Geert Aarts

Geert Aarts
Wageningen University & Research | WUR · Wageningen Marine Research

About

82
Publications
21,489
Reads
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2,587
Citations
Citations since 2017
23 Research Items
1486 Citations
2017201820192020202120222023050100150200250
2017201820192020202120222023050100150200250
2017201820192020202120222023050100150200250
2017201820192020202120222023050100150200250
Additional affiliations
August 2011 - present
Wageningen University & Research
Position
  • PostDoc Position
Education
May 2003 - May 2006
Sea Mammal Research Unit
Field of study
  • Modelling marine mammal spatial distribution and habitat preference
September 1997 - August 2002
Wageningen University & Research
Field of study
  • Biology: Animal Ecology

Publications

Publications (82)
Preprint
Spatial segregation of foraging areas among conspecifics breeding in different colonies has been observed in several colonial vertebrates and is assumed to originate from competition and information use. Segregation between sub-groups of foraging animals from the same colony (hereafter sub-colonies) has comparatively received limited attention, eve...
Article
Given the patchiness and long-term predictability of marine resources, memory of high-quality foraging grounds is expected to provide fitness advantages for central place foragers. However, it remains challenging to characterize how marine predators integrate memory with recent prey encounters to adjust fine-scale movement and use of foraging patch...
Article
Full-text available
Many ecological studies rely on count data and involve manual counting of objects of interest, which is time-consuming and especially disadvantageous when time in the field or lab is limited. However, an increasing number of works uses digital imagery, which opens opportunities to automatise counting tasks. In this study, we use machine learning to...
Article
Full-text available
Climate warming in the Arctic has led to warmer and earlier springs, and as a result, many food resources for migratory animals become available earlier in the season, as well as become distributed further northwards. To optimally profit from these resources, migratory animals are expected to arrive earlier in the Arctic, as well as shift their own...
Article
Full-text available
Central place foragers often segregate in space, even without signs of direct agonistic interactions. Using parsimonious individual-based simulations, we show that for species with spatial cognitive abilities, individual-level memory of resource availability can be sufficient to cause spatial segregation in the foraging ranges of colonial animals....
Article
Full-text available
The increase in anthropogenic activities and their potential impact on wildlife requires the establishment of monitoring programs and identification of indicator species. Within marine habitats, marine mammals are often used as ecosystem sentinels, which has led to investigations into their abundance, distribution, and mortality patterns. However,...
Article
Full-text available
To support sustainable management of apex predator populations, it is important to estimate population size and understand the drivers of population trends to anticipate the consequences of human decisions. Robust population models are needed, which must be based on realistic biological principles and validated with the best available data. A team...
Article
Full-text available
Understanding why animals move as they do when searching for resources is a central question in ecology, and a prerequisite for the development of predictive process-based models for conservation and management. Many species are central-place foragers (CPF). While several models for CPFs have been proposed, they often assume well-defined return rul...
Book
Full-text available
Ecologists develop species-habitat association (SHA) models to understand where species occur, why they are there and where else they might be. This knowledge can be used to designate protected areas, estimate anthropogenic impacts on living organisms and assess risks from invasive species or disease spill-over from wildlife to humans. Here, we des...
Article
Organisms need access to particular habitats for their survival and reproduction. However, even if all necessary habitats are available within the broader environment, they may not all be easily reachable from the position of a single individual. Many species distribution models consider populations in environmental (or niche) space, hence overlook...
Article
High-resolution vessel monitoring (VMS) data have led to detailed estimates of the distribution of fishing in both time and space. While several studies have documented large-scale changes in fishing distribution, fine-scale patterns are still poorly documented, despite VMS data allowing for such analyses. We apply a methodology that can explain an...
Article
Full-text available
Abstract Historic hunting has led to severe reductions of many marine mammal species across the globe. After hunting ceased, some populations have recovered to pre‐exploitation levels and may have regained their prominent position as top predator in marine ecosystems. Also, the harbor seal population in the international Wadden Sea grew at an expon...
Article
Full-text available
This erratum concerns Figure 9 of the original article in which the line delimiting two effect types ("Permanent hearing loss increasingly likely" and "Permanent hearing loss very likely") was misplaced. This error, which has now been corrected, affects neither the main text nor the conclusion of the study. The authors apologize for the error.
Preprint
Full-text available
