scholarly journals Effects of abiotic variables on the distribution of fish assemblages in streams with different anthropogenic activities in southern Brazil

2012 ◽  
Vol 10 (3) ◽  
pp. 643-652 ◽  
Author(s):  
Vanessa Salete Daga ◽  
Éder André Gubiani ◽  
Almir Manoel Cunico ◽  
Gilmar Baumgartner
Keyword(s):  
Native Species ◽  
Fish Assemblages ◽  
Anthropogenic Activities ◽  
Southern Brazil ◽  
Urbanization Gradient ◽  
Composition And Structure ◽  
Matrix Correlation ◽  
Abiotic Variables ◽  
The Relationship ◽  
Distribution Of Fish

Studies on fish assemblages in streams point out, that understanding the relationship between species and their environment is crucial for conservation. The present study aimed at evaluating the effects of changes in abiotic variables on the composition and structure of fish assemblages in Neotropical urban streams from southern Brazil with different levels of urbanization. The composition and structure of fish assemblages showed significant differences along the urbanization gradient observed in the streams. Tolerant and non-native species were found in more urbanized sites. A matrix correlation revealed a relationship between abiotic variables and the spatial pattern of structure and composition of fish assemblages. Abiotic variables, such as total phosphorus, dissolved oxygen, and conductivity, determined the distribution of fish assemblages. Streams without urban influence exhibited intrinsically low species richness, suggesting that they are highly susceptible to species loss and diversity reduction. Thus, changes in water quality or hydrological conditions induced by urbanization may intensify these impacts.

scholarly journals Influence of limnological zones on the spatial distribution of fish assemblages in three Brazilian reservoirs

2015 ◽  
Author(s):  
Bárbara Becker ◽  
Bárbara De Oliveira Sanches Galhardo ◽  
Diego Rodrigues Macedo ◽  
Robert M. Hughes ◽  
Marcos Callisto ◽  
...  
Keyword(s):  
Native Species ◽  
Satellite Images ◽  
Suspended Solids ◽  
Fish Assemblages ◽  
Migratory Species ◽  
Negative Effects ◽  
Long Distance ◽  
Assemblage Composition ◽  
Species Abundances ◽  
Distribution Of Fish

Reservoirs can have both positive and negative effects on differing fish species depending on the species concerned and reservoir morphology, flow regime, and basin location.  We assessed the influence of limnological zones on the ichthyofauna of three large Neotropical reservoirs in two different river basins. We sampled fish through use of gill nets set at 40 systematically selected sites on each reservoir. We used satellite images, algae, and suspended solids concentrations to classify those sites as lacustrine or riverine. We observed significant differences in assemblage composition between riverine and lacustrine zones of each reservoir. We either tested if the same region (lacustrine or riverine) showed the same patterns in different reservoirs. In São Simão, the riverine zone produced greater abundances of native species, long-distance migratory species, diversity, and richness, whereas the lacustrine zone supported greater total and non-native species abundances. Conversely, in Três Marias, the riverine zone supported greater total and non-native species abundances, whereas the others traits evaluated did not differ significantly between zones. Only lacustrine sites occurred in Volta Grande Reservoir. The same zones in the three reservoirs usually had significantly different patterns in the traits evaluated. The differences in spatial patterns observed between reservoirs could be explained partly by the differing morphologies (complex versus linear), the differential influence of tributaries of each reservoir and basin positions (presence or absence of upstream dams) of the reservoirs.

scholarly journals Longitudinal use of feeding resources and distribution of fish trophic guilds in a coastal Atlantic stream, southern Brazil

2013 ◽  
Vol 11 (2) ◽  
pp. 375-386 ◽  
Author(s):  
Luciano Lazzarini Wolff ◽  
Natalia Carniatto ◽  
Norma Segatti Hahn
Keyword(s):  
Fish Assemblages ◽  
Food Resources ◽  
Trophic Guilds ◽  
Southern Brazil ◽  
Trophic Specialization ◽  
River Continuum ◽  
Longitudinal Gradient ◽  
Terrestrial Insects ◽  
Density And Biomass ◽  
Distribution Of Fish

