Basisinformatie over de Borkumer Stenen, Bruine Bank en Gasfonteinen, potentieel te beschermen gebieden op het NCP

In dit rapport worden drie gebieden in de Noordzee nader beschouwd: de Borkumer Stenen, Gasfonteinen en de Bruine Bank, zoals aangekondigd in het in 2005 verschenen rapport ‘Gebieden met bijzondere ecologische waarden op het Nederlands Continentaal Plat’ (Lindeboom et al. 2005). De informatie in dit rapport is bijeen gebracht door middel van literatuuronderzoek en een korte veldstudie. De studie is uitgevoerd om te beoordelen of de Borkumer Stenen, Gasfonteinen en de Bruine Bank ook als Natura 2000 gebieden zouden kunnen worden aangemerkt

Foraging rhythm of great crested grebes Podiceps cristatus adjusted to diel variations in the vertical distribution of their prey Osmerus eperlanus in a shallow eutrophic lake in The Netherlands

Great crested grebes Podiceps cristatus only foraged for an hour or two during dawn and again during dusk on Lake IJsselmeer in August-September. During this time of the year the adult birds are in wing moult and temporarily unable to fly. The food of grebes consisted almost exclusively of smelt Osmerus eperlanus, the most numerous pelagic fish. Simultaneous sonar registrations and trawl net fishing showed that smelt moved to the water surface during the twilight periods. During day and night they were concentrated near the bottom. We argue that grebes have the best foraging opportunities during twilight when much of their prey is near the surface, where light intensities allow the fish to be detected and captured. When the smelt are in the upper water layers the distance to be covered to get the prey (i.e. diving time and cost) is also least

Competitive food exploitation of smelt Osmerus eperlanus by great crested grebes Podiceps cristatus and perch Perca fluviatilis at Lake IJsselmeer, The Netherlands

The impact of predation by an avian predator (great crested grebe Podiceps cristatus) and a predatory fish (perch Perca fluviatilis) on a common resource, the small planktivorous fish smelt (Osmerus eperlanus) was studied in Lake IJsselmeer, The Netherlands, in July-October 1985-1988. At this time of the year the grebes are in simultaneous wing-moult and therefore temporarily flightless. Four factors limit the predation pressure by grebes: (1) an underwater visibility threshold of c. 40 cm Secchi depth is the lower limit at which large numbers attend the moulting site, (2) a lower density threshold of exploitable smelt biomass of c. 30 kg/ha determines the actual fishing areas, (3) a fish size threshold of 6.5 cm total length further limits prey availability, and (4) the vertical movements of the prey impose a strong (diel) time constraint on the birds, allowing only crepuscular foraging. Perch, the other main predator in this system, is less restricted in its foraging. Perch were found to be in direct competition with the grebes, preying heavily on the juvenile smelt. Over the 4 years of study 90% of all predation from 15 July to 15 October (72 233 kg/ha) was due to perch. The high level of predation by birds and fish was only possible due to a continuous immigration of smelt into the area (1.45 kg/ha per day). In three of the four years, however, the combined predation by fish and birds surpassed the immigration rate of the prey, which led to a strong reduction in smelt stocks in the study area. A conceptual model is developed to describe the different sets of constraints on the grebes' foraging. First, the state of eutrophication in relation to the weather condition determines the degree of algal blooms, and thus underwater visibility, in late summer. This is the major factor governing the numbers of grebes on the moulting area. Second, the size of the population of predatory fish determines the overall food availability (biomass and size distribution of smelt). These factors are partly interconnected and related to human action (pollution, fisheries). It is suggested that, despite deteriorating visibility conditions, the largest moulting site for grebes in Europe at Lake IJsselmeer exists because the stocks of predatory fish are kept low by overfishing

Unscheduled return visits to a Dutch inner-city emergency department

© 2014, van der Linden et al.; licensee Springer. Background: Unscheduled return visits to the emergency department (ED) may reflect shortcomings in care. This study characterized ED return visits with respect to incidence, risk factors, reasons and post-ED disposition. We hypothesized that risk factors for unscheduled return and reasons for returning would differ from previous studies, due to differences in health care systems. Methods: All unscheduled return visits occurring within 1 week and related to the initial ED visit were selected. Multivariable logistic regression was conducted to determine independent factors associated with unscheduled return, using patient information available at the initial visit. Reasons for returning unscheduled were categorized into illness-, patient- or physician-related. Post-ED disposition was compared between patients with unscheduled return visits and the patients who did not return. Results: Five percent (n = 2,492) of total ED visits (n = 49,341) were unscheduled return visits. Patients with an urgent triage level, patients presenting during the night shift, with a wound or local infection, abdominal pain or urinary problems were more likely to return unscheduled. Reasons to revisit unscheduled were mostly illness-related (49%) or patient-related (41%). Admission rates for returning patients (16%) were the same as for the patients who did not return (17%). Conclusions: Apart from abdominal complaints, risk factors for unscheduled return differ from previous studies. Short-term follow-up at the outpatient clinic or general practitioner for patients with urgent triage levels and suffering from wounds or local infections, abdominal pain or urinary problem might prevent unscheduled return

Self-referring patients at the emergency department: appropriateness of ED use and motives for self-referral

© 2014, van der Linden et al.; licensee Springer. Background: Nearly all Dutch citizens have a general practitioner (GP), acting as a gatekeeper to secondary care. Some patients bypass the GP and present to the emergency department (ED). To make best use of existing emergency care, Dutch health policy makers and insurance companies have proposed the integration of EDs and GP cooperatives (GPCs) into one facility. In this study, we examined ED use and assessed the characteristics of self-referrals and non-self-referrals, their need for hospital emergency care and self-referrals' motives for presenting at the ED. Methods: A descriptive cohort study was conducted in a Dutch level 1 trauma centre. Differences in patient characteristics, time of presentation and need for hospital emergency care were analysed using χ2 tests and t tests. A patient was considered to need hospital emergency care when he/she was admitted to the hospital, had an extremity fracture and/or when diagnostic tests were performed. Main determinants of self-referral were identified via logistic regression. Results: Of the 5,003 consecutive ED patients registering within the 5-week study period, 3,028 (60.5%) were self-referrals. Thirty-nine percent of the self-referrals had urgent acuity levels, as opposed to 65% of the non-self-referrals. Self-referrals more often suffered from injuries (49 vs. 20%). One third of the self-referrals presented during office hours. Of all self-referrals, 51% needed hospital emergency care. Younger age; non-urgent acuity level; chest pain, ear, nose or throat problems; and injuries were independent predictors for self-referral. Most cited motives for self-referring were ‘accessibility and convenience’ and perceived ‘medical necessity’. Conclusions: A substantial part of the self-referrals needed hospital emergency care. The 49% self-referrals who were eligible for GP care presented during out-of-hours as well as during office hours. This calls for an integrative approach to this health care problem