http://sedici.unlp.edu.ar:80/handle/10915/69247 2026-07-19T15:52:15Z 2026-07-19T15:52:15Z Instituto de Limnología "Dr. Raul A. Ringuelet" http://sedici.unlp.edu.ar:80/handle/10915/69531 2022-04-12T17:45:06Z 2006-03-01T00:00:00Z

Edicion de revista III Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP) (Tandil, 11 y 12 de noviembre de 2004); Biología Acuática; no. 22 Recopilación de los trabajos completos presentados en el III Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP), celebrado en Tandil (Buenos Aires) en 2004.

2006-03-01T00:00:00Z Recopilación de los trabajos completos presentados en el III Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP), celebrado en Tandil (Buenos Aires) en 2004. Vanotti, M. D. Tanzola, Rubén Daniel http://sedici.unlp.edu.ar:80/handle/10915/69529 2021-03-24T19:15:43Z 2006-03-01T00:00:00Z

Articulo III Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP) (Tandil, 11 y 12 de noviembre de 2004); Biología Acuática; no. 22 The purpose of the present research is to evaluate the degree of the statistical association between the total burden of parasites in the South American Catfish, Rhamdia sapo, and hematological variables studied under natural conditions. The following 12 parasite species were identified: 2 ciliate protozoans, 1 flagellate, 1 monogenean, 3 digeneans, 1 cestode, 2 nematodes, and 2 crustaceans. Of the parasite species collected from the tegument, branchias, body cavity, and digestive tube, some of them (namely, Argulus violaceus, Urocleidoides mastigatus, Hysterothylacium rhamdiae, Acanthostomun gnerii, Proteocephalus jamdiae, Trichodina sp. and Cucullanus sp.) have been previously cited. However, Ichthyophthirius multifiliis, Spironucleus sp., Lernaea cyprinacea, and Thometrema sp. are cited for the first time in Argentina as a parasite of this fish. The non-parametrical Spearman’s rank correlation test indicated that the total burden of parasites in the South American Catfish, Rhamdia sapo, exerts no significant action under the hematological variables studied in this research, namely, red blood cell count, white blood cell count, thrombocyte count, hemoglobin concentration, hematocrit, mean corpuscular volume, mean corpuscular hemoglobin, and mean corpuscular hemoglobin concentration.

2006-03-01T00:00:00Z The purpose of the present research is to evaluate the degree of the statistical association between the total burden of parasites in the South American Catfish, Rhamdia sapo, and hematological variables studied under natural conditions. The following 12 parasite species were identified: 2 ciliate protozoans, 1 flagellate, 1 monogenean, 3 digeneans, 1 cestode, 2 nematodes, and 2 crustaceans. Of the parasite species collected from the tegument, branchias, body cavity, and digestive tube, some of them (namely, Argulus violaceus, Urocleidoides mastigatus, Hysterothylacium rhamdiae, Acanthostomun gnerii, Proteocephalus jamdiae, Trichodina sp. and Cucullanus sp.) have been previously cited. However, Ichthyophthirius multifiliis, Spironucleus sp., Lernaea cyprinacea, and Thometrema sp. are cited for the first time in Argentina as a parasite of this fish. The non-parametrical Spearman’s rank correlation test indicated that the total burden of parasites in the South American Catfish, Rhamdia sapo, exerts no significant action under the hematological variables studied in this research, namely, red blood cell count, white blood cell count, thrombocyte count, hemoglobin concentration, hematocrit, mean corpuscular volume, mean corpuscular hemoglobin, and mean corpuscular hemoglobin concentration. Ruiz, Gonzalo Carlos Solari, Lía Cristina Gabellone, Néstor Adrián http://sedici.unlp.edu.ar:80/handle/10915/69521 2020-09-11T16:58:23Z 2006-03-01T00:00:00Z

Articulo III Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP) (Tandil, 11 y 12 de noviembre de 2004); Biología Acuática; no. 22 Shallow lakes can present two alternative stable states with or without submerged macrophytes that produce significant structural changes in plankton and nutrient dynamics. The aim of this study is to analyse the changes in the phytoplankton structure related to different conditions of zooplankton predation in an arreic lake. Four cylindrical pvc enclosures of 700 L of capacity were placed in the lake, two of them in free-vegetation waters and the other two in an area dominated by emerged and submerged macrophytes (Scirpus californicus and Potamogeton striatus respectively) with and without predation conditions on the grazer zooplankton. Samples were taken every eight hours for three days during the 2003/2004 summer period. Temperature, pH, dissolved oxygen, conductivity, turbidity and transparency were measured in situ. Water samples were taken to determine the different phosphorus and nitrogen forms and to analyse the phytoplankton. In all treatments, the conductivity oscillated between 1.520 and 1.550 μS.cm -1. Turbidity varied from 48 to 54 NTU and the pH was slightly alkaline (8,48-8,81). Chlorophytes and cyanophytes increased in free-vegetation-water enclosures with fish while no changes were found in the vegetated area. Preliminarily, we can say that the predation effect on zooplankton was more important in the enclosure placed in free-vegetation waters with fish. It was there that the biggest densities of eatable cholorophyte algae (Crucigenia quadrata, Dictyosphaerium pulchellum var. minor, Chlamydomonas sp. and Oocystis parva) were found towards the end of the experiment. Contribución científica Nº 792 del Instituto de Limnología "Dr. R. A. Ringuelet" (ILPLA).

2006-03-01T00:00:00Z Shallow lakes can present two alternative stable states with or without submerged macrophytes that produce significant structural changes in plankton and nutrient dynamics. The aim of this study is to analyse the changes in the phytoplankton structure related to different conditions of zooplankton predation in an arreic lake. Four cylindrical pvc enclosures of 700 L of capacity were placed in the lake, two of them in free-vegetation waters and the other two in an area dominated by emerged and submerged macrophytes (Scirpus californicus and Potamogeton striatus respectively) with and without predation conditions on the grazer zooplankton. Samples were taken every eight hours for three days during the 2003/2004 summer period. Temperature, pH, dissolved oxygen, conductivity, turbidity and transparency were measured in situ. Water samples were taken to determine the different phosphorus and nitrogen forms and to analyse the phytoplankton. In all treatments, the conductivity oscillated between 1.520 and 1.550 μS.cm -1. Turbidity varied from 48 to 54 NTU and the pH was slightly alkaline (8,48-8,81). Chlorophytes and cyanophytes increased in free-vegetation-water enclosures with fish while no changes were found in the vegetated area. Preliminarily, we can say that the predation effect on zooplankton was more important in the enclosure placed in free-vegetation waters with fish. It was there that the biggest densities of eatable cholorophyte algae (Crucigenia quadrata, Dictyosphaerium pulchellum var. minor, Chlamydomonas sp. and Oocystis parva) were found towards the end of the experiment. Remes Lenicov, Mauricio Colautti, Darío César López, Hugo Luis http://sedici.unlp.edu.ar:80/handle/10915/69520 2020-05-07T00:50:41Z 2006-03-01T00:00:00Z

Articulo III Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP) (Tandil, 11 y 12 de noviembre de 2004); Biología Acuática; no. 22 Knowledge about ictiofaunal spatial distribution and composition of the lotic enviroment pampean plain is scarce. The purpose of this paper is to characterize fish community living in the Rodríguez Stream, located in the urban northeastern area of the province of Buenos Aires in Argentina. Limnological data was collected and analyzed along the stream. Ichthyological samples were taken using different methods to determine the quali-quantitative composition of the fish and their changes tendencie to change in relation to related to some diferent variables. The low oxygen concentration in the middle course caused by the highest anthropic pressure, was the key factor wich was responsible for the largest changes in the composition and species abundance of the fauna. This contribution, besides considering biological aspects of the ichthyofauna of this stream for the first time provides a diagnosis how this is affected by the growing urban impact within the metropolitan area of Buenos Aires.

