Did the pile driving during the construction of the Offshore Wind Farm Egmond aan Zee, the Netherlands, impact porpoises?

The Dutch consortium "NoordzeeWind" has built the first offshore wind farm in Dutch North Sea waters, known as "Offshore Wind farm Egmond aan Zee" (OWEZ) Part of the construction works consisted of driving 36 monopiles into the sea floor, during April-June 2006. The noise levels that attended this activity may have been detrimental to marine life forms. Cetaceans in particular are sensitive to very high noise levels and a possible impact on the most abundant cetacean living off the Dutch coast, the harbour porpoise was therefore studied. Direct observations were hard to conduct, given the low (summer) densities of porpoises around the construction site. Pathological observations on stranded specimen failed to produce clear results. Inner ears of freshly stranded porpoises were examined for possible damage, but before necropsies could be conducted the animals had been stored frozen and this had destroyed any visible signs of noise-induced damage to the inner ear. Thus, the spatiotemporal pattern of porpoise strandings was examined. Porpoises did not strand in higher numbers on the coastal stretch directly east of the construction site, or to the north-east of this location (downstream) compared to other parts of the country. Porpoises also did not strand in higher than expected numbers near the construction site, at the time of construction. It was therefore concluded that the construction did not lead to visibly increased mortality of harbour porpoises. In retrospect this might have been expected, given that densities of porpoises are normally very low in summer at the site, that the building process is noisy anyway, scaring porpoises off (to safe distances) before the actual pile driving commences. A ramp-up procedure and usage of a pinger further helped to ward off porpoises from the site, before full-power pile driving started. These factors combined (timing and high before-pile driving noise levels) made it very unlikely that porpoises got in harm’s way during the construction of OWEZ

Local Birds in and around the Offhore wind Farm Egmond aan Zee (OWEZ)

This report presents the final results of a four-year study of seabird distribution patterns in and around the first offshore wind farm in Dutch North Sea waters. This wind farm, known as OWEZ (Offshore Wind farm Egmond aan Zee) is situated 10 - 18 km off the Dutch mainland coast, northwest of the port of IJmuide

Are white-beaked dolphins Lagenorhynchus albirostris food specialst? Their diet in the southern North Sea

The white-beaked dolphin Lagenorhynchus albirostris is the most numerous cetacean after the harbour porpoise Phocoena phocoena in the North Sea, including Dutch coastal waters. In this study, the diet of 45 white-beaked dolphins stranded on the Dutch coast between 1968 and 2005 was determined by analysis of stomach contents. Although 25 fish species were identified, the diet was dominated by Gadidae (98.0% by weight, 40.0% in numbers), found in all stomachs. All other prey species combined contributed little to the diet by weight (2.0%W). The two most important prey species were whiting Merlangius merlangus (91.1% frequency of occurrence (FO), 30.5%N, 37.6%W) and cod Gadus morhua (73.3%FO, 7.4%N, 55.9%W). In numbers, gobies were most common (54.6%N), but contributed little to the diet by weight (0.6%W). Three stomachs contained different prey compared to the others: one animal had taken 2250 gobies, accounting for 96.4% of all gobies found; one animal had fed on 29 small sepiolids; and one animal had solely taken haddock Melanogrammus aeglefinus. Squid and haddock were not found in any other stomach. The overall diet showed a lasting predominance of whiting and cod, without clear changes over time (35 years) or differences between sexes or size-classes of dolphins. This study adds to earlier published and unpublished data for Dutch coastal waters and agrees well with studies of white-beaked dolphins from other parts of the species’ range, in the North Sea and in Canadian waters, with Gadidae dominating the diet on both sides of the Atlantic

Shortlist Masterplan Wind Ship-based monitoring of seabirds and cetaceans

During April 2010 – February 2011, monthly surveys of seabirds and marine mammals were conducted aboard ships engaged in plankton surveys. After many years of little or no effort in far offshore areas of the DCS, this series of surveys provided the first recent ship-based data on seabirds, covering a large area (the entire Dutch Continental Shelf (DCS), including some Belgian and British waters) almost yearround. Due to changes in the design of the survey grid, the use of several ships, spells of bad weather conditions and seasonal differences in the number of daylight hours, the resulting coverage is not evenly spread in space and time. Still, both in terms of areas covered and detailed data gathered, this series of surveys complement the aerial surveys carried out under the same programme Shortlist Masterplan Wind. By surveying beyond the designated areas for round II offshore wind farms on the DCS, areas that might be targeted for round III, such as the shallow Dogger Bank area, got a first boost in T-zero survey effort. From April 2010 till February 2011 11 surveys, totalling to 48 at-sea days, 4610 5-minute counts were conducted over a distance of 9021 km. At a counting strip width of mostly 300 m (200 m over a very small percentage of the counts), this amounts to a total surveyed area of 2706 km2. The surveys have provided rough data on seabird distribution in far offshore areas. In total, 54,593 individuals of 90 bird species were recorded, from which 15,003 individuals of 36 species were recorded within the counting strip. Marine mammals were represented by 616 individuals of seven species, of which 389 individuals of six species were seen within the counting strip. Flying heights were noted for 5044 clusters of individuals, covering 75 species. Behaviour was noted for 1790 (clusters of) individuals. Apart from birds and marine mammals, 352 balloons were counted (of which 164 were within the counting strip) and proved omnipresent in periods of offshore winds. These surveys have identified several issues that should be taken into account in future planning of wind farms. Divers, which are the highest ranked species in terms of sensitivity to wind farms, can be encountered migrating anywhere in offshore waters and sightings of White-billed Divers at the Dogger Bank suggest the existence of a small wintering population of this near-threatened species. In relation to this, potential effects of wind farms on offshore species, such as Northern Fulmars, Atlantic Puffins, Little Auks and cetaceans, are unknown as current wind farms are located near shore where these species do not occur in large numbers

