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Thousands of offshore oil and gas platforms have been installed throughout the world's oceans and more structures are being installed as part of the transition to renewable energy. These structures increase the availability of ecological niches by providing hard substrate in midwater and complex 3D habitat on the seafloor. This can lead to 'hotspots' of biodiversity, or increased densities of flora and fauna, which potentially spill over into the local area. However, the distances over which these higher densities extend (the 'range of influence') can be highly variable. Fish aggregate at such structures, but the range of influence and any implications for wider fish populations, are unclear. We investigated the relationship between fish and platform areal densities using high resolution fisheries acoustic data. Data were collected in the waters surrounding the vessel exclusions zones around 16 oil and gas platforms in the North Sea, and throughout the wider area. We estimated densities of schooling fish using echo-integration, and densities of non-schooling fish using echo-counting. At 10 platforms, non-schooling fish densities were elevated near the platform relative to background levels in the equivalent wider area. The range of influence, defined here as the range to which fish densities were elevated above background, varied from 0.8 to 23 km. In areas of high platform density, fish schools were encountered more often, and non-schooling fish densities were higher, when controlling for other sources of environmental variation. This is the first time such long-range effects have been identified; previously, ranges of influence have been reported in the order of just 10s-100s of metres. These findings suggest that the environmental impact of these structures may extend further than previously thought, which may be relevant in the context of upcoming management decisions around the decommissioning of these structures., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Lawrence et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

The changing Arctic environment is affecting zooplankton that support its abundant wildlife. We examined how these changes are influencing a key zooplankton species, Calanus finmarchicus, principally found in the North Atlantic but expatriated to the Arctic. Close to the ice-edge in the Fram Strait, we identified areas that, since the 1980s, are increasingly favourable to C. finmarchicus. Field-sampling revealed part of the population there to be capable of amassing enough reserves to overwinter. Early developmental stages were also present in early summer, suggesting successful local recruitment. This extension to suitable C. finmarchicus habitat is most likely facilitated by the long-term retreat of the ice-edge, allowing phytoplankton to bloom earlier and for longer and through higher temperatures increasing copepod developmental rates. The increased capacity for this species to complete its life-cycle and prosper in the Fram Strait can change community structure, with large consequences to regional food-webs., (© 2021. The Author(s).)

Projecting the consequences of warming and sea-ice loss for Arctic marine food web and fisheries is challenging due to the intricate relationships between biology and ice. We used StrathE2EPolar, an end-to-end (microbes-to-megafauna) food web model incorporating ice-dependencies to simulate climate-fisheries interactions in the Barents Sea. The model was driven by output from the NEMO-MEDUSA earth system model, assuming RCP 8.5 atmospheric forcing. The Barents Sea was projected to be > 95% ice-free all year-round by the 2040s compared to > 50% in the 2010s, and approximately 2 °C warmer. Fisheries management reference points (F MSY and B MSY ) for demersal fish (cod, haddock) were projected to increase by around 6%, indicating higher productivity. However, planktivorous fish (capelin, herring) reference points were projected to decrease by 15%, and upper trophic levels (birds, mammals) were strongly sensitive to planktivorous fish harvesting. The results indicate difficult trade-offs ahead, between harvesting and conservation of ecosystem structure and function., (© 2021. The Author(s).)

Stimulated Brillouin scattering experiments in the ionospheric plasma using a single electromagnetic pump wave have previously been observed to generate an electromagnetic sideband wave, emitted by the plasma, together with an ion- acoustic wave. Here we report results of a controlled, pump and probe beat-wave driven Brillouin scattering experiment, in which an ion-acoustic wave generated by the beating of electromagnetic pump and probe waves, results in electromagnetic sideband waves that are recorded on the ground. The experiment used the EISCAT facility in northern Norway, which has several high power electromagnetic wave transmitters and receivers in the radio frequency range. An electromagnetic pump consisting of large amplitude radio waves with ordinary (O) or extraordinary (X) mode polarization was injected into the overhead ionosphere, along with a less powerful probe wave, and radio sideband emissions observed on the ground clearly show stimulated Brillouin emissions at frequencies agreeing with, and changing with, the pump and probe frequencies. The experiment was simulated using a numerical full-scale model which clearly supports the interpretation of the experimental results. Such controlled beat-wave experiments demonstrate a way of remotely investigating the ionospheric plasma parameters., (© 2021. The Author(s).)

