Movements of marine fish and decapod crustaceans: Process, theory and application

Many marine species have a multi-phase ontogeny, with each phase usually associated with a spatially and temporally discrete set of movements. For many fish and decapod crustaceans that live inshore, a tri-phasic life cycle is widespread, involving: (1) the movement of planktonic eggs and larvae to nursery areas; (2) a range of routine shelter and foraging movements that maintain a home range; and (3) spawning migrations away from the home range to close the life cycle. Additional complexity is found in migrations that are not for the purpose of spawning and movements that result in a relocation of the home range of an individual that cannot be defined as an ontogenetic shift. Tracking and tagging studies confirm that life cycle movements occur across a wide range of spatial and temporal scales. This dynamic multi-scale complexity presents a significant problem in selecting appropriate scales for studying highly mobile marine animals. We address this problem by first comprehensively reviewing the movement patterns of fish and decapod crustaceans that use inshore areas and present a synthesis of life cycle strategies, together with five categories of movement. We then examine the scale-related limitations of traditional approaches to studies of animal-environment relationships. We demonstrate that studies of marine animals have rarely been undertaken at scales appropriate to the way animals use their environment and argue that future studies must incorporate animal movement into the design of sampling strategies. A major limitation of many studies is that they have focused on: (1) a single scale for animals that respond to their environment at multiple scales or (2) a single habitat type for animals that use multiple habitat types. We develop a hierarchical conceptual framework that deals with the problem of scale and environmental heterogeneity and we offer a new definition of 'habitat' from an organism-based perspective. To demonstrate that the conceptual framework can be applied, we explore the range of tools that are currently available for both measuring animal movement patterns and for mapping and quantifying marine environments at multiple scales. The application of a hierarchical approach, together with the coordinated integration of spatial technologies offers an unprecedented opportunity for researchers to tackle a range of animal-environment questions for highly mobile marine animals. Without scale-explicit information on animal movements many marine conservation and resource management strategies are less likely to achieve their primary objectives

Albert Durer : biographie critique

Università degli Studi di Triest

YBa2Cu3O7 tapes prepared by sol-gel deposition techniques: microstructure and structural characterizations

We report on the preparation conditions of YBa2Cu3O7 polycrystalline superconducting tapes by a sol-gel deposition technique. We present some discussion on the compatibility between the nature of the substrate, the use of a buffer layer, and the conditions used to prepare appropriate superconducting YBa2Cu3O7,, materials. We report also on the microstructural characterizations performed in order to evaluate the crystallites size, degree of orientation and connectivity. (C) 2002 Elsevier Science B.V. All rights reserved

Trophic relationships in an interlinked mangrove-seagrass ecosystem as traced by delta C-13 and delta N-15

The food web structure of a mangrove forest and adjacent seagrass beds in Gazi Bay, Kenya, was examined with stable carbon and nitrogen isotope ratio techniques. A carbon isotopic ratio gradient was found from mangroves with mean (+/-SD) delta(13)C value of -26.75 +/- 1.64 parts per thousand to seagrass beds with -16.23 +/- 4.35 parts per thousand. Seagrasses close to the mangroves were more depleted in C-13 than seagrasses close to the major coral reef. Macroinvertebrates collected along this mangrove seagrass bed transect showed a similar delta(13)C gradient. Fishes collected near the mangroves were depleted in C-13 compared to fishes collected in the seagrass meadows. The fish community was differentiated on the basis of its carbon isotopic ratios and the site where individuals were collected. Three groups were identified: (1) species occurring in seagrass meadows in the close vicinity of the mangrove swamps; (2) species migrating between mangroves and the seagrass meadows, together with species occurring throughout the entire seagrass area, from close to the mangroves to the outer bay; and (3) species that use the seagrass meadows proper as a lifetime habitat. The results show that seagrass stands are the main feeding grounds providing food for all fish species studied. delta(15)N signatures allowed to the identification of the following trophic levels: (1) fish species feeding on seagrasses and macroalgae (herbivores); (2) fish feeding on zoo/benthos- plankton (zoobenthiplanktivores); and (3) other fish and/or macro-crustacea (piscivores/benthivores). A N-15 isotepe enrichment of <2 parts per thousand was found between successive trophic levels suggesting significant omnivory. [KEYWORDS: delta C-13; delta N-15; mangroves; seagrasses; fishes; trophic relationships Gazi bay; carbon; kenya; isotopes; marine]

Comparison of different methods for characterizing multi-walled carbon nanotubes

Four complementary and independent methods are used to characterize nanotube samples: (i) TEM observation coupled with image analysis, (ii) nitrogen and krypton adsorption isotherm analysis, (iii) thermogravimetry and (iv) wide angle X-ray scattering. The methodology is discussed on the basis of two multi-walled carbon nanotube samples produced by the CCVD technique with very different reaction rates. It is shown that the total amount of deposited carbon is larger for the sample produced at the higher rate, that the fraction of nanotubes in the deposited carbon does not seem to be significantly different, but that the crystallinity of the nanotubes wall is larger for the sample produced at the lowest reaction rate. (C) 2004 Elsevier B.V. All rights reserved