2006-03-01T00:00:00Z Knowledge about ictiofaunal spatial distribution and composition of the lotic enviroment pampean plain is scarce. The purpose of this paper is to characterize fish community living in the Rodríguez Stream, located in the urban northeastern area of the province of Buenos Aires in Argentina. Limnological data was collected and analyzed along the stream. Ichthyological samples were taken using different methods to determine the quali-quantitative composition of the fish and their changes tendencie to change in relation to related to some diferent variables. The low oxygen concentration in the middle course caused by the highest anthropic pressure, was the key factor wich was responsible for the largest changes in the composition and species abundance of the fauna. This contribution, besides considering biological aspects of the ichthyofauna of this stream for the first time provides a diagnosis how this is affected by the growing urban impact within the metropolitan area of Buenos Aires. Quaíni, Karina Paola Gabellone, Néstor Adrián Ardohain, Diego Martín Solari, Lía Cristina http://sedici.unlp.edu.ar:80/handle/10915/69518 2019-12-17T18:47:46Z 2006-03-01T00:00:00Z

Articulo III Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP) (Tandil, 11 y 12 de noviembre de 2004); Biología Acuática; no. 22 Dredging works in several sectors of Salado River are probably the most important activity of disturbance in a pampean aquatic ecosystem, with implications in a RAMSAR site (Samborombón Bay). The interventions are taking place in the lower basin and considered as a reference of disturbance for future and major works as the dredging of almost 100 km of the Salado River main channel. Physical and chemical conditions were analysed in two sectors: upstream (El Destino, ED) and downstream (Guerrero, G) of La Postrera. This study was done before and during the extraction of a river restriction and the old bridge replacement. Samples were collected during 18 weeks (3/04-7/04) (2 or 3 times/week). Each sample was the result of the water sample integration on a transversal transect of the stream. The physical and chemical parameters measured «in situ» were: pH, conductivity, turbidity, dissolved oxygen, temperature and salinity. Fractions of phosphorus and suspended solids were analysed. The simulation of different sampling frequencies showed that variables related to physic environment (temperature, conductivity and pH) can be explained by monthly and biweekly sampling. On the other hand, the main variations of total phosphorus, suspended solids and turbidity can be only explained by the daily sampling. Suspended solids concentration was higher upstream (mean: 0.12 g.L -1 ) than downstream (mean: 0.10 g.L -1 ). Maximum mean phosphorus concentration values were reached at ED. Soluble reactive phosphorus concentrations were similar at both river sectors (305.81 and 307.08 μg.L -1 in ED and G, respectively). Conductivity diminished from 6,770to 2,530 μS.cm -1 due to the discharge increase. Total particulate phosphorus, suspended solids and turbidity increased at ED and diminished at G. The dredging works in moments of low waters, and taking care of the extracting material location, as recommended the environmental management techniques, did not affect sediment transport through the river. The phosphorus concentration differences between both river sectors could be by the settlement processes in La Tigra Lake and the availability of this nutrient to the phytoplankton and macrophytes.

2006-03-01T00:00:00Z Dredging works in several sectors of Salado River are probably the most important activity of disturbance in a pampean aquatic ecosystem, with implications in a RAMSAR site (Samborombón Bay). The interventions are taking place in the lower basin and considered as a reference of disturbance for future and major works as the dredging of almost 100 km of the Salado River main channel. Physical and chemical conditions were analysed in two sectors: upstream (El Destino, ED) and downstream (Guerrero, G) of La Postrera. This study was done before and during the extraction of a river restriction and the old bridge replacement. Samples were collected during 18 weeks (3/04-7/04) (2 or 3 times/week). Each sample was the result of the water sample integration on a transversal transect of the stream. The physical and chemical parameters measured «in situ» were: pH, conductivity, turbidity, dissolved oxygen, temperature and salinity. Fractions of phosphorus and suspended solids were analysed. The simulation of different sampling frequencies showed that variables related to physic environment (temperature, conductivity and pH) can be explained by monthly and biweekly sampling. On the other hand, the main variations of total phosphorus, suspended solids and turbidity can be only explained by the daily sampling. Suspended solids concentration was higher upstream (mean: 0.12 g.L -1 ) than downstream (mean: 0.10 g.L -1 ). Maximum mean phosphorus concentration values were reached at ED. Soluble reactive phosphorus concentrations were similar at both river sectors (305.81 and 307.08 μg.L -1 in ED and G, respectively). Conductivity diminished from 6,770to 2,530 μS.cm -1 due to the discharge increase. Total particulate phosphorus, suspended solids and turbidity increased at ED and diminished at G. The dredging works in moments of low waters, and taking care of the extracting material location, as recommended the environmental management techniques, did not affect sediment transport through the river. The phosphorus concentration differences between both river sectors could be by the settlement processes in La Tigra Lake and the availability of this nutrient to the phytoplankton and macrophytes. Pezzani, S. Poretti, T. http://sedici.unlp.edu.ar:80/handle/10915/69517 2019-04-05T12:13:24Z 2006-03-01T00:00:00Z

Articulo III Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP) (Tandil, 11 y 12 de noviembre de 2004); Biología Acuática; no. 22 The gasteropods distribution was studied and it was analyzed the influence of the aquatic macrophytes biomass fluctuation and the structuring environmental factors. Sampling was carried out in Las Flores stream, a Lujan river tributary, from April 2000 to February 2002. Egeria densa (submerged), Hydrocotyle ranunculoides and Alternanthera philoxeroides (rooted) were the most representative macrophytes. Heleobia piscium and Gundlachia concentrica occurred as the dominant gasteropods. For all other associated macroinvertebrates on macrophytes, Hyalella sp. was predominat. The rainfall and the consequent inflow increase were influenced on the macrophytes biomass and their associated fauna. The macrophytes biomass was one of the factor related to the temporal abundance of gasteropods. However, these variations in the abundance of the gasteropods were more related with the life cycle. Their largest gasteropods and anfipods density was shown on rooted macrophytes. Heleobia piscium, G. concentrica and Hyalella sp. coexist on the same macrophyte during the low abundance periods without any competition. Although, during the breeding period, the displacement of the other macroinvertebrates populations was observed. This suggests interespecific competition by substrate and food between the two gasteropods species while the competition with the anfipods is mainly by substrate. Gasteropods and anfipods consume different type of food. Heleobia piscium and G. concentrica colonize these macrophytes with some preferance. These gasteropods are opportunists species whose distribution and supervivence strategy is as follow: to colonize different aquatic macrophytes showing each species some preference by sumerged or rooted macrophytes; to have an annual breeding period with a high recruitment of individuals which allow to maintain the populations despite the disturbances effect.

