Landings and discards on the pulse trawl MFV "Vertrouwen"TX68 in 2009

The catches in terms of landings and discards were monitored onboard MFV “Vertrouwen” TX68, fishing with two pulse trawls using the Verburg-Holland system during four weeks in June-August 2009. The average fishing speed was about 5 knots. The fishing area of the four trips was east of the coast of England and fishing depth was 36m on average with a minimum depth of 20 m and a maximum depth of 46 m. For this study the standard sampling procedure for the yearly monitoring of discards of conventional beam trawl fleet was applied (van Helmond and van Overzee, 2008). Sampled numbers of fish per haul were raised to numbers and weight per hour, for both. When compared with conventional beam trawls in previous years it seems that with the pulse trawl more sole in number and weights per unit of time was discarded and less plaice was discarded. However, the average discard percentages of as well plaice as sole for the pulse trawl of this study were within range with the average discard percentages of conventional beam trawls in 2005, 2006 and 2007 (van Keeken, 2006; van Helmond and van Overzee, 2007; van Helmond and van Overzee, 2008) . This study gives a general impression of the performance in terms of catches of fishing with a pulse trawl using the Verburg-Holland system. However it is recommended to conduct a comparative study on performance of a beam trawl and a pulse trawl, where the two vessels of similar size fish simultaneously, like was done in 2006 by van Marlen et al. This is to exclude the effects of time and area of fishing

Development and distribution of the non-indigenous Pacific oyster (Crassostrea gigas) in the Dutch Wadden Sea

Pacific oysters (Crassostrea gigas) were first observed in the Dutch Wadden Sea near Texel in 1983. The population increased slowly in the beginning but grew exponentially from the mid-1990s onwards, although now some stabilisation seems to be occurring. They occur on a variety of substrates such as mussel beds (Mytilus edulis), shell banks, dikes and poles. After initial settlement spat may fall on older individuals and congregate to dense clumps and subsequently form reefs. Individual Pacific oysters grow 3–4 cm long in their first year and 2–3 cm in their second year. Many mussel beds (Mytilus edulis) are slowly taken over by Pacific oysters, but there are also several reports of mussel spat settling on Pacific oyster reefs. This might in the end result in combined reefs. Successful Pacific oyster spat fall seems to be related to high summer temperatures, but also after mild summers much spat can be found on old (Pacific oyster) shells. Predation is of limited importance. Mortality factors are unknown, but every now and then unexplained mass mortality occurs. The gradual spread of the Pacific oyster in the Dutch Wadden Sea is documented in the first instance based on historical and anecdotal information. At the start of the more in-depth investigation in 2002, Pacific oysters of all size classes were already present near Texel. Near Ameland the development could be followed from the first observed settlement. On dense reefs each square metre may contain more than 500 adult Pacific oysters, weighing more than 100 kg per m² fresh weigh

Initial results of finger imaging using Photoacoustic Computed Tomography

We present a photoacoustic computed tomography investigation on a healthy human finger, to image blood vessels with a focus on vascularity across the interphalangeal joints. The cross-sectional images were acquired using an imager specifically developed for this purpose. The images show rich detail of the digital blood vessels with diameters between 100 $\mu$m and 1.5 mm in various orientations and at various depths. Different vascular layers in the skin including the subpapillary plexus could also be visualized. Acoustic reflections on the finger bone of photoacoustic signals from skin were visible in sequential slice images along the finger except at the location of the joint gaps. Not unexpectedly, the healthy synovial membrane at the joint gaps was not detected due to its small size and normal vascularization. Future research will concentrate on studying digits afflicted with rheumatoid arthritis to detect the inflamed synovium with its heightened vascularization, whose characteristics are potential markers for disease activity.Comment: 2 figure

Implementing strategies to overcome social-ecological traps: the role of community brokers and institutional bricolage in a locally managed marine area

We examine collaborative arrangements for resource management between communities and external agencies, with a particular interest in how community-based interventions are integrated into local contexts. This timely inquiry comes in a period when participatory resource management approaches are increasingly being applied to overcome the perpetual cycles of poverty in which poor resource-dependent people find themselves, i.e., social-ecological traps. Much of the literature on social-ecological traps has focused on identifying conditions, factors, and responses that are important in, for example, alleviating systemic poverty or developing sustainable resource management systems. However, insufficient focus has been placed on understanding the practical processes by which strategies are implemented, and how these can reflexively affect the system itself. Drawing from a case study of a locally managed marine area in Indonesia, we examine the interactions between a nongovernment organization and a target community during the implementation of a fisheries management plan. Applying insights from rural development studies, we show how external interventions, designed to pull people out of social-ecological traps, are operationalized into forms that make them locally familiar and appropriate through actions of community brokers and processes of institutional bricolage. We argue that as a consequence of implementing processes, such interventions should be expected to diverge from their initial science-based justification

