Defining habitat characteristics influencing the distribution, density and growth of Plaice (Pleuronectes Platessa) and Dab (Limanda Limanda) on west of Ireland nursery grounds

Plaice (Pleuronectes platessa, L.) and dab (Limanda limanda, L.) are among the most abundant flatfishes in the north-eastern Atlantic region and the dominant species in shallow coastal nursery grounds. With increasing pressures on commercial flatfish stocks in combination with changing coastal environments, better knowledge of population dynamics during all life stages is needed to evaluate variability in year-class strength and recruitment to the fishery. The aim of this research was to investigate the complex interplay of biotic and abiotic habitat components influencing the distribution, density and growth of plaice and dab during the vulnerable juvenile life stage and to gain insight in spatial and temporal differences in nursery habitat quality along the west coast of Ireland. Intraspecific variability in plaice diet was observed at different spatial scales and showed a link with condition, recent growth and morphology. This highlights the effect of food availability on habitat quality and the need to consider small scale variation when attempting to link habitat quality to feeding, growth and condition of juvenile flatfish. There was evidence of trophic, spatial and temporal resource partitioning between juvenile plaice and dab allowing the co-existence of morphologically similar species in nursery grounds. In the limited survey years there was no evidence that the carrying capacity of the studied nursery grounds was reached but spatial and interannual variations in fish growth indicated fluctuating environments in terms of food availability, predator densities, sediment features and physico-chemical conditions. Predation was the most important factor affecting habitat quality for juvenile plaice and dab with crab densities negatively correlated to fish condition whereas shrimp densities were negatively associated with densities of small-sized juveniles in spring. A comparison of proxies for fish growth showed the advantage of Fulton’s K for routine use whereas RNA:DNA ratios proved less powerful when short-term environmental fluctuations are lacking. This study illustrated how distinct sets of habitat features can drive spatial variation in density and condition of juvenile flatfish highlighting the value of studying both variables when modeling habitat requirements. The habitat models generated in this study also provide a powerful tool to predict potential climate and anthropogenic impacts on the distribution and condition of juveniles in flatfish nurseries. The need for effective coastal zone management was emphasized to ensure a sustainable use of coastal resources and successful flatfish recruitment to the fishery.

Solubilidade de fosfatos naturais em solução de ácido cítrico a 2%: modificação nas condições de agitação

This paper deals with a modification in the solubilization technique of natural phophates in the 2% citric acid solution. The proposed technique is as follows: 2,5 g of phosphatic material and 250 ml of 2% citric acid solution, in a 500 ml Erlenmeyer flask, are shaken for 30 minutes at 30-40 rpm. The phosphorus (P2O5) was determined by the usual method. The data obtained were compared with the conventional technique in which a Stohmann bottle is used. The natural phosphates used were: Phosphorita de Olinda (Pernambuco), Flórida Phosphate (USA) and Hiperphosphate (África). Statistical analysis was applied to the data and the following conclusions were arrived at: a) The precision is equivalent in both techniques. b) There is no significant variation between the means obtained with the two technique.

Sôbre uma modificação no método de Neubauer

O presente trabalho relata os dados obtidos, segundo uma modificação do método de Neubauer, comparados aos obtidos pelo método usual do citado autor. A modificação consistiu no uso de cristalizadores menores e no emprêgo de um número de plantas e de um pêso de terra muito menores. Assim, foram colocadas 25 sementes de arroz em 20 g de terra, intimamente misturadas com 40 g de areia de praia lavada, em cristalizadores de 80 mm de diâmetro, por 20 mm de altura. Decorridos 18 dias após a germinação, as plantas foram colhidas, incineradas e o potássio foi determinado por fotômetro de chama. Os resultados foram comparados com os dados obtidos através de um experimento feito com as mesmas amostras de terra e no mesmo tempo, conforme a técnica usual de Neubauer. Praticamente, os dois métodos se equivalem, conforme mostram os dados do quadro 1 em Resultados e Discussão. As principais vantagens do método modificado, em relação ao método usual de Neubauer, podem ser resumidas nas seguintes: redução do pêso da amostra de 100 para 20 g e redução do pêso da areia de praia lavada de 350 para 70 g; redução da área ocupada pelos cristalizadores para menos de um terço; redução do número de plantas para um quarto (de 100 para 25 plantas) e redução do trabalho exigido para a execução do método, desde o preparo dos cristalizadores, até o preparo das plantas, incineração e análise.

