Publications by authors named "Morten Frederiksen"

21 Publications

  • Page 1 of 1

A microneedle platform for buccal macromolecule delivery.

Sci Adv 2021 Jan 22;7(4). Epub 2021 Jan 22.

Department of Chemical Engineering and Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.

Alternative means for drug delivery are needed to facilitate drug adherence and administration. Microneedles (MNs) have been previously investigated transdermally for drug delivery. To date, drug loading into MNs has been limited by drug solubility in the polymeric blend. We designed a highly drug-loaded MN patch to deliver macromolecules and applied it to the buccal area, which allows for faster delivery than the skin. We successfully delivered 1-mg payloads of human insulin and human growth hormone to the buccal cavity of swine within 30 s. In addition, we conducted a trial in 100 healthy volunteers to assess potential discomfort associated with MNs when applied in the oral cavity, identifying the hard palate as the preferred application site. We envisage that MN patches applied on buccal surfaces could increase medication adherence and facilitate the painless delivery of biologics and other drugs to many, especially for the pediatric and elderly populations.
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http://dx.doi.org/10.1126/sciadv.abe2620DOI Listing
January 2021

Meeting Paris agreement objectives will temper seabird winter distribution shifts in the North Atlantic Ocean.

Glob Chang Biol 2021 Apr 20;27(7):1457-1469. Epub 2021 Jan 20.

Centre d'Etudes Biologiques de Chizé (CEBC), UMR 7372 CNRS-Univ. La Rochelle, La Rochelle, France.

We explored the implications of reaching the Paris Agreement Objective of limiting global warming to <2°C for the future winter distribution of the North Atlantic seabird community. We predicted and quantified current and future winter habitats of five North Atlantic Ocean seabird species (Alle alle, Fratercula arctica, Uria aalge, Uria lomvia and Rissa tridactyla) using tracking data for ~1500 individuals through resource selection functions based on mechanistic modeling of seabird energy requirements, and a dynamic bioclimate envelope model of seabird prey. Future winter distributions were predicted to shift with climate change, especially when global warming exceed 2°C under a "no mitigation" scenario, modifying seabird wintering hotspots in the North Atlantic Ocean. Our findings suggest that meeting Paris agreement objectives will limit changes in seabird selected habitat location and size in the North Atlantic Ocean during the 21st century. We thereby provide key information for the design of adaptive marine-protected areas in a changing ocean.
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http://dx.doi.org/10.1111/gcb.15497DOI Listing
April 2021

Ingestible transiently anchoring electronics for microstimulation and conductive signaling.

Sci Adv 2020 Aug 28;6(35):eaaz0127. Epub 2020 Aug 28.

Department of Chemical Engineering and David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.

Ingestible electronic devices enable noninvasive evaluation and diagnosis of pathologies in the gastrointestinal (GI) tract but generally cannot therapeutically interact with the tissue wall. Here, we report the development of an orally administered electrical stimulation device characterized in ex vivo human tissue and in in vivo swine models, which transiently anchored itself to the stomach by autonomously inserting electrically conductive, hooked probes. The probes provided stimulation to the tissue via timed electrical pulses that could be used as a treatment for gastric motility disorders. To demonstrate interaction with stomach muscle tissue, we used the electrical stimulation to induce acute muscular contractions. Pulses conductively signaled the probes' successful anchoring and detachment events to a parenterally placed device. The ability to anchor into and electrically interact with targeted GI tissues controlled by the enteric nervous system introduces opportunities to treat a multitude of associated pathologies.
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http://dx.doi.org/10.1126/sciadv.aaz0127DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7455191PMC
August 2020

Deservingness put into practice: Constructing the (un)deservingness of migrants in four European countries.

Br J Sociol 2020 Jan;71(1):112-126

Centre for Comparative Welfare Studies, Aalborg University, Aalborg, Denmark.