Phenotypic plasticity plays an important role in the survival of individuals. In microbial host-virus systems, previous studies have shown the stabilizing effect that host plasticity has on the coexistence of the system. By contrast, it remains uncertain how the dependence of the virus on the metabolism of the host (i.e. "viral plasticity") shapes bacteria-phage population dynamics in general, or the stability of the system in particular. Moreover, bacteria-phage models that do not consider viral plasticity are now recognised as overly simplistic. For these reasons, here we focus on the effect of viral plasticity on the stability of the system under different environmental conditions. We compared the predictions from a standard bacteria-phage model, which neglects plasticity, with those of a modification that includes viral plasticity. We investigated under which conditions viral plasticity promotes coexistence, with or without oscillatory dynamics. Our analysis shows that including viral plasticity reveals coexistence in regions of the parameter space where models without plasticity predict a collapse of the system. We also show that viral plasticity tends to reduce population oscillations, although this stabilizing effect is not consistently observed across environmental conditions: plasticity may instead reinforce dynamic feedbacks between the host, the virus, and the environment, which leads to wider oscillations. Our results contribute to a deeper understanding of the dynamic control of bacteriophage on host populations observed in nature., (Copyright © 2020 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

We examine long-term trends in the average growth rates and maturation schedules of herring and sprat populations using survey data collected from the North Sea and west of Scotland since the 1960s and 1980s respectively. Otolith age data and maturity data are used to calculate time series of mean lengths at age, von Bertalanffy growth parameters, and probabilistic maturation reaction norms. As the growth and maturation of fish is known to be influenced by temperature and stock abundances, we account for these variables using Generalised Additive Models. Each of the herring populations displayed either steady declines in mean length across multiple age groups, or declines in length followed years later by some recovery. Depending on region, lengths at age of sprat increased or decreased over time. Varying temporal trends in maturation propensity at age and length were observed across herring populations. Many of the trends in growth rate and maturation were correlated to population abundance and/or temperature. In general, abundance is shown to be negatively correlated to growth rates in herring and sprat, and positively correlated with maturation propensity in herring. Temperature is also shown to be correlated to growth and maturation, and although the effect is consistent within species, the temperature effects differ between herring and sprat. This study provides detailed information about long-term trends in growth and maturation, which is lacking for some of these pelagic stocks, especially in the west of Scotland., Competing Interests: The authors have declared that no competing interests exist.

There is an urgent need for a better understanding of animal migratory ecology under the influence of climate change. Most current analyses require long-term monitoring of populations on the move, and shorter-term approaches are needed. Here, we analysed the ecological drivers of seabird migration within the framework of the energyscape concept, which we defined as the variations in the energy requirements of an organism across geographical space as a function of environmental conditions. We compared the winter location of seabirds with their modelled energy requirements and prey fields throughout the North Atlantic. Across six winters, we tracked the migration of 94 little auks ( Alle alle ), a key sentinel Arctic species, between their East Greenland breeding site and wintering areas off Newfoundland. Winter energyscapes were modelled with Niche Mapper™, a mechanistic tool which takes into account local climate and bird ecophysiology. Subsequently, we used a resource selection function to explain seabird distributions through modelled energyscapes and winter surface distribution of one of their main prey, Calanus finmarchicus . Finally, future energyscapes were calculated according to IPCC climate change scenarios. We found that little auks targeted areas with high prey densities and moderately elevated energyscapes. Predicted energyscapes for 2050 and 2095 showed a decrease in winter energy requirements under the high emission scenario, which may be beneficial if prey availability is maintained. Overall, our study demonstrates the great potential of the energyscape concept for the study of animal spatial ecology, in particular in the context of global change., Competing Interests: We have no competing interests.