Historic hunting has led to severe reductions of many marine mammal species across the globe. After hunting ceased, some populations have recovered to pre-exploitation levels, and may again act as a top-down regulatory force on marine ecosystems. Also the harbour seal population in the international Wadden Sea grew at an exponential rate following...
Article
Full-text available
Terrestrial and marine wildlife populations have been severely reduced by hunting, fishing and habitat destruction, especially in the last centuries. Although management regulations have led to the recovery of some populations, the underlying processes are not always well understood. This study uses a 40-year time series of counts of harbour seals...
Data
Overview of number of surveys per year. M = moult, P = pupping season. (DOCX)
Data
Annual maximum counts for total numbers (during moult) and pups. Left column indicates the periods. (DOCX)
Technical Report
Full-text available
The so-called FaunaGuard-PM (FG-PM) has been developed to deter harbour porpoises from localised offshore anthropogenic activities in order to minimize potential negative effects of these activities on porpoise hearing. The efficiency of the FG-PM was tested in a pool and the distance up to which it would deter porpoises in the field has been model...
Poster
Full-text available
The combined method of passive acoustic and visual monitoring has proven successful for studying elusive harbour porpoises (Phocoena phocoena). However, to convert the recorded numbers of echolocation clicks to densities, detectability estimates are needed. So far, the estimated best detection distance is between 22-107m (Tougaard et al., 2006; Kos...
Article
Full-text available
Surveys of gray seals (Halichoerus grypus) during the molt period, when they are abundant on land, can be used to monitor changes in population size, but accurate interpretation of results requires an understanding of the molt process and how it may vary between years. This study investigates variability in onset (start date) and duration of visibl...
Article
Full-text available
Anthropogenic sound in the marine environment can have negative consequences for marine fauna. Since most sound sources are intermittent or continuous, estimating how many individuals are exposed over time remains challenging, as this depends on the animals’ mobility. Here we explored how animal movement influences how many, and how often, animals...
Article
Full-text available
Within the Gulf of Guinea high levels of fisheries-related cetacean mortality (bycatch and direct-capture) has been documented. For locally rare species such removals could potentially lead to significant population level effects. However, information on the cetacean abundance and distribution is scarce. Similarly, it remains largely unreported whe...
Article
Full-text available
Effective species conservation and management requires information on species distribution patterns, which is challenging for highly mobile and cryptic species that may be subject to multiple anthropogenic stressors across international boundaries. Understanding species-habitat relationships can improve the assessment of trends and distribution by...
Conference Paper
Full-text available
New island development is not very often observed in the Dutch Wadden Sea. Richel had long been an unvegetated sand bar, located on the Wadden Sea side of Vlieland. The past ten years, vegetation has established and an embryonic dune field has developed. The dune field is dominated by Sand Couch (Elytrigia juncea), and was in 2014 home to at least...
Article
Full-text available
Large amounts of legacy unexploded ordnance (UXO) are still present in the North Sea. UXO are frequently accidentally encountered by fishermen and dredging vessels. Out of concern for human safety and to avoid damage to equipment and infrastructure from uncontrolled explosions, most reported UXO found in the Dutch Continental Shelf (DCS) are detona...
Article
Full-text available
The European Union requires member states to achieve or maintain good environmental status for their marine territorial waters and explicitly mentions potentially adverse effects of underwater sound. In this study, we focused on producing maps of underwater sound from various natural and anthropogenic origins in the Dutch North Sea. The source prop...
Technical Report
Full-text available
Atlantic grey seals (Halichoerus grypus grypus) started recolonising Dutch coastal haul-outs in the 1950s, after >2000 years of rarity in the Dutch coastal zone which was caused mainly by human hunting. The first pup-birth was recorded in 1985 at the Wadden Sea sandbank of Engelschhoek. Sandbanks in the Wadden Sea form and recede in periods of de...
Article
Full-text available
Estimating the spatial position of organisms is essential to quantify interactions between the organism and the characteristics of its surroundings, for example, predator–prey interactions, habitat selection, and social associations. Because marine mammals spend most of their time under water and may appear at the surface only briefly, determining...
Article
Full-text available
Although classical ecological theory (e.g., on ideal free consumers) recognizes the potential effect of population density on the spatial distribution of animals, empirical species distribution models assume that species-habitat relationships remain unchanged across a range of population sizes. Conversely, even though ecologicalmodels and experimen...
Article
Gray seals were first observed breeding in the Dutch Wadden Sea in 1985, after centuries of absence. The breeding colony there is now the largest on the European continent. We describe the changes in gray seal numbers and their geographical expansion, and estimate how these processes were influenced by immigration from other colonies. Counts of hau...