The increased comparative research on perceptions of public welfare deservingness studies the extent to which different subgroups of citizens are deemed worthy or unworthy of receiving help from the welfare state. The concept of deservingness criteria plays a crucial role in this research, as it theorizes a universal heuristic that citizens apply to rank people in terms of their welfare deservingness. Due to the mainly quantitative nature of the research and despite the indisputable progress it has made, the subjective existence and actual application of these deservingness criteria remain a bit of a black box. What criteria of deservingness do citizens actually apply, and how do they apply them? This article opens the black box of welfare deservingness and sheds light on the nature and practice of deservingness criteria. Empirically, the paper explores how the deservingness of immigrants is discussed and established within 20 focus groups conducted in Slovenia, Denmark, UK, and Norway in 2016 with a total of 160 participants. All 20 focus groups discussed the welfare deservingness of immigrants based on similar vignette stimuli. Our analysis shows that (1) deservingness criteria are used both to construct images of target groups and as normative yardsticks; (2) deservingness criteria do not work independently of each other, but rather co-function in specific hybridized discourses; and (3) the moral logic of deservingness is supplemented by alternative moral logics, at least in the case of migrants.
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http://dx.doi.org/10.1111/1468-4446.12721DOI Listing
January 2020

Consequences of past and present harvest management in a declining flyway population of common eiders .

Ecol Evol 2019 Nov 2;9(22):12515-12530. Epub 2019 Oct 2.

Department of Bioscience Aarhus University Roskilde Denmark.

Harvested species population dynamics are shaped by the relative contribution of natural and harvest mortality. Natural mortality is usually not under management control, so managers must continuously adjust harvest rates to prevent overexploitation. Ideally, this requires regular assessment of the contribution of harvest to total mortality and how this affects population dynamics.To assess the impact of hunting mortality on the dynamics of the rapidly declining Baltic/Wadden Sea population of common eiders , we first estimated vital rates of ten study colonies over the period 1970-2015. By means of a multi-event capture-recovery model, we then used the cause of death of recovered individuals to estimate proportions of adult females that died due to hunting or other causes. Finally, we adopted a stochastic matrix population modeling approach based on simulations to investigate the effect of past and present harvest regulations on changes in flyway population size and composition.Results showed that even the complete ban on shooting females implemented in 2014 in Denmark, where most hunting takes place, was not enough to stop the population decline given current levels of natural female mortality. Despite continued hunting of males, our predictions suggest that the proportion of females will continue to decline unless natural mortality of the females is reduced.Although levels of natural mortality must decrease to halt the decline of this population, we advocate that the current hunting ban on females is maintained while further investigations of factors causing increased levels of natural mortality among females are undertaken. . At the flyway scale, continuous and accurate estimates of vital rates and the relative contribution of harvest versus other mortality causes are increasingly important as the population effect of adjusting harvest rates is most effectively evaluated within a model-based adaptive management framework.
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http://dx.doi.org/10.1002/ece3.5707DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6875579PMC
November 2019

Demographic reconstruction from ancient DNA supports rapid extinction of the great auk.

Elife 2019 11 26;8. Epub 2019 Nov 26.

Department of Anatomy, University of Otago, Dunedin, New Zealand.

The great auk was once abundant and distributed across the North Atlantic. It is now extinct, having been heavily exploited for its eggs, meat, and feathers. We investigated the impact of human hunting on its demise by integrating genetic data, GPS-based ocean current data, and analyses of population viability. We sequenced complete mitochondrial genomes of 41 individuals from across the species' geographic range and reconstructed population structure and population dynamics throughout the Holocene. Taken together, our data do not provide any evidence that great auks were at risk of extinction prior to the onset of intensive human hunting in the early 16 century. In addition, our population viability analyses reveal that even if the great auk had not been under threat by environmental change, human hunting alone could have been sufficient to cause its extinction. Our results emphasise the vulnerability of even abundant and widespread species to intense and localised exploitation.
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http://dx.doi.org/10.7554/eLife.47509DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6879203PMC
November 2019

A luminal unfolding microneedle injector for oral delivery of macromolecules.

Nat Med 2019 10 7;25(10):1512-1518. Epub 2019 Oct 7.

Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA.

