A statistical model for estimation of fish density including correlation in size, space, time and between species from research survey data

Trawl survey data with high spatial and seasonal coverage were analysed using a variant of the Log Gaussian Cox Process (LGCP) statistical model to estimate unbiased relative fish densities. The model estimates correlations between observations according to time, space, and fish size and includes zero observations and over-dispersion. The model utilises the fact the correlation between numbers of fish caught increases when the distance in space and time between the fish decreases, and the correlation between size groups in a haul increases when the difference in size decreases. Here the model is extended in two ways. Instead of assuming a natural scale size correlation, the model is further developed to allow for a transformed length scale. Furthermore, in the present application, the spatial- and size-dependent correlation between species was included. For cod (Gadus morhua) and whiting (Merlangius merlangus), a common structured size correlation was fitted, and a separable structure between the time and space-size correlation was found for each species, whereas more complex structures were required to describe the correlation between species (and space-size). The within-species time correlation is strong, whereas the correlations between the species are weaker over time but strong within the year

Localisation of nursery areas based on comparative analyses of the horizontal and vertical distribution patterns of juvenile Baltic cod (Gadus morhua)

Knowledge of the spatial distribution of juvenile cod is essential for obtaining precise recruitment data to conduct sustainable management of the eastern and western Baltic cod stocks. In this study, the horizontal and vertical distribution and density patterns of settled juvenile 0- and 1-group Baltic cod are determined, and their nursery areas are localised according to the environmental factors affecting them. Comparative statistical analyses of biological, hydrographic and hydroacoustic data are carried out based on standard ICES demersal trawl surveys and special integrated trawl and acoustic research surveys. Horizontal distribution maps for the 2001-2010 cohorts of juvenile cod are further generated by applying a statistical log-Gaussian Cox process model to the standard trawl survey data. The analyses indicate size-dependent horizontal and distinct vertical and diurnal distribution patterns related to the seabed topography, water layer depth, and the presence of hydrographic frontal zones (pycnoclines) as well as intraspecific patterns in relation to the presence of adult cod. The extent of the nursery areas also depends on the cod year class strength. Juvenile cod (≥3 cm) are present in all areas of the central Baltic Sea (CBS), showing broad dispersal. However, their highest density in the Baltic Basins is found at localities with a 40-70 m bottom depth in waters with oxygen concentrations above 2 ml O₂.l⁻¹ and temperatures above 5°C. The smallest juveniles are also found in deep sea localities down to a 100 m depth and at oxygen concentrations between 2-4 ml O₂.l⁻¹. The vertical, diurnally stratified and repeated trawling and hydroacoustic target strength-depth distributions obtained from the special surveys show juvenile cod concentrations in frontal zone water layers (pycnocline). However, the analyses indicate that in the CBS, juvenile cod of all sizes do not appear to aggregate in dense schooling patterns, which differs from what has been reported from the North Sea

Food webs under changing biodiversity - Top-down control

Report on effects of changing predation pressure on benthic and pelagic specie

A survey of uncontrolled satellite reentry and impact prediction

The primary goal of this thesis is to identify the 'state-of-the-art' in orbit-decay-induced uncontrolled reentry/impact prediction methods, with an emphasis on the physics of the final few revolutions to impact. This was accomplished through a comprehensive literature survey from the 1950's to the present of unclassified military and civil databases. The results of the survey show that the current U.S. and international reentry/impact prediction methodologies are based on analysis which is over 30 years old. Of the various 'extensions' to the current reentry theory, of which the NORAD method is recognized as the international standard, there does not appear to be any one method which is singularly superior to the others. It has also been shown that numerous reentry investigations made simplifying assumptions due to insufficient data needed to accurately model reentry and also because of computing limitations of their day. Also, current deterministic dynamic models appear to inadequately describe the actual uncontrolled reentry process, due to a lack of observational data, uncertainty in determining aerodynamic coefficients, atmospheric density, and point mass modeling where changes in vehicle configuration, attitude and lift are neglected. Stochastic and statistical methods could be applied to the current methodology, to better analyze the various uncertainties, which could help to improve the overall predicted impact time and location; however, further research into these methods along with the physics of uncontrolled reentry is necessary. Reentry, Uncontrolled reentry, Reentry effects, Reentry prediction, Impact prediction, Reentry motion, Reentry aerothermodynamics, Satellite breakup, Atmospheric density models, Reentry/ impact modelshttp://archive.org/details/surveyofuncontro00neueLieutenant Commander (sel), United States NavyLieutenant, United States NavyApproved for public release; distribution is unlimited

Cultural politics and a music recording project: producing Strike Em!: Contemporary voices from the Torres Strait

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