Diapause plays a key role in the life cycle of high latitude zooplankton. During diapause, animals avoid starving in winter by living in deep waters where metabolism is lower and met by lipid reserves. Global warming is therefore expected to shorten the maximum potential diapause duration by increasing metabolic rates and by reducing body size and lipid reserves. This will alter the phenology of zooplankton, impact higher trophic levels and disrupt biological carbon pumps. Here, we project the impacts of climate change on the key North Atlantic copepod Calanus finmarchicus under IPCC RCP 8.5. Potential diapause duration is modelled in relation to body size and overwintering temperature. The projections show pronounced geographic variations. Potential diapause duration reduces by more than 30% in the Western Atlantic, whereas in the key overwintering centre of the Norwegian Sea it changes only marginally. Surface temperature rises, which reduce body size and lipid reserves, will have a similar impact to deep-water changes on diapause in many regions. Because deep-water warming lags that at the surface, animals in the Labrador Sea could offset warming impacts by diapausing in deeper waters. However, the ability to control diapause depth may be limited., (© 2016 John Wiley & Sons Ltd.)

In this Letter, we present theory and particle-in-cell simulations describing cyclotron radio emission from Earth's auroral region and similar phenomena in other astrophysical environments. In particular, we find that the radiation, generated by a down-going electron horseshoe distribution is due to a backward-wave cyclotron-maser emission process. The backward wave nature of the radiation contributes to upward refraction of the radiation that is also enhanced by a density inhomogeneity. We also show that the radiation is preferentially amplified along the auroral oval rather than transversely. The results are in agreement with recent Cluster observations.

Discarding by fisheries is perceived as contrary to responsible harvesting. Legislation seeking to end the practice is being introduced in many jurisdictions. However, discarded fish are food for a range of scavenging species; so, ending discarding may have ecological consequences. Here we investigate the sensitivity of ecological effects to discarding policies using an ecosystem model of the North Sea--a region where 30-40% of trawled fish catch is currently discarded. We show that landing the entire catch while fishing as usual has conservation penalties for seabirds, marine mammals and seabed fauna, and no benefit to fish stocks. However, combining landing obligations with changes in fishing practices to limit the capture of unwanted fish results in trophic cascades that can benefit birds, mammals and most fish stocks. Our results highlight the importance of considering the broader ecosystem consequences of fishery management policy, since species interactions may dissipate or negate intended benefits.

Climate fluctuations and human exploitation are causing global changes in nutrient enrichment of terrestrial and aquatic ecosystems and declining abundances of apex predators. The resulting trophic cascades have had profound effects on food webs, leading to significant economic and societal consequences. However, the strength of cascades-that is the extent to which a disturbance is diminished as it propagates through a food web-varies widely between ecosystems, and there is no formal theory as to why this should be so. Some food chain models reproduce cascade effects seen in nature, but to what extent is this dependent on their formulation? We show that inclusion of processes represented mathematically as density-dependent regulation of either consumer uptake or mortality rates is necessary for the generation of realistic 'top-down' cascades in simple food chain models. Realistically modelled 'bottom-up' cascades, caused by changing nutrient input, are also dependent on the inclusion of density dependence, but especially on mortality regulation as a caricature of, e.g. disease and parasite dynamics or intraguild predation. We show that our conclusions, based on simple food chains, transfer to a more complex marine food web model in which cascades are induced by varying river nutrient inputs or fish harvesting rates., (© 2013 The Authors. Ecology Letters published by John Wiley & Sons Ltd and CNRS.)

