Jose Santos | Universidad Dominicana O & M (original) (raw)

Papers by Jose Santos

Ecological Indicators, 2011

Species tolerances are frequently used in multi-metric ecological quality indices, and typically ... more Species tolerances are frequently used in multi-metric ecological quality indices, and typically have the strongest responses to disturbances. Usually the tolerances of many species are based on expert judgment, with little support from empirical ecological or physiological data. This is particularly true for fish of Mediterranean-type rivers, in which there are many basin-endemic taxa with little information on basic life history traits. In addition, the apparent tolerance of native Mediterranean freshwater fish species to naturally harsh environments and their short-term resilience may mask responses to man-made pressures. Consequently, we evaluated different statistical techniques and procedures for quantifying Mediterranean lotic fish tolerances and compared expert judgment of species tolerances with empirically determined tolerance values. We used eight alternative approaches to compute fish tolerance values for the Mediterranean basins of SW Europe. Three types of approaches were used: (1) those based on the concept of niche breadth along an environment/pressure gradient (five models); (2) those based on deviations from expected values at disturbed sites as predicted by statistical models describing relationships between species and environmental variables (generalized linear modelling (GLM) and generalized additive modelling (GAM), two models); and (3) one model based on the relatively independent contributions of pressure variables to the data variation explained by statistical models. Tolerance estimates based on the used/available pressure gradient and the average general pressure value had the highest mean correlations with the expert judgment classification (mean r = 0.4) and with the other approaches (mean r of 0.48 and 0.46, respectively). The high degree of uncertainty in tolerance estimates should be accounted for when applying them in ecological assessments. Results also highlights the need for better designed research to separate effects of natural and disturbance gradients on species occurrences and densities.

Ecological Engineering, 2012

The construction of pool-type fishways has greatly increased in recent years in response to wides... more The construction of pool-type fishways has greatly increased in recent years in response to widespread river fragmentation by man-made structures. However, the performance of such facilities has often been questioned, particularly for non-salmonid fish fauna, which are frequently the predominant group of species found in rivers. This study presents the main findings from field and experimental research conducted over the last 10 years on pool-type fishways in Portugal. Specific goals were: (i) to catalogue and evaluate the effectiveness of pool-type fishways built at small hydropower plants (SHP); (ii) to assess passage patterns of migrant fish populations through a "highly suitable" facility; (iii) to assess fish use for submerged orifices and surface notches under different flow regimes in experimental conditions and (iv) to determine the effect of hydraulic parameters on upstream movements of fish within these fishways. More than half (n = 19, 51%) of the visited fishways were considered to be unsuitable for the target potamodromous species. Seasonal movements peaked in the spring (>70%) and occurred independently of time of day. Laboratory experiments showed a significantly greater proportion of movements occurring through submerged orifices rather than surface notches. Of all the analyzed hydraulic parameters, the Reynolds shear stress was the one that most influenced fish movements within the fishways investigated. The results of this study provide new information and insights that could have important implications on the design of future fishways, particularly for larger potamodromous cyprinids.

Journal of Applied Ichthyology, 2002

From March 1998 to February 1999, upstream fish passage was continuously monitored by video tape ... more From March 1998 to February 1999, upstream fish passage was continuously monitored by video tape analysis at the fish lift Touvedo Dam on the Lima River, northern Portugal. A total of 1194 individuals from seven species were transferred by the lift. Cyprinids were the dominant group collected, with Iberian nase Chondrostoma polylepis (Steindachner) (31.8%) being the most abundant species, followed by Iberian barbel Barbus bocagei (Steindachner) (21.1%), Iberian dace Leuciscus carolitertii (Doadrio) (19.2%) and Iberian red roach Rutilus arcasii (Steindachner) (7.1%). Brown trout Salmo trutta fario (L.) and European eel Anguilla anguilla (L.) accounted for 10.8%, whereas Atlantic salmon Salmo salar (L.) was rarely observed. Most cyprinid seasonal movements were observed in the spring and were associated with reproduction. The timing of the run varied and its beginning appeared to be mainly dependent on water temperature. Roach, dace and nase used the fish lift intensively from mid-April until the end of summer. Barbel use of the lift intensified in mid-May in association with warmer water. Salmonids migrated in June–July and autumn. Significant differences were not found in hourly activity, except for nase and barbel, in June and July, respectively. Fish passage was not related to river discharge. The relative effectiveness of the fish lift is discussed in relation to the various species.

Journal of Applied Ichthyology, 2005

Throughout Europe in the last decade there has been a steady shift away from more technical fish ... more Throughout Europe in the last decade there has been a steady shift away from more technical fish pass designs to more nature-like passes, such as nature-like bypass channels. Upstream fish passage in a nature-like bypass channel was investigated in a lowland river, the Lima River, for 117 days from March 2000 to May 2002. Fish passage was recorded using an automatic video recording system. Electrofishing samples within the bypass and below the weir were compared with species abundance found on the tape recordings. More than 7500 individuals of eight species passed through the bypass channel. Species composition was dominated by striped mullet (65.3%) and potamodromous species (34.3%), which used the bypass mainly at night. Of the environmental variables considered, bypass discharge explained most of the variation in the number of cyprinids, whereas water temperature was more important for diadromous species. Comparing species composition below the weir using passage recordings provided a useful tool to assess species efficacy of the bypass, although biological requirements should also be taken into account. This study proved the efficacy of the bypass for passage of almost all occurring species and life stages and also for providing suitable habitat for fish fauna, highlighting the use of these facilities for river restoration schemes.

