Two types of modification of the hydrological system are present in the same regulated segment of the Lima River (NW Portugal): (a) a reduced and constant flow from hypolimnetic release; (b) an intense irregular flow (daily and seasonal). Using multivariate techniques it was possible to compare the effects of these two kinds of disturbance on the macroinvertebrate communities. The communities colonizing both sites exhibited a higher variation in composition and diversity when compared to undisturbed sites. However, such variability was even more evident in the first case, in spite of the stability of the environmental conditions. Such temporal replacement of species is linked to the dominance of tolerant taxa with short life cycles. In the regulated segment the poor water quality and the lack of litter input impacted mainly on the shredders group. This work shows the failure of the practice of releasing constant flows as an attempt to mitigate regulation impacts.
Species that are able to solve novel problems through social learning from either a conspecific or a heterospecific may gain a significant advantage in new environments. We tested the ability of a highly successful invasive species, the Italian wall lizard Podarcis sicula , to solve a novel foraging task when social information was available from both a conspecific and an unfamiliar heterospecific ( Podarcis bocagei ). We found that Italian wall lizards that had access to social information made fewer errors, regardless of whether the demonstrator was a conspecific or a heterospecific, compared to Italian wall lizards that individually learnt the same task. We suggest that social learning could be a previously underappreciated, advantageous mechanism facilitating invasions.
10The aim of this paper is to present a global study on the hydrodynamics, water quality and their influence on aquatic fauna. The case study was conducted on a segment of the Lima river (North Portugal), downstream of the Touvedo dam, which was mainly constructed for hydroelectric power production. The ISIS FLOW program was used to simulate the hydrodynamics. This model also generates the necessary input data for the water quality simulation using the ISIS QUALITY module. Two basic principles govern the ISIS programs: conservation of mass and momentum. Water quality parameters (dissolved oxygen and temperature) were simulated for different operational conditions of the Touvedo dam: different discharges (water quantity and duration) and two levels of the water withdrawal, where different water characteristics have been measured. We observed a modification in the hydrodynamics and in the water quality as a function of the outflow volume and discharge level by simulating the variation of dissolved oxygen and temperature downstream of the dam. 25The response of the fish community to this modification appeared to result in a negative impact on the migratory fish and in the salmonids being replaced by the more tolerant cyprinids. 27This work shows that the relation between physical habitat and the targeted aquatic species is a necessary but not sufficient condition for a viable population of aquatic species.
ISI Document Delivery No.: AB5KQ Times Cited: 0 Cited Reference Count: 32 Cited References: Alsdorf DE, 2007, REV GEOPHYS, V45, DOI 10.1029/2006RG000197 ANA (Agencia Nacional de Aguas), 2011, HYDR DAT BAS BAMBER JL, 1994, INT J REMOTE SENS, V15, P925 Bates B., 2008, CLIMATE CHANGE WATER Beneveniste J, 2004, ESA B, V117 Birkett CM, 1998, WATER RESOUR RES, V34, P1223, DOI 10.1029/98WR00124 Bittencourt Maria Mercedes, 2007, Acta Amazonica, V37, P303, DOI 10.1590/S0044-59672007000200019 Callede J, 2010, REV SCI EAU, V23, P247 Calmant S, 2008, SURVEY GEOPHYS, V29, P1573, DOI [10.1007/10712-008-9051-1, DOI 10.1007/10712-008-9051-1] Calmant S, 2006, CR GEOSCI, V338, P1113, DOI 10.1016/j.crte.2006.05.012 Cretaux JF, 2006, CR GEOSCI, V338, P1098, DOI 10.1016/j.crte.2006.08.002 Frappart F, 2006, REMOTE SENS ENVIRON, V100, P252, DOI 10.1016/j.rse.2005.10.027 Guyot JL, 1999, INT S HYDR GEOCH PRO Kabat P, 2004, VEGETATION WATER HUM Legresy B, 1997, J GLACIOL, V43, P265 Legresy B, 1995, CTEDTUUD96188 CNES Mercier F, 2011, HANDBOOK