Long-term effects of no-take zones in Swedish waters

Marine protected areas (MPAs) are increasingly established worldwide to protect and restore degraded ecosystems. However, the level of protection varies among MPAs and has been found to affect the outcome of the closure. In no-take zones (NTZs), no fishing or extraction of marine organisms is allowed. The EU Commission recently committed to protect 30% of European waters by 2030 through the updated Biodiversity Strategy. Importantly, one third of these 30% should be of strict protection. Exactly what is meant by strict protection is not entirely clear, but fishing would likely have to be fully or largely prohibited in these areas. This new target for strictly protected areas highlights the need to evaluate the ecological effects of NTZs, particularly in regions like northern Europe where such evaluations are scarce. The Swedish NTZs made up approximately two thirds of the total areal extent of NTZs in Europe a decade ago. Given that these areas have been closed for at least 10 years and can provide insights into long-term effects of NTZs on fish and ecosystems, they are of broad interest in light of the new 10% strict protection by 2030 commitment by EU member states.In total, eight NTZs in Swedish coastal and offshore waters were evaluated in the current report, with respect to primarily the responses of focal species for the conservation measure, but in some of the areas also ecosystem responses. Five of the NTZs were established in 2009-2011, as part of a government commission, while the other three had been established earlier. The results of the evaluations are presented in a synthesis and also in separate, more detailed chapters for each of the eight NTZs. Overall, the results suggest that NTZs can increase abundances and biomasses of fish and decapod crustaceans, given that the closed areas are strategically placed and of an appropriate size in relation to the life cycle of the focal species. A meta-regression of the effects on focal species of the NTZs showed that CPUE was on average 2.6 times higher after three years of protection, and 3.8 times higher than in the fished reference areas after six years of protection. The proportion of old and large individuals increased in most NTZs, and thereby also the reproductive potential of populations. The increase in abundance of large predatory fish also likely contributed to restoring ecosystem functions, such as top-down control. These effects appeared after a 5-year period and in many cases remained and continued to increase in the longer term (>10 years). In the two areas where cod was the focal species of the NTZs, positive responses were weak, likely as an effect of long-term past, and in the Kattegat still present, recruitment overfishing. In the Baltic Sea, predation by grey seal and cormorant was in some cases so high that it likely counteracted the positive effects of removing fisheries and led to stock declines in the NTZs. In most cases, the introduction of the NTZs has likely decreased the total fishing effort rather than displacing it to adjacent areas. In the Kattegat NTZ, however, the purpose was explicitly to displace an unselective coastal mixed bottom-trawl fishery targeting Norway lobster and flatfish to areas where the bycatches of mature cod were smaller. In two areas that were reopened to fishing after 5 years, the positive effects of the NTZs on fish stocks eroded quickly to pre-closure levels despite that the areas remained closed during the spawning period, highlighting that permanent closures may be necessary to maintain positive effects.We conclude from the Swedish case studies that NTZs may well function as a complement to other fisheries management measures, such as catch, effort and gear regulations. The experiences from the current evaluation show that NTZs can be an important tool for fisheries management especially for local coastal fish populations and areas with mixed fisheries, as well as in cases where there is a need to counteract adverse ecosystem effects of fishing. NTZs are also needed as reference for marine environmental management, and for understanding the effects of fishing on fish populations and other ecosystem components in relation to other pressures. MPAs where the protection of both fish and their habitats is combined may be an important instrument for ecosystembased management, where the recovery of large predatory fish may lead to a restoration of important ecosystem functions and contribute to improving decayed habitats.With the new Biodiversity Strategy, EUs level of ambition for marine conservation increases significantly, with the goal of 30% of coastal and marine waters protected by 2030, and, importantly, one third of these areas being strictly protected. From a conservation perspective, rare, sensitive and/or charismatic species or habitats are often in focus when designating MPAs, and displacement of fisheries is then considered an unwanted side effect. However, if the establishment of strictly protected areas also aims to rebuild fish stocks, these MPAs should be placed in heavily fished areas and designed to protect depleted populations by accounting for their home ranges to generate positive outcomes. Thus, extensive displacement of fisheries is required to reach benefits for depleted populations, and need to be accounted for e.g. by specific regulations outside the strictly protected areas. These new extensive EU goals for MPA establishment pose a challenge for management, but at the same time offer an opportunity to bridge the current gap between conservation and fisheries management

Fish communities in gravel pit lakes: The impact of fisheries management and littoral structures