Insulin and other injectable biologic drugs have transformed the treatment of patients suffering from diabetes, yet patients and healthcare providers often prefer to use and prescribe less effective orally dosed medications. Compared with subcutaneously administered drugs, oral formulations create less patient discomfort, show greater chemical stability at high temperatures, and do not generate biohazardous needle waste. An oral dosage form for biologic medications is ideal; however, macromolecule drugs are not readily absorbed into the bloodstream through the gastrointestinal tract. We developed an ingestible capsule, termed the luminal unfolding microneedle injector, which allows for the oral delivery of biologic drugs by rapidly propelling dissolvable drug-loaded microneedles into intestinal tissue using a set of unfolding arms. During ex vivo human and in vivo swine studies, the device consistently delivered the microneedles to the tissue without causing complete thickness perforations. Using insulin as a model drug, we showed that, when actuated, the luminal unfolding microneedle injector provided a faster pharmacokinetic uptake profile and a systemic uptake >10% of that of a subcutaneous injection over a 4-h sampling period. With the ability to load a multitude of microneedle formulations, the device can serve as a platform to orally deliver therapeutic doses of macromolecule drugs.
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http://dx.doi.org/10.1038/s41591-019-0598-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7218658PMC
October 2019

Linking demographic and food-web models to understand management trade-offs.

Ecol Evol 2019 Aug 17;9(15):8587-8600. Epub 2019 Jul 17.

U.S. Geological Survey Washington Cooperative Fish and Wildlife Research Unit, School of Environmental and Forest Sciences (SEFS) and School of Aquatic and Fishery Sciences (SAFS) University of Washington Seattle Washington USA.

Alternatives in ecosystem-based management often differ with respect to trade-offs between ecosystem values. Ecosystem or food-web models and demographic models are typically employed to evaluate alternatives, but the approaches are rarely integrated to uncover conflicts between values. We applied multistate models to a capture-recapture dataset on common guillemots breeding in the Baltic Sea to identify factors influencing survival. The estimated relationships were employed together with Ecopath-with-Ecosim food-web model simulations to project guillemot survival under six future scenarios incorporating climate change. The scenarios were based on management alternatives for eutrophication and cod fisheries, issues considered top priority for regional management, but without known direct effects on the guillemot population. Our demographic models identified prey quantity (abundance and biomass of sprat ) as the main factor influencing guillemot survival. Most scenarios resulted in projections of increased survival, in the near (2016-2040) and distant (2060-2085) future. However, in the scenario of reduced nutrient input and precautionary cod fishing, guillemot survival was projected to be lower in both future periods due to lower sprat stocks. Matrix population models suggested a substantial decline of the guillemot population in the near future, 24% per 10 years, and a smaller reduction, 1.1% per 10 years, in the distant future. To date, many stakeholders and Baltic Sea governments have supported reduced nutrient input and precautionary cod fishing and implementation is underway. Negative effects on nonfocal species have previously not been uncovered, but our results show that the scenario is likely to negatively impact the guillemot population. Linking model results allowed identifying trade-offs associated with management alternatives. This information is critical to thorough evaluation by decision-makers, but not easily obtained by food-web models or demographic models in isolation. Appropriate datasets are often available, making it feasible to apply a linked approach for better-informed decisions in ecosystem-based management.
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http://dx.doi.org/10.1002/ece3.5385DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6686646PMC
August 2019

An ingestible self-orienting system for oral delivery of macromolecules.

Science 2019 02;363(6427):611-615

Department of Chemical Engineering and David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.

Biomacromolecules have transformed our capacity to effectively treat diseases; however, their rapid degradation and poor absorption in the gastrointestinal (GI) tract generally limit their administration to parenteral routes. An oral biologic delivery system must aid in both localization and permeation to achieve systemic drug uptake. Inspired by the leopard tortoise's ability to passively reorient, we developed an ingestible self-orienting millimeter-scale applicator (SOMA) that autonomously positions itself to engage with GI tissue. It then deploys milliposts fabricated from active pharmaceutical ingredients directly through the gastric mucosa while avoiding perforation. We conducted in vivo studies in rats and swine that support the applicator's safety and, using insulin as a model drug, demonstrated that the SOMA delivers active pharmaceutical ingredient plasma levels comparable to those achieved with subcutaneous millipost administration.
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http://dx.doi.org/10.1126/science.aau2277DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6430586PMC
February 2019

A Test of Positive Association for Detecting Heterogeneity in Capture for Capture-Recapture Data.

