Long-term changes in spatial overlap between interacting cod and flounder in the Baltic Sea

The strength of interspecific competition and predator\u2013prey interactions depends on the area of co-occurrence of the interacting species. Therefore, it is necessary to quantify the changes in the spatial overlap of trophically connected species to understand the outcomes of species interactions. In the Baltic Sea, the interplay between cod and flounder has previously been neglected. In this study, we use four decades of data on cod and flounder distributions covering the southern and central Baltic Sea to: (1) model and map the changes in the distributions of the two species using generalized additive models; (2) quantify the temporal changes in the potential competitive and predator\u2013prey interactions between them using spatial overlap indices; (3) relate these changes in overlap to the known dynamics of the different cod and flounder populations in the Baltic Sea. Competition overlap has continuously increased for cod, from the beginning of the time-series. This is a possible cause of the observed decline in feeding levels and body condition of small and intermediate sized cod. Flounder overlap with large cod instead has decreased substantially, suggesting a predation release of flounder, potentially triggering its increase in abundance and distribution range observed in the last decades

Modelling indices of abundance and size-based indicators of cod and flounder stocks in the Baltic Sea using newly standardized trawl survey data

Standardized indices of abundance and size-based indicators are of extreme importance for monitoring \ufb01sh population status. The main objectives of the current study were to (i) combine and standardize recently performed trawl survey with historical ones, (ii) explore and discuss the trends in abundance, and (iii) the trends in maximum length (Lmax) for cod (Gadus morhua) and \ufb02ounder (Platichthys \ufb02esus) stocks in the Baltic Sea. Standardization of catch per unit of effort (CPUE) from trawl surveys from 1978 to 2014 to swept area per unit of time was conducted using information on trawling speed and horizontal opening of the trawls. CPUE data for cod and \ufb02ounder stocks were modelled using generalized additive models (GAMs) in a delta modelling approach framework, while the Lmax data were modelled using ordinary GAMs. The CPUE time series of the Eastern Baltic cod stock closely resembles the spawning stock biomass trend from analytical stock assessment. The results obtained furnish evidence of the cod spill-over from Subdivisions (SD) 25\u201328 to SD 24. The decline of Lmax in recent years was evident for both species in all the stocks analysed indicating that the demersal \ufb01sh community is becoming progressively dominated by small individuals. It is concluded that the standardization of long time series of \ufb01sheries-independent data constitutes a powerful tool that could help improve our knowledge on the dynamics of \ufb01shed populations, thus promoting a long-term sustainable use of these marine resources

Stickleback increase in the Baltic Sea \u2013 a thorny issue for coastal predatory fish?

In the Baltic Sea, the mesopredator three-spined stickleback (Gasterosteus aculeatus) spends a large part of its life cycle in the open sea, but reproduces in shallowcoastal habitats. In coastal waters, it may occur in high abundances, is a potent predatoron eggs and larvae of \ufb01sh, and has been shown to induce trophic cascades with resulting eutrophication symptoms through regulation of invertebrate grazers. Despite its potential signi\ufb01cance for the coastal food web, little is known about its life history and population ecology. This paper provides a description of life history traits, migration patterns and spatiotemporal development of the species in the Baltic Sea during the past decades, and tests the hypothesis that stickleback may have a negative impact on populations of coastal predatory \ufb01sh. Offshore and coastal data during the last 30 years show that stickleback has increased fourfold in the Bothnian Sea, 45-fold in the Central Baltic Sea and sevenfold in the Southern Baltic Sea. The abundances are similar in the two northern basins, and two orders of magnitude lower in the Southern Baltic Sea. The coastward spawning migration of sticklebacks from offshore areas peaks in early May, with most spawners being two years of age at a mean length of 65 mm. The early juvenile stage is spent at the coast, whereafter sticklebacks perform a seaward feeding migration in early autumn at a size of around 35 mm. A negative spatial relation between the abundance of stickleback and earlylife stages of perch and pike at coastal spawning areas was observed in spatial survey data, indicating strong interactions between the species. A negative temporal relationship was observed also between adult perch and stickleback in coastal \ufb01sh monitoring programmes supporting the hypothesis that stickleback may have negative population level effects on coastal \ufb01sh predators. The recent increase in stickleback populations in different basins of the Baltic Sea in combination with negative spatiotemporal patterns and previously observed interactions between stickleback and coastal predatory \ufb01sh suggests that this species may have gained a key role in the coastal food webs of the Baltic Sea. Through its migrations, stickleback may also constitute an important vector linking coastal and open sea ecosystem Dynamics

Recruitment failure of coastal predatory fish in the Baltic Sea is related to an offshore system shift

