InvaCost, a public database of the economic costs of biological invasions worldwide.

Biological invasions are responsible for tremendous impacts globally, including huge economic losses and management expenditures. Efficiently mitigating this major driver of global change requires the improvement of public awareness and policy regarding its substantial impacts on our socio-ecosystems. One option to contribute to this overall objective is to inform people on the economic costs linked to these impacts; however, until now, a reliable synthesis of invasion costs has never been produced at a global scale. Here, we introduce InvaCost as the most up-to-date, comprehensive, harmonised and robust compilation and description of economic cost estimates associated with biological invasions worldwide. We have developed a systematic, standardised methodology to collect information from peer-reviewed articles and grey literature, while ensuring data validity and method repeatability for further transparent inputs. Our manuscript presents the methodology and tools used to build and populate this living and publicly available database. InvaCost provides an essential basis (2419 cost estimates currently compiled) for worldwide research, management efforts and, ultimately, for data-driven and evidence-based policymaking.

FishMORPH - An agent-based model to predict salmonid growth and distribution responses under natural and low flows.

Predicting fish responses to modified flow regimes is becoming central to fisheries management. In this study we present an agent-based model (ABM) to predict the growth and distribution of young-of-the-year (YOY) and one-year-old (1+) Atlantic salmon and brown trout in response to flow change during summer. A field study of a real population during both natural and low flow conditions provided the simulation environment and validation patterns. Virtual fish were realistic both in terms of bioenergetics and feeding. We tested alternative movement rules to replicate observed patterns of body mass, growth rates, stretch distribution and patch occupancy patterns. Notably, there was no calibration of the model. Virtual fish prioritising consumption rates before predator avoidance replicated observed growth and distribution patterns better than a purely maximising consumption rule. Stream conditions of low predation and harsh winters provide ecological justification for the selection of this behaviour during summer months. Overall, the model was able to predict distribution and growth patterns well across both natural and low flow regimes. The model can be used to support management of salmonids by predicting population responses to predicted flow impacts and associated habitat change.

Predicting global invasion risks: a management tool to prevent future introductions.

Predicting regions at risk from introductions of non-native species and the subsequent invasions is a fundamental aspect of horizon scanning activities that enable the development of more effective preventative actions and planning of management measures. The Asian cyprinid fish topmouth gudgeon Pseudorasbora parva has proved highly invasive across Europe since its introduction in the 1960s. In addition to direct negative impacts on native fish populations, P. parva has potential for further damage through transmission of an emergent infectious disease, known to cause mortality in other species. To quantify its invasion risk, in regions where it has yet to be introduced, we trained 900 ecological niche models and constructed an Ensemble Model predicting suitability, then integrated a proxy for introduction likelihood. This revealed high potential for P. parva to invade regions well beyond its current invasive range. These included areas in all modelled continents, with several hotspots of climatic suitability and risk of introduction. We believe that these methods are easily adapted for a variety of other invasive species and that such risk maps could be used by policy-makers and managers in hotspots to formulate increased surveillance and early-warning systems that aim to prevent introductions and subsequent invasions.

Eutrophication as a driver of r-selection traits in a freshwater fish.

This study tested whether eutrophication could influence life-history traits of a cyprinid, Chanodichthys erythropterus, in 10 Chinese lakes. Using the von Bertalanffy growth model, the asymptotic length (L∞ ) and the growth performance index (IGRO ) were significantly affected by eutrophication. The gonado-somatic index (IG ) and relative fecundity (FR ) were significantly lower in mesotrophic lakes than in eutrophic and hypertrophic lakes. These results indicate that increasing eutrophication affects the life-history tactics of a freshwater fish.

Rapid growth increases intrinsic predation risk in genetically modified Cyprinus carpio: implications for environmental risk.