J Agric Biol Environ Stat 2018 11;23(1):1-19. Epub 2017 Dec 11.

4Centre d'Ecologie Fonctionnelle et Evolutive UMR 5175, CNRS - Université de Montpellier - Université Paul-Valéry, Montpellier - EPHE, Montpellier, France.

The Cormack-Jolly-Seber (CJS) model assumes that all marked animals have equal recapture probabilities at each sampling occasion, but heterogeneity in capture often occurs and should be taken into account to avoid biases in parameter estimates. Although diagnostic tests are generally used to detect trap-dependence or transience and assess the overall fit of the model, heterogeneity in capture is not routinely tested for. In order to detect and identify this phenomenon in a CJS framework, we propose a test of positive association between previous and future encounters using Goodman-Kruskal's gamma. This test is based solely on the raw capture histories and makes no assumption on model structure. The development of the test is motivated by a dataset of Sandwich terns (), and we use the test to formally show that they exhibit heterogeneity in capture. We use simulation to assess the performance of the test in the detection of heterogeneity in capture, compared to existing and corrected diagnostic goodness-of-fit tests, Leslie's test of equal catchability and Carothers' extension of the Leslie test. The test of positive association is easy to use and produces good results, demonstrating high power to detect heterogeneity in capture. We recommend using this new test prior to model fitting as the outcome will guide the model-building process and help draw more accurate biological conclusions. Supplementary materials accompanying this paper appear online.

Electronic Supplementary Material: Supplementary materials for this article are available at 10.1007/s13253-017-0315-4.
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http://dx.doi.org/10.1007/s13253-017-0315-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6954010PMC
December 2017

Variation in Growth Drives the Duration of Parental Care: A Test of Ydenberg's Model.

Am Nat 2017 May 8;189(5):526-538. Epub 2017 Mar 8.

The duration of parental care in animals varies widely, from none to lifelong. Such variation is typically thought to represent a trade-off between growth and safety. Seabirds show wide variation in the age at which offspring leave the nest, making them ideal to test the idea that a trade-off between high energy gain at sea and high safety at the nest drives variation in departure age (Ydenberg's model). To directly test the model assumptions, we attached time-depth recorders to murre parents (fathers [which do all parental care at sea] and mothers; [Formula: see text] of each). Except for the initial mortality experienced by chicks departing from the colony, the mortality rate at sea was similar to the mortality rate at the colony. However, energy gained by the chick per day was ∼2.1 times as high at sea compared with at the colony because the father spent more time foraging, since he no longer needed to spend time commuting to and from the colony. Compared with the mother, the father spent ∼2.6 times as much time diving per day and dived in lower-quality foraging patches. We provide a simple model for optimal departure date based on only (1) the difference in growth rate at sea relative to the colony and (2) the assumption that transition mortality from one life-history stage to the other is size dependent. Apparently, large variation in the duration of parental care can arise simply as a result of variation in energy gain without any trade-off with safety.
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http://dx.doi.org/10.1086/691097DOI Listing
May 2017

Sympatric breeding auks shift between dietary and spatial resource partitioning across the annual cycle.

PLoS One 2013 30;8(8):e72987. Epub 2013 Aug 30.

Department of Bioscience, Aarhus University, Roskilde, Denmark.

