Spatially explicit estimates of length and biomass of Micromesistius poutassou (Blue Whiting) from acoustic and trawl surveys in the North-East Atlantic in May 2010

Acoustic estimates of herring and blue whiting abundance were obtained during the surveys using the Simrad ER60 scientific echosounder. The allocation of NASC-values to herring, blue whiting and other acoustic targets were based on the composition of the trawl catches and the appearance of echo recordings. To estimate the abundance, the allocated NASC -values were averaged for ICES-squares (0.5° latitude by 1° longitude). For each statistical square, the unit area density of fish (rA) in number per square nautical mile (N*nm-2) was calculated using standard equations (Foote et al., 1987; Toresen et al., 1998). To estimate the total abundance of fish, the unit area abundance for each statistical square was multiplied by the number of square nautical miles in each statistical square and then summed for all the statistical squares within defined subareas and over the total area. Biomass estimation was calculated by multiplying abundance in numbers by the average weight of the fish in each statistical square then summing all squares within defined subareas and over the total area. The Norwegian BEAM soft-ware (Totland and Godø 2001) was used to make estimates of total biomass.

Results of hydrological and geological investigations in Benin

Focus of this study is the analysis of a local hydrogeological system in the subhumid outer tropics in the western African country of Benin. The aim was to characterize, qualify and quantify the hydrogeological and hydrological properties of the approx. 30 km2 big study area and to develop a conceptual hydrogeological model. This model should provide the basis for further studies on a regional scale. The main goal was to obtain the process knowledge of the hydrogeological system and to determine the process and the quantity of the groundwater recharge in the working area. According to the objectives, a broad hydrogeological approach was chosen. In a spacious network on the local scale TDR probes, suction cups and groundwater observation bores were installed. Also in a multidisciplinary cooperation with hydrology, geography, soil science, biology, meteorology and plant nutrition sciences, instruments like discharge gauging stations, tensiometers, lysimeter, climate stations, runoff plots and erosion pins were installed in the test site for the investigation of the relevant parameters of the hydrological cycle.