The intrinsic effect of feeding regime on survival and predation-induced mortality was experimentally tested in genetically modified (GM) Cyprinus carpio and wild specimens. The results clearly indicate a knock-on effect of the GH gene (gcGH) introduction into the C. carpio genome on their vulnerability to predation. The experiments unequivocally showed that it is the genetic nature of the C. carpio rather than its size that affects the risk of predation. In addition, fed C. carpio were more susceptible to predation risk. Thus, the study characterizes the existence of a trade-off between somatic growth and predator avoidance performance. Current research in Europe suggests that high uncertainty surrounding the potential environmental effects of escapee transgenic fishes into the wild is largely due to uncertainty in how the modified gene will be expressed. Understanding variables such as the cost of rapid growth on antipredator success would prove to be pivotal in setting up sound risk assessments for GM fishes and in fully assessing the environmental risk associated with GM fish escapees.

Individual genetic tagging for teleosts: an empirical validation and a guideline for ecologists.

The efficiency of individual genetic tagging was determined by using passive integrated transponders (PIT) as a comparative conventional tagging method. Fifty-five common dace Leuciscus leuciscus were captured in the wild, PIT tagged and fin clipped (for DNA analysis). Thirty fish were recaptured on three occasions and tissue samples were collected. Using 18 microsatellite loci, 79-94% of the recaptures were correctly assigned. Experience with scoring L. leuciscus microsatellites led to more individuals correctly assigned. Allowing matches that differed by one or two alleles resulted in 100% of all recaptures successfully assigned irrespective of the observer. Reducing the set of loci to five to six loci appropriately selected did not affect the assignment rate, demonstrating that costs can be subsequently reduced. Despite their potential benefits, the application of genetic tags for teleosts has been limited. Here, it was demonstrated that genetic tagging could be applied, and a clear guideline (flowchart) is provided on how this method can be developed for teleosts and other organisms, with subsequent practical applications to ecology, evolutionary biology and conservation management.

Out of sight out of mind: current knowledge of Chinese cave fishes.

Caves and karsts are among the most threatened ecosystems in the world. They are very fragile, balanced habitats with high levels of endemic species that are extremely sensitive to environmental changes. In recent decades, however, threats from rapid economic growth have increased the need for conservation efforts for cave-dwelling communities. In addition, difficulties in accessing and sampling these habitats mean that they remain as one of the least known ecosystems in the world with modern studies of cave fishes only starting in China during the 1980s. Here, the current status of cave fishes in China is reviewed. China is host to the highest number of cave fish species in the world, with 48 troglobite species out of a total of 101 cave fish species. All of these cave fish species (one order and three families) and half of the genera are endemic to China with Sinocyclocheilus being the most speciose cave fish genus. Species from this genus possess horns and humpbacks resulting from processes of parallel evolution, but the function of these features remains unknown. With the exception of Onychostoma macrolepis distributed in north China, all other species are found in the karst environment of the Yunnan-Guizhou Plateau. Sympatric distribution is common, and sometimes several different cave fish species can be found in the same cave or subterranean river. For this reason, Chinese cave fishes represent an important evolutionary framework.

Sphaerothecum destruens pathology in cyprinids.

Sphaerothecum destruens is a significant intracellular parasite of fish which has caused disease and mortalities in cultured north American Chinook salmon Oncorhynchus tshawytscha and Atlantic salmon Salmo salar. Several hosts for S. destruens have been identified within the Salmonidae family, and the histopathology of the infection can differ between hosts. Recently, S. destruens has been associated with the most invasive cyprinid species in Europe, topmouth gudgeon Pseudorasbora parva. Accurate disease identification based on thorough descriptions of clinical signs and histopathology in this new range of hosts is thus paramount to support further epizootiological studies. In this study, the associated histopathology of S. destruens infection is described along with its pathogenesis in the endangered cyprinid sunbleak Leucaspius delineatus. Histological examination of 100 L. delineatus in a wild population in the south of England revealed the presence of S. destruens infections, with a prevalence of 5% with S. destruens, suggesting an over-dispersed distribution within the L. delineatus sample. Clinical signs of the infection were absent, but histological examination revealed the presence of both disseminated and nodular lesions in several organs.