When species competing for the same resources coexist, some segregation in the way they utilize those resources is expected. However, little is known about how closely related sympatric breeding species segregate outside the breeding season. We investigated the annual segregation of three closely related seabirds (razorbill Alcatorda, common guillemot Uriaaalge and Brünnich's guillemot U. lomvia) breeding at the same colony in Southwest Greenland. By combining GPS and geolocation (GLS) tracking with dive depth and stable isotope analyses, we compared spatial and dietary resource partitioning. During the breeding season, we found the three species to segregate in diet and/or dive depth, but less in foraging area. During both the post-breeding and pre-breeding periods, the three species had an increased overlap in diet, but were dispersed over a larger spatial scale. Dive depths were similar across the annual cycle, suggesting morphological adaptations fixed by evolution. Prey choice, on the other hand, seemed much more flexible and therefore more likely to be affected by the immediate presence of potential competitors.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0072987PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3758292PMC
April 2014

Climate, copepods and seabirds in the boreal Northeast Atlantic - current state and future outlook.

Glob Chang Biol 2013 Feb 27;19(2):364-72. Epub 2012 Nov 27.

Department of Bioscience, Aarhus University, Roskilde, Denmark.

The boreal Northeast Atlantic is strongly affected by current climate change, and large shifts in abundance and distribution of many organisms have been observed, including the dominant copepod Calanus finmarchicus, which supports the grazing food web and thus many fish populations. At the same time, large-scale declines have been observed in many piscivorous seabirds, which depend on abundant small pelagic fish. Here, we combine predictions from a niche model of C. finmarchicus with long-term data on seabird breeding success to link trophic levels. The niche model shows that environmental suitability for C. finmarchicus has declined in southern areas with large breeding seabird populations (e.g. the North Sea), and predicts that this decline is likely to spread northwards during the 21st century to affect populations in Iceland and the Faroes. In a North Sea colony, breeding success of three common piscivorous seabird species [black-legged kittiwake (Rissa tridactyla), common guillemot (Uria aalge) and Atlantic puffin (Fratercula arctica)] was strongly positively correlated with local environmental suitability for C. finmarchicus, whereas this was not the case at a more northerly colony in west Norway. Large seabird populations seem only to occur where C. finmarchicus is abundant, and northward distributional shifts of common boreal seabirds are therefore expected over the coming decades. Whether or not population size can be maintained depends on the dispersal ability and inclination of these colonial breeders, and on the carrying capacity of more northerly areas in a warmer climate.
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http://dx.doi.org/10.1111/gcb.12072DOI Listing
February 2013

Effects of fish farm waste on Posidonia oceanica meadows: synthesis and provision of monitoring and management tools.

Mar Pollut Bull 2008 Sep 9;56(9):1618-29. Epub 2008 Jul 9.

Institute of Biology, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark.

This paper provides a synthesis of the EU project MedVeg addressing the fate of nutrients released from fish farming in the Mediterranean with particular focus on the endemic seagrass Posidonia oceanica habitat. The objectives were to identify the main drivers of seagrass decline linked to fish farming and to provide sensitive indicators of environmental change, which can be used for monitoring purposes. The sedimentation of waste particles in the farm vicinities emerges as the main driver of benthic deterioration, such as accumulation of organic matter, sediment anoxia as well as seagrass decline. The effects of fish farming on P. oceanica meadows are diverse and complex and detected through various metrics and indicators. A safety distance of 400 m is suggested for management of P. oceanica near fish farms followed by establishment of permanent seagrass plots revisited annually for monitoring the health of the meadows.
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http://dx.doi.org/10.1016/j.marpolbul.2008.05.020DOI Listing
September 2008

Differential effects of a local industrial sand lance fishery on seabird breeding performance.

Ecol Appl 2008 Apr;18(3):701-10

Centre for Ecology and Hydrology, Hill of Brathens, Banchory AB31 4BW, UK.