This study described the use of food resources and the distribution of fish trophic guilds along the longitudinal gradient of a coastal Atlantic stream, southern Brazil. Allochthonous resources (terrestrial insects) predominated in the headwaters, whereas autochthonous food items (algae, fish) and detritus predominated in the mouth section. Detritivorous, aquaticinvertivorous, and terrestrial- and aquatic-insectivorous species occurred throughout the gradient, while omnivorous and piscivorous in the headwaters and middle stretches, respectively, and herbivorous in the middle and mouth. Detritivores and aquatic-insectivores were significantly more specialized than the other guilds, however, there was no evidence of a longitudinal increase in trophic specialization. Density and biomass of aquatic-invertivores and aquatic-insectivores decreased, whereas that of detritivores increased longitudinally. The distribution of trophic guilds was significantly associated with the stream section, where aquatic and terrestrial insectivorous were more frequent in rocky and flowed stretches from the headwater and detritivores in deeper environments with finer particles of substrate from the mouth. This suggests that fish assemblages in coastal streams with a steep longitudinal gradient may follow patterns in the use of food resources according with the food availability along the river, as predicted by the River Continuum Concept.

Board of Director Characteristics, Institutional Ownership, and Fraud: Evidence from Australia

2004 ◽  
Vol 23 (2) ◽  
pp. 105-117 ◽  
Author(s):  
Vineeta D. Sharma
Keyword(s):  
Research Evidence ◽  
Institutional Ownership ◽  
Board Of Director ◽  
Composition And Structure ◽  
High Incidence ◽  
The Board Of Directors ◽  
Director Characteristics ◽  
The Relationship ◽  
The U.S

Due to the high incidence of fraud in Australia, regulatory reports suggest strengthening the monitoring role of the board of directors (BOD). These reports recommend greater independence and no duality (chairperson of the BOD should not be the CEO) on the BOD. While there is no Australian evidence, research evidence in the U.S. supports these suggested reforms. It is not clear whether the research evidence observed in the U.S. will generalize to the Australian setting because of contextual differences. This study extends the U.S. findings to the Australian context and investigates the relationship between two attributes of the BOD, independence and duality, and fraud. In addition, I examine whether institutional ownership plays a role in the context of fraud. The more highly concentrated institutional ownership in Australia suggests the presence of some relationship. Using a matched sample of fraud and no-fraud firms from 1988–2000, I find that as the percentage of independent directors and the percentage of independent institutional ownership increases, the likelihood of fraud decreases. As expected, the results show a positive relationship between duality and the likelihood of fraud. These results support the call for strengthening the composition and structure of the BOD in Australia.

scholarly journals Factors influencing the occurrence of negative interactions between people and crocodilians in Mexico

Oryx ◽  
2021 ◽  
pp. 1-9
Author(s):  
Giovany Arturo González-Desales ◽  
Luis Sigler ◽  
Jesús García-Grajales ◽  
Pierre Charruau ◽  
Martha Mariela Zarco-González ◽  
...  
Keyword(s):  
Anthropogenic Activities ◽  
Biosphere Reserve ◽  
Rigorous Evaluation ◽  
Caiman Crocodilus ◽  
Crocodylus Acutus ◽  
American Crocodile ◽  
Nesting Sites ◽  
The Relationship ◽  
Nesting Season ◽  
Negative Interactions

Abstract Negative interactions between people and crocodilians have increased worldwide, but in Mexico there have been few systematic reports and no rigorous evaluation of this problem. We compiled information on negative interactions between people and the spectacled caiman Caiman crocodilus and American crocodile Crocodylus acutus from the Worldwide Crocodilian Attack Database for 1993–2018, and we investigated interactions in greater depth, through interviews with people in La Encrucijada Biosphere Reserve. We examined the relationship between the occurrence of negative interactions between people and C. acutus and the species' nesting season and abundance, and presence records. In Mexico, the frequency of negative interactions increases when anthropogenic activities occur close to nesting sites (< 30 km) and during the nesting season (February–September). In La Encrucijada, following negative interactions with crocodiles, the local inhabitants killed 30 crocodiles measuring > 2.5 m long in 2011–2012. The frequency of negative human–crocodilian interactions was not correlated with the abundance of crocodilians but was correlated with the number of presence records of crocodiles. Strategies to minimize these interactions include warnings at nesting sites, increased monitoring of anthropogenic activities during the nesting season, and management of nests to prevent them being destroyed by people.

scholarly journals Disease Risk, Spatial Patterns, and Incidence-Severity Relationships of Fusarium Head Blight in No-till Spring Wheat Following Maize or Soybean