Bruinvisstrandingen in Nederland in 2006: achtergronden, leeftijdsverdeling, sexratio, voedselkeuze en mogelijke oorzaken

Bruinvissen komen in steeds grotere aantallen voor in de Nederlandse (kust)wateren. In de periode 1960␂ 1985 was de bruinvis vrijwel uitgestorven in Nederland, maar de soort heeft een spectaculaire comeback gemaakt. Terwijl het aantal waarnemingen sterk toenam werd er ook een toename gevonden in het aantal dieren dat dood op de kust aanspoelde. In september 2006 werden 64 bruinvissen onderzocht die eerder dat jaar dood op de Nederlandse kust waren aangespoel

Duurzaamheid van de mechanische wadpierenvisserij in de Waddenzee

In de Waddenzee beoefenen vier bedrijven de mechanische wadpierenvisserij: drie bedrijven op het oostelijke Balgzand en één bedrijf bij Texel. Samen vissen zij momenteel jaarlijks rond de 11,5 miljoen wadpieren (Arenicola marina) op. De pieren dienen als aas in de sportvisserij. Het bedrijf bij Texel slaagt erin al jarenlang met eenzelfde visserijinspanning min of meer dezelfde vangsten te halen. Op het Balgzand is de pierenstand sterk teruggelopen, mogelijk door overbevissing, en zijn de vangsten ongeveer gehalveerd terwijl het brandstofgebruik min of meer hetzelfde is gebleven. Om tot uitspraken te komen over de mate van duurzaamheid van deze vorm van visserij zijn de bedrijfsgegevens geanalyseerd van de pierenwinbedrijven, uitgaande van de stelling: Een visserij is duurzaam, als over een lange reeks van jaren de opbrengst niet daalt, en de zogenaamde catch per unit effort (CPU) (pieren per liter brandstof) niet verandert. De ontwikkeling van het wadpierenbestand op het Balgzand is geanalyseerd aan de hand van NIOZ data (beviste/onbeviste delen). Tevens is in dit rapport literatuuronderzoek verricht naar de ecologie van de wadpier, de effecten van pierenvisserij op het bodemleven en naar beheer bij andere kleinschalige vormen van bodemvisserij. De resultaten van deze studie zijn van belang in het kader van de vergunningverlening en voor het (verder) verduurzamen van deze vorm van visserij

The <i>Tricolor</i> oil spill: characteristics of seabirds found oiled in The Netherlands

Between 28 January and 9 February 2003, c. 4000 heavily oiled seabirds washed ashore in The Netherlands, representing 21% of c. 20,000 casualties of the Tricolor oil spill recovered in northern France, Belgium and The Netherlands. Common Guillemot Uria aalge, Razorbill Alca torda and Black-legged Kittiwake Rissa tridactyla together represented 91% of the birds found and collected. Nearly 600 Common Guillemots and 267 Razorbills were examined in more detail and a large part of these birds were dissected. Autopsies revealed that the auks were in excellent condition when they died, indicating instant death through suffocation in oil. Of 440 Guillemots that could be aged, 76% were mature birds, with a sex ratio significantly different from equal (65% males). Of 262 Razorbills, 77% were adults and 62% were males. Biometrics suggested that the Guillemots belonged to the nominate subspecies, whereas the Razorbills were classified as A.t. islandica. Using the European cline in wing length, the Guillemots possibly originated from Scottish colonies (57°N), a finding that was supported by ringing recoveries (Scottish east coast). The total mortality caused by the Tricolor spill, 2-5 times the number of casualties recovered, may be estimated at 40 000-100 000 seabirds (25 000-62 500 Guillemots, 8000-20 000 Razorbills). With such a high proportion of mature birds in excellent pre-breeding condition being killed, an immediate effect on the breeding population is foreseen, rather than a diffuse and delayed effect if more immatures would have been killed. It is argued that effect of the Tricolor on seabirds would have been considerably less, had the salvage operation be postponed till summer. The Channel area is of the highest vulnerability to oil pollution only in winter (Dec-Mar)