Fisheries management across the world is moving toward an ecosystem-based approach, implying that fishery effects on nontarget species should be taken into account. However, such effects are often not well understood, partly because, they can be difficult to distinguish from impacts of environmental fluctuations. We evaluated the effects of an industrial sand lance (Ammodytes marinus) fishery off the North Sea coast of the United Kingdom, which has been opened and closed in a quasi-experimental fashion, on sand-lance-dependent breeding seabirds. Controlling for environmental variation (sea surface temperature, abundance of larval sand lance, and size of adult sand lance), we found that, when the fishery was operating, breeding productivity in the intensively studied seabird colony on the Isle of May was significantly depressed for one surface-feeding seabird species, the Black-legged Kittiwake (Rissa tridactyla), but not for four diving species. Analyzing Kittiwake data from 12 colonies inside and outside the closure zone in a replicated before-after control-impact design, we again found that breeding productivity was significantly depressed in the closure zone when the fishery was active, whereas no effect was found in the control zone. Furthermore, Kittiwake breeding productivity was negatively correlated with fishery effort during the fishery period in the closure zone, but not in the control zone. The contrasting findings in the two zones could be related to environmental differences or to the fact that only one study colony in the control zone was exposed to high fishery effort within the typical foraging range of Kittiwakes during the breeding season. The strong impact on Kittiwakes, but not on diving species, could result from (1) inherently high sensitivity to reduced prey availability, (2) changes in the vertical distribution of sand lance at lower densities, (3) sand lance showing avoidance behavior to fishery vessels, or a combination of some or all of these factors. These findings indicate that local fishery closures can benefit sensitive predators and should be considered as a tool for future ecosystem-based fisheries management.
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http://dx.doi.org/10.1890/07-0797.1DOI Listing
April 2008

Reproductive senescence in a long-lived seabird: rates of decline in late-life performance are associated with varying costs of early reproduction.

Am Nat 2008 Feb;171(2):E89-E101

Institute of Evolutionary Biology, King's Buildings, University of Edinburgh, Edinburgh EH9 3JT, UK.

Evolutionary theories of senescence predict that rates of decline in performance parameters should be shaped by early-life trade-offs between reproduction and somatic maintenance. Here we investigate factors influencing the rate of reproductive senescence in a long-lived seabird, the common guillemot Uria aalge, using data collected over a 23-year period. In the last 3 years of life, individual guillemots had significantly reduced breeding success and were less likely to hold a site or attempt to breed. Females senesced at a significantly faster rate than males. At the individual level, high levels of reproductive output earlier in life were associated with increased senescence later in life. This trade-off between early- and late-life reproduction was evident independent of the fact that as birds age, they breed later in the season. The rate of senescence was additionally dependent on environmental conditions experienced earlier in life, with evidence that harsh conditions amplified later declines in breeding success. Overall, individuals with intermediate levels of early-life productivity lived longer. These results provide support for the antagonistic-pleiotropy and disposable-soma theories of senescence and demonstrate for the first time in a wild bird population that increased rates of senescence in reproductive performance are associated with varying costs of reproduction early in life.
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http://dx.doi.org/10.1086/524957DOI Listing
February 2008

From plankton to top predators: bottom-up control of a marine food web across four trophic levels.

J Anim Ecol 2006 Nov;75(6):1259-68

Centre for Ecology and Hydrology, Hill of Brathens, Banchory AB31 4BW, UK.

1. Abundant mid-trophic pelagic fish often play a central role in marine ecosystems, both as links between zooplankton and top predators and as important fishery targets. In the North Sea, the lesser sandeel occupies this position, being the main prey of many bird, mammal and fish predators and the target of a major industrial fishery. However, since 2003, sandeel landings have decreased by > 50%, and many sandeel-dependent seabirds experienced breeding failures in 2004. 2. Despite the major economic implications, current understanding of the regulation of key constituents of this ecosystem is poor. Sandeel abundance may be regulated 'bottom-up' by food abundance, often thought to be under climatic control, or 'top-down' by natural or fishery predation. We tested predictions from these two hypotheses by combining unique long-term data sets (1973-2003) on seabird breeding productivity from the Isle of May, SE Scotland, and plankton and fish larvae from the Continuous Plankton Recorder survey. We also tested whether seabird breeding productivity was more tightly linked to sandeel biomass or quality (size) of individual fish. 3. The biomass of larval sandeels increased two- to threefold over the study period and was positively associated with proxies of the abundance of their plankton prey. Breeding productivity of four seabirds bringing multiple prey items to their offspring was positively related to sandeel larval biomass with a 1-year lag, indicating dependence on 1-year-old fish, but in one species bringing individual fish it was strongly associated with the size of adult sandeels. 4. These links are consistent with bottom-up ecosystem regulation and, with evidence from previous studies, indicate how climate-driven changes in plankton communities can affect top predators and potentially human fisheries through the dynamics of key mid-trophic fish. However, the failing recruitment to adult sandeel stocks and the exceptionally low seabird breeding productivity in 2004 were not associated with low sandeel larval biomass in 2003, so other mechanisms (e.g. predation, lack of suitable food after metamorphosis) must have been important in this case. Understanding ecosystem regulation is extremely important for predicting the fate of keystone species, such as sandeels, and their predators.
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http://dx.doi.org/10.1111/j.1365-2656.2006.01148.xDOI Listing
November 2006