Plant Disease ◽  
2015 ◽  
Vol 99 (10) ◽  
pp. 1360-1366 ◽  
Author(s):  
Pierri Spolti ◽  
Denis A. Shah ◽  
José Maurício C. Fernandes ◽  
Gary C. Bergstrom ◽  
Emerson M. Del Ponte
Keyword(s):  
Fusarium Head Blight ◽  
Large Scale ◽  
Disease Risk ◽  
Random Pattern ◽  
Southern Brazil ◽  
Head Blight ◽  
Previous Crop ◽  
Regional Sources ◽  
Epidemiological Surveys ◽  
The Relationship

The first large-scale survey of Fusarium head blight (FHB) in commercial wheat fields in southern Brazil was conducted over three years (2009 to 2011). The objectives were to: (i) evaluate whether increased FHB risk is associated with within-field maize residue; (ii) determine the spatial pattern of FHB incidence; and (iii) quantify the relationship between FHB incidence and severity. FHB was assessed in a total of 160 fields between early milk and dough. Incidence ranged from 1.0 to 89.9% (median = 25%) and severity from 0.02 to 18.6% (median = 1.3%). FHB risk was neither lower nor higher in wheat following maize than in wheat following soybean. Only 18% of fields were classified as having aggregated patterns of FHB-symptomatic spikes. A binary power law description of the variances was consistent with an overall random pattern of the disease. These results conform with the hypothesis that FHB epidemics in southern Brazil are driven by sufficient atmospherically-transported inoculum from regional sources. The incidence-severity relationship was coherent across growing season, growth stage, and previous crop; one common fitted curve described the relationship across all observations. Estimating severity from incidence may be useful in reducing the workload in epidemiological surveys.

scholarly journals Anuran larvae diet from agroecosystem’s ponds: environmental quality and implications for their populations

2016 ◽  
Author(s):  
Selene Babini ◽  
Luciana Cibils Martina ◽  
Elisa Luque ◽  
Noemi Gari ◽  
Nancy Salas ◽  
...  
Keyword(s):  
Environmental Quality ◽  
Native Species ◽  
Morphometric Parameters ◽  
Diet Analysis ◽  
Temporary Ponds ◽  
Nitzschia Palea ◽  
Composition And Structure ◽  
Structural Variables ◽  
Algal Abundance

<p>Agriculture is considered an important factor for the decline of amphibians recorded in the last decades. Intensive agriculture requires the application of great amounts of pesticides and fertilizers, consequently many aquatic habitats have been altered. The over-enrichment of waters with nutrients from agriculture causes growth of algae and cyanobacteria and the shift of the community composition toward the dominance of tolerant taxa. The aim of this study was to analyze the diet of tadpoles and the size of larvae and metamorphs of the native species <em>Rhinella arenarum </em>in agroecosystems of central Argentina. Four sampling sites with different degree of human disturbance were selected, three temporary ponds from agroecosystems (A1, A2, A3), and a pond in a semi-modified landscape, not affected by agriculture or cattle. The sites were visited once a week from October 2013 to January 2014. Tadpoles and metamorphs were captured, anesthetize and preserved. Morphometric parameters were measured on tadpoles and metamorphs and for 20 tadpoles the complete intestine was removed and their contents analyzed. Phosphate values were higher in agroecosystem ponds. Body size and mass of tadpoles and metamorphs were different between sites, being smaller in agricultural ponds. Diet analysis revealed that all larvae mainly consumed microalgae. Larval diets allowed differentiating the sites, larvae from A1 and A3 sites showed a diet with a similar composition and structure (with a predominance of <em>Nitzschia palea</em>), meanwhile larvae from A2 and SM showed different diets. In SM, the larvae mainly consumed <em>Trachelomonas </em>sp. Analysis of structural variables revealed a higher algal abundance in the diet of larvae from A3, a lower richness in SM and that there were no differences between sites in diversity and evenness of diets. Our hypothesis was support in part, given that resistant algae taxa were found in agroecosystem ponds and tadpoles and metamorphs were smaller, but larval diets showed higher abundance and richness. The analysis of the diet of aquatic stages of <em>R. arenarum</em> allowed us to know the trophic availability and environmental quality of temporary ponds from agroecosystems. </p>

scholarly journals Freshwater temperature in the state of Rio Grande do Sul, Southern Brazil, and its implication for fish culture