Ecology of Freshwater Fish, 2000

Abstract – Factors associated with the spatial and temporal variation of the lower Guadiana basin... more Abstract – Factors associated with the spatial and temporal variation of the lower Guadiana basin (southern Iberia) fish community were determined using data from 20 sites sampled during the summer of 1994 (dry year following a period of low discharge, total discharge from 1992 to 1994=1.45×109 m3) and again during the summer of 1996 (wet year following a period of higher discharge, total discharge from January 1995 to August 1996=6.18×109 m3). From the 17 explanatory variables initially considered six were retained for analysis by a forward selection procedure: maximum depth, altitude, channel width, substrate coarseness, SALT (a dummy variable identifying sampling locations belonging to tributaries that discharge to the brackish Guadiana) and YEAR (a dummy variable identifying the sampling year). Further, we partitioned the total variability in the Guadiana fish community into that accounted uniquely by selected environmental variables (34.9%), uniquely by sampling year (4.1%), by both sampling year and environmental variables (0.3%), and unexplained (60.7%).NOTE

Aquatic Sciences, 2011

Knowledge of the distribution of species life stages at multiple spatial scales is fundamental to... more Knowledge of the distribution of species life stages at multiple spatial scales is fundamental to both a proper assessment of species management and conservation programmes and the ability to predict the consequences of human disturbances for river systems. The habitat requirements of three native cyprinid species—the Iberian barbel Barbus bocagei Steindachner, the Iberian straight-mouth nase Pseudochondrostoma polylepis (Steindachner), and the Northern straight-mouth nase Pseudochondrostoma duriense (Coelho)—were examined at 174 undisturbed or minimally disturbed sites in 8 river catchments across western Iberia, by modelling occurrence and counts of species life stages at two spatial scales—large (regional) and instream (local)—using hurdle models. All the life stages of the barbel showed a negative association with upstream high-gradient river reaches, whereas juvenile P. duriense favoured such areas. Stream width and openness were negatively related with the occurrence of juvenile and small adult barbel, but not with large adults. Juvenile nase, on the other hand, were found to be mainly confined to fast-flowing habitats with high instream cover and coarser substrata. Advanced life stages of the barbel were mainly associated with the “pure” regional and shared components, whereas the purely local attributes accounted for much of the model variation among nases, in particular juveniles, and juvenile barbel. The results of this study are useful for setting or refining management goals, and highlight the need to separately consider life stages when performing conservation-related studies of species distribution.

Cheminform, 2009

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Revista Brasileira De Coloproctologia, 2009

Colitis cystica profunda comprises submucous mucus-filled cysts, located mainly in rectum and lef... more Colitis cystica profunda comprises submucous mucus-filled cysts, located mainly in rectum and left colon. Its etiology is controversial, with about 200 cases reported in the literature. This disease is important clinically in that mimics colorectal malignancies. We report a case of colitis cystica profunda localized in rectum treated surgically, its follow-up and review of the literature.

Magnetic Resonance Imaging, 2008

To demonstrate drop in brain ADC measurements from low to high b values; to evaluate the structur... more To demonstrate drop in brain ADC measurements from low to high b values; to evaluate the structural information provided based on those changes; and to discuss the anatomical reasons for ADC differences.Four cerebral ROI (precuneus-PRC, hippocampus-HIP, and the genu-GCC and splenium-SCC of the corpus callosum-CC) were drawn for ADC measurements with low (1000) and high (3000) b-value DWI in 50 normal subjects. ANOVA and Bonferroni correction tested ADC differences between areas, between both hemispheres, between GCC and SCC, and between b-value related ADC drop within areas. Pearson test evaluated dependence of interhemispheric and intercallosum ADC measurements obtained with the same b-value, dependence between areas of intrazonal drop, and the interhemispheric and intercallosum dependence of intrazonal drop.ADCs differed between areas (P<.0001). Interhemispheric ADC only differed in PRC with low b-value (P<.027). No HIP asymmetries occurred regardless the b-value. ADC drop within PRC and HIP was similar but differed (P<.0001) from ADC drop within both CC ROI. ADC drop was also different between GCC and SCC (P<.0001). In PRC and HIP, ADC showed a significant interhemispheric and intrazonal dependence (P<.0001). There was no GCC to SCC ADC dependence. Intrazonal dependence in the CC was only significant in the SCC (P<.001). Interhemispheric dependence of intrazonal drop was significant (PRC P=.007; HIP P<.0001) but failed to reach significance in the CC.Low and high b-value measurements show different diffusion behaviours within different tissues, especially in a highly anisotropic structure as the corpus callosum. This fact can provide valuable information about brain structure and different diffusion compartments in clinical DWI.

World Journal of Gastroenterology, 2008

FA responses differed significantly from those for the other two groups (P < 0.01).

Ecology of Freshwater Fish, 2007

Abstract – Knowledge of fishes’ habitat requirements is an essential tool for species conservati... more Abstract – Knowledge of fishes’ habitat requirements is an essential tool for species conservation. We examined the habitat requirements of nine native freshwater fish species using 165 undisturbed or minimally disturbed sites from eight river basins in western Iberia (northern and central Portugal). Six environmental descriptors were considered at the regional level, and six descriptors at a local scale. Statistical associations between local assemblage structure and environmental variables were quantified by canonical correspondence analyses. Logistic regression was performed for each species to identify regional and local factors related to its distribution at the sample sites. The results suggested a reasonable degree of specialisation in the use of local variables and dependence on regional variables. Logistic regression models showed a good adjustment (0.75 < AUC < 0.93). Results of habitat modelling using minimally disturbed sites helped to clarify species preferences for specific abiotic drivers.