Plenary Speaker: Conciliating fish ecology and river fragmentation in South American large rivers: Are fish passages appropriate tools?

Abstract: South America, the most fluvial continent, is increasingly been impacted by river damming having dams construction expanded in last 50 years and fragmenting more than 3,000 km. At present, the upper Parana basin exhibits 130 dams higher than 10 m, but most of future planned dams will be located along the Amazon watershed. Although increasing attention and research efforts have been devoted to assess functioning of fish passage in South America, objectives and support for installation can differ among basins according to river ecological characteristics, conservation goals, fisheries demands, etc. A noticeable asymmetry still exists between salmonids and non-salmonids fish passages in terms of information, research funds availability, human resources, availability of technological tools, etc. Whereas South American passes have shown a wide efficacy range, efficiency appears to be rather low for most of large migratory species challenging managers and scientists for considering how fragmentation effects on migratory fish population can be mitigated. Clearly non-salmonid fishways need to be designed to accommodate different life history traits exhibited by neotropical fishes inhabit rivers with different hydrological and geomorphological characteristics. Questions about how principles and rules derived from salmonid passages apply and what efficiency should mean and is required in South American large rivers remain still under debate as fish adaptation to cope with river fragmentation impacts may differ among basins based on hydrological and geomorphological features and dams/reservoirs characteristics. Managers and scientists face with the need to assess the feasibility of installing fish passages within a broader context that incorporate fish conservation issues according to current and predicted ecological characteristics and socio-economic scenarios at basin scale

Biology of growth of Hoplias aff. malabaricus (Bloch, 1794) in a shallow pampean lake Argentina

The trahira Hoplias aff. malabaricus is a top predator in pampean shallow lakes and is highly appreciated by recreational anglers and artisanal fishermen. Trahira growth from Yalca shallow lake was determined by lepidological analysis and age validated by marginal increment. When growth was fitted to the von Bertalanffy model, annual classes exhibited a bimodal pattern as a result of the presence of spring and summer annual cohorts associated with a three month spawning season, each period in turn showing different growth patterns. The trahira population-age structure at Yalca shallow lake showed a truncated profile with very low numbers of large adults and few individuals older than three to four years, thus producing an unbalanced length-structure population. Growth parameters and growth performance were similar to the corresponding parameters estimated for other shallow pampean lakes of the region, but strongly diverged from the data for those populations inhabiting subtropical and tropical environments. Such differences could be accounted for by dissimilarity in metabolic rates associated with thermal differences accompanying seasonal variability among latitudes as well as by the development of adaptive physiologic and demographic responses to cope with the high thermal amplitude and hydrologic instability observed in pampean lakes.A traíra Hoplias aff. malabaricus é um predador de topo encontrado em lagoas rasas nos Pampas, muito apreciada nas pescas comerciais e esportivas. O crescimento da traíra no lago Yalca foi determinado através de análises lepidológicas, validadas a partir do incremento marginal. O crescimento foi ajustado ao modelo de von Bertalanffy, sendo que as classes de tamanho anuais apresentaram padrão bimodal devido à presença de coortes de primavera e verão, associadas à uma longa estação reprodutiva com diferentes padrões de crescimento. A estrutura etária da traíra do lago Yalca apresentou um perfil truncado, com um número pequeno de adultos de maior porte e poucos indivíduos com mais de três ou quatro anos, produzindo uma estrutura em tamanho desbalanceada. Os parâmetros e a performance de crescimento foram similares aos estimados para outros lagos rasos da região, mas fortemente divergentes de populações encontradas em ambientes tropicais e subtropicais. Tais diferenças podem estar relacionadas à diferentes taxas metabólicas associadas à variação térmica sazonal entre latitudes e ao desenvolvimento de respostas adaptativas fisiológicas e demográficas em resposta aos padrões termais altamente variáveis e instabilidade hidrológica observados nos lagos da região dos Pampas.Fil: Balboni, Leandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús). Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús); ArgentinaFil: Colautti, Dario César. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús). Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús); ArgentinaFil: Baigún, Claudio Rafael M.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús). Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús); Argentin

Conserving the Paraguay-Paraná Fluvial Corridor in the XXI Century: Conflicts, Threats, and Challenges