2006-03-01T00:00:00Z The gasteropods distribution was studied and it was analyzed the influence of the aquatic macrophytes biomass fluctuation and the structuring environmental factors. Sampling was carried out in Las Flores stream, a Lujan river tributary, from April 2000 to February 2002. Egeria densa (submerged), Hydrocotyle ranunculoides and Alternanthera philoxeroides (rooted) were the most representative macrophytes. Heleobia piscium and Gundlachia concentrica occurred as the dominant gasteropods. For all other associated macroinvertebrates on macrophytes, Hyalella sp. was predominat. The rainfall and the consequent inflow increase were influenced on the macrophytes biomass and their associated fauna. The macrophytes biomass was one of the factor related to the temporal abundance of gasteropods. However, these variations in the abundance of the gasteropods were more related with the life cycle. Their largest gasteropods and anfipods density was shown on rooted macrophytes. Heleobia piscium, G. concentrica and Hyalella sp. coexist on the same macrophyte during the low abundance periods without any competition. Although, during the breeding period, the displacement of the other macroinvertebrates populations was observed. This suggests interespecific competition by substrate and food between the two gasteropods species while the competition with the anfipods is mainly by substrate. Gasteropods and anfipods consume different type of food. Heleobia piscium and G. concentrica colonize these macrophytes with some preferance. These gasteropods are opportunists species whose distribution and supervivence strategy is as follow: to colonize different aquatic macrophytes showing each species some preference by sumerged or rooted macrophytes; to have an annual breeding period with a high recruitment of individuals which allow to maintain the populations despite the disturbances effect. Marano, Agostina Virginia Steciow, Mónica Mirta http://sedici.unlp.edu.ar:80/handle/10915/69516 2019-04-05T12:13:28Z 2006-03-01T00:00:00Z

Articulo III Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP) (Tandil, 11 y 12 de noviembre de 2004); Biología Acuática; no. 22 We study the «in situ» colonization of different kinds of substrata by zoosporic fungi (S.D Mastigomycotina), making weekly samplings during a month in the streams «El Zanjón» and «Las Cañas» (Ensenada, Bs. As., Argentina). In those sites we put twelve different substrata, both naturals (monocotyledon leaves, crustacean shells, Rosa sp. fruits, snake sheds and little fishes) and artificial ones (cellophane fragments, polypropylene bags, slides, and two kinds of different plastic materials). The substrata were put separately in drilled plastic bags, and left for a week to allow colonization. In both sites, we observed that Saprolegnia colonized every kind of substratum (both natural and artificial ones), while Achlya was encountered in the majority of them (little fishes, slides, cellophane fragments, pieces of X-rays, Rosa sp. fruits, and monocotyledon leaves), Dichtyuchus was observed in fishes and Rosa sp. fruits, Brevilegnia and Pythium in pieces of X-rays plate and Aphanomyces only in plastic materials. Based on these preliminary results, we can infer that there is an apparent selection of some genera for particular substrata. It’s interesting to emphasize that colonization of artificial substrata by Saprolegnia, Achlya, Brevilegnia, Pythium and Aphanomyces, might suggest the possibility of using these genera in superficial biodegradation of plastic materials.

2006-03-01T00:00:00Z We study the «in situ» colonization of different kinds of substrata by zoosporic fungi (S.D Mastigomycotina), making weekly samplings during a month in the streams «El Zanjón» and «Las Cañas» (Ensenada, Bs. As., Argentina). In those sites we put twelve different substrata, both naturals (monocotyledon leaves, crustacean shells, Rosa sp. fruits, snake sheds and little fishes) and artificial ones (cellophane fragments, polypropylene bags, slides, and two kinds of different plastic materials). The substrata were put separately in drilled plastic bags, and left for a week to allow colonization. In both sites, we observed that Saprolegnia colonized every kind of substratum (both natural and artificial ones), while Achlya was encountered in the majority of them (little fishes, slides, cellophane fragments, pieces of X-rays, Rosa sp. fruits, and monocotyledon leaves), Dichtyuchus was observed in fishes and Rosa sp. fruits, Brevilegnia and Pythium in pieces of X-rays plate and Aphanomyces only in plastic materials. Based on these preliminary results, we can infer that there is an apparent selection of some genera for particular substrata. It’s interesting to emphasize that colonization of artificial substrata by Saprolegnia, Achlya, Brevilegnia, Pythium and Aphanomyces, might suggest the possibility of using these genera in superficial biodegradation of plastic materials. Mancini, M. Nicola, I. Larriestra, A. Salinas, V. Bucco, C. http://sedici.unlp.edu.ar:80/handle/10915/69486 2019-04-05T12:13:35Z 2006-03-01T00:00:00Z

Articulo III Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP) (Tandil, 11 y 12 de noviembre de 2004); Biología Acuática; no. 22 Several internal and external parasites have been reported in the wild population of the pejerrey, Odontesthes bonariensis, although most of previous studies have focused on taxonomy. The aims of this research were to describe the seasonal variation and the age prevalence pattern of the nematode Contracaecum sp., and to characterize the association between the pejerrey parasitic infestation with body condition score. Four samples, one per season, were collected during the years 2002 and 2003 in a shallow lake located in the southern area of Cordoba, Argentina (34° 36’S, 64° 24’W). The fishes caught were subject to age estimation using the Von Bertalanffy’s equation, the assessment of the relative weight (Wr) and the determination of abundance and intensity of the parasite infestation. The standard length average (n = 283) was 185,5 mm (range 38 - 380). The proportion of fishes with at least one parasite was 10,1%. The highest abundance (0,94) and prevalence (24,6%) were observed in summer, and the highest average intensity in autumn (5,7 parasites /fish). Fishes > 2 years old showed 5,99 more times (odds ratio IC95% 2,41 - 14,84) of being parasited with Contracaecum sp. in comparison to younger fishes. The Wr was lower for infested fishes (85,45; IC95% 81,82 - 89,08) in comparison to non infested specymens even after the statistical adjustment for season and age effects. Since Contracaecum sp. is zoonotic, the prevalence reported may pose a risk to humans due to the common habits of consuming uncontrolled fishes in recreational fisheries. In addition to that, parasitic infestation may also reduce body condition in fishes of commercial size.

