The sensitivity of stock assessment’s outcomes to the variation of Natural Mortality (M) in the Spanish Mediterranean fisheries

Stock assessments involve statistical and mathematical methods to make quantitative statements about the status of harvested populations and predictions about how they are likely to respond to alternative management choices. There are often considerable uncertainties in the population parameter estimates used in the assessment models, particularly for parameters such as growth rates, Natural Mortality, Fishing Mortality patterns and spawning stock biomass and its relationships with recruitment. Assumptions recurrently have to be made in order to facilitate the tasks for the decision-makers but also for built scientific bases for fisheries management advice. A strong focus on natural selection factors such as natural mortality may be necessary to better understand the stock’s behaviour as well as the relationship that exists with fishing mortality, so defining exploitation rates. As a result, to be able to develop a vision of a good management plan in the best estimate of the reference points which are considered as a scientific basis and necessary step for the decision-making process. This parameter is treated almost like an externally defined parameter which corresponds for the most of time to 0.2/ year. Regarding this, the present case of study, which focus on the Spanish Mediterranean trawl fisheries, has been undertaken to describe the importance of the natural mortality rate (M) in the stock assessment process and how this could be sensitive to change of its results. Following an argued method by the GFCM and used by the majority of the Mediterranean countries, the XSA was run with different values of M calculated with methods depending or not to age, using the FLR library, to test the sensitivity to this parameter and then describe possible changes in management advice

The relations between the rainfall erosivity index AI and the hydraulics of overland flow and sediment concentration in sandy soils

The purpose of this study is to investigate the effects of rainfall erosivity index AI on the hydraulics of overland flow parameters such as the flow velocity, the flow depth, the flow regime, overland flow power and on soil surface characteristics, such as surface roughness and sediment concentration. The erosivity index AI represents six rainfall intensities, 31.40 mm·h-1; 37.82 mm·h-1; 69.49 mm·h-1; 81.85 mm·h-1; 90.39 mm·h-1 and 101.94 mm·h-1 generated by a rainfall simulator. To simulate the soil plot, a soil tray was filled with remolded agricultural sandy soil. The results found have shown that the AI represents better the rainfall than rainfall intensity and related to drop diameter with a power function. Overland flow never exceeded the laminar and subcritical regime; the Reynolds number reacted differently with AI and rainfall intensity, whereas the Froude number has similar reaction with both parameters. Re, Fr and n follow with AI logarithmic, linear and power functions respectively. Finally, AI is a good predictor of soil erosion

New approach to estimate the shear stress and the force of raindrops and their effect on erodibility of agricultural soils

The objective of this work was to the study the erosive force of raindrops and the shear stress on the soil erodibility of disturbed and saturated agricultural soil. A mathematical development was used to determine a new approach to the shear stress. The soil erodibility is calculated using the WEPP (water erosion prediction project) model. To realize this work, an experimental study was led in a laboratory using the rainfall simulator. The soil tray used in this study has a length of 2 m, width of 50 cm and a depth of 15 cm and the slope was adjusted with a system. The soils used were sandy and silty agricultural soils. The results show that the relationship between the erosive force of raindrops and the shear stress on the soil erodibility increased respectively as a power and linear function with an important coeffiient of determination. As regards the relationships between soil erodibility and the mean raindrop diameter, the evolution is represented by a power function with high coeffiient of determination

The fate and behaviour of gunshot residue: recreational shooter distribution

Despite continued improvements in gunshot residue (GSR) detection and analysis, there are still challenges in the interpretation of GSR evidence. The level and distribution of GSR present on an individual can be influenced by many factors, dependent upon the context of any given case. Due and diligent attention must therefore be placed upon fate and behaviour processes in relation to GSR when assessing and interpreting any case findings. The distribution of GSR upon the body of a recreational shooter was assessed. Samples were taken from 17 positions across a shooter’s body immediately after the discharge of one round of ammunition. The shooting hand prevailed as the most GSR-contaminated area, with as many as 351 characteristic GSR particles identified. The face and supporting hand also exhibited high levels of GSR contamination. This level of contamination raises questions concerning the fate and behaviour of GSR particles within the general environment, specifically with regard to transfer processes

The Effect of Soil Surface Slope on Splash Distribution under Water Drop Impact

The effects of down slope steepness on soil splash distribution under a water drop impact have been investigated in this study. The equipment used are the burette to simulate a water drop, a splash cup filled with sandy soil which forms the source area and a splash board to collect the ejected particles. The results found in this study have shown that the apparent mass increased with increasing downslope angle following a linear regression equation with high coefficient of determination. In the same way, the radial soil splash distribution over the distance has been analyzed statistically, and an exponential function was the best fit of the relationship for the different slope angles. The curves and the regressions equations validate the well known FSDF and extend the theory of Van Dijk

The Effect of Soil Surface Slope on Splash Distribution under Water Drop Impact

The effects of down slope steepness on soil splash distribution under a water drop impact have been investigated in this study. The equipment used are the burette to simulate a water drop, a splash cup filled with sandy soil which forms the source area and a splash board to collect the ejected particles. The results found in this study have shown that the apparent mass increased with increasing downslope angle following a linear regression equation with high coefficient of determination. In the same way, the radial soil splash distribution over the distance has been analyzed statistically, and an exponential function was the best fit of the relationship for the different slope angles. The curves and the regressions equations validate the well known FSDF and extend the theory of Van Dijk

The Effect of Soil Surface Slope on Splash Distribution under Water Drop Impact

The effects of down slope steepness on soil splash distribution under a water drop impact have been investigated in this study. The equipment used are the burette to simulate a water drop, a splash cup filled with sandy soil which forms the source area and a splash board to collect the ejected particles. The results found in this study have shown that the apparent mass increased with increasing downslope angle following a linear regression equation with high coefficient of determination. In the same way, the radial soil splash distribution over the distance has been analyzed statistically, and an exponential function was the best fit of the relationship for the different slope angles. The curves and the regressions equations validate the well known FSDF and extend the theory of Van Dijk