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A new genus and species of stromateiform fish, Butyrumichthys henricii gen. et sp. nov., from the Eocene Fur Formation of Denmark is described. The description is based on six well-preserved, almost complete articulated skeletons plus a well-preserved head. All the specimens originate from the carbonate concretion horizons of the Fur Formation. The fossils were investigated also through element-mapping of strontium and phosphorus using a micro-XRF spectrometer in order to expose and enhance the skeletal anatomy. Butyrumichthys gen. nov. exhibits a unique combination of characters that support its recognition as a new stromateoiform genus, including jaws with uniserially arranged, small conical teeth, preopercle with at least 15 prominent spines, 37–38 (17–18 + 20) vertebrae, dorsal fin with 5–6 weak spines and 27–28 soft rays, and anal fin with two spines and 19–20 soft rays. The new fossil stromateoid described herein shows several morphological similarities to certain species of the genus SchedophilusCocco, 1839, especially S. pemarco (Poll, 1959) and S. medusophagus (Cocco, 1839), and is tentatively referred to the family Centrolophidae. The exceptionally preserved fossil fishes of the Fur Formation increase our knowledge of the diversity of Paleogene marine teleosts, also providing some of the earliest occurrences of modern lineages based on articulated skeletal remains, including that of the stromateiforms. [ABSTRACT FROM AUTHOR]

Stoat (Mustela erminea) and weasel (M. nivalis) are hard to monitor as they are elusive of nature and leave few identifying marks in their surroundings. Stoat and weasel are both fully protected in Denmark and are thought to be widely distributed throughout the country. Despite this stoat and weasel were listed on the Danish Red List as Near Threatened in 2019, as their densities and population trends are unknown. Using a modified novel camera trapping device, the Double‐Mostela, a wooden box comprising a tracking tunnel and two camera traps, we attempted to obtain density estimates based on identification of individual stoats and weasels. We deployed camera traps both inside Double‐Mostela traps and externally in three different study areas in northern Zealand, Denmark, and tested commercial, American scent‐based lures to attract stoat and weasel. We obtained very low seasonal trapping rates of weasel in two study areas, but in one study area, we obtained a seasonal trapping rate of stoat larger compared to another study using the Mostela. In one study area, both species were absent. We observed no effect of scent‐based lures in attracting small mustelids compared to non‐bait traps. Potential reasons behind low capture rates of weasel and stoat are suboptimal habitat placement and timing of deployment of the Double‐Mostelas, land‐use changes over the last 200 years, predation from larger predators, as well as unintended secondary poisoning with rodenticides. Due to the scarcity of weasel and stoat captures, we were unable to make density estimates based on identification of individuals; however, we identified potential features that could be used for identification and density estimates with more captures. [ABSTRACT FROM AUTHOR]

A new genus and species of stromateiform fish, Butyrumichthys henricii gen. et sp. nov., from the Eocene Fur Formation of Denmark is described. The description is based on six well-preserved, almost complete articulated skeletons plus a well-preserved head. All the specimens originate from the carbonate concretion horizons of the Fur Formation. The fossils were investigated also through element-mapping of strontium and phosphorus using a micro-XRF spectrometer in order to expose and enhance the skeletal anatomy. Butyrumichthys gen. nov. exhibits a unique combination of characters that support its recognition as a new stromateoiform genus, including jaws with uniserially arranged, small conical teeth, preopercle with at least 15 prominent spines, 37–38 (17–18 + 20) vertebrae, dorsal fin with 5–6 weak spines and 27–28 soft rays, and anal fin with two spines and 19–20 soft rays. The new fossil stromateoid described herein shows several morphological similarities to certain species of the genus Schedophilus Cocco, 1839, especially S. pemarco (Poll, 1959) and S. medusophagus (Cocco, 1839), and is tentatively referred to the family Centrolophidae. The exceptionally preserved fossil fishes of the Fur Formation increase our knowledge of the diversity of Paleogene marine teleosts, also providing some of the earliest occurrences of modern lineages based on articulated skeletal remains, including that of the stromateiforms. [ABSTRACT FROM AUTHOR]

The earliest Eocene (Ypresian) Fur Formation (Denmark) is globally renowned for its exceptionally well-preserved fossils, including birds, sea turtles, insects, plants, and fishes. Fishes, albeit abundant and diverse, however, are only superficially known and very few detailed, taxonomic studies have been realized to date. A new polymixiiform fish, Polyspinatus fluere gen. et sp. nov., from the Fur Formation is described based on seven well-preserved, nearly complete specimens. All the specimens were studied by traditional stereomicroscopy, and by micro-X-ray fluorescence-element mapping. Digital 2D-element images of strontium-, phosphorus-, and calcium distributions of each specimen were directly applied for the taxonomic descriptions presented herein. Polyspinatus fluere gen. et sp. nov. is the first known Eocene record of the family Polymixiidae based on articulated skeletal remains. Polyspinatus gen. nov. exhibits a unique combination of characters that support its recognition as a new genus of the Polymixiidae. Its specialized hyoid apparatus with the first and second branchiostegal rays being sinuous and parallel to each other, and the third being wide and plate-like, followed by four saber-like elements, is strikingly similar to that of Polymixia, supporting a possible sister-group relationship with extant beardfishes. [ABSTRACT FROM AUTHOR]