2006-03-01T00:00:00Z Several internal and external parasites have been reported in the wild population of the pejerrey, Odontesthes bonariensis, although most of previous studies have focused on taxonomy. The aims of this research were to describe the seasonal variation and the age prevalence pattern of the nematode Contracaecum sp., and to characterize the association between the pejerrey parasitic infestation with body condition score. Four samples, one per season, were collected during the years 2002 and 2003 in a shallow lake located in the southern area of Cordoba, Argentina (34° 36’S, 64° 24’W). The fishes caught were subject to age estimation using the Von Bertalanffy’s equation, the assessment of the relative weight (Wr) and the determination of abundance and intensity of the parasite infestation. The standard length average (n = 283) was 185,5 mm (range 38 - 380). The proportion of fishes with at least one parasite was 10,1%. The highest abundance (0,94) and prevalence (24,6%) were observed in summer, and the highest average intensity in autumn (5,7 parasites /fish). Fishes > 2 years old showed 5,99 more times (odds ratio IC95% 2,41 - 14,84) of being parasited with Contracaecum sp. in comparison to younger fishes. The Wr was lower for infested fishes (85,45; IC95% 81,82 - 89,08) in comparison to non infested specymens even after the statistical adjustment for season and age effects. Since Contracaecum sp. is zoonotic, the prevalence reported may pose a risk to humans due to the common habits of consuming uncontrolled fishes in recreational fisheries. In addition to that, parasitic infestation may also reduce body condition in fishes of commercial size. López Cazorla, Andrea C. Sidorkewicj, N. S. http://sedici.unlp.edu.ar:80/handle/10915/69485 2019-04-05T12:13:40Z 2006-03-01T00:00:00Z

Articulo III Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP) (Tandil, 11 y 12 de noviembre de 2004); Biología Acuática; no. 22 The objective of the present work was to determine the age that reaches Cheirodon interruptus (Jenyns, 1842) in the Sauce Grande river basin, and to estimate its growth parameters. Sampling was performed seasonally by electrofishing, in three sites along the main river. A total of 164 individuals were caught, and total length (TL, mm) and weight (W, g) were recorded. The age was determined over a sub-sample of 154 fish, by means of scale reading. The growth parameters of von Bertalanffy’s equation were estimated using Least Squares method. Fish size ranged between 29 - 62 mm, with a mean of 44.73 mm (± 7.46). Mean TL by season was 38.17 mm (± 5.47) in summer, 43.25 mm (± 9.00) in autumn, 45.00 mm (± 5.10) in winter and 47.73 mm (± 6.45) in spring. Length-weight relationship for the total population was W = 6 x 10 -5 TL 2.61 (R 2 = 0.88). One annulus formation occurred yearly, at the end of autumn, assigning one year to each mark. Three age classes were determined (0 – 2), being age 0 the most abundant (84 %). The growth parameters for the total population were : L∞ = 57.63 mm; k = 0.69 y t 0 = -1.72.

2006-03-01T00:00:00Z The objective of the present work was to determine the age that reaches Cheirodon interruptus (Jenyns, 1842) in the Sauce Grande river basin, and to estimate its growth parameters. Sampling was performed seasonally by electrofishing, in three sites along the main river. A total of 164 individuals were caught, and total length (TL, mm) and weight (W, g) were recorded. The age was determined over a sub-sample of 154 fish, by means of scale reading. The growth parameters of von Bertalanffy’s equation were estimated using Least Squares method. Fish size ranged between 29 - 62 mm, with a mean of 44.73 mm (± 7.46). Mean TL by season was 38.17 mm (± 5.47) in summer, 43.25 mm (± 9.00) in autumn, 45.00 mm (± 5.10) in winter and 47.73 mm (± 6.45) in spring. Length-weight relationship for the total population was W = 6 x 10 -5 TL 2.61 (R 2 = 0.88). One annulus formation occurred yearly, at the end of autumn, assigning one year to each mark. Three age classes were determined (0 – 2), being age 0 the most abundant (84 %). The growth parameters for the total population were : L∞ = 57.63 mm; k = 0.69 y t 0 = -1.72. Grosman, Fabián Sanzano, Pablo Rudzik, Gabriela http://sedici.unlp.edu.ar:80/handle/10915/69484 2019-04-05T12:13:44Z 2006-03-01T00:00:00Z

Articulo III Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP) (Tandil, 11 y 12 de noviembre de 2004); Biología Acuática; no. 22 The territory of Puán County encompasses 133 shallow lakes, which resources are barely used. Technical knowledge of the shallow lakes is limited, hence the management policy currently being applied is generic. The aim of this paper is to make a primary proposal for the strategic use of the fisheries, supported by an expeditious diagnostic of various environments. Each shallow lake exhibits particular characteristics. The CPUE ranges from 0 to very abundant. In general, the rate of exploitation is low, producing an excellent yield and high quality fish resources. The trophic chain is short, with relevant zooplankton size and density, sustaining an abundant pejerrey Odontesthes bonariensis population. The services offered to the anglers in the shores are few or nonexistent. Tourism development is scarce in spite of the strong potential. Weaknesses and strengths are analyzed considering different parameters and situations. The use of resources through sport fishing is proposed, targeting on high-income fishermen looking for high quality pejerrey catch in a near pristine shallow lake and enjoying privacy. Such a fisherman demands quality and professionalism in the services received, as well as personal or exclusive attention by providers. On the other hand, those shallow lakes not selected for a sport fishing circuit, can be managed by the local government allowing the catch of pejerrey, controlling the correct use of gill nets, creating more jobs, and also providing fish to the town’s popular kitchens feeding the needy. The potential emergent problems contemplated in the execution of the project are listed and compared to the current situation.

2006-03-01T00:00:00Z The territory of Puán County encompasses 133 shallow lakes, which resources are barely used. Technical knowledge of the shallow lakes is limited, hence the management policy currently being applied is generic. The aim of this paper is to make a primary proposal for the strategic use of the fisheries, supported by an expeditious diagnostic of various environments. Each shallow lake exhibits particular characteristics. The CPUE ranges from 0 to very abundant. In general, the rate of exploitation is low, producing an excellent yield and high quality fish resources. The trophic chain is short, with relevant zooplankton size and density, sustaining an abundant pejerrey Odontesthes bonariensis population. The services offered to the anglers in the shores are few or nonexistent. Tourism development is scarce in spite of the strong potential. Weaknesses and strengths are analyzed considering different parameters and situations. The use of resources through sport fishing is proposed, targeting on high-income fishermen looking for high quality pejerrey catch in a near pristine shallow lake and enjoying privacy. Such a fisherman demands quality and professionalism in the services received, as well as personal or exclusive attention by providers. On the other hand, those shallow lakes not selected for a sport fishing circuit, can be managed by the local government allowing the catch of pejerrey, controlling the correct use of gill nets, creating more jobs, and also providing fish to the town’s popular kitchens feeding the needy. The potential emergent problems contemplated in the execution of the project are listed and compared to the current situation. Grosman, Fabián Sanzano, Pablo Agüería, D. http://sedici.unlp.edu.ar:80/handle/10915/69483 2019-04-05T12:13:49Z 2006-03-01T00:00:00Z