The Paraguay-Paraná river system represents a unique, free-flowing corridor that extends about 3500 km southwards from the Pantanal to the Rio de la Plata estuary, crossing four countries. The absence of fragmentation along the main channels and its still well-connected floodplains have preserved longitudinal and lateral functional and structural connectivity, defining critical ecological gradients for the biota and species life cycles. The lack of dams represents a noticeable feature that benefits migratory species supporting small-scale fisheries providing food security and the conservation of other ecosystem services with associated livelihoods. The ecological integrity of this corridor could be severely affected by the potential expansion of the Hidrovía Paraguay-Paraná for improving commercial trade, the foreseen installation of new dams in the Paraná basin, in addition to other current impacts and threats. Conservation of the corridor for societal benefits, involving the sustainable development of activities associated with the use of the fluvial territory, requires maintaining the natural ecological process that sustains livelihoods and biodiversity. This calls for innovative strategies encompassing water governance process, social and environmental information related to expected impacts, a better understanding of synergies between processes, and foremost an interdisciplinary approach to design and apply integrative and multi-scale management policies.Fil: Baigún, Claudio Rafael M.. Universidad Nacional de San Martín. Instituto de Investigación e Ingeniería Ambiental. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigación e Ingeniería Ambiental; ArgentinaFil: Minotti, Priscilla Gail. Universidad Nacional de San Martín. Instituto de Investigación e Ingeniería Ambiental. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigación e Ingeniería Ambiental; Argentin

Cambios en los indices biológicos de la tararira, hoplias malabaricus (bloch, 1794) en un ciclo anual en la Laguna Yalca, provincia de Buenos Aires, Argentina

Fil: Balboni, Leandro. Instituto Tecnológico de Chascomús, IIB-INTECH. Chascomús; ArgentinaFil: Colautti, Darío César. Instituto de Limnología Dr. Raúl A. Ringuelet (ILPLA). Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Baigún, Claudio Rafael Mariano. Instituto Tecnológico de Chascomús, IIB-INTECH. Chascomús; Argentin

Edad, crecimiento, mortalidad e incidencia de las variaciones del nivel hidrométrico del río Paraná en la abundancia del surubí pintado (Pseudoplatystoma corruscans)

Los objetivos son determinar los parámetros de crecimiento, índice de mortalidad e incidencia de las variaciones del nivel hidrométrico en la abundancia de las poblaciones del surubí pintado. Se analizaron las tallas de 3.332 ejemplares capturados en 34 concursos de pesca desde 1996 a 2008. Participaron 32.766 pescadores que totalizaron 369.044 horas de pesca. Se dispuso información de pesquerías comerciales desde 1976. La edad y el crecimiento se determinaron en base a la descomposición de las polimodales de las pseudocohortes de los concursos de pesca Reconquista y Goya y se validaron con lecturas de las marcas anuales en los radios duros de las aletas pectorales. Los parámetros de la ecuación de von Bertalanffy determinados, fueron: L∞ de 185 cm, K: 0.0653; t0: - 3.4. El surubí nace en primavera-verano y marcan los anillos en invierno, el primero a los 6 meses. En el período de crecimiento a los 4+ años reabsorbe el primer anillo y luego a los 5+, 7+ y 9+ años con el segundo, tercero y cuarto anillo respectivamente. Las variaciones de la mortalidad (Z) se asocian a las capturas de sábalo. El análisis de la CPUE mostró la disminución de tallas superiores a la primera reproducción (91 cm). El porcentaje de reproductores en 1976-77 era del 63%, en el 2002-03 diminuyó al 30% y en los concursos de Goya y Reconquista desde el 2004, no supera el 11%. El mejor ajuste de los surubíes pintado de edad 4+ capturados en Goya y Reconquista (cohortes 1999 al 2004) se dio con el promedio del nivel hidrométrico de octubre a diciembre. Niveles hidrométricos más elevados producirían cohortes más abundantes.Age, growth, mortality and incidence of the variations of the Paraná River hydrometric level in abundance of "spotted sorubim" (Pseudoplatystoma corruscans). The goals are to determine the growth patterns, mortality rate and incidence of the hydrometric level variations in the abundance of Pseudoplatystoma corruscans populations. We analyzed the sizes of 3,332 fish caught in 34 fishing tournaments from 1996-2008. Age and growth were determined based on the decomposition of the pseudo-cohort polimodals of the Reconquista and Goya fishing tournaments and were validated with readings of the annual markers at the hard radius of the pectoral fin. The P. corruscans is born in spring-summer and marks the growing rings in winter, towards the first 6 months. During growing period to the 4+ years it reabsorbs the first mark and then towards the 5+, 7+ and 9+ years it reabsorbs with the second, third and fourth marks respectively. Mortality variations (Z) are related with Prochilodus lineatus captures. The percentage of breeders in 1976-77 was 63%, in the period 2002-03 it decreased to 30% and in the Goya and Reconquista tournaments since 2004, does not exceed 11%. The best adjustment of the 'spotted sorubim’ of 4+ years caught is Goya and Reconquista (1999-2004 cohorts) was achieved with the average hydrometric level on spring. Higher hydrometric levels would allow more abundant cohortsFil: Oldani, Norberto Oscar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico Para la Industria Química (i); ArgentinaFil: Ecclesia, Ovidio. Subdirección de Fauna y Flora de Corrientes; ArgentinaFil: Baigún, Claudio Rafael M.. Universidad Nacional de General San Martín; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Instituto de Investigaciones Biotecnológicas - Instituto Tecnológico Chascomús. Instituto de Investigaciones Biotecnológicas (sede Chascomús); Argentin