Influence of host reproductive state on Sphaerothecum destruens prevalence and infection level.

Sphaerothecum destruens is an obligate intracellular parasite with the potential to cause high mortalities and spawning inhibition in the endangered cyprinid Leucaspius delineatus. We investigated the influence of L. delineatus's reproductive state on the prevalence and infection level of S. destruens. A novel real time quantitative polymerarse chain reaction (qPCR) was developed to determine S. destruens' prevalence and infection level. These parameters were quantified and compared in reproductive and non-reproductive L. delineatus. The detection limit of the S. destruens specific qPCR was determined to be 1 pg of purified S. destruens genomic DNA. Following cohabitation in the lab, reproductive L. delineatus had a significantly higher S. destruens prevalence (P<0.05) and infection levels (P<0.01) compared to non-reproductive L. delineatus. S. destruens prevalence was 19% (n=40) in non-reproductive L. delineatus and 41% (n=32) in reproductive L. delineatus. However, there was no difference in S. destruens prevalence in reproductive and non-reproductive fish under field conditions. Mean infection levels were 18 and 99 pg S. destruens DNA per 250 ng L. delineatus DNA for non-reproductive and reproductive L. delineatus respectively. The present work indicates that S. destruens infection in L. delineatus can be influenced by the latter's reproductive state and provides further support for the potential adverse impact of S. destruens on the conservation of L. delineatus populations.

Temperature influence on production and longevity of Sphaerothecum destruens zoospores.

The majority of pathogens that cause high host mortalities are capable of infecting more than 1 host species. One characteristic of pathogens, which enables infection of multiple hosts, is the existence of free-living infectious stages, e.g., zoospores that are produced in vast numbers. Understanding the influence of environmental factors, particularly temperature, on the production and survival of these free-living stages is key to predicting future spread and emergence of disease. The rosette agent, Sphaerothecum destruens, is a significant multi-host intracellular fish parasite, with an obligate intracellular spore stage and a free-living (extracellular), potentially infectious, zoospore stage. It has caused high mortalities in endangered and commercially important fish species. Here we investigate the influence of temperature on S. destruens zoospore production and longevity. Our results indicate a wide temperature tolerance of the spore and zooflagellate stage with later onset and longer lifespan of zoospores at lower temperatures. This has important implications for the environmental persistence of S. destruens and provides additional information on the pathogen's life cycle with direct implications for S. destruens risk assessment.

Morphological variability of the Asiatic cyprinid, topmouth gudgeon Pseudorasbora parva, in its introduced European range.

To assess the spatial variability in external morphology of non-native populations of topmouth gudgeon Pseudorasbora parva within an ontogenetic context, triple regression analysis (distance-based measurements) was applied to data from eight European populations (two Slovak, four Romanian, one English and one French). The data from Slovakia were also subjected to geometrical analysis (co-ordinates-based measurements) to obtain a more complex picture of the species' overall morphology. Great phenotypic variability was observed, being expressed not only in the formation of different definite phenotypes but also in the manner by which the phenotypes are achieved. Thus, both the definite phenotype and the patterns of development in invasive P. parva may be highly influenced by environmental conditions. Such great morphological (phenotypic) variability is likely to be one of the attributes that make this species such a successful invader.

Twenty-four hours in the life of Zingel asper.

For the first time, radio-tracking observations were made over 24 h cycles during the growing season to quantify the habitat use and home range of Zingel asper, a critically endangered fish species, endemic to the Rhône River with a high risk of extinction (IUCN). New advances in radio telemetry with regard to the size of tags provided an opportunity to collect behavioural and habitat use information while remaining non-lethal. Zingel asper was characterized by small ranges of habitat use and, contrary to previous assumptions, the species was diurnal as illustrated by a smaller home range during the night than during daytime.