Articulo III Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP) (Tandil, 11 y 12 de noviembre de 2004); Biología Acuática; no. 22 During the last decades lagunas were massively incorporated to the circuit of sport fishing, as a reaction to quality and quantity increase of the demand for this activity’s practice. «Domino effect» was the main responsible for opening of this fishermen helped by attracting economic yields. Laguna La Peregrina is a typical case. From the human point of view, the pejerrey Odontesthes bonarienses has not been taken advantage of as there have been very few extractions. To use the environment with profitable purposes, a diagnosis of fishing resources was made in order to schedule a plan for taking advantage thereof. Samplings were made in autumn 2003. Information from the physicchemical and biological aspects was obtained with emphasis on ichthyocenosis. Density was low related to scarce density of phytoplankton, dominated by cyanophytas. Zooplankton was abundant. Fish diversity was low with pejerrey predominance, whose catch per unit effort (cpue) was very high, and specimen had excellent bearing and condition. Specimens greater than 300 mm Lstd were zooplanktophagous, the rest of the status were from other communities.It was highlighted size distribution, gonadal activity, alevins capture, decompensate relation of sexes, greater length average of females and disorder in scales. The raised hypotheses allude to a sampling error, different growth for each sex, thermo dependence sexual regulation, and presence of a estrogenic substances in the aquatic environment. Processed diagnosis showed that plankton chain constitutes the base of the main trophodynamics relations of the system. Phytoplankton was intensely grassing by zooplankton, which, in trophic terms, maintains ichthyocenosis dominated by the pejerrey, whose demographic parameters and condition are totally favorable to establish a sport fisheries. Previously, water quality analysis must be performed to explain potential presence of polluting agents of agricultural origin.

2006-03-01T00:00:00Z During the last decades lagunas were massively incorporated to the circuit of sport fishing, as a reaction to quality and quantity increase of the demand for this activity’s practice. «Domino effect» was the main responsible for opening of this fishermen helped by attracting economic yields. Laguna La Peregrina is a typical case. From the human point of view, the pejerrey Odontesthes bonarienses has not been taken advantage of as there have been very few extractions. To use the environment with profitable purposes, a diagnosis of fishing resources was made in order to schedule a plan for taking advantage thereof. Samplings were made in autumn 2003. Information from the physicchemical and biological aspects was obtained with emphasis on ichthyocenosis. Density was low related to scarce density of phytoplankton, dominated by cyanophytas. Zooplankton was abundant. Fish diversity was low with pejerrey predominance, whose catch per unit effort (cpue) was very high, and specimen had excellent bearing and condition. Specimens greater than 300 mm Lstd were zooplanktophagous, the rest of the status were from other communities.It was highlighted size distribution, gonadal activity, alevins capture, decompensate relation of sexes, greater length average of females and disorder in scales. The raised hypotheses allude to a sampling error, different growth for each sex, thermo dependence sexual regulation, and presence of a estrogenic substances in the aquatic environment. Processed diagnosis showed that plankton chain constitutes the base of the main trophodynamics relations of the system. Phytoplankton was intensely grassing by zooplankton, which, in trophic terms, maintains ichthyocenosis dominated by the pejerrey, whose demographic parameters and condition are totally favorable to establish a sport fisheries. Previously, water quality analysis must be performed to explain potential presence of polluting agents of agricultural origin. González Naya, M. J. Gómez, Sergio Enrique Ramírez, L. http://sedici.unlp.edu.ar:80/handle/10915/69482 2019-04-05T12:13:53Z 2006-03-01T00:00:00Z

Articulo III Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP) (Tandil, 11 y 12 de noviembre de 2004); Biología Acuática; no. 22 The cichlidae are recognized as maneauver specialists characterized by low crusing speeds and some acceleration capacity. In this work the swimming capacity of Gymnogeophagus meridionalis and the relation it has with some morphometric variables were experimentally evaluated under laboratory conditions and compared with others cichlid species. Using a flow chamber where the water flowed at a constant velocity of 6.8 cm.s-1, fatigue times (TA) between 84 and 853 min were obtained for 10 specimens between 22.9 and 70.0 mm of standard length (Lst). The maximum swimming speed was estimated in 5.5 Lst.s-1 and the cruising speed was approximately 2.0 Lst.s-1. Comparatively, G. meridionalis’ average fatigue time (376.1 min) was longer than that mentioned for C. facetum (169.1 min) and shorter than preliminary data of Crenicichla sp. These differences are related to the corporal morphology. Whereas Crenicichla sp. presented the most elongated body shape with an average body height as a percent of Lst (AC%) about 22%; inside the orbicular cichlids group, G. meridionalis and C. facetum presented AC% of 43.2 y 47.5% respectively. The differences in swimming capacity between Gymnogeophagus meridionalis and C. facetum, both maneuver specialists, could be owed to a smaller body height and a narrow caudal peduncle.

2006-03-01T00:00:00Z The cichlidae are recognized as maneauver specialists characterized by low crusing speeds and some acceleration capacity. In this work the swimming capacity of Gymnogeophagus meridionalis and the relation it has with some morphometric variables were experimentally evaluated under laboratory conditions and compared with others cichlid species. Using a flow chamber where the water flowed at a constant velocity of 6.8 cm.s-1, fatigue times (TA) between 84 and 853 min were obtained for 10 specimens between 22.9 and 70.0 mm of standard length (Lst). The maximum swimming speed was estimated in 5.5 Lst.s-1 and the cruising speed was approximately 2.0 Lst.s-1. Comparatively, G. meridionalis’ average fatigue time (376.1 min) was longer than that mentioned for C. facetum (169.1 min) and shorter than preliminary data of Crenicichla sp. These differences are related to the corporal morphology. Whereas Crenicichla sp. presented the most elongated body shape with an average body height as a percent of Lst (AC%) about 22%; inside the orbicular cichlids group, G. meridionalis and C. facetum presented AC% of 43.2 y 47.5% respectively. The differences in swimming capacity between Gymnogeophagus meridionalis and C. facetum, both maneuver specialists, could be owed to a smaller body height and a narrow caudal peduncle. González Naya, M. J. Gómez, Sergio Enrique Ramírez, L. http://sedici.unlp.edu.ar:80/handle/10915/69451 2019-04-05T12:13:57Z 2006-03-01T00:00:00Z

Articulo III Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP) (Tandil, 11 y 12 de noviembre de 2004); Biología Acuática; no. 22 G. affinis is a native poecilid of North America. It was introduced in Argentina in 1945, since then G. affinis has established as stable populations in several provinces like Cordoba and Buenos Aires up to 35º S approximately. On this work, three different kinds of experiences have been made to obtain some ecophysiological features of this exotic fish. The results were compared with those of Cnesterodon decemmaculatus, a native poecilid widely used in bioassays in Argentina. Some comments were made upon the morphological and pigmentation aspects of both species. The incipient lethal level of pH (96 h) was estimated at 10.3. The average swimming capacity using the Fatigue Time technique with a constant velocity of 6.8 cm.s-1 was 46.6 min and the lethal temperature obtained by means of the Critical Maximum technique was 41.21 ºC. All the analyzed parameters were larger than those noted for C. decemmaculatus. Both species showed a significant loss in their pigmentation when they were exposed to light or high temperatures. However, there are not any references of presence for G. cf. affinis in Patagonia nor in Pampasian lagunas, it has shown to be more eurithopic than C. decemmaculatus suggesting that it fulfills all the requirements to be found in these regions together with other Cyprinodontiforms.