Ictiólogos de la Argentina : Norberto Oscar Oldani

Fil: López, Hugo Luis. División Zoología Vertebrados. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Baigún, Claudio Rafael Mariano. Instituto Tecnológico de Chascomús (IIB-INTECH). Universidad Nacional de General San Martín; Chascomús; ArgentinaFil: Ponte Gómez, Justina. División Zoología Vertebrados. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; Argentin

Nutrient concentrations and trophic state of small patagonian andean lakes

We analyzed nutrient, chlorophyll, and ionic concentrations in 17 lakes along a strip of land located in the rainy Andes Mountains and the ecotone with the dry Patagonian steppe, from 36 to 44° S latitude. Most of the sampled lakes had the ionic composition of Andean lakes and showed ultraoligotrophic conditions, while a few with the ionic composition of Patagonian Plateau lakes showed higher nutrient concentrations. Chlorophyll was correlated to P and N concentrations, but chlorophyll/TP ratio was lower than reported in previous worldwide surveys. A lithology dominated by igneous rock together with the remoteness and pristine character of the basins contribute to the oligotrophic status of the lakes. Two other factors appear to be important in maintaining the oligotrophic condition. Andisols, allophanic soils developed over volcanic ash deposits in the rainy areas, have large P retention capability and therefore decrease the load of P to the lakes. Natural dense Nothofagus spp. forests, with a geographical distribution coincident with that of the andisols, are efficient mechanisms for nitrogen retention through nitrogen resorption from senescent leaves.Instituto de Limnología "Dr. Raul A. Ringuelet

Nutrient concentrations and trophic state of small patagonian andean lakes

We analyzed nutrient, chlorophyll, and ionic concentrations in 17 lakes along a strip of land located in the rainy Andes Mountains and the ecotone with the dry Patagonian steppe, from 36 to 44° S latitude. Most of the sampled lakes had the ionic composition of Andean lakes and showed ultraoligotrophic conditions, while a few with the ionic composition of Patagonian Plateau lakes showed higher nutrient concentrations. Chlorophyll was correlated to P and N concentrations, but chlorophyll/TP ratio was lower than reported in previous worldwide surveys. A lithology dominated by igneous rock together with the remoteness and pristine character of the basins contribute to the oligotrophic status of the lakes. Two other factors appear to be important in maintaining the oligotrophic condition. Andisols, allophanic soils developed over volcanic ash deposits in the rainy areas, have large P retention capability and therefore decrease the load of P to the lakes. Natural dense Nothofagus spp. forests, with a geographical distribution coincident with that of the andisols, are efficient mechanisms for nitrogen retention through nitrogen resorption from senescent leaves.Instituto de Limnología "Dr. Raul A. Ringuelet

Manejo de recursos pesqueros continentales: el uso de una caja de herramientas

Practical and conceptual tools are presented and discussed to optimize freshwater resources management, particularly in absence of suitable information. Such issues involve among others the ambiguous concept of sustainability, scale effect in asking right management questions, application of an holistic approach for developing those processes related to management following hierachical and articulated steps, understanding the value of information and its publications, using sinthetic indicators with diagnostic and predictive value value and developing robust sampling protocols upon stratified designs as usually is required for freshwater fisheries studies. Such tools represent a valuable alternative to ordinate the fisheries, to improve the information basis and to apply management guidelines based on using suitable assessment methods.Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) - Instituto de Limnología "Dr. Raul A. Ringuelet" (ILPLA