Inferring functional extinction based on sighting records

© The Author(s), 2016. This is the author's version of the work and is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Biological Conservation 199 (2016): 84-87, doi:10.1016/j.biocon.2016.04.034.The term functional extinction is used to describe a permanent failure of reproduction or recruitment in a population. Functional extinction results in a truncation of the age distribution, but this can be very difficult to detect in poorly studied populations. Here, we describe a novel statistical method for detecting functional extinction based on a sighting record of individuals of known or estimated ages. The method is based on a simple population dynamics model and simulation results show that it works well even with limited data. The method is illustrated using a sighting record of the ship sturgeon (Acipenser nudiventris) in the Danube River. The results indicate that this population is functionally extinct, most likely by 2002. Management implications of this finding are discussed.The authors also acknowledge the sponsorship provided by the Alexander von Humboldt Foundation and the Federal German Ministry for Education and Research, as well as the support by the Project No. 173045, funded by the Ministry of Education, Science and Technological Development of the Republic of Serbia.2017-05-1

Freshwater megafauna shape ecosystems and facilitate restoration

Freshwater megafauna, such as sturgeons, giant catfishes, river dolphins, hippopotami, crocodylians, large turtles, and giant salamanders, have experienced severe population declines and range contractions worldwide. Although there is an increasing number of studies investigating the causes of megafauna losses in fresh waters, little attention has been paid to synthesising the impacts of megafauna on the abiotic environment and other organisms in freshwater ecosystems, and hence the consequences of losing these species. This limited understanding may impede the development of policies and actions for their conservation and restoration. In this review, we synthesise how megafauna shape ecological processes in freshwater ecosystems and discuss their potential for enhancing ecosystem restoration. Through activities such as movement, burrowing, and dam and nest building, megafauna have a profound influence on the extent of water bodies, flow dynamics, and the physical structure of shorelines and substrata, increasing habitat heterogeneity. They enhance nutrient cycling within fresh waters, and cross-ecosystem flows of material, through foraging and reproduction activities. Freshwater megafauna are highly connected to other freshwater organisms via direct consumption of species at different trophic levels, indirect trophic cascades, and through their influence on habitat structure. The literature documenting the ecological impacts of freshwater megafauna is not evenly distributed among species, regions, and types of ecological impacts, with a lack of quantitative evidence for large fish, crocodylians, and turtles in the Global South and their impacts on nutrient flows and food-web structure. In addition, population decline, range contraction, and the loss of large individuals have reduced the extent and magnitude of megafaunal impacts in freshwater ecosystems, rendering a posteriori evaluation more difficult. We propose that reinstating freshwater megafauna populations holds the potential for restoring key ecological processes such as disturbances, trophic cascades, and species dispersal, which will, in turn, promote overall biodiversity and enhance nature's contributions to people. Challenges for restoration actions include the shifting baseline syndrome, potential human–megafauna competition for habitats and resources, damage to property, and risk to human life. The current lack of historical baselines for natural distributions and population sizes of freshwater megafauna, their life history, trophic interactions with other freshwater species, and interactions with humans necessitates further investigation. Addressing these knowledge gaps will improve our understanding of the ecological roles of freshwater megafauna and support their full potential for facilitating the development of effective conservation and restoration strategies to achieve the coexistence of humans and megafauna

Science responses to IUCN Red Listing

The IUCN Red List of Threatened Species is often advocated as a tool to assist decision-making in conservation investment and research focus. It is frequently suggested that research efforts should prioritize species in higher threat categories and those that are Data Deficient (DD). We assessed the linkage between IUCN listing and research effort in DD and Critically Endangered (CR) species, two groups generally advocated as research priorities. The analysis of the change in the research output following species classification indicated a listing effect in DD species, while such effect was observed in only a minority of CR species groups. DD species, while chronically understudied, seem to be recognized as research priorities, while research effort for endangered species appears to be driven by various factors other than the IUCN listing. Optimized conservation research focus would require international science planning efforts, harmonized through international mechanisms and promoted by financial and other incentives