Invloed van luchtvochtigheid op het scheuren van radijs

Referaat Veel gescheurde radijs bij hoge RV tijdens knolvorming In de winter geeft een hoge luchtvochtigheid tijdens de knolvormingsfase duidelijk meer gescheurde radijsknollen. Dit gebeurt met name als de luchtvochtigheid in de eerste teeltfase juist laag is geweest. Dit bleek uit onderzoek bij Wageningen UR Glastuinbouw in Bleiswijk. Bij oogst in januari scheuren radijsknollen veel gemakkelijker dan bij oogst in februari of maart. Vooral bij een knoldiameter van circa 8 mm zijn radijsjes gevoelig voor een hoge luchtvochtigheid. Om in de wintermaanden gescheurde radijs te voorkomen is het dus gewenst dat telers proberen om de luchtvochtigheid tijdens de knolvormingsfase te verlagen door meer te ventileren en/of wat te verwarmen. Abstract High humidity causes more splitting of radish tubers In winter season, high humidity in the greenhouse causes more cracking or splitting of the tubers of radish. This happens especially when humidity in the first growing phase is low. This became clear in a research by Wageningen UR Greenhouse Horticulture in Bleiswijk. Harvesting in January gives far more splitting of radish tubers than harvesting in February or March. Especially tubers with a diameter around 8 mm seems susceptible for splitting at circumstances with a high humidity. Growers are being advised to try to decrease the humidity in glasshouses by ventilating and or heating

Attentional processes of high-skilled soccer players with congenital hemiparesis: Differences related to the side of the hemispheric lesion

Contains fulltext : 72909.pdf (publisher's version ) (Closed access)We investigated attentional processes that support the performance of high-skilled soccer players with hemiparetic cerebral palsy. Participants (N = 10) dribbled a slalom course as quickly and accurately as possible under two attentional-focus manipulation conditions. In the task-relevant focus condition, they attended to the foot that was in contact with the ball, whereas in the task-irrelevant focus condition, they monitored a series of words played on a tape. The time taken to complete the slalom course was registered. Performances of individuals with left and right hemiparesis were compared to explore differential effects of hemispheric lesion. The high-skilled players with congenital hemiparesis showed similar attentional-focus effects as those previously reported in the literature for high-skilled players without neurological disorders (Beilock et al., 2002; Ford et al., 2005). Task-relevant focus increased dribbling time, whereas a task-irrelevant focus did not result in a significant change in dribbling time. These findings generalized to each of the five participants with left hemiparesis (i.e., damage to the right hemisphere). By contrast, the effects of a task-relevant focus were less consistent for participants with right hemiparesis (i.e., left-hemisphere damage). This corroborates suggestions that the reinvestment of procedural knowledge is a left-lateralized function. The implications for the training of individuals with congenital brain damage are discussed

A Framework for Directional and Higher-Order Reconstruction in Photoacoustic Tomography

Photoacoustic tomography is a hybrid imaging technique that combines high optical tissue contrast with high ultrasound resolution. Direct reconstruction methods such as filtered backprojection, time reversal and least squares suffer from curved line artefacts and blurring, especially in case of limited angles or strong noise. In recent years, there has been great interest in regularised iterative methods. These methods employ prior knowledge on the image to provide higher quality reconstructions. However, easy comparisons between regularisers and their properties are limited, since many tomography implementations heavily rely on the specific regulariser chosen. To overcome this bottleneck, we present a modular reconstruction framework for photoacoustic tomography. It enables easy comparisons between regularisers with different properties, e.g. nonlinear, higher-order or directional. We solve the underlying minimisation problem with an efficient first-order primal-dual algorithm. Convergence rates are optimised by choosing an operator dependent preconditioning strategy. Our reconstruction methods are tested on challenging 2D synthetic and experimental data sets. They outperform direct reconstruction approaches for strong noise levels and limited angle measurements, offering immediate benefits in terms of acquisition time and quality. This work provides a basic platform for the investigation of future advanced regularisation methods in photoacoustic tomography.Comment: submitted to "Physics in Medicine and Biology". Changes from v1 to v2: regularisation with directional wavelet has been added; new experimental tests have been include