Survey for small cetaceans over the Dogger Bank and adjacent areas in summer 2011

Review of New Information on Population Size, Distribution, Structure and Causes of Any Changes. The distribution of small cetaceans in the offshore areas of the North Sea has been in the interest of researchers for many years. Information on abundance and distribution is essential to assess the impact of bycatch and other anthropogenic threats, and as basis for management plans to ensure the favourable conservation status of these species. In 2011 we conducted a dedicated aerial line transect survey of the Dogger Bank and adjacent areas (UK, NL, DK, GE waters) in order to investigate the importance of this marine feature as summer habitat for marine mammals

Spatiotemporal mortality and demographic trends in a small cetacean: Strandings to inform conservation management

With global increases in anthropogenic pressures on wildlife populations comes a responsibility to manage them effectively. The assessment of marine ecosystem health is challenging and often relies on monitoring indicator species, such as cetaceans. Most cetaceans are however highly mobile and spend the majority of their time hidden from direct view, resulting in uncertainty on even the most basic population metrics. Here, we discuss the value of long-term and internationally combined stranding records as a valuable source of information on the demographic and mortality trends of the harbour porpoise (Phocoena phocoena) in the North Sea. We analysed stranding records (n = 16,181) from 1990 to 2017 and demonstrate a strong heterogeneous seasonal pattern of strandings throughout the North Sea, indicative of season-specific distribution or habitat use, and season-specific mortality. The annual incidence of strandings has increased since 1990, with a notable steeper rise particularly in the southern North Sea since 2005. A high density of neonatal strandings occurred specifically in the eastern North Sea, indicative of areas important for calving, and large numbers of juvenile males stranded in the southern parts, indicative of a population sink or reflecting higher male dispersion. These findings highlight the power of stranding records to detect potentially vulnerable population groups in time and space. This knowledge is vital for managers and can guide, for example, conservation measures such as the establishment of time-area-specific limits to potentially harmful human activities, aiming to reduce the number and intensity of human-wildlife conflicts

Harbour porpoise (<i>Phocoena phocoena</i>) in the Wadden Sea World Heritage Site and requirements for trilateral monitoring

The harbour porpoise (Phocoena phocoena) is considered part of the ‘Outstanding Universal Value’ characterising the Wadden Sea World Heritage Site (WS WHS). The Trilateral Wadden Sea Plan aims to preserve the conservation status of the Trilateral Wadden Sea Cooperation Area, encompassing the WS WHS. The plan has specified two conservation targets for the harbour porpoise: (1) viable stocks and a natural reproduction capacity and (2) conservation of habitat quality for its conservation. To assess the current occurrence of the harbour porpoise in the Wadden Sea area, we collated and analysed data from regional and national research projects using telemetry, aerial surveys, strandings and passive acoustic monitoring, obtained over the years 1990–2020. The results illustrate that porpoises occur in both offshore and intertidal waters, showing seasonal movements and changes in local occurrence over time. Some porpoises displayed limited home ranges throughout the year, suggesting a possible residency for some of the animals using the Wadden Sea area. We also showed that methods, frequency and spatial coverage of monitoring activities vary among the countries Denmark, Germany and the Netherlands. We discuss the suitability of the different methods both regarding the challenges of monitoring in the complex Wadden Sea habitat as well as their ability to target the conservation aims of the WHS. We give several recommendations to assess the status of the species to meet the identified conservation aims

The stranding anomaly as population indicator: the case of Harbour Porpoise <i>Phocoena phocoena</i> in North-Western Europe

Ecological indicators for monitoring strategies are expected to combine three major characteristics: ecological significance, statistical credibility, and cost-effectiveness. Strategies based on stranding networks rank highly in cost-effectiveness, but their ecological significance and statistical credibility are disputed. Our present goal is to improve the value of stranding data as population indicator as part of monitoring strategies by constructing the spatial and temporal null hypothesis for strandings. The null hypothesis is defined as: small cetacean distribution and mortality are uniform in space and constant in time. We used a drift model to map stranding probabilities and predict stranding patterns of cetacean carcasses under H-0 across the North Sea, the Channel and the Bay of Biscay, for the period 1990-2009. As the most common cetacean occurring in this area, we chose the harbour porpoise <i>Phocoena phocoena</i> for our modelling. The difference between these strandings expected under H-0 and observed strandings is defined as the stranding anomaly. It constituted the stranding data series corrected for drift conditions. Seasonal decomposition of stranding anomaly suggested that drift conditions did not explain observed seasonal variations of porpoise strandings. Long-term stranding anomalies increased first in the southern North Sea, the Channel and Bay of Biscay coasts, and finally the eastern North Sea. The hypothesis of changes in porpoise distribution was consistent with local visual surveys, mostly SCANS surveys (1994 and 2005). This new indicator could be applied to cetacean populations across the world and more widely to marine megafauna

Retrospective evaluation of whole exome and genome mutation calls in 746 cancer samples

Funder: NCI U24CA211006Abstract: The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC) curated consensus somatic mutation calls using whole exome sequencing (WES) and whole genome sequencing (WGS), respectively. Here, as part of the ICGC/TCGA Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium, which aggregated whole genome sequencing data from 2,658 cancers across 38 tumour types, we compare WES and WGS side-by-side from 746 TCGA samples, finding that ~80% of mutations overlap in covered exonic regions. We estimate that low variant allele fraction (VAF < 15%) and clonal heterogeneity contribute up to 68% of private WGS mutations and 71% of private WES mutations. We observe that ~30% of private WGS mutations trace to mutations identified by a single variant caller in WES consensus efforts. WGS captures both ~50% more variation in exonic regions and un-observed mutations in loci with variable GC-content. Together, our analysis highlights technological divergences between two reproducible somatic variant detection efforts