Freshwater megafauna shape ecosystems and facilitate restoration

Freshwater megafauna, such as sturgeons, giant catfishes, river dolphins, hippopotami, crocodylians, large turtles, and giant salamanders, have experienced severe population declines and range contractions worldwide. Although there is an increasing number of studies investigating the causes of megafauna losses in fresh waters, little attention has been paid to synthesising the impacts of megafauna on the abiotic environment and other organisms in freshwater ecosystems, and hence the consequences of losing these species. This limited understanding may impede the development of policies and actions for their conservation and restoration. In this review, we synthesise how megafauna shape ecological processes in freshwater ecosystems and discuss their potential for enhancing ecosystem restoration. Through activities such as movement, burrowing, and dam and nest building, megafauna have a profound influence on the extent of water bodies, flow dynamics, and the physical structure of shorelines and substrata, increasing habitat heterogeneity. They enhance nutrient cycling within fresh waters, and cross-ecosystem flows of material, through foraging and reproduction activities. Freshwater megafauna are highly connected to other freshwater organisms via direct consumption of species at different trophic levels, indirect trophic cascades, and through their influence on habitat structure. The literature documenting the ecological impacts of freshwater megafauna is not evenly distributed among species, regions, and types of ecological impacts, with a lack of quantitative evidence for large fish, crocodylians, and turtles in the Global South and their impacts on nutrient flows and food-web structure. In addition, population decline, range contraction, and the loss of large individuals have reduced the extent and magnitude of megafaunal impacts in freshwater ecosystems, rendering a posteriori evaluation more difficult. We propose that reinstating freshwater megafauna populations holds the potential for restoring key ecological processes such as disturbances, trophic cascades, and species dispersal, which will, in turn, promote overall biodiversity and enhance nature's contributions to people. Challenges for restoration actions include the shifting baseline syndrome, potential human–megafauna competition for habitats and resources, damage to property, and risk to human life. The current lack of historical baselines for natural distributions and population sizes of freshwater megafauna, their life history, trophic interactions with other freshwater species, and interactions with humans necessitates further investigation. Addressing these knowledge gaps will improve our understanding of the ecological roles of freshwater megafauna and support their full potential for facilitating the development of effective conservation and restoration strategies to achieve the coexistence of humans and megafauna.Villum Fonden http://dx.doi.org/10.13039/100008398Leibniz‐Gemeinschaft http://dx.doi.org/10.13039/501100001664Danmarks Frie Forskningsfond http://dx.doi.org/10.13039/501100004836Danmarks Grundforskningsfond http://dx.doi.org/10.13039/501100001732Deutscher Akademischer Austauschdienst http://dx.doi.org/10.13039/501100001655Chinese Academy of Sciences http://dx.doi.org/10.13039/501100002367Peer Reviewe