Sôbre uma modificação na determinação do Molibdênio em Plantas

The author proposed a new modification on the thiocyanate-stannous chloride method for the determination of molibdenum, when is used a heavier-than-water solvent for extrating the colored molybdenum thiocyanate complex. Carbon tetrachloride - butyl alcohol is the mixture proposed, and the results obtained give a good precision and more sensibility than the other method that use carbon tetrachloride-isoamyl alcohol as extractant.

Modificação ao método de Bray para avaliar a fertilidade do solo

Neste trabalho é apresentada uma modificação ao método de BRAY (1948) para se construir uma curva de calibração de nutrientes disponíveis no solo. Basicamente, trata-se de se estimar o valor da constante da equação de Mitscherlich, na forma linear, por meio de regressão linear e com esse valor construir uma curva de calibração.

Species richness, relative abundance, and habitat of reproduction of terrestrial frogs in the Triângulo Mineiro region, Cerrado biome, southeastern Brazil

Based on field observations and pitfall sampling, we determined the species richness, relative abundance, and reproductive habitat of terrestrial frogs in three municipalities in the Triângulo Mineiro region, south Cerrado biome, in southeastern Brazil. We found thirty-two species of terrestrial frogs, belonging to the families Brachycephalidae, Bufonidae, Cycloramphidae, Dendrobatidae, Leiuperidae, Leptodactylidae and Microhylidae. Most of the species were found in open areas and reproduced in human-generated environments, such as artificial lakes (10 species) and ponds (14 species). Dominance was high, with Physalaemus cuvieri Fitzinger, 1826 (Leiuperidae) representing 48% of sampled frogs. A larger number of individuals was captured in the wet season, when most of the species were reproducing. Compared to other areas of Cerrado biome, the Triângulo Mineiro sites presented a larger number of species, which may be attributed to the larger sampled area and greater sampling effort, lower altitude and presence of human generated habitats. The richness of terrestrial frogs was also larger than that in some forested localities in southeastern Brazil, indicating that the number of species cannot be explained only by precipitation and type of vegetation cover. The greater abundance of individuals during the wet season may be related to a greater movement of adults to breeding sites and to juvenile recruitment/dispersion. The heterogeneity of environments in the Cerrado biome, including its several isolated highlands, contributes to its high (local and regional) diversity of frogs.

Habitat use by a tree frog species of Scinax (Amphibia, Hylidae) at an urban forest fragment from south-eastern Brazil

We studied the pattern of habitat use by the tree frog Scinax aff. perereca. Fieldworks were performed from August 1996 to August 1997 at Parque das Mangabeiras, Belo Horizonte, State of Minas Gerais, southeastern Brazil. Calling males were observed in September, October and December 1996, February to April and June 1997. Females were found only in October 1996. Specimens were found perched on vegetation, on the ground or on stones near waterfall. At Parque das Mangabeiras, S. aff. perereca occupied nine types of substrata. The most frequently used substrata were shrubs, stones at the stream edges, and fallen trunks. The pattern of spatial occupation varied among months. Males were found calling in aggregations on the vegetation and spatial niche breadth was related to species abundance.

Variações ecomorfológicas e de uso de habitat em Piabina argentea (Characiformes, Characidae) da bacia do Rio das Velhas, Minas Gerais, Brasil

O presente estudo teve como objetivo investigar os padrões local e regional de uso de habitat de Piabina argentea Reinhardt, 1867 em quatro diferentes rios da bacia do rio das Velhas. Os habitat amostrados foram caracterizados quanto à velocidade da água, profundidade e tipo de substrato. Para a análise ecomorfológica, foram calculados 17 atributos ecomorfológicos de 40 exemplares de cada rio. Embora estas populações tenham se sobreposto no espaço ecomorfológico, a Análise Discriminante Canônica mostrou haver diferença significativa entre elas, principalmente da população do rio das Velhas em relação às demais. A separação se deu em termos do índice de compressão, altura relativa do corpo e índice de achatamento ventral. Os padrões locais de seleção de habitat não foram congruentes em todos os rios, mas em geral, houve predomínio do padrão regional: habitat lênticos, profundidade entre 20 e 40 cm e 60 e 80 cm e substrato areia, silte+argila e banco de folhas. Considerando as características físicas de cada rio e o padrão regional da espécie, a maior parte dos seus requerimentos de habitat é contemplada nos quatro rios. Entretanto, um corpo d'água assoreado como o trecho do rio das Velhas, tende a ter maiores velocidades da água, menores profundidades e substrato finos, o que atende em parte à seleção de habitat da espécie estudada.

