Odontesthes bonariensis). The zooplankton specific richness (15 taxa) was lower than other organic turbid shallow lakes of La Pampa, but closer to the observed in other high salinity shallow lakes. Another common feature with shallow saline lakes of La Pampa was the prevalence, among the microcrustaceans, of the halophilic calanoid Boeckella poopoensis. Cladocerans, on the other hand, were rarely registered; they had very low abundances and they were small-sized, since they could not prosper related to the predatory pressure by the planktivorous fish that inhabit this lake Cabo, L. de Casares, M. V. Seoane, R. http://sedici.unlp.edu.ar:80/handle/10915/68193 2019-04-06T04:03:36Z 2009-01-01T00:00:00Z

Articulo V Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP) (Luján, 2008); Biología Acuática; no. 26 Nutrient uptake and competitive ability of the aquatic species Lemna gibba and Salvinia minima were evaluated. The experiment was carried out in a greenhouse and plants were grown as mono-plant cultures and mixed-plant cultures. Three different media were used: tap water and the chemically defined media Lemna and Hutner 1/10. Duration of the experiment was 7 days. Initial and final dry weights and DIN and SRP concentrations were determined. Relative growth rates (RGR) and nutrient uptake rates were calculated. L. gibba´s RGR values increased significantly in Hutner 1/10 medium when types of cultures were analyzed separately. RGR values decreased in Lemna and Hutner 1/10 media in mixed-plant cultures. S. minima did not show significant differences in its RGR values. In mono-plant cultures N and P uptake rates in Lemna medium were significantly larger for L. gibba. In Hutner 1/10 medium P uptake rate was greater for S. minima and N uptake rate was larger for L. gibba. The presence of S. minima negatively affected L. gibba´s growth.

2009-01-01T00:00:00Z Nutrient uptake and competitive ability of the aquatic species Lemna gibba and Salvinia minima were evaluated. The experiment was carried out in a greenhouse and plants were grown as mono-plant cultures and mixed-plant cultures. Three different media were used: tap water and the chemically defined media Lemna and Hutner 1/10. Duration of the experiment was 7 days. Initial and final dry weights and DIN and SRP concentrations were determined. Relative growth rates (RGR) and nutrient uptake rates were calculated. L. gibba´s RGR values increased significantly in Hutner 1/10 medium when types of cultures were analyzed separately. RGR values decreased in Lemna and Hutner 1/10 media in mixed-plant cultures. S. minima did not show significant differences in its RGR values. In mono-plant cultures N and P uptake rates in Lemna medium were significantly larger for L. gibba. In Hutner 1/10 medium P uptake rate was greater for S. minima and N uptake rate was larger for L. gibba. The presence of S. minima negatively affected L. gibba´s growth. Colautti, Darío César Maroñas, Miriam Edith Sendra, Eduardo Daniel Protogino, Lucila Cristina Brancolini, Florencia Campanella, Daniela http://sedici.unlp.edu.ar:80/handle/10915/68191 2020-05-07T00:54:27Z 2009-01-01T00:00:00Z

Articulo V Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP), (Luján, 2008); Biología Acuática; no. 26 As part of the project “Global changes in river systems: effects on biodiversity, food web and system functioning” fish community of La Choza stream was initially estimated and then compared with existing literature of pampean plain streams. From May 2007 to June 2008 five fish samples were taken in two sampling stations. Species occurrence, diversity (H´) and evenness (J) were estimated. Similarity in species composition with ten pampean streams was performed using cluster analysis. 2935 specimens collected represented 23 species (13 permanent, 7 semi-permanent and 3 occasional) and 10 families. Characiformes and Siluriformes were dominant. Although species richness was similar in both sites, diversity index was higher at downstream station. Differences between stations could be related to channel shape, bottom profile and sediment type. The cluster analysis showed that position of the water course within the basin and pollution are both important in the ichthyofauna composition determination.

2009-01-01T00:00:00Z As part of the project “Global changes in river systems: effects on biodiversity, food web and system functioning” fish community of La Choza stream was initially estimated and then compared with existing literature of pampean plain streams. From May 2007 to June 2008 five fish samples were taken in two sampling stations. Species occurrence, diversity (H´) and evenness (J) were estimated. Similarity in species composition with ten pampean streams was performed using cluster analysis. 2935 specimens collected represented 23 species (13 permanent, 7 semi-permanent and 3 occasional) and 10 families. Characiformes and Siluriformes were dominant. Although species richness was similar in both sites, diversity index was higher at downstream station. Differences between stations could be related to channel shape, bottom profile and sediment type. The cluster analysis showed that position of the water course within the basin and pollution are both important in the ichthyofauna composition determination. Colautti, Darío César García de Souza, Javier Ricardo Miranda, Leandro http://sedici.unlp.edu.ar:80/handle/10915/68190 2020-05-07T01:07:24Z 2009-01-01T00:00:00Z

Articulo V Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP) (Luján, 2008); Biología Acuática; no. 26 In the last years pejerrey culture has been developed in an intensive form using circular tanks. Employing this system is possible to obtain fish of commercial size but the production costs are high making this activity not profitable. An alternative to reduce costs is to rear pejerrey employing a mix system using cages in natural lagoons anda posterior culture in tanks until commercial size (250g). In a first step, pejerrey fish hatched and reared for 25 days at IIB-INTECH aquaculture facilities were transferred to floating cages of 16 m3 (50 fish/m3) placed at Lacombe Lagoon (Chascomús County). After 11 months, and only eating natural food, these fish had a total length (TL) of 15 ± 0.19 cm and a weight of (W) 25.27 ± 1.5 g. During this period of time the mean survival was 18 %. Then, 400 fish were transported to the IIB-INTECH and placed in an outdoor tank of 20.000 liters with an open water flow system and a salinity of 15 g/L. They were fed twice a day to satiation with artificial diets designed for pejerrey. After 26 months posthatching the fish had a TL of 30.66 ± 0.65 cm and a weight of 254.79 ± 9.72 g. During this period the mean water temperature was 18 °C and the survival was around 95 %. Taking together these results we conclude that is possible to rear pejerrey in a mix system until the commercial size in 26 months, reducing the costs of the first year. This method also gives the possibility to produce juveniles in a cheap way or to grow pejerrey up to commercial size as independent activities.

2009-01-01T00:00:00Z In the last years pejerrey culture has been developed in an intensive form using circular tanks. Employing this system is possible to obtain fish of commercial size but the production costs are high making this activity not profitable. An alternative to reduce costs is to rear pejerrey employing a mix system using cages in natural lagoons anda posterior culture in tanks until commercial size (250g). In a first step, pejerrey fish hatched and reared for 25 days at IIB-INTECH aquaculture facilities were transferred to floating cages of 16 m3 (50 fish/m3) placed at Lacombe Lagoon (Chascomús County). After 11 months, and only eating natural food, these fish had a total length (TL) of 15 ± 0.19 cm and a weight of (W) 25.27 ± 1.5 g. During this period of time the mean survival was 18 %. Then, 400 fish were transported to the IIB-INTECH and placed in an outdoor tank of 20.000 liters with an open water flow system and a salinity of 15 g/L. They were fed twice a day to satiation with artificial diets designed for pejerrey. After 26 months posthatching the fish had a TL of 30.66 ± 0.65 cm and a weight of 254.79 ± 9.72 g. During this period the mean water temperature was 18 °C and the survival was around 95 %. Taking together these results we conclude that is possible to rear pejerrey in a mix system until the commercial size in 26 months, reducing the costs of the first year. This method also gives the possibility to produce juveniles in a cheap way or to grow pejerrey up to commercial size as independent activities.