2006-03-01T00:00:00Z G. affinis is a native poecilid of North America. It was introduced in Argentina in 1945, since then G. affinis has established as stable populations in several provinces like Cordoba and Buenos Aires up to 35º S approximately. On this work, three different kinds of experiences have been made to obtain some ecophysiological features of this exotic fish. The results were compared with those of Cnesterodon decemmaculatus, a native poecilid widely used in bioassays in Argentina. Some comments were made upon the morphological and pigmentation aspects of both species. The incipient lethal level of pH (96 h) was estimated at 10.3. The average swimming capacity using the Fatigue Time technique with a constant velocity of 6.8 cm.s-1 was 46.6 min and the lethal temperature obtained by means of the Critical Maximum technique was 41.21 ºC. All the analyzed parameters were larger than those noted for C. decemmaculatus. Both species showed a significant loss in their pigmentation when they were exposed to light or high temperatures. However, there are not any references of presence for G. cf. affinis in Patagonia nor in Pampasian lagunas, it has shown to be more eurithopic than C. decemmaculatus suggesting that it fulfills all the requirements to be found in these regions together with other Cyprinodontiforms. Gómez, Sergio Enrique Menni, Roberto Carlos http://sedici.unlp.edu.ar:80/handle/10915/69450 2019-04-05T12:14:03Z 2006-03-01T00:00:00Z

Articulo III Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP) (Tandil, 11 y 12 de noviembre de 2004); Biología Acuática; no. 22 Within the Pampas ecoregion during the XX century, heavy climate changes resulting in fish fauna displacements westward of meridian 61. These movements implied three elements: climate change, topographic changes, and animal transport. From the northwest of this region, where fish were not present in the recent past, 10 species from the La Amarga swamps, 10 from the neighborhood of General Villegas and 4 from Trenque Lauquen are known at present. In the three cases, water is hard and alkaline. Their fish fauna have a similarity index (Jaccard) of 44 % with that from the Salado River basin, and of 57,9 % with that from the «lagunas» Encadenadas del Oeste. In the latter environment, the number of species increased from 7 to 18 in thirty years, having at present 75% similarity with that from the Salado River basin. In the western Pampasia, data from 6 meteorological stations in a polygonal area 16,500 km2 in extension, show a heavy climatic change, with a progressive significant increase of rainfall and the minimum mean annual temperature, which are limiting factors for fishes. Mean annual rainfall increased from 700 to 950 mm and the minimum mean temperature from 8,9 to 10,1º C in the last 40 years. New water bodies were formed and other increased their volume. At the same time, construction of discharge channels, embankments, and modification of slopes, connected western Pampasic areas with the Salado River basin, allowing them to be colonized by more eurytopic fishes. The Pampas ecoregión has his present western border about 64º W, including the La Amarga dells. We think that, as a result of environmental change and the above mentioned processes, new environments with Brazilian fishes will be formed in the western Pampasia in the near future.

2006-03-01T00:00:00Z Within the Pampas ecoregion during the XX century, heavy climate changes resulting in fish fauna displacements westward of meridian 61. These movements implied three elements: climate change, topographic changes, and animal transport. From the northwest of this region, where fish were not present in the recent past, 10 species from the La Amarga swamps, 10 from the neighborhood of General Villegas and 4 from Trenque Lauquen are known at present. In the three cases, water is hard and alkaline. Their fish fauna have a similarity index (Jaccard) of 44 % with that from the Salado River basin, and of 57,9 % with that from the «lagunas» Encadenadas del Oeste. In the latter environment, the number of species increased from 7 to 18 in thirty years, having at present 75% similarity with that from the Salado River basin. In the western Pampasia, data from 6 meteorological stations in a polygonal area 16,500 km2 in extension, show a heavy climatic change, with a progressive significant increase of rainfall and the minimum mean annual temperature, which are limiting factors for fishes. Mean annual rainfall increased from 700 to 950 mm and the minimum mean temperature from 8,9 to 10,1º C in the last 40 years. New water bodies were formed and other increased their volume. At the same time, construction of discharge channels, embankments, and modification of slopes, connected western Pampasic areas with the Salado River basin, allowing them to be colonized by more eurytopic fishes. The Pampas ecoregión has his present western border about 64º W, including the La Amarga dells. We think that, as a result of environmental change and the above mentioned processes, new environments with Brazilian fishes will be formed in the western Pampasia in the near future. Gari, N. Corigliano, M. del C. http://sedici.unlp.edu.ar:80/handle/10915/69449 2019-04-05T12:14:09Z 2006-03-01T00:00:00Z

Articulo III Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP) (Tandil, 11 y 12 de noviembre de 2004); Biología Acuática; no. 22 Confluence zones are important places to analyze discontinuities that succeed in the river continuum, when two streams of different order link up with their collector. In this work we analyzed the periphyton composition and structure in the confluence of two mountain streams, where Chocancharava river (Cuarto river) foothill reach begins, in Córdoba province. Monthly periphyton samples were taken by scraping a known surface, in three sites located in Piedras Blancas and San Bartolomé stream confluence at 550 m a.s.l. TWINSPAN classification and sample and species ordinations by means of Canonic Correspondence Analysis (CCA) were carried out. Seventy one algae species were determined. Bacillarophyceae and Chlorophyceae presented higher species richness. Dominant species were Cocconeis placentula var. euplypta and Achnanthidium minutissimum, both exhibited an annual bimodal distribution pattern, with maximal densities in autumn and spring. CCA clusters demonstrated seasonal changes in periphyton structure. Summer species were associated to higher temperature and precipitations, and winter species (were associated) to higher conductivity and pH. The tributary of minor order, San Bartolomé stream, evidenced a wider distance in the sample grouping; its flora was different in winter months, during the phase of low water levels. From the obtained results it is concluded that at the confluence sectors the composition and structure of the higher order stream is continuous with the principal river during low water levels while, during high water levels, the periphyton of both tributaries colonize the receiving river.