Freshwater megafauna shape ecosystems and facilitate restoration

Author Keywords: body size; conservation; dispersal; ecosystem function; keystone species; large animal; nature's contributions to people; reintroduction; top predator; trophic complexity.Freshwater megafauna, such as sturgeons, giant catfishes, river dolphins, hippopotami, crocodylians, large turtles, and giant salamanders, have experienced severe population declines and range contractions worldwide. Although there is an increasing number of studies investigating the causes of megafauna losses in fresh waters, little attention has been paid to synthesising the impacts of megafauna on the abiotic environment and other organisms in freshwater ecosystems, and hence the consequences of losing these species. This limited understanding may impede the development of policies and actions for their conservation and restoration. In this review, we synthesise how megafauna shape ecological processes in freshwater ecosystems and discuss their potential for enhancing ecosystem restoration. Through activities such as movement, burrowing, and dam and nest building, megafauna have a profound influence on the extent of water bodies, flow dynamics, and the physical structure of shorelines and substrata, increasing habitat heterogeneity. They enhance nutrient cycling within fresh waters, and cross-ecosystem flows of material, through foraging and reproduction activities. Freshwater megafauna are highly connected to other freshwater organisms via direct consumption of species at different trophic levels, indirect trophic cascades, and through their influence on habitat structure. The literature documenting the ecological impacts of freshwater megafauna is not evenly distributed among species, regions, and types of ecological impacts, with a lack of quantitative evidence for large fish, crocodylians, and turtles in the Global South and their impacts on nutrient flows and food-web structure. In addition, population decline, range contraction, and the loss of large individuals have reduced the extent and magnitude of megafaunal impacts in freshwater ecosystems, rendering a posteriori evaluation more difficult. We propose that reinstating freshwater megafauna populations holds the potential for restoring key ecological processes such as disturbances, trophic cascades, and species dispersal, which will, in turn, promote overall biodiversity and enhance nature’s contributions to people. Challenges for restoration actions include the shifting baseline syndrome, potential human–megafauna competition for habitats and resources, damage to property, and risk to human life. The current lack of historical baselines for natural distributions and population sizes of freshwater megafauna, their life history, trophic interactions with other freshwater species, and interactions with humans necessitates further investigation. Addressing these knowledge gaps will improve our understanding of the ecological roles of freshwater megafauna and support their full potential for facilitating the development of effective conservation and restoration strategies to achieve the coexistence of humans and megafauna.Villum Fonden. Grant Number: 16549Leibniz-GemeinschaftDanmarks Frie Forskningsfond. Grant Number: 1131-00006BDanmarks Grundforskningsfond. Grant Number: DNRF173Deutscher Akademischer AustauschdienstChinese Academy of Sciences. Grant Number: E355S12

Diversity of immunoglobulin light chain genes in non-teleost ray-finned fish uncovers IgL subdivision into five ancient isotypes

<p>The aim of this study was to fill important gaps in the evolutionary history of immunoglobulins by examining the structure and diversity of IgL genes in non-teleost ray-finned fish. First, based on the bioinformatic analysis of recent transcriptomic and genomic resources, we experimentally characterized the IgL genes in the chondrostean fish, Acipenser ruthenus (sterlet). We show that this species has three loci encoding IgL kappa-like chains with a translocon-type gene organization and a single VJC cluster, encoding homogeneous lambda-like light chain. In addition, sterlet possesses sigma-like VL and J-CL genes, which are transcribed separately and both encode protein products with cleavable leader peptides. The Acipenseriformes IgL dataset was extended by the sequences mined in the databases of species belonging to other non-teleost lineages of ray-finned fish: Holostei and Polypteriformes. Inclusion of these new data into phylogenetic analysis showed a clear subdivision of IgL chains into five groups. The isotype described previously as the teleostean IgL lambda turned out to be a kappa and lambda chain paralog that emerged before the radiation of ray-finned fish. We designate this isotype as lambda-2. The phylogeny also showed that sigma-2 IgL chains initially regarded as specific for cartilaginous fish are present in holosteans, polypterids, and even in turtles. We conclude that there were five ancient IgL isotypes, which evolved differentially in various lineages of jawed vertebrates.</p

Paddlefish (Polyodon spathula) in Europe: An aquaculture species and a potential invader

The paddlefish (Polyodon spathula) was first introduced to Europe in 1974, mainly due to its potential for rearing in natural polyculture ponds and large temperate reservoirs. The information on the history of paddlefish aquaculture efforts in Europe is scarce, as well as data on current paddlefish aquaculture status and trends. In addition, there is a lack of data on its presence and potential establishment in the wild, while its invasive potential and associated risks and impacts are largely unknown. In order to evaluate its current status in Europe, we conducted a survey among scientists, aquaculture producers and other stakeholders, and reviewed literature and data on the Internet. Based on the results obtained, we discuss the potential and the challenges in European paddlefish aquaculture development, and analyze paddlefish invasive potential and risks associated with its naturalization. Paddlefish aquaculture is well established only regionally in Europe, but offers relatively high potential for further development in pond farms. Nevertheless, future development will require careful planning, especially regarding market development and improved marketing strategies. While paddlefish likely represents a low-risk invader, improved control and reporting on trade and intentional and unintentional releases will be required. Given the lack of knowledge on potential impacts following its introduction, due caution seems highly advisable.This is the peer reviewed version of the following article: Jarić I, Bronzi P, Cvijanović G, Lenhardt M, Smederevac-Lalić M, Gessner J. Paddlefish (Polyodon spathula) in Europe: An aquaculture species and a potential invader. J Appl Ichthyol. 2018, which has been published in final form at [http://doi.org/10.1111/jai.13672]. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving

WePass Störe am Eisernen Tor Wiederherstellung der Durchgängkeit an den Staustufen Iron Gate 1 & 2 in der Unteren Donau

Das Einzugsgebiet der 2.857 km langen Donau ist mit einer Gesamtfläche von 801.463 km² - rund 10% des europäischen Festlands - das zweitgrößte Flusseinzugsgebiet in Europa. Es erstreckt sich über 19 Länder und ist damit das internationalste Flusseinzugsgebiet der Welt. Über 100 Fischarten sind in der Donau nachgewiesen, darunter vier hochgradig gefährdete Störarten, die charakteristischen Flaggschiffarten der Donau (SCHIEMER ET AL. 2004). Die diadromen Donaufischarten (z. B. Störe (Acipenser spp.), Pontischer Maifisch (Alosa immaculata), Asowscher Maifisch (Alosa tanaica) und Schwarzmeerforelle (Salmo labrax)) sind zwingend darauf angewiesen ihren Lebenszyklus im Süß- und Salzwasser zu vollziehen. Einige Arten wandern bzw. wanderten dabei über sehr große Distanzen, beispielsweise der Beluga-Stör (Huso huso) vom Schwarzen Meer bis zu den Laichgründen >2.500 km ins Landesinnere (SCHMALL & FRIEDRICH 2014). Aber auch potamodrome Arten migrieren in der Donau über weite Strecken; für Döbel (Leuciscus cephalus), Barbe (Barbus barbus) und Nase (Chondrostoma nasus) sind z. B. Wanderungen über 169, 318 und 446 km nachgewiesen (STEINMANN ET AL. 1937, VAN TREECK ET AL. 2022). Die Fischartenzusammensetzung und der Fischbestand sind wichtige Indikatoren für die Gewässerqualität der Donau. Die Ergebnisse des jüngsten Joint Danube Survey 4 zeigen, dass die Fischartengemeinschaft entlang des gesamten Flusslaufs bedroht ist. Andererseits ist die Vielfalt der Fischtaxa immer noch auf einem Niveau, als dass wirksame Gewässerentwicklungsmaßnahmen dazu beitragen können den ökologischen Zustand bzw. das ökologische Potential zu verbessern und die Ziele der EG-WRRL zu erreichen (BĂNĂDUC ET AL. 2014, ICPDR 2021)

WEPASS Project - Making the Iron Gate Dams passable for migratory fish

European rivers are obstructed by more than one million barriers that have resulted in excessive loss of river continuity. On the main course of the Danube River there are 83 longitudinal continuity interruptions, out of which 65 dams are used for hydropower (ICPDR 2022a). The Iron Gate Hydropower and Navigation System is one of the largest river engineering projects undertaken in Europe, with the dams mainly built to provide hydropower and flood protection, and to facilitate navigation along the Danube. These infrastructures represent introduced barriers to fish migration. Hence, ensuring passage opportunities for fish at the Iron Gate dams is considered to be of major importance for the conservation of migratory fish populations in the Danube River basin. Restoration of river continuity at these sites would reopen an additional 900 km for migration up to the Gabčikovo dam, providing suitable habitats and spawning grounds along the Danube and its tributaries. Knowledge about fish behavior and movements in the vicinity of these river infrastructures is required to build effective up- and downstream passage facilities to allow the migration of fish species. To gain insight in the approach routes and aggregation areas a refined approach to acoustic telemetry is employed to support migration facilitation