The dominant coastal predatory \ufb01sh in the southwestern Baltic Sea, perch and pike, have decreased markedly in abundance during the past decade. An investigation into their recruitment at 135 coastal sites showed that both species suffered from recruitment failures, mainly in open coastal areas. A detailed study of 15 sites showed that areas with recruitment problems were also notable for mortality of early-stage larvae at the onset of exogenous food-intake. At those sites, zooplankton abundance predicted 83 and 34% of the variation in young of the year perch and pike, respectively, suggesting that the declines were caused by recruitment failure attributable to zooplankton food limitation. Incidences of recruitment failure match in time an offshore trophic cascade that generated massive increases in planktivorous sprat and decreases in zooplankton biomass in the early 1990s. Therefore, sprat biomass explained 53% of the variation in perch recruitment from 1994 to 2007 at an open coastal site, where threespined stickleback also increased exponentially after 2002. The results indicate that the dramatic change in the offshore ecosystem may have propagated to the coast causing declines of the dominating coastal predators perch and pike followed by an increase in the abundance of small-bodied \ufb01sh

Effects of altered offshore food webs on coastal ecosystems emphasize the need for cross-ecosystem management

By mainly targeting larger predatory fish, commercial fisheries have indirectly promoted rapid increases in densities of their prey; smaller predatory fish like sprat, stickleback and gobies. This process, known as mesopredator release, has effectively transformed many marine offshore basins into mesopredator-dominated ecosystems. In this article, we discuss recent indications of trophic cascades on the Atlantic and Baltic coasts of Sweden, where increased abundances of mesopredatory fish are linked to increased nearshore production and biomass of ephemeral algae. Based on synthesis of monitoring data, we suggest that offshore exploitation of larger predatory fish has contributed to the increase in mesopredator fish also along the coasts, with indirect negative effects on important benthic habitats and coastal water quality. The results emphasize the need to rebuild offshore and coastal populations of larger predatory fish to levels where they regain their control over lower trophic levels and important links between offshore and coastal systems are restored

Predator 12prey body size relationships of cod in a low-diversity marine system

How predators select their prey largely defines ecosystem trophic structure, function and dynamics. In aquatic systems, organism body size is an important trait explaining predator 12 prey interactions. Here, we used a unique Atlantic cod Gadus morhua stomach content dataset with diet information from over 100 000 individuals collected from the Baltic Sea in 1963 122014, to explore prey size distribution and predator 12prey mass ratios in the diet of Eastern Baltic cod. Maximum and average prey sizes increased with predator size, as for cod in other systems. However, the prey size spectra found in Eastern Baltic cod stomachs reflect the low species diversity in the Baltic Sea. In general, Eastern Baltic cod feed on smaller prey in relation to their body size than other cod populations. Due to the truncated prey size distribution in the Baltic Sea, cod cannibalism functions as a compensatory mechanism that allows Baltic cod to reach their prey size potential. On the other hand, small- and intermediate-sized cod prey mainly on a few invertebrate prey species, potentially making them vulnerable to changes in these prey populations. Our results encourage further studies disentangling the relative effects of prey preference and prey availability on cod trophodynamics in species-poor systems such as the Baltic Sea

Characterizing and predicting the distribution of Baltic Sea flounder (Platichthys flesus) during the spawning season

Identi\ufb01cation of essential \ufb01sh habitats (EFH), such as spawning habitats, is important for nature conservation, sustainable \ufb01sheries management and marine spatial planning. Two sympatric \ufb02ounder (Platichthys \ufb02esus) ecotypes are present in the Baltic Sea, pelagic and demersal spawning \ufb02ounder, both displaying ecological and physiological adaptations to the low-salinity environment of this young inland sea. In this study we have addressed three main research questions: 1) What environmental conditions characterize the spatial distribution and abundance of adult \ufb02ounder during the spawning season? 2) What arethe main factors de\ufb01ning the habitats of the two \ufb02ounder ecotypes during the spawning season? 3) Where are the potential spawning areas of \ufb02ounder? We modelled catch per unit of e\ufb00ort (CPUE) of \ufb02ounder from gillnet surveys conducted over the southern and central Baltic Sea in the spring of 2014 and 2015 using generalized additive models. A general model included all the stations \ufb01shed during the survey while two other models, one for the demersal and one for the pelagic spawning \ufb02ounder, included only the stations where each \ufb02ounder ecotype should dominate. The general model captured distinct ecotype-speci\ufb01c signals as it identi\ufb01ed dual salinity and water depth responses. The model for the demersal spawning \ufb02ounder revealed a negative relation with the abundance of round goby (Neogobius melanostomus) anda positiverelation withSecchi depth and codabundance. Vegetation and substrate did not play an important role in the choice of habitat for the demersal ecotype. The model for the pelagic spawning \ufb02ounder showed a negative relation with temperature and bottom current and a positive relation with salinity. Spatial predictions of potential spawning areas of \ufb02ounder showed a decrease in habitat availability for the pelagic spawning \ufb02ounder over the last 20 years in the central part of the Baltic Sea, which may explain part of the observed changes in populations' biomass. We conclude that spatiotemporal modelling of habitat availability can improve our understanding of \ufb01sh stock dynamics and may provide necessary biological knowledge for the development of marine spatial plans

