Predator persistence through variability of resource productivity in Tritrophic systems

The trophic structure of species communities depends on the energy transfer between trophic levels. Primary productivity varies strongly through time, challenging the persistence of species at higher trophic levels. Yet resource variability has mostly been studied in systems with only one or two trophic levels. We test the effect of variability in resource productivity in a tritrophic model system including a resource, a size-structured consumer, and a size-specific predator. The model complies with fundamental principles of mass conservation and the body-size dependence of individual-level energetics and predator-prey interactions. Surprisingly, we find that resource variability may promote predator persistence. The positive effect of variability on the predator arises through periods with starvation mortality of juvenile prey, which reduces the intraspecific competition in the prey population. With increasing variability in productivity and starvation mortality in the juvenile prey, the prey availability increases in the size range preferred by the predator. The positive effect of prey mortality on the trophic transfer efficiency depends on the biologically realistic consideration of body size–dependent and food-dependent functions for growth and reproduction in our model. Our findings show that variability may promote the trophic transfer efficiency, indicating that environmental variability may sustain species at higher trophic levels in natural ecosystems

Harvesting forage fish can prevent fishing-induced population collapses of large piscivorous fish

acceptedVersio

Framework for assessing and mitigating the impacts of offshore wind energy development on marine birds

Offshore wind energy development (OWED) is rapidly expanding globally and has the potential to contribute significantly to renewable energy portfolios. However, development of infrastructure in the marine environment presents risks to wildlife. Marine birds in particular have life history traits that amplify population impacts from displacement and collision with offshore wind infrastructure. Here, we present a broadly applicable framework to assess and mitigate the impacts of OWED on marine birds. We outline existing techniques to quantify impact via monitoring and modeling (e.g., collision risk models, population viability analysis), and present a robust mitigation framework to avoid, minimize, or compensate for OWED impacts. Our framework addresses impacts within the context of multiple stressors across multiple wind energy developments. We also present technological and methodological approaches that can improve impact estimation and mitigation. We highlight compensatory mitigation as a tool that can be incorporated into regulatory frameworks to mitigate impacts that cannot be avoided or minimized via siting decisions or alterations to OWED infrastructure or operation. Our framework is intended as a globally-relevant approach for assessing and mitigating OWED impacts on marine birds that may be adapted to existing regulatory frameworks in regions with existing or planned OWED

Feasibility study of the development of population models for the northern fulmar (Fulmarus glacialis) and the Atlantic puffin (Fratercula arctica)

This memo assesses whether sufficient information is available to develop stage-structured matrix population models for two species of seabirds, the northern fulmar (Fulmarus glacialis) and the Atlantic puffin (Fratercula arctica). Development of such models requires age-specific estimates of survival and reproduction rates. For both species, there is sufficient information on adult survival rate and colony productivity (reproduction rate), but the survival of immature birds is less well studied. There is little evidence for density-dependent effects on survival and reproduction. We conclude that density-independent population models for these species can be developed and that model robustness with respect to immature survival should be addressed during model analysis. We advise to go ahead with the development of the models for these species

Visecologie in de vooroever

Het voorliggend rapport presenteert de bevindingen uit de onderzoekslijn "vooroever", gericht op de ecologie van vis en dan met name het belang van de vooroever als kinderkamer

A general size- and trait-based model of plankton communities

Multicellular zooplankton, such as copepods, are the main link between primary producers and fish. Most models of plankton communities, such as NPZ-type models, ignore the life-cycle (ontogeny) of multicellular zooplankton. Ontogeny has profound implications on population dynamics and community structure. Our aim is to provide a generic food-web framework of planktonic communities that accounts for zooplankton ontogeny. We propose a model framework along the Nutrient–Unicellular–Multicellular axis – a “NUM” framework – as an alternative to the NPZ modelling paradigm. NUM is a mechanistic size- and trait-based model based on traits and trade-offs at the individual level. Here the multicellular component describes the population dynamics of key copepod groups, characterized by their adult size and feeding mode. The unicellular compartment accounts for auto- mixo- and heterotrophic protists. We also consider nitrogen dynamics and carbon export from copepod fecal pellets. All parameters have been fitted to cross-species data. By approximate analytical solutions and dynamic simulations, in both constant and seasonal environments, we investigate the patterns of body sizes and traits that emerge within the community. We show that copepods of several adult sizes and feeding modes commonly coexist, and that competition and predation by large copepods on small/juvenile copepods is an important factor in shaping the community. We also show competition between heterotrophic protists and small copepods through intraguild predation. Finally, we discuss how copepods can attenuate the fecal pellet export. This conceptually simple, yet realistic framework opens the possibility to improve end-to-end size-structured models of marine systems and investigate biogeochemical processes.</p