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Life history plasticity can be a strong predictor of the establishment and invasion success of introduced fishes. Here, the life‐history traits of four P. parva populations in adjacent ponds in Southern England were measured throughout 2013 to determine the timing and length of their reproductive season and the extent of trait plasticity. The relative abundance of the populations (as catch per unit effort) was similar, with low variability in their traits relating to reproductive effort and somatic growth. All the populations were male dominated. Both sexes matured at small body sizes, with fish as small as 30 mm being mature in both sexes, with the age at maturity for both sexes being age 1+ years. The peak spawning period, characterised by female fish investing heavily in reproduction when their gonado‐somatic index (GSI) values were highest and declined thereafter, occurred in May and June, and after a mean of 212 ± 24 degree‐days >12°C, and with water temperatures being 13.2–14.6°C. There were no further peaks in GSI, despite the species being considered to have prolonged spawning periods across spring and summer. These results also suggest that whilst the expression of life‐history traits of invasive fishes often vary with density, they can be highly consistent between populations at similar abundances and locations. [ABSTRACT FROM AUTHOR]

Policies and legislation for the importation and use of non-native (NN) freshwater fishes have been rapidly evolving in several countries around the world in response to heightened evidence of their adverse ecological and economic impacts. In China, the already large and growing number of NN freshwater fishes being imported from foreign countries or translocated within China has necessitated the development of management strategies supported by policies at both national and regional levels. Despite increasing awareness of the damage caused by NN fishes, such initiatives in China continue to lag behind those already implemented in other countries. This study endeavors to narrow this policy gap by: (i) providing a synoptic overview of the vectors and pathways of NN freshwater fish introductions and dispersal both into and within China; (ii) evaluating existing policies and legislation relative to those currently implemented in Europe, the USA and Canada; (iii) examining the role of decision-support tools for identifying and assessing the risks posed by NN fishes; and (iv) proposing perspectives and possible options for NN fish policies, legislation and management in China. [ABSTRACT FROM AUTHOR]

The crucian carp Carassius carassius, a cyprinid fish characteristic of small ponds, is in decline throughout most of its European range, including in England where it is currently thought to be non‐native.The present study, undertaken by the Norfolk Crucian Project, reports on reductions in pond populations of crucian carp in Norfolk, eastern England as well as the success of recent introduction/re‐introduction efforts in terms of crucian survival, recruitment and growth over the last 10 years.A 72% decline in crucian carp distribution was observed between the 1950s–1980s and the 2010s. Of 18 crucian carp introductions/re‐introductions to restored and suitable existing ponds, 17 were successful in terms of survival, increasing the number of current crucian sites in Norfolk by 37%. Recruitment of young crucian carp was demonstrated for 12 of the 18 stocked ponds, with apparent elevated juvenile growth relative to other English and European populations.Delays in, or a lack of, crucian recruitment in some ponds appeared to result from the presence of other fish species (especially threespine stickleback Gasterosteus aculeatus) with predation and interspecific competition possible contributory factors.This study shows that, through combinations of pond rehabilitation and stocking, it has been possible to achieve a substantial recovery of crucian carp populations in the study region. Although the crucian carp is currently presumed to be non‐native within England, given other scientific studies that show a lack of adverse impacts of this species on native biota, and because it is greatly threatened in its native range, the call is sounded for more crucian carp conservation projects in other parts of England as well as in Europe more generally. [ABSTRACT FROM AUTHOR]

Information about the socioeconomic drivers of Silurus glanis anglers in the UK were collected using questionnaires from a cross section of mixed cyprinid fisheries to elucidate human dimensions in angling and non-native fisheries management. Respondents were predominantly male (95%), 30–40 years of age with <10 yr angling experience for S. glanis; most had received college rather than university education. The majority (34%) were employed with low-moderate income status (<£30k per annum), which may restrict time and expenditure spent on angling. Highest angling expenditure was on equipment and bait with most from southern England (54%) spending >£500 per annum. The proportion of time spent angling for S. glanis was significantly related to angler motivations; fish size, challenge in catch, tranquil natural surroundings, escape from daily stress and to be alone were considered important drivers of increased time spent angling. Overall, poor awareness of: the risks and adverse ecological impacts associated with introduced S. glanis, non-native fisheries legislation, problems in use of unlimited ground bait and high fish stocking rates in angling lakes were evident, possibly related to inadequate training and information provided by angling organisations to anglers, as many stated that they were insufficiently informed. [ABSTRACT FROM AUTHOR]

Plasticity in life-history traits provides advantages for introduced fish in overcoming demographic bottlenecks that would otherwise inhibit establishment. Here, the influence of population density, temperature and latitude was tested on the growth increments and growth rates of invasive populations of topmouth gudgeon Pseudorasbora parva, a small Asian cyprinid fish that is invasive across Europe. Aquaria experiments tested the roles of fish number and temperature on growth increments under a fixed food supply, pond experiments tested the role of density on growth increments, and a field study completed in England and Wales tested the influence of density and latitude on growth rates. In aquaria experiments, whilst growth increments were higher at 21 and 23 °C than at 19 and 25 °C, fish number had a greater influence on growth than temperature. Higher growth increments were produced at lower densities. In experimental ponds, growth increments were significantly higher in ponds with low densities of P. parva compared with those at elevated densities. In the field study comprising 10 wild populations across a latitudinal gradient of 4.0°N, a difference in mean air temperatures of approximately 3 °C, and estimated densities between 0.5 and 65.0 m−2, population density was the only significant predictor of growth rates. Whilst populations at very low densities comprised of significantly faster growing individuals, there were no significant differences when densities were between 15 and 65 m−2. Thus, invasive P. parva populations have considerable growth plasticity, especially at low densities, with this likely to be important in their ability to colonise new environments. [ABSTRACT FROM AUTHOR]

ABSTRACT Accidental introductions of non-native species into aquatic environments often result in invasive populations that cause substantial conservation concerns. They account for 8% of all fish introductions and often occur when fish consignments are intentionally released into the wild ('stocked') but are unknowingly contaminated with a 'hitch-hiking' species that is also released., This study tested the efficacy of a fish stocking audit procedure in preventing the introduction of a model hitch-hiking fish ( Pseudorasbora parva) within a