Im ersten Teil meiner Arbeit habe ich den Einfluss von Seeentstehung und fischereilicher Bewirtschaftung auf Artenreichtum und Zusammensetzung der Fischgemeinschaften in kleinen Seen untersucht. Dafür habe ich fischereilich ungenutzte Naturseen als Referenz herangezogen und deren Fischgemeinschaft mit der von unbewirtschafteten Baggerseen, sowie fischereilich genutzten Baggerseen und Naturseen verglichen. Im zweiten Teil meiner Arbeit habe ich die Mechanismen der Totholzrekrutierung in Baggerseen untersucht und die Wichtigkeit von Totholz und anderen Litoralstrukturen im Vergleich zu den klassischen Seenvariablen Nährstoffgehalt und Seemorphologie auf die Fischabundanz im Litoral analysiert. Des Weiteren habe ich die Habitat-spezifischen Effekte auf die artspezifische, litorale Fischabundanz und die Effekte von zusätzlich eingebrachten Totholzbündeln auf die Abundanz typischer Fischarten in Baggerseen analysiert. Ich habe herausgefunden, dass fischereiliche Bewirtschaftung die Anzahl der Fischarten in Bagger- und Naturseen erhöht ohne die Zusammensetzung der Fischgemeinschaft im Vergleich zu fischereilich ungenutzten Naturseen signifikant zu verändern. Im Gegensatz dazu unterscheidet sich die Fischgemeinschaft in fischereilich ungenutzten Baggerseen durch das Fehlen von typischen Seefischarten und eine hohe Variabilität in der Zusammensetzung zwischen den Gewässern. Ich konnte zeigen, dass die litorale Totholzmenge in Baggerseen durch die Baumdichte am Ufer in Kombination mit der Windrichtung, durch fischereiliche Bewirtschaftung in Interaktion mit der Uferneigung und das Alter der Gewässer getrieben wird und entsprechend in jungen Baggerseen niedriger ist als in alten Naturseen. Ich fand heraus, dass Litoralstrukturen, wie Totholz, wertvolle Lebensräume darstellen, wichtige Deskriptoren der art-spezifischen, litoralen Fischabundanz sind und die Fischabundanz grundsätzlich mit der Strukturmenge ansteigt.In the first part of my thesis, I studied the effects of lake genesis and fisheries management on fish species richness and community composition in small lakes. I used fish communities in unmanaged natural lakes as reference and compared them to unmanaged gravel pit lakes as well as managed gravel pit and natural lakes. In the second part, I investigated the recruitment of littoral deadwood in gravel pit lakes and analysed the importance of deadwood and other littoral structures on littoral fish abundance in gravel pit lakes compared to the lake environmental variables such as nutrient level and lake morphology. I further analysed habitat-specific effects on species-specific littoral fish abundance and focussed explicitly on the effects of deadwood bundles implemented in the littoral zone. I found fisheries management to increase the number of fish species in gravel pit and natural lakes, but not leading to different fish community compositions compared to unmanaged natural lakes. By contrast, unmanaged gravel pit lakes were characterized by a lack of typical lake fish species and a high variation in fish community composition among lakes (β-diversity). I detected littoral deadwood densities in gravel pit lakes to be mainly driven by lake age, riparian tree density in interaction with wind direction and littoral slope in angler-managed lakes, with lowest deadwood densities in shallow areas of angler-managed lakes. Furthermore, deadwood densities were lower in young gravel pit lakes compared to old natural lakes. I detected littoral structures, such as littoral deadwood, as appropriate habitats and important descriptors of the species-specific, littoral fish abundance in gravel pit lakes with generally positive effects of structure extension on fish abundance. Littoral habitat characteristics were mostly of similar, or even higher, importance for fish abundance compared to lake environmental factors

Effects of fish predation on density and size spectra of prey fish communities in lakes

Planktivorous and benthivorous fish have been documented to influence the density and size structure of their prey communities in lakes. We hypothesized that piscivorous fish modify their prey fish communities in the same way and sought to find evidence for such predation effects from a comparison across 356 lakes located in nine European ecoregions. We categorized individual fish as being either piscivore, non-piscivore or prey of piscivores, depending on species and individual size. We calculated piscivore, non-piscivore and piscivore prey densities, respectively, and fit linear abundance size spectra (SS) on lake-specific piscivore, non-piscivore and piscivore prey size distributions. Multiple linear regressions were calculated to quantify the effect of piscivore density and SS slopes on non-piscivore and piscivore prey densities and SS slopes, by accounting for potentially confounding factors arising from lake morphometry, productivity and local air temperature. Piscivore density correlated positively with piscivore prey density, but was uncorrelated to density of non-piscivores. Across a subset of 76 lakes for which SS slopes of piscivores were statistically significant, SS slopes of piscivores were uncorrelated with SS slopes of either non-piscivores or piscivore prey. However, densities of piscivores, non-piscivores or piscivore prey were a significant negative predictor of SS slopes of the respective groups. Our analyses suggest that direct predation effects by piscivorous fish on density and size structure of prey fish communities are weak in European lakes, likely caused by low predator-prey size ratios and the resulting size refuges for prey fish. In contrast, competition may substantially contribute to between-lake variability in fish density and size