2006-03-01T00:00:00Z Confluence zones are important places to analyze discontinuities that succeed in the river continuum, when two streams of different order link up with their collector. In this work we analyzed the periphyton composition and structure in the confluence of two mountain streams, where Chocancharava river (Cuarto river) foothill reach begins, in Córdoba province. Monthly periphyton samples were taken by scraping a known surface, in three sites located in Piedras Blancas and San Bartolomé stream confluence at 550 m a.s.l. TWINSPAN classification and sample and species ordinations by means of Canonic Correspondence Analysis (CCA) were carried out. Seventy one algae species were determined. Bacillarophyceae and Chlorophyceae presented higher species richness. Dominant species were Cocconeis placentula var. euplypta and Achnanthidium minutissimum, both exhibited an annual bimodal distribution pattern, with maximal densities in autumn and spring. CCA clusters demonstrated seasonal changes in periphyton structure. Summer species were associated to higher temperature and precipitations, and winter species (were associated) to higher conductivity and pH. The tributary of minor order, San Bartolomé stream, evidenced a wider distance in the sample grouping; its flora was different in winter months, during the phase of low water levels. From the obtained results it is concluded that at the confluence sectors the composition and structure of the higher order stream is continuous with the principal river during low water levels while, during high water levels, the periphyton of both tributaries colonize the receiving river. García Romero, Nicolás Plaul, Silvia Elena Santelices Iglesias, Olga Andrea Fontana, Paula Andrea http://sedici.unlp.edu.ar:80/handle/10915/69447 2020-10-09T19:46:18Z 2006-03-01T00:00:00Z

Articulo III Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP) (Tandil, 11 y 12 de noviembre de 2004); Biología Acuática; no. 22 Giardia sp. is a genus of endoparasite protozoo of the small intestine, responsible for infections generally asymptomatic, especially in children. They can cause acute, sub acute, and chronic diarrheas and duodenal irritation with increment of the mucus and deficiencies in the absorption of liposolubles vitamins. Giardia sp. can inhibit the activity of the pancreatic lipasa causing mal absorption of fats. Their cysts remain viable more than two weeks in humid areas and the way of infection is by ingestion of water or polluted foods with cysts. Studies carried out in the Canadian goose (Branta canadensis) determined the presence of cysts of Giardia sp. in the faecal pellets of these birds, and considering their migratory nature the possible dissemination of the parasite has special interest. Giardia sp.has been also identified in feces of other aquatic birds that are considered reservoirs. The small gallareta (Fulica leucoptera) possesses a wide and profuse distribution in Argentina. It occupies a similar ecological niche of that of the Canadian goose, so their possible participation in the contamination of the superficial waters with cysts of Giardia sp. can be considere. With the purpose of testing this possibility, were captured some gallaretas in the complex Nordelta-Tigre (Bs. As., Argentina), taking samples of faecal pellets and duodenal content. The carried out studies did not showed Giardia sp. Anyway, it should be taken in to consideration the small size of the sample and it restricted geographical representation before possible epidemic inferences. The results provide original information on the rol of the wild aquatic birds as possible agents of dispersion of parasitosis whit importance in public health.

2006-03-01T00:00:00Z Giardia sp. is a genus of endoparasite protozoo of the small intestine, responsible for infections generally asymptomatic, especially in children. They can cause acute, sub acute, and chronic diarrheas and duodenal irritation with increment of the mucus and deficiencies in the absorption of liposolubles vitamins. Giardia sp. can inhibit the activity of the pancreatic lipasa causing mal absorption of fats. Their cysts remain viable more than two weeks in humid areas and the way of infection is by ingestion of water or polluted foods with cysts. Studies carried out in the Canadian goose (Branta canadensis) determined the presence of cysts of Giardia sp. in the faecal pellets of these birds, and considering their migratory nature the possible dissemination of the parasite has special interest. Giardia sp.has been also identified in feces of other aquatic birds that are considered reservoirs. The small gallareta (Fulica leucoptera) possesses a wide and profuse distribution in Argentina. It occupies a similar ecological niche of that of the Canadian goose, so their possible participation in the contamination of the superficial waters with cysts of Giardia sp. can be considere. With the purpose of testing this possibility, were captured some gallaretas in the complex Nordelta-Tigre (Bs. As., Argentina), taking samples of faecal pellets and duodenal content. The carried out studies did not showed Giardia sp. Anyway, it should be taken in to consideration the small size of the sample and it restricted geographical representation before possible epidemic inferences. The results provide original information on the rol of the wild aquatic birds as possible agents of dispersion of parasitosis whit importance in public health. Gantes, P. Momo, Fernando Roberto Sánchez Caro, A. Gómez, J. http://sedici.unlp.edu.ar:80/handle/10915/69446 2019-04-05T12:14:16Z 2006-03-01T00:00:00Z

Articulo III Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP) (Tandil, 11 y 12 de noviembre de 2004); Biología Acuática; no. 22 The macrophytes contribute significantly to the autochthonous primary production of the streams of the Buenos Aires province. Their biomass is partly exported, mainly during floods, and partly incorporated to the detritus pathway of the water bodies. The aim of this study is to determine the losses in weight and nitrogen along the process of decomposition of Lemna gibba and Ceratophyllum demersum, two of the dominant species in the Las Flores stream. A total of 40 bags with 4 g (fresh weight) of L. gibba and 10 g of C. demersum were set in two sites of the stream. Periodically, 4 samples of each species were redrawn, and the dry weight and total nitrogen concentration were determined. L. gibba lost 50% of its weight in 4 days, from then on and until the end of the incubation period (50 days) the weight kept approximately constant, fitted to a Hill’s function with a maximum rate of 0.158 day-1. The weight of C. demersum was almost stable until day 44, and at the end of the following 42 days it was observed that it had lost 62% of its initial weight, with a constant rate of k = 0.0203 day-1. In L. gibba essay, nitrogen concentration lowered from 3.4% to 2.4% in the first 48 hours, thus representing a 52% loss of the total nitrogen content of the plant. For C. demersum, nitrogen concentration decayed from 4.1% until 3.2%; by the end of the sampling, the total nitrogen content had reduced to 33.5% of the initial value. The results indicate that, given the quickness of the decomposition and nutrient release, an important part of the production can be incorporated to the material cycles of the stream before the plants are washed downstream during floods.

2006-03-01T00:00:00Z The macrophytes contribute significantly to the autochthonous primary production of the streams of the Buenos Aires province. Their biomass is partly exported, mainly during floods, and partly incorporated to the detritus pathway of the water bodies. The aim of this study is to determine the losses in weight and nitrogen along the process of decomposition of Lemna gibba and Ceratophyllum demersum, two of the dominant species in the Las Flores stream. A total of 40 bags with 4 g (fresh weight) of L. gibba and 10 g of C. demersum were set in two sites of the stream. Periodically, 4 samples of each species were redrawn, and the dry weight and total nitrogen concentration were determined. L. gibba lost 50% of its weight in 4 days, from then on and until the end of the incubation period (50 days) the weight kept approximately constant, fitted to a Hill’s function with a maximum rate of 0.158 day-1. The weight of C. demersum was almost stable until day 44, and at the end of the following 42 days it was observed that it had lost 62% of its initial weight, with a constant rate of k = 0.0203 day-1. In L. gibba essay, nitrogen concentration lowered from 3.4% to 2.4% in the first 48 hours, thus representing a 52% loss of the total nitrogen content of the plant. For C. demersum, nitrogen concentration decayed from 4.1% until 3.2%; by the end of the sampling, the total nitrogen content had reduced to 33.5% of the initial value. The results indicate that, given the quickness of the decomposition and nutrient release, an important part of the production can be incorporated to the material cycles of the stream before the plants are washed downstream during floods. Freyre, Lauce Rubén Maroñas, Miriam E. Sendra, Eduardo Daniel Dománico, Alejandro http://sedici.unlp.edu.ar:80/handle/10915/69433 2019-04-05T12:14:19Z 2006-03-01T00:00:00Z