Influence of seasonal changes in daily activity and annual life cycle of Geotrigona mombuca (Hymenoptera, Apidae) in a Cerrado habitat, São Paulo, Brazil

The foraging activity of Geotrigona mombuca Smith, 1863 was studied under natural conditions aiming to verify the influence of seasonal changes on daily flight activity and annual cycle of the colony. Daily flight activity was monitored for a year based on the observation and counting of foragers leaving and entering the hive, as well as the kind of material transported and meteorological factors such as day time, temperature and relative humidity. The influence of seasonal changes was evidenced by alterations on daily rhythm of flight activity and by differences on transportation of food resources, building material and garbage. These data indicate that forager behavior is related to daily microclimate conditions and it is synchronized with the requirements of colony annual cycle, which determines an intense pollen collection in the summer. Thus, the recomposition of the intranidal population in spring and summer can be ensured, which is characterized both for a higher intensity of flight activity and increase in garbage and resin transport, as well as the swarming process in the spring. In this way, an action targeting the preservation or management of the species in a natural environment should consider that survival and reproduction of the colony depends greatly on the amount of available pollen in late winter.

Diversity and habitat preference of medium and large-sized mammals in an urban forest fragment of southwestern Amazon

We assessed the species composition and abundance of medium and large-sized mammals in an urban forest fragment in the Brazilian Amazon, and recorded the preference of some species for particular phytophysiognomies. We placed nine transects with 20 sand plots each in three phytophysiognomies: open rainforest with a dominance of bamboos (OFB), open rainforest with palm trees (OFP), and dense rainforest (DF). We calculated species abundance as the number of records/plot.day, in a total of 2,700 plots.day. We recorded twelve mammal species; Sylvilagus brasiliensis (Linnaeus, 1758) and Dasyprocta fuliginosa (Wagler, 1831) were the most abundant. The results differed among phytophysiognomies: DF presented the highest mammal diversity, whereas the species composition of OFP was less similar than that of other phytophysiognomies. Rodents showed higher preference for OFP and Sylvilagus brasiliensis was more abundant in OFB. The study area showed high species richness, with the occurrence of mesopredators, but there was a predominance of common species adaptable to disturbed environments, which reflects the severe isolation degree of the forest fragment and the hunting pressure that is still present.

Bird-habitat associations in coastal rangelands of southern Brazil

Nearly all remnants of temperate grasslands in southeastern South America are used for livestock ranching and are subject to habitat degradation resulting from this activity. Exploring how habitat features affect the composition of grassland avifaunal communities is a first step to understand how current cattle-ranching management practices impact avian diversity. We used canonical ordination to test for relationships between five habitat variables and the composition of the bird community in coastal grasslands in southern Brazil. We sampled pastures with different heights, from overgrazed short-grass to tall herbaceous vegetation. We recorded 1,535 individuals and 27 species of birds. The first ordination axis indicated a strong contribution of mean vegetation height on the composition of the bird community, whereas the second axis revealed the influence of herbaceous vegetation patchiness and woody vegetation cover. Three groups of species were revealed by the ordination: one more diffuse associated with intermediate and tall herbaceous vegetation, another with short grass, and a third with vegetation patchiness and woody vegetation. Species restricted to tall herbaceous vegetation are negatively impacted from habitat degradation resulting from overgrazing and trampling by livestock, and mowing and burning of tall plants. Occurrence of these species in our study area is related with the presence of swales immediately behind the dune system and where remnants of tall vegetation persist. Birds of pastures with ample cover of short herbaceous plants, including one globally threatened species and six other restricted to short-grass habitat, apparently benefit from local livestock management practices. Woody vegetation possibly functions as a keystone structure, enabling the occurrence in grasslands of avian species that rely on shrubby habitat. Although livestock ranching promotes the diversity of habitats by creating distinct patches of vegetation height in grasslands, current management practices directed to the maintenance of short grass pastures may eliminate an entire subset of species, including regionally threatened taxa, and reduce avian diversity. The maintenance of large patches of tall herbaceous plants is needed to ensure the survival of species reliant on this type of grassland structure in our study area.

Balloniscus glaber (Crustacea, Isopoda, Balloniscidae), a habitat specialist species in a disturbed area of Brazil

ABSTRACT Balloniscus glaber Araujo & Zardo, 1995 (Balloniscidae), a Neotropical Oniscidea, has been recorded historically in environments with low or no human interference. In one of these areas, it was determined as aK-strategist. Recently, however, this species was documented in a disturbed forest within urban limits. The present work revealed that the population in the urban area has high density, high number of ovigerous females and mancae in the population, a long reproductive period, and early sexual maturity. These results suggest that modified environments may provide favorable conditions and that the species is not negatively affected by human influence.