Seasonal distribution of harbour porpoises and possible intereference of offshore wind farms in the German North Sea

The seasonal distribution of harbour porpoises in the German North Sea was investigated, hot spot areas were identified and the proportion of porpoises potentially affected by the imminent construction of offshore wind farms was estimated. Data were collected during dedicated aerial surveys conducted year-round between 2002 and 2006 following line transect methodology. Survey effort amounted to 44 739 km during which a total of 5121 harbour porpoises was detected, including 258 calves. Our data suggest that porpoises move to distinct areas on a seasonal basis as their biological requirements change. They move into German waters in early spring, reach high numbers in early summer and move out of the area in autumn. The abundance estimates for the German exclusive economic zone and 12 n mile zone were highest in spring (55 048 animals; 95% CI: 32 395 to 10 1671) and summer (49 687 animals; 95% CI: 29 009 to 96 385) and lowest in autumn with 15 394 animals (95% CI: 8906 to 29 470). Important aggregation zones were detected in offshore waters: in spring, 2 hot spots, Borkum Reef Ground and Sylt Outer Reef (SOR), were identified as key foraging areas. In summer, only the large hot spot SOR persisted, causing a strong north¿south density gradient. In autumn, porpoises were more evenly distributed. Most mother-calf pairs were observed during spring and summer in the SOR, underlining its importance as a foraging area when reproductive costs are high. Spatial overlap exists between important areas for porpoises and areas where offshore wind farms are currently licensed or planned. The proportion of the national stock possibly exposed to the construction noise of 18 licensed wind farms was estimated applying different scenarios. Within a 20 km zone of responsiveness - as worst case scenario - 39% of the harbour porpoise stock in the German EEZ could be affected during construction

Harbour porpoise Phocoena phocoena abundance in the southwestern Baltic Sea

Harbour porpoise Phocoena phocoena is the only cetacean species resident in the Baltic Sea. At least 2 different subpopulations occur in this area, with a presumed demarcation line in the western Baltic Sea. Aerial surveys were conducted during different seasons in the years 2002 to 2006, to obtain estimates of porpoise abundance for the southwestern Baltic. Within the survey area, 3 strata were defined. In total, 46 surveys were completed for these strata. Abundance estimates and corresponding confidence intervals (CI) were calculated for each stratum separately for each survey. Density between areas varied seasonally and spatially, with the western study area (Kiel Bight) generally showing the highest density. Whenever all 3 strata were covered within 25 consecutive days, abundance for the overall survey area was calculated. Ten surveys met these criteria. Overall abundance in the western Baltic varied between surveys, with the lowest value in March 2003 (457 ind.; 95% CI: 0 to 1632), and the highest estimate in May 2005 (4610 ind.; 95% CI: 2259 to 9098). The results of all other surveys were in the range from 1352 to 2905 ind., with largely overlapping confidence intervals. Applying the only available bycatch estimates (which include no measure of precision) currently available for the German Baltic region, the percent of porpoise bycatch in the western Baltic lies within a range of 1.78 to 17.94% of the local population. To increase the precision of bycatch rates, more detailed bycatch estimates for this region are needed. Nevertheless, the results indicate that bycatch is a major threat to harbour porpoises throughout the western Baltic Sea

Survey for small cetaceans over the Dogger Bank and adjacent areas in summer 2011

Review of New Information on Population Size, Distribution, Structure and Causes of Any Changes. The distribution of small cetaceans in the offshore areas of the North Sea has been in the interest of researchers for many years. Information on abundance and distribution is essential to assess the impact of bycatch and other anthropogenic threats, and as basis for management plans to ensure the favourable conservation status of these species. In 2011 we conducted a dedicated aerial line transect survey of the Dogger Bank and adjacent areas (UK, NL, DK, GE waters) in order to investigate the importance of this marine feature as summer habitat for marine mammals

Modelling harbour porpoise seasonal density as a function of the German Bight environment: implications for management

A classical user–environment conflict could arise between the recent expansion plans of offshore wind power in European waters and the protection of the harbour porpoise Phocoena phocoena, an important top predator and indicator species in the North Sea. There is a growing demand for predictive models of porpoise distribution to assess the extent of potential conflicts and to support conservation and management plans. Here, we used a range of oceanographic parameters and generalised additive models to predict harbour porpoise density and to investigate seasonal shifts in porpoise distribution in relation to several static and dynamic predictors. Sightings were collected during dedicated line-transect aerial surveys conducted year-round between 2002 and 2005. Over the 4 yr, survey effort amounted to 38720 km, during which 3887 harbour porpoises were sighted. Porpoises aggregated in distinct hot spots within their seasonal range, but the importance of key habitat descriptors varied between seasons. Predictors explaining most of the variance were the hydrographical parameter ‘residual current’ and proxies for primary production and fronts (chlorophyll and nutrients) as well as the interaction ‘distance to coast/water depth’. Porpoises preferred areas with stronger currents and concentrated in areas where fronts are likely. Internal cross-validation indicated that all models were highly robust. In addition, we successfully externally validated our summer model using an independent data set, which allowed us to extrapolate our predictions to a more regional scale. Our models improve the understanding of determinants of harbour porpoise habitat in the North Sea as a whole and inform management frameworks to determine safe limits of anthropogenic impact