Article
Full-text available
On land, species from all trophic levels have adapted to fill vacant niches in environments heavily modified by humans (e.g. [1 • Gloor S. • Bontadina F. • Hegglin D. • Deplazes P. • Breitenmoser U. The rise of urban fox populations in Switzerland.Mammal. Biol. 2001; 66: 155-164 • Google Scholar ]). In the marine environment, ocean infrastructure...
Conference Paper
Full-text available
Little is known about the distribution of small cetaceans in the offshore areas of the North Sea. However, information on abundance and distribution is essential to assess the impact of climate change and other anthropogenic stressors, to infer on the conservation status and to identify areas of high ecological importance for the species involved....
Article
Full-text available
The influence of topographic and temporal variables on cetacean distribution at a fine-scale is still poorly understood. To study the spatial and temporal distribution of harbour porpoise Phocoena phocoena and the poorly known Risso's dolphin Grampus griseus we carried out land-based observations from Bardsey Island (Wales, UK) in summer (2001-2007...
Conference Paper
Full-text available
Worldwide, many seal populations have increased dramatically in recent decades. The increases may be related to a range of local influences, however, the global distribution of such increases suggests non-local factors are involved. One seal that has exhibited such an increase is the Australian fur seal, Arctocephalus pusillus doriferus. This South...
Article
Full-text available
Engelhard, G. H., Peck, M. A., Rindorf, A., Smout, S. C., van Deurs, M., Raab, K., Andersen, K. H., Garthe, S., Lauerburg, R. A. M., Scott, F., Brunel, T., Aarts, G., van Kooten, T., and Dickey-Collas, M. Forage fish, their fisheries, and their predators: who drives whom? – ICES Journal of Marine Science, 71: . The North Sea has a diverse forage fi...
Article
Full-text available
Dickey-Collas, M., Engelhard, G. H., Rindorf, A., Raab, K., Smout, S., Aarts, G., van Deurs, M., Brunel, T., Hoff, A., Lauerburg R. A. M., Garthe, S., Haste Andersen, K., Scott, F., van Kooten, T., Beare, D., and Peck, M. A. Ecosystem-based management objectives for the North Sea: riding the forage fish rollercoaster. – ICES Journal of Marine Scien...
Article
Full-text available
The harbour porpoise (Phocoena phocoena) returned in Dutch waters in the late 20th century after a near absence of approximately three decades. Inspired by historical studies of harbour porpoises in the Marsdiep area (western Wadden Sea), mainly in the 1930s and 1940s, a study was initiated in the same area in 2011 to see if porpoises are now as co...
Article
Full-text available
The determination of temporal niche dynamics under field conditions is an important component of a species’ ecology. Recent developments in niche mapping, and the possibility to account for spatial autocorrelation in species distributions, hold promise for the statistical approach explored here. Using species counts from a landscape-scale benthic m...
Article
Full-text available
If animals moved randomly in space, the use of different habitats would be proportional to their availability. Hence, deviations from proportionality between use and availability are considered the tell-tale sign of preference. This principle forms the basis for most habitat selection and species distribution models fitted to use-availability or co...
Article
Full-text available
1. The problems of analysing used-available data and presence-only data are equivalent, and this paper uses this equivalence as a platform for exploring opportunities for advancing analysis methodology. 2. We suggest some potential methodological advances in used-available analysis, made possible via lessons learnt in the presence-only literature,...
Article
Full-text available
Coastal protection measures are planned and executed worldwide to combat the effects of global warming and climate change, in particular the acceleration of sea level rise, higher storm surge flooding and extensive coastal inundation. The extent to which these defensive measures may impact coastal and estuarine ecosystems is still poorly understood...
Article
Surveys are often insufficient to accurately capture the distribution of a species in both space and time. Complementary to the use of research vessel data, platforms of opportunity can be a powerful strategy to monitor species distributions at high temporal and spatial resolution.In this study we use data from commercial fishing vessels, collectin...
Article
Full-text available
The harbour porpoise (Phocoena phocoena) is the most abundant marine mammal species in Dutch waters. Nevertheless until 2010 abundance estimates for the entire Dutch Continental Shelf (DCS) were missing. Aerial surveys along designed track lines in July 2010, October/November 2010 and March 2011 provided density and abundance estimates for the DCS....
Article
Full-text available
The harbour porpoise returned in Dutch waters in the late 20th century after a near-absence of approximately three decades. Inspired by historical studies of harbour porpoises in the Marsdiep area (western Wadden Sea), mainly in the 1930s and 1940s, a feasibility study was initiated in the same area in 2011 to see if porpoises are now common enough...
Article
Full-text available
The development and maintenance of spatial patterns and the way they affect the dynamics of populations and ecosystems is a key issue in ecology. Since each individual and each species experiences the environment on a unique range of scales, it is vital to determine the spatial scales across which organisms interact with each other and the structur...