2008 ◽  
Vol 6 (2) ◽  
pp. 275-281 ◽  
Author(s):  
Luciano de Oliveira Garcia ◽  
Carlos Eduardo Copatti ◽  
Flávio Wachholz ◽  
Waterloo Pereira Filho ◽  
Bernardo Baldisserotto
Keyword(s):  
Water Temperature ◽  
Fish Species ◽  
Native Species ◽  
Amazon Basin ◽  
Rio Grande ◽  
The State ◽  
Tropical Species ◽  
Southern Brazil ◽  
Rio Grande Do Sul ◽  
Lower Growth

In this study we verified data of water temperatures collected by CORSAN-RS from 1996 to 2004 in several cities of the state of Rio Grande do Sul, southern Brazil, and analyzed the possibility of raising the most cultivated fish species in Brazil. The water temperature from 1996 to 2004 was 16 to 28ºC in summer, 17 to 23ºC in fall, 14 to 17ºC (down to 9ºC in the coldest months) in winter and 14 to 21ºC in spring. Native species of this state, such as silver catfish (Rhamdia quelen), traíra (Hoplias malabaricus), dorado (Salminus brasiliensis), pintado (Pimelodus maculatus), as well as carps (family Cyprinidae), are resistant to the low winter temperatures. These species have a lower growth rate in coldest months (winter/spring) but a good development in warmer months (summer/fall), reaching a satisfactory performance throughout the year. In the periods of more intense cold, mortality of some introduced species, such as surubim from Amazon Basin (Pseudoplatystoma sp.), pirapitinga (Piaractus brachypomus), pirarucu (Arapaimas gigas), pacu (Piaractus mesopotamicus), tambaqui (Colossoma macropomum) and Nile tilapia (Oreochromis niloticus) may occur. In addition, as most tropical species have a thermal range for growth and reproduction between 20 to 28ºC, some species may have poor development even in fall. Therefore, water temperature in this state should be considered in the choice of fish species to be cultivated.

scholarly journals The contribution of environmental factors to fish assemblages in the Río Acahuapa, a small drainage in Central America

2017 ◽  
Vol 15 (3) ◽  
Author(s):  
Francisco S. Álvarez ◽  
Wilfredo A. Matamoros ◽  
Francisco A. Chicas
Keyword(s):  
Fish Species ◽  
Habitat Structure ◽  
Fish Assemblages ◽  
Species Abundance ◽  
Main Channel ◽  
Estuarine Fish ◽  
Species Origin ◽  
High Temperature Water ◽  
Distribution Of Fish ◽  
Temperature Water

ABSTRACT The ichthyofauna of the Río Acahuapa was analyzed sampling 17 sites that included the basin main channel and its tributaries. Fish were collected using dip-nets, seine-nets and electrofishing. Fish standard length and species abundance were recorded. Species origin and salinity tolerance criteria were used to classify fish species. Water physicochemical variables, habitat structure and sampling sites elevation were recorded. A total of 33 fish species were registered, 12.1% are primary, 45.5% are secondary and 42.4% are of marine derivation. Fish species richness declined with increase of elevation (R2=0.55, p=0.0006). Two assemblages of fishes were identified: the first one associated to sites of low elevations (19-184 masl), composed mainly of secondary and marine-estuarine fish species related with high temperature, water velocity, river width, dissolved oxygen and low sand and silt substrate cover; the second one associated to sites of middle and higher elevations (185-519 masl), composed by primary and secondary freshwater fishes related with high pH, logs and rocks substrate cover. In summary, elevation and environmental variables contributed to the composition and distribution of fish in the Río Acahuapa.

scholarly journals Use of the flooded forest by fish assemblages in lakes of the National Park of Anavilhanas (Amazonas, Brazil)

2012 ◽  
Vol 42 (4) ◽  
pp. 561-566 ◽  
Author(s):  
Janette Noveras ◽  
Kedma C. Yamamoto ◽  
Carlos E.C. Freitas
Keyword(s):  
Species Diversity ◽  
Correspondence Analysis ◽  
National Park ◽  
Fish Assemblages ◽  
Open Water ◽  
Flooded Forest ◽  
Rio Negro ◽  
Flooded Forests ◽  
Filter Feeders ◽  
Distribution Of Fish

We evaluated diversity and distribution of fish species in two habitats: flooded forest and open water of lakes of Rio Negro. Each of four lakes within the Anavilhanas Archipelago was sampled three times from 2009-2010. Species diversity generally was higher in flooded forests and at night, according to correspondence analysis. Predators were most active at night, but showed no preference between the flooded forest and open water habitats. Omnivores, filter feeders, and detritivores were most active during the day.

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