Proceedings of the FEniCS Conference 2017

Proceedings of the FEniCS Conference 2017 that took place 12-14 June 2017 at the University of Luxembourg, Luxembourg

SASSY21: A 3-D Seismic Structural Model of the Lithosphere and Underlying Mantle Beneath Southeast Asia From Multi-Scale Adjoint Waveform Tomography

Abstract: We present the first continental‐scale seismic model of the lithosphere and underlying mantle beneath Southeast Asia obtained from adjoint waveform tomography (often referred to as full‐waveform inversion or FWI), using seismic data filtered at periods from 20 to 150 s. Based on >3,000 hr of analyzed waveform data gathered from ∼13,000 unique source‐receiver pairs, we image isotropic P‐wave velocity, radially anisotropic S‐wave velocity and density via an iterative non‐linear inversion that begins from a 1‐D reference model. At each iteration, the full 3‐D wavefield is determined through an anelastic Earth, accommodating effects of topography, bathymetry and ocean load. Our data selection aims to maximize sensitivity to deep structure by accounting for body wave arrivals separately. SASSY21, our final model after 87 iterations across seven period bands, is able to explain true‐amplitude data from events and receivers not included in the inversion. The trade‐off between inversion parameters is estimated through an analysis of the Hessian‐vector product. SASSY21 reveals detailed anomalies down to the mantle transition zone, including multiple subduction zones. The most prominent feature is the (Indo‐)Australian plate descending beneath Indonesia, which is imaged as one continuous slab along the 180° curvature of the Banda Arc. The tomography confirms the existence of a hole in the slab beneath Mount Tambora and locates a high S‐wave velocity zone beneath northern Borneo that may be associated with subduction termination in the mid‐late Miocene. A previously undiscovered feature beneath the east coast of Borneo is also revealed, which may be a signature of post‐subduction processes, delamination or underthrusting from the formation of Sulawesi

Regionalizing Aquatic Ecosystems Based on the River Subbasin Taxonomy Concept and Spatial Clustering Techniques

Aquatic ecoregions were increasingly used as spatial units for aquatic ecosystem management at the watershed scale. In this paper, the principle of including land area, comprehensiveness and dominance, conjugation and hierarchy were selected as regionalizing principles. Elevation and drainage density were selected as the regionalizing indicators for the delineation of level I aquatic ecoregions, and percent of construction land area, percent of cultivated land area, soil type and slope for the level II. Under the support of GIS technology, the spatial distribution maps of the two indicators for level I and the four indicators for level II aquatic ecoregion delineation were generated from the raster data based on the 1,107 subwatersheds. River subbasin taxonomy concept, two-step spatial clustering analysis approach and manual-assisted method were used to regionalize aquatic ecosystems in the Taihu Lake watershed. Then the Taihu Lake watershed was divided into two level I aquatic ecoregions, including Ecoregion I1 and Ecoregion I2, and five level II aquatic subecoregions, including Subecoregion II11, Subecoregion II12, Subecoregion II21, Subecoregion II22 and Subecoregion II23. Moreover, the characteristics of the two level I aquatic ecoregions and five level II aquatic subecoregions in the Taihu Lake watershed were summarized, showing that there were significant differences in topography, socio-economic development, water quality and aquatic ecology, etc. The results of quantitative comparison of aquatic life also indicated that the dominant species of fish, benthic density, biomass, dominant species, Shannon-Wiener diversity index, Margalef species richness index, Pielou evenness index and ecological dominance showed great spatial variability between the two level I aquatic ecoregions and five level II aquatic subecoregions. It reflected the spatial heterogeneities and the uneven natures of aquatic ecosystems in the Taihu Lake watershed

Performance and programmability comparison of the thick control flow architecture and current multicore processors

Commercial multicore central processing units (CPU) integrate a number of processor cores on a single chip to support parallel execution of computational tasks. Multicore CPUs can possibly improve performance over single cores for independent parallel tasks nearly linearly as long as sufficient bandwidth is available. Ideal speedup is, however, difficult to achieve when dense intercommunication between the cores or complex memory access patterns is required. This is caused by expensive synchronization and thread switching, and insufficient latency toleration. These facts guide programmers away from straight-forward parallel processing patterns toward complex and error-prone programming techniques. To address these problems, we have introduced the Thick control flow (TCF) Processor Architecture. TCF is an abstraction of parallel computation that combines self-similar threads into computational entities. In this paper, we compare the performance and programmability of an entry-level TCF processor and two Intel Skylake multicore CPUs on commonly used parallel kernels to find out how well our architecture solves these issues that greatly reduce the productivity of parallel software development. Code examples are given and programming experiences recorded

Multiscale approach applied to fires in tunnels, Model optimization and development

L'abstract è presente nell'allegato / the abstract is in the attachmen