Responding to environmental change: plastic responses vary little in a synchronous breeder.

Proc Biol Sci 2006 Nov;273(1602):2713-9

Institute of Evolutionary Biology, University of Edinburgh, King's Buildings, Edinburgh EH9 3JT, UK.

The impact of environmental change on animal populations is strongly influenced by the ability of individuals to plastically adjust key life-history events. There is therefore considerable interest in establishing the degree of plasticity in traits and how selection acts on plasticity in natural populations. Breeding time is a key life-history trait that affects fitness and recent studies have found that females vary significantly in their breeding time-environment relationships, with selection often favouring individuals exhibiting stronger plastic responses. In contrast, here, we show that although breeding time in the common guillemot, Uria aalge, is highly plastic at the population level in response to a large-scale environmental cue (the North Atlantic Oscillation, NAO), there is very little between-individual variation-most individuals respond to this climate cue very similarly. We demonstrate strong stabilizing selection against individuals who deviate from the average population-level response to NAO. This species differs significantly from those previously studied in being a colonial breeder, in which reproductive synchrony has a substantial impact on fitness; we suggest that counter selection imposed by a need for synchrony could limit individuals in their response and potential for directional selection to act. This demonstrates the importance of considering the relative costs and benefits of highly plastic responses in assessing the likely response of a population to the environmental change.
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http://dx.doi.org/10.1098/rspb.2006.3631DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1635500PMC
November 2006

Recruitment to a seabird population depends on environmental factors and on population size.

J Anim Ecol 2006 Jan;75(1):228-38

Centre for Ecology and Hydrology, Hill of Brathens, Banchory, Aberdeenshire AB31 4BW, UK

1. A novel capture-mark-recapture (CMR) method was used to build a multistate model of recruitment by young birds to a breeding population of common guillemots Uria aalge on the Isle of May, Scotland. Recruitment of a total of 2757 individually marked guillemots over 17 years was modelled as a process where individuals had to move from an unobservable state at sea, through a nonbreeding state present in the colony, to the breeding state. The probabilities of individuals returning to the colony in a given year, at age 2 and 3-4 years, were positively correlated with an environmental covariate, the winter North Atlantic Oscillation index (WNAO) in the previous years. 2. For 2 year olds, there was a negative relationship with breeding population size, suggesting that density dependence operated in this colony through limitation of food or some other resource. 3. Survival over the first 2 years of life varied with cohort, but was unrelated to the WNAO. Mean survival over this 2-year period was high at 0.576 (95% CI: 0.444; 0.708). 4. This high survival, combined with a low 'local' survival after age 5 years of 0.695 (0-654; 0.733) and observations of Isle of May chicks at other colonies, suggests that most surviving chicks return to the natal colony before deciding whether to recruit there or move elsewhere.
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http://dx.doi.org/10.1111/j.1365-2656.2006.01035.xDOI Listing
January 2006

Evidence for density-dependent survival in adult cormorants from a combined analysis of recoveries and resightings.

J Anim Ecol 2000 Sep;69(5):737-752

National Environmental Research Institute, Department of Coastal Zone Ecology, Kalø, Grenåvej 12, DK-8410 Rønde, Denmark.