Mikhailov VN, 2010, WATER RESOUR+, V37, P145, DOI 10.1134/S009780781002003X MOLINIER M, 1995, COLLOQ SEMI, P335 Pavlis NK, 2008, P 2008 GEN ASS EUR G Peel MC, 2011, PROG PHYS GEOG, V35, P249, DOI 10.1177/0309133311402550 Ronchail J, 2006, IAHS PUBL, V308, P1 Roux E, 2010, HYDROLOG SCI J, V55, P104, DOI 10.1080/02626660903529023 Seyler F, 2009, HYDROL PROCESS, V23, P3173, DOI 10.1002/hyp.7397 Silva JS, 2012, INT J REMOTE SENS, V33, P3323, DOI 10.1080/01431161.2010.531914 Silva JS, 2010, ALTIMETRIA ESPACIAL Silva JS, 2010, REMOTE SENS ENVIRON, V114, P2160, DOI [10.1016/j.rse.2010.04.020, DOI 10.1016/J.RSE.2010.04.020] van Dijk AIJM, 2011, HYDROL EARTH SYST SC, V15, P39, DOI 10.5194/hess-15-39-2011 Wingham DJ, 1986, ESA, P1339 World Water Assessment Programme, 2006, 2 UNESCO WORLD WAT A World Water Assessment Programme, 2009, 3 UNESCO WORLD WAT A World Water Assessment Programme, 2009, WORLD WAT ASS PROGR da Silva, Joecila Santos Calmant, Stephane Seyler, Frederique Moreira, Daniel Medeiros Oliveira, Daniel Monteiro, Achiles CNPq; FAPEAM; CAPES; CPRM; IRD Authors are indebted to the reviewers who greatly helped in rewriting the preliminary version of the manuscript. Their work is part of the CASAM, DS BIODIVA, CLIVAR and HIDRAS projects, respectively funded by CNPq, FAPEAM and CAPES. CPRM and IRD participated to funding the study in the frame of the Project Hidrodinamica Fluvial, and CNES participated with the project TOSCA/FOAM. The authors would like to acknowledge the ANA (Agencia Nacional de Aguas, Brazil) for the gauge data, the CTOH (Centre de Topographie des Oceans et de l'Hydrosphere, LEGOS, France) for the access to T/P, ERS-2, ENVISAT and JASON-2 GDRs and additional tropospheric corrections via their on line database system and ESA (European Space Agency) for granting the use of the data. Acquisition of the JERS-1 SAR imagery was made possible by NASDA's Global Rain Forest Mapping Project. We thank Aline Correa de Souza and Taina Sampaio Xavier Conchy for the aid in the operation of the virtua...
Habitat use by stocked and native brown trout (Salmo trutta L.) was assessed in two headwater streams of North-eastern Portugal. Underwater observations were made during the summer season in three successive years to evaluate the effect of supplemental trout stocking. Multivariate analysis techniques applied to data sets on microhabitat use were exploited to identify the focal elevation (distance of fish from the bottom), total depth and cover as the variables that contribute most to the discrimination between stocked and native trout. Preference curves computed for native and stocked trout of the same age (1 + ), showed a distinct pattern in their ability to explore the available microhabitat resources. Stocked trout tended to occupy deeper pools (total depth > 100 cm vs. 60-100 cm for native trout), holding higher focal elevations (140-160 cm vs. < 20 cm for native) with lower water column velocities (< 10 cm.s -1 vs. 10-20 cm.s -1 for native) and no specific preference for cover. In contrast, native trout displayed a clear preference for microhabitats with coarse substrate (particle size > 22.5 cm) and cover (combination of boulders and overhanging vegetation or undercut banks). Furthermore, a high poststocking movement of 80% hatchery-reared fish was verified just one month after their release, suggesting that stocking did not contribute to the sustainable populations in either stream, and is far from being an adequate management technique. Key-words:Salmo trutta, snorkelling, restocking, microhabitat, preference curves. UTILISATION DE L'HABITAT PAR LA TRUITE COMMUNE (SALMO TRUTTA L.) SAUVAGE ET CELLE D'ÉLEVAGE, DANS DEUX RIVIÈRES DU NORD-EST DU PORTUGAL RÉSUMÉL'utilisation de l'habitat par la truite de repeuplement et par la truite commune (Salmo trutta) a été évaluée dans deux rivières du Nord-Est du Portugal. Des observations en plongée ont été faites en période estivale pendant trois années successives pour évaluer l'efficacité des repeuplements. Des techniques d'analyses multivariées appliquées à l'ensemble des données du microhabitat ont permis d'identifier la position Article available at
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