Atlantic salmon exhibit a partially heritable polymorphism in which the morphs are distinguished by the duration and location of the sea-phase of their life-cycle. These morphs co-occur, albeit in characteristically different proportions, in most Scottish rivers and in both the spring and autumn spawner runs; early running fish being generally associated with upland spawning locations while late running fish are associated with lowland spawning. Thus, differences in riverine and marine environment appear to be linked to differences in the relative abundance of the morphs, rather than to the specific morph which is optimally adapted. In this paper, we report a model-based synthetic study aimed at understanding the key dynamic elements which determine the long-term stability of this polymorphism, and thus determine the relative abundance of the various sea-age morphs. Given the recent accumulation of evidence for a genetic basis for the polymorphism, we argue that the key dynamic mechanism which equalises the realized fitness of the sea-age morphs must be one or more morph-specific density dependencies in the riverine phase of the life-history. We explore a number of specific mechanisms, firmly based in known salmon biology, by which such morph-specific density dependence could occur and investigate the robustness of the co-existence which they imply. We conclude that the co-occurrence of multiple sea-age morphs of Atlantic salmon in Scottish rivers is a stable genetic polymorphism, maintained by some combination of physical separation and asymmetric competition between spawners of different morphs or the riverine stages of their offspring or both.

Following the repeal in 1962 of a long-standing ban on trawling, yields of demersal fish from the Firth of Clyde, southwest Scotland, increased to a maximum in 1973 and then declined until the directed fishery effectively ceased in the early 2000s. Since then, the only landings of demersal fish from the Firth have been by-catch in the Norway lobster fishery. We analysed changes in biomass density, species diversity and length structure of the demersal fish community between 1927 and 2009 from scientific trawl surveys, and related these to the fishery harvesting rate. As yields collapsed, the community transformed from a state in which biomass was distributed across numerous species (high species evenness) and large maximum length taxa were common, to one in which 90 per cent of the biomass was vested in one species (whiting), and both large individuals and large maximum length species were rare. Species evenness recovered quickly once the directed fishery ceased, but 10 years later, the community was still deficient in large individuals. The changes partly reflected events at a larger regional scale but were more extreme. The lag in response with respect to fishing has implications for attempts at managing a restoration of the ecosystem.

This paper is concerned with characterizing the quasistatic mechanical behaviour of arterial tissue undergoing finite deformation through hyperelastic constitutive functions. Commonly the parameters of constitutive functions are established by a process of optimization based on experimental data. Instead we construct a finite element model of a representative volume element of the material and compute its homogenized response to a range of deformations. These data are then used to provide objective functions for optimizing the parameters of two analytical models from the literature.

Common shrews (Sorex araneus L.) were presented with two prey types at various densities in a depleting environment. Observed diet choice was compared to predictions of the classical optimal diet model and of "shrew-specific" simulations incorporating patch depletion. Two strategies were simulated: expansion of the diet from taking only profitable prey to taking both types, and fixed partial preference. The simulations predict partial preference over a narrow range of initial densities of profitable prey. However, within this range, energetic benefits are relatively insensitive to diet composition. Shrews preferred more profitable prey and were more selective when encounter rate with profitable prey was higher, broadly as predicted by all the models. Partial preference was observed, but neither of the mechanisms simulated was strongly supported by results for the shrews. Univariate and multivariate analyses were used to identify cues involved in selecting prey. Instantaneous measures of encounter rates and encounters per unit search distance were the best predictors of subsequent prey choice, but decisions appear to have been made on a probabilistic basis., (Copyright © 1993. Published by Elsevier B.V.)

The ability of insect parasitoids to discriminate between parasitized and unparasitized hosts is well documented. Despite this, hosts that have been parasitized more than once are frequently found, an occurrence known as superparasitism. Since superparasitism results in interlarval competition, it was generally assumed to be caused by discriminatory 'mistakes'. Recently, theoretical studies have suggested that under certain circumstances superparasitism can be optimal. Superparasitism can thus be viewed as an active foraging strategy rather than as a passive process. Because parasitoids show a direct link between foraging success and reproductive output, they afford important opportunities to test evolutionary models of behaviour., (Copyright © 1991. Published by Elsevier Ltd.)