Near resonance acoustic scattering from organized schools of juvenile Atlantic bluefin tuna (Thunnus thynnus)

Schools of Atlantic bluefin tuna (Thunnus thynnus) can exhibit highly organized spatial structure within the school. This structure was quantified for dome shaped schools using both aerial imagery collected from a commercial spotter plane and 400 kHz multibeam echo sounder data collected on a fishing vessel in 2009 in Cape Cod Bay, MA. Observations from one school, containing an estimated 263 fish within an approximately ellipsoidal volume of 1900 m3, were used to seed an acoustic model that estimated the school target strength at frequencies between 10 and 2000 Hz. The fish\u27s swimbladder resonance was estimated to occur at approximately 50 Hz. The acoustic model examined single and multiple scattering solutions and also a completely incoherent summation of scattering responses from the fish. Three levels of structure within the school were examined, starting with fish locations that were constrained by the school boundaries but placed according to a Poisson process, then incorporating a constraint on the distance to the nearest neighbor, and finally adding a constraint on the bearing to the nearest neighbor. Results suggest that both multiple scattering and spatial organization within the school should be considered when estimating the target strength of schools similar to the ones considered here

A Statistical Analysis for Estimating Fish Number Density with the Use of a Multibeam Echosounder

Fish number density can be estimated from the normalized second moment of acoustic backscatter intensity [Denbigh et al., J. Acoust. Soc. Am. 90, 457-469 (1991)]. This method assumes that the distribution of fish scattering amplitudes is known and that the fish are randomly distributed following a Poisson volume distribution within regions of constant density. It is most useful at low fish densities, relative to the resolution of the acoustic device being used, since the estimators quickly become noisy as the number of fish per resolution cell increases. New models that include noise contributions are considered. The methods were applied to an acoustic assessment of juvenile Atlantic Bluefin Tuna, Thunnus thynnus. The data were collected using a 400 kHz multibeam echo sounder during the summer months of 2009 in Cape Cod, MA. Due to the high resolution of the multibeam system used, the large size (approx. 1.5 m) of the tuna, and the spacing of the fish in the school, we expect there to be low fish densities relative to the resolution of the multibeam system. Results of the fish number density based on the normalized second moment of acoustic intensity are compared to fish packing density estimated using aerial imagery that was collected simultaneously

Characteristics of sustainable polyculture production systems on terra firme.

The combination of soil science, forestry, agronomy and biology allowed an analytical comparison of various experimental mixed culture systems. From these studies, a descriptor system was developed which allows to understand the contribution of each plant species to nutrient cycling, water distribution, litter formation, overall biomass production and crop production. This knowledge allows to combine plants so that their properties interact to form a system, which minimizes mineral losses and which regulates air humidity and water distribution and thus leads to stable crop production. The general conclusion which can be drawn after eight years of polyculture study is: a) stable productions systems for samllholder families have bee developed; b) the systems are variable; they can be adapted to the respective site conditions; c) the manager of these plantations requires a deeper understanding of the cultivation systems and an intensive dissemination of knowledge and a well develope on-farm training system for farmers

Characteristics of sustainable polyculture production systems on terra firme.

The combination of soil science, forestry, agronomy and biology allowed an analytical comparison of various experimental mixed culture systems. From these studies, a descriptor system was developed which allows to understand the contribution of each plant species to nutrient cycling, water distribution, litter formation, overall biomass production and crop production. This knowledge allows to combine plants so that their properties interact to form a system, which minimizes mineral losses and which regulates air humidity and water distribution and thus leads to stable crop production. The general conclusion which can be drawn after eight years of polyculture study is: a) stable productions systems for samllholder families have bee developed; b) the systems are variable; they can be adapted to the respective site conditions; c) the manager of these plantations requires a deeper understanding of the cultivation systems and an intensive dissemination of knowledge and a well develope on-farm training system for farmers

Soil quality parameters of a xanthic ferralsol in the Amazon basin.

A Fertbio 2002 reuniu a XXV Reunião Brasileira de Fertilidade do Solo e Nutrição de Plantas, a IX Reunião Brasileira sobre Micorrizas, o VII Simpósio Brasileiro de Microbiologia do Solo e a Reunião Brasileira de Biologia do Solo, sob o tema: "Agricultura: bases ecológicas para o desenvolvimento social e econômico sustentado

Pest and disease incidence in agroforestry systems of the Brazilian Central Amazon.

In Central Amazonia there are no examples of pests or diseases whose incidence is reduced in agroforestry systems

Development and production of several tropical species in agroforestry systems in the Brazilian Central Amazonia during six years.

In the Central Amazonia, large land area nowadays are degraded and/or abandoned, which were previously used for shifting cultivation, pasture or monocultures. Agroforestry systems appear to be a good alternative to occupy these areas

Development and production of cupuaçu plants (Theobroma grandiflorum) on degraded areas: implications of water relations.

In the study presented here we investigated the development and production of the crop tree Theobroma grandiflorum (in Brazil named "cupuaçu") under varying agro-environments

Economic analysis of agroforestry systems in Central Amazonia, Brazil.

In this study the financial analysis of four AF was made

Significant subsoil accumulation of mineral nitrogen under perennial crops in a ferralitic Amazonian upland soil: effects of land use systems and single-tree patterns.

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