The European weather loach ( Misgurnus fossilis ) represents one of many European freshwater fishes in decline. Efficient monitoring is essential if conservation efforts are to be successful, but due to the species’ cryptic biology, traditional monitoring methods currently in use are inefficient, time consuming and likely prone to non-detection error. Here, we investigate the usefulness of environmental DNA (eDNA) monitoring as an alternative or supplementary method for surveying the Danish weather loach population, which is presumed to consist primarily of a single group of no more than 50 individuals. In 2008, the majority of historical Danish localities were surveyed, using traditional fishing techniques. We then applied eDNA methods to a number of these, as well as other potential localities. We successfully detected the weather loach at multiple sites in the single known remaining locality; a result that was later confirmed when local managers caught eight live specimens. Furthermore, the eDNA method indicated presence of the weather loach in another historical locality, where the species has not been observed since 1995. At the remaining localities, weather loach eDNA was not detected, providing further evidence for its absence. Importantly, the eDNA survey required less effort in person-hours and lower costs than the traditional fishing survey. This study confirms that eDNA monitoring is a valid supplement to traditional monitoring methods currently applied to monitor rare freshwater fishes. We propose that by providing reliable distribution data at lower cost and limited effort, the eDNA method can allow for increased management efficiency of endangered freshwater species such as the European weather loach. [ABSTRACT FROM AUTHOR]

Forest successional trajectories covering the last 2000 yr from a mixed deciduous forest in Denmark show a gradual shift in dominance fromTilia cordatatoFagus sylvaticaand a recent increase in total forest basal area since direct management ceased in 1948. The successions are reconstructed by combining a fifty-year record of direct tree observations with local pollen diagrams from Draved Forest, Denmark. Five of the seven successions record a heathland phase of Viking Age dating from 830 AD. The anthropogenic influence is considerable throughout the period of study even though Draved contains some of the most pristine forest stands in Denmark. Anthropogenic influence including felling masks the underlying natural dynamics, with the least disturbed sites showing the smallest compositional change. Some effects of former management, such as loss ofTilia cordatadominance, are irreversible. Artificial disturbance, particularly drainage, has accelerated and amplified the shift towardsFagusdominance that would have occurred on a smaller scale and at a slower rate in the absence of human intervention. [ABSTRACT FROM AUTHOR]

The round goby (Neogobius melanostomus) was first observed in the Baltic Sea in 1990 and has since displayed substantial secondary dispersal, establishing numerous dense populations where they may outcompete native fish and negatively impact prey species. There have been multiple round goby diet studies from both the Baltic Sea and the North American Great Lakes where they are similarly invasive. However, studies that quantify their effects on recipient ecosystems and, specifically, their impacts on the benthic invertebrate macrofauna are rare, particularly from European waters. In this study, we conducted the first before-after study of the potential effects of round goby on benthic invertebrate macrofauna taxa in marine-brackish habitats in Europe, focusing of two sites in the Western Baltic Sea, Denmark. Results were in line with those from the Great Lakes, indicating negative impacts on specific molluscan taxa (e.g. Cardiidae bivalves and Neritidae gastropods, which both showed a fall in detected densities of approximately 98% within the Guldborgsund Strait). In contrast, many other groups appeared to be largely unaffected or even show positive trends following invasion. Round goby gut content data were available at one of our study sites from the period immediately after the invasion. These data confirmed that round goby had in fact been preying on the subset of taxa displaying negative trends. [ABSTRACT FROM AUTHOR]

The round goby (Neogobius melanostomus) was first observed in the Baltic Sea in 1990 and has since displayed substantial secondary dispersal, establishing numerous dense populations where they may outcompete native fish and negatively impact prey species. There have been multiple round goby diet studies from both the Baltic Sea and the North American Great Lakes where they are similarly invasive. However, studies that quantify their effects on recipient ecosystems and, specifically, their impacts on the benthic invertebrate macrofauna are rare, particularly from European waters. In this study, we conducted the first before-after study of the potential effects of round goby on benthic invertebrate macrofauna taxa in marine-brackish habitats in Europe, focusing of two sites in the Western Baltic Sea, Denmark. Results were in line with those from the Great Lakes, indicating negative impacts on specific molluscan taxa (e.g. Cardiidae bivalves and Neritidae gastropods, which both showed a fall in detected densities of approximately 98% within the Guldborgsund Strait). In contrast, many other groups appeared to be largely unaffected or even show positive trends following invasion. Round goby gut content data were available at one of our study sites from the period immediately after the invasion. These data confirmed that round goby had in fact been preying on the subset of taxa displaying negative trends. [ABSTRACT FROM AUTHOR]

The shallow, brackish waters of the western Baltic Sea play a significant role in the life cycle of several commercial fishes, both as nursery and foraging areas. The fish assemblages of the inner 100 m is, however, surprisingly poorly studied, due to lack of effective methods for monitoring all fish species. In the present study, we applied Snorkel Visual Census (SVC) as a tool in monitoring shallow water (< 5 m) fish assemblages at two brackish shallow water localities in the Sound, Denmark. The survey was conducted through 15 consecutive months (June 2013-August 2014), during which a total of 36 species were registered. Assemblages were numerically dominated by Gobiusculus flavescens (Fabricius, 1779) (50%) and Gasterosteus aculeatus Linnaeus, 1758 (45%). Analysis of temporal, spatial and environmental factors revealed that temperature was the single most powerful factor affecting species richness, and had a significant effect on fish abundance, which in addition showed significant seasonal variations. Species richness showed a quadratic correlation to temperature with an optimum of ~14°C. Abundances of individual species were affected by temperature and salinity, and showed both seasonal, spatial and diel variations. The negative effect of high temperatures on species richness was not seen at night, indicating that marine species utilize these areas as nocturnal feeding grounds or to avoid larger predators. Our findings show that SVC is effective in monitoring diversity of shallow, temperate water fish communities providing both qualitative and quantitative information on seasonal variations in species abundance and assemblage structure. [ABSTRACT FROM AUTHOR]