Meta-analysis of mould and dampness exposure on asthma and allergy in eight European birth cohorts: an ENRIECO initiative

Abstract BACKGROUND: Several cross-sectional studies during the past 10 years have observed an increased risk of allergic outcomes for children living in damp or mouldy environments. OBJECTIVE: The objective of this study was to investigate whether reported mould or dampness exposure in early life is associated with the development of allergic disorders in children from eight European birth cohorts. METHODS: We analysed data from 31 742 children from eight ongoing European birth cohorts. Exposure to mould and allergic health outcomes were assessed by parental questionnaires at different time points. Meta-analyses with fixed- and random-effect models were applied. The number of the studies included in each analysis varied based on the outcome data available for each cohort. RESULTS: Exposure to visible mould and/or dampness during first 2 years of life was associated with an increased risk of developing asthma: there was a significant association with early asthma symptoms in meta-analyses of four cohorts [0-2 years: adjusted odds ratios (aOR), 1.39 (95% CI, 1.05-1.84)] and with asthma later in childhood in six cohorts [6-8 years: aOR, 1.09 (95% CI, 0.90-1.32) and 3-10 years: aOR, 1.10 (95% CI, 0.90-1.34)]. A statistically significant association was observed in six cohorts with symptoms of allergic rhinitis at school age [6-8 years: aOR, 1.12 (1.02-1.23)] and at any time point between 3 and 10 years [aOR, 1.18 (1.09-1.28)]. CONCLUSION: These findings suggest that a mouldy home environment in early life is associated with an increased risk of asthma particularly in young children and allergic rhinitis symptoms in school-age children

Conceptual uncertainties in modelling the interaction between engineered and natural barriers of nuclear waste repositories in crystalline rocks

Nuclear waste disposal in geological formations relies on a multi-barrier concept that includes engineered components – which, in many cases, include a bentonite buffer surrounding waste packages – and the host rock. Contrasts in materials, together with gradients across the interface between the engineered and natural barriers, lead to complex interactions between these two subsystems. Numerical modelling, combined with monitoring and testing data, can be used to improve our overall understanding of rock–bentonite interactions and to predict the performance of this coupled system. Although established methods exist to examine the prediction uncertainties due to uncertainties in the input parameters, the impact of conceptual model decisions on the quantitative and qualitative modelling results is more difficult to assess. A Swedish Nuclear Fuel and Waste Management Company Task Force project facilitated such an assessment. In this project, 11 teams used different conceptualizations and modelling tools to analyse the Bentonite Rock Interaction Experiment (BRIE) conducted at the \uc4sp\uf6 Hard Rock Laboratory in Sweden. The exercise showed that prior system understanding along with the features implemented in the available simulators affect the processes included in the conceptual model. For some of these features, sufficient characterization data are available to obtain defensible results and interpretations, whereas others are less supported. The exercise also helped to identify the conceptual uncertainties that led to different assessments of the relative importance of the engineered and natural barrier subsystems. The range of predicted bentonite wetting times encompassed by the ensemble results were considerably larger than the ranges derived from individual models. This is a consequence of conceptual uncertainties, demonstrating the relevance of using a multi-model approach involving alternative conceptualizations

Body mass index trajectory classes and incident asthma in childhood: Results from 8 European Birth Cohorts-a Global Allergy and Asthma European Network initiative.

BACKGROUND: The causal link between body mass index (BMI) or obesity and asthma in children is still being debated. Analyses of large longitudinal studies with a sufficient number of incident cases and in which the time-dependent processes of both excess weight and asthma development can be validly analyzed are lacking. OBJECTIVE: We sought to investigate whether the course of BMI predicts incident asthma in childhood. METHODS: Data from 12,050 subjects of 8 European birth cohorts on asthma and allergies were combined. BMI and doctor-diagnosed asthma were modeled during the first 6 years of life with latent growth mixture modeling and discrete time hazard models. Subpopulations of children were identified with similar standardized BMI trajectories according to age- and sex-specific "World Health Organization (WHO) child growth standards" and "WHO growth standards for school aged children and adolescents" for children up to age 5 years and older than 5 years, respectively (BMI-SDS). These types of growth profiles were analyzed as predictors for incident asthma. RESULTS: Children with a rapid BMI-SDS gain in the first 2 years of life had a higher risk for incident asthma up to age 6 years than children with a less pronounced weight gain slope in early childhood. The hazard ratio was 1.3 (95% CI, 1.1-1.5) after adjustment for birth weight, weight-for-length at birth, gestational age, sex, maternal smoking in pregnancy, breast-feeding, and family history of asthma or allergies. A rapid BMI gain at 2 to 6 years of age in addition to rapid gain in the first 2 years of life did not significantly enhance the risk of asthma. CONCLUSION: Rapid growth in BMI during the first 2 years of life increases the risk of asthma up to age 6 years