1. The increasing population of cormorants (Phalacrocorax carbo sinensis) in Europe since 1970 has led to conflicts with fishery interests. Control of cormorant populations is a management issue in many countries and a predictive population model is needed. However, reliable estimates of survival are lacking as input for such a model 2. Capture-recapture estimates of survival of dispersive species like cormorants suffer from an unknown bias due to permanent emigration from the study area. However, a combined analysis of resightings and recovery of dead birds allows unbiased estimates of survival and emigration. 3. We use data on 11 000 cormorants colour-ringed as chicks in the Danish colony Vorsø 1977-97 to estimate adult survival and colony fidelity. Recent statistical models allowing simultaneous use of recovery and resighting data are employed. We compensate for variation in colour-ring quality, and study the effect of population size and winter severity on survival, as well as of breeding success on fidelity by including these factors as covariates in statistical models. 4. Annual adult survival fluctuated from year to year (0·74-0·95), with a mean of 0·88. A combination of population size in Europe and winter temperatures explained 52-64% of the year-to-year variation in survival. Differences in survival between sexes was less than 1%. Cormorants older than ≈ 12 years experienced lower survival, whereas second-year birds had survival similar to adults. Colony fidelity declined after 1990 from nearly 1 to ≈ 0·90, implying 10% permanent emigration per year. This change coincided with a decline in food availability. 5. Apparently, survival was more severely affected by winter severity when population size was high. This could be caused by saturation of high-quality wintering habitat, forcing some birds to winter in less good habitat where they would be more vulnerable to cold winters. There was thus evidence for density dependence in adult survival, at least in cold winters. 6. The high population growth rate sustained by European Ph. c. sinensis in the 1970s and 1980s can partly be accounted for by unusually high survival of immature and adult birds, probably caused by absence of hunting, low population density and high food availability.
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http://dx.doi.org/10.1046/j.1365-2656.2000.00435.xDOI Listing
September 2000

Diagnosing a decline in return rate of 1-year-old cormorants: mortality, emigration or delayed return?

J Anim Ecol 2000 Sep;69(5):753-761

National Environmental Research Institute, Department of Coastal Zone Ecology, Kalø, Grenåvej 12, DK-8410 Rønde, Denmark.

1. In long-lived birds with delayed recruitment, variation in prebreeding population parameters is difficult to study, although potentially important. Cormorants (Phalacrocorax carbo sinensis) often return to their natal colony when 1 year old, enabling direct study of first-year survival and emigration. Density-dependent regulation mechanisms may be strong at this stage of the life cycle. 2. In the Danish cormorant colony Vorsø, 11 000 chicks have been colour-ringed between 1977 and 1997. Returning birds have been resighted in the colony and dead recoveries have been collected. Since 1990, the proportion of a cohort observed in the colony as 1-year-olds (return rate) has declined from 0·40 to 0·10. Possible explanations include increased mortality, increased emigration and a later age of first return to the colony. Breeding success has also declined strongly as a consequence of low food availability. 3. We used capture-recapture analysis of recovery and resighting data to investigate variation in first-year survival, emigration and resighting probabilities. Survival fluctuated widely (0·42-0·75, mean 0·58); emigration increased in the 1990s from 0·05 to 0·15; resighting probability declined from 0·75 to 0·20 after 1990. 4. First-year survival was particularly low in 1993 and 1996. The causes of the year-to-year variation were not clear. Survival may have been affected by food availability during the post-fledging period. 5. The declining return rate was caused mainly by decreasing resighting probability of 1-year-olds, although increasing emigration also contributed. The biological mechanism was that increasing numbers of cormorants did not return to the natal colony as 1-year-olds. We suggest that this was a consequence of low physiological condition among newly fledged young, caused by low food availability in the 1990s. 6. We conclude that declining food availability has had several consequences for colony dynamics. First-year emigration and the age of first return to the colony have increased and, in the worst years, survival has decreased. If the decline in food availability was due to cormorant predation, this would constitute an example of density-dependent regulation of immature colony attendance.
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September 2000