Articulo III Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP) (Tandil, 11 y 12 de noviembre de 2004); Biología Acuática; no. 22 The small silver characin, Bryconamericus iheringii, is an important species in the fish community structure because among the accompanying species of the silver side, Odontesthes bonariensis, it is most density important and has a planctophagous regime which partially overlaps with that of this atherinid as well. The objective of this paper is to describe the individual growth, analyzing size structure and using modal progression analysis as first stage for its demographic appraisal. The catches were carried out with a beach seine net (opening of the mesh in the bag 10 mm) between October of 1997 and October of 1998. The application of modal progression method is hindered by the wide seasonally oscillating growth and by capturability. The obtained parameters for the Lacombe population, assuming the interpretation of two annual cohorts (Sendra & Freyre for Chascomús shallow lake) but fitting the generalized Pauly’s seasonal model of von Bertalanffy, compared with those obtained by the scale they would be close by. However the interpretation of a single annual cohort is more compatible with the lepidologic interpretation.

2006-03-01T00:00:00Z The small silver characin, Bryconamericus iheringii, is an important species in the fish community structure because among the accompanying species of the silver side, Odontesthes bonariensis, it is most density important and has a planctophagous regime which partially overlaps with that of this atherinid as well. The objective of this paper is to describe the individual growth, analyzing size structure and using modal progression analysis as first stage for its demographic appraisal. The catches were carried out with a beach seine net (opening of the mesh in the bag 10 mm) between October of 1997 and October of 1998. The application of modal progression method is hindered by the wide seasonally oscillating growth and by capturability. The obtained parameters for the Lacombe population, assuming the interpretation of two annual cohorts (Sendra & Freyre for Chascomús shallow lake) but fitting the generalized Pauly’s seasonal model of von Bertalanffy, compared with those obtained by the scale they would be close by. However the interpretation of a single annual cohort is more compatible with the lepidologic interpretation. Freyre, Lauce Rubén Maroñas, Miriam E. Sendra, Eduardo Daniel Cornejo, A. http://sedici.unlp.edu.ar:80/handle/10915/69432 2019-04-05T12:14:25Z 2006-03-01T00:00:00Z

Articulo III Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP) (Tandil, 11 y 12 de noviembre de 2004); Biología Acuática; no. 22 Between the 18 and 20 of April of 1998 a silvers side fish kill was observed in Monte urban shallow lake. Rains preceded the phenomenon without being observed lake water level variations, but iridescence in the surface was noticed. Sampled dead fish were obtained for measurement and autopsies were carried out as well. The size range was between 90 and 180 mm of standard length. The fish measurements were made in 21 specimens with best conservation condition and results concerning cephalic index and condition factor were compared with those obtained in previous years. Since most presented high degree of decomposition it was only possible to dissect the gills. Microscopic images of these didn’t record the presence infectious agents so it was discarded as a possible cause. The somatic relationships and indexes show that these fish have suffered growth difficulties which, coupled with the analysis of the gills, supports the hypothesis of an environmental alteration as responsible for the fish kill. Variation leading to an increment in the concentration of organic matter (MO) in the lake produced by the rain induced transport of MO accumulated in the basin of the tributary (channeled), possibly further potentates by the incorporation of hydrocarbons, given the observed iridescence. But this cannot be confirmed by lack of water sample. The made interpretations don’t allow to deduce the cause of the fish kill but enable to point out that the environmental phenomenon that provoked it possibly had not lead to the recorded consequences if the population had been less susceptible, more like under the conditions of previous years.

2006-03-01T00:00:00Z Between the 18 and 20 of April of 1998 a silvers side fish kill was observed in Monte urban shallow lake. Rains preceded the phenomenon without being observed lake water level variations, but iridescence in the surface was noticed. Sampled dead fish were obtained for measurement and autopsies were carried out as well. The size range was between 90 and 180 mm of standard length. The fish measurements were made in 21 specimens with best conservation condition and results concerning cephalic index and condition factor were compared with those obtained in previous years. Since most presented high degree of decomposition it was only possible to dissect the gills. Microscopic images of these didn’t record the presence infectious agents so it was discarded as a possible cause. The somatic relationships and indexes show that these fish have suffered growth difficulties which, coupled with the analysis of the gills, supports the hypothesis of an environmental alteration as responsible for the fish kill. Variation leading to an increment in the concentration of organic matter (MO) in the lake produced by the rain induced transport of MO accumulated in the basin of the tributary (channeled), possibly further potentates by the incorporation of hydrocarbons, given the observed iridescence. But this cannot be confirmed by lack of water sample. The made interpretations don’t allow to deduce the cause of the fish kill but enable to point out that the environmental phenomenon that provoked it possibly had not lead to the recorded consequences if the population had been less susceptible, more like under the conditions of previous years. Ferrati, R. Vargas Russo, M. Saavedra, P. Canziani, G. http://sedici.unlp.edu.ar:80/handle/10915/69431 2019-04-05T12:14:31Z 2006-03-01T00:00:00Z

Articulo III Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP) (Tandil, 11 y 12 de noviembre de 2004); Biología Acuática; no. 22 The pampean shallow lakes present different distributions in their trophic chains, the latter being cause and consequence of the state of the lacunar systems. In order to determine how each of the measured variables —climatic, edaphic, morphometric, physicochemical and biological— in contributes to the general state of the lake, an Artificial Neural Network (ANN) model is built. The ANN is capable of processing a large number of variables and returning a classification that will allow determining it’s the trophic state. The information from satellite images is one of the input variables. Hence, on a first stage, the construction of a ANN model is intended to obtain a weight for each one of the visible specter bands and near infrared bands from LANDSAT and to pick the most representative value that the image returns. This value will be used as input to the ANN that will be then trained to return a classification of the shallow lakes according to the three observed patterns in the relation between phytoplankton, zooplankton, fish and their link with to nutrient abundance and watershed management.

2006-03-01T00:00:00Z The pampean shallow lakes present different distributions in their trophic chains, the latter being cause and consequence of the state of the lacunar systems. In order to determine how each of the measured variables —climatic, edaphic, morphometric, physicochemical and biological— in contributes to the general state of the lake, an Artificial Neural Network (ANN) model is built. The ANN is capable of processing a large number of variables and returning a classification that will allow determining it’s the trophic state. The information from satellite images is one of the input variables. Hence, on a first stage, the construction of a ANN model is intended to obtain a weight for each one of the visible specter bands and near infrared bands from LANDSAT and to pick the most representative value that the image returns. This value will be used as input to the ANN that will be then trained to return a classification of the shallow lakes according to the three observed patterns in the relation between phytoplankton, zooplankton, fish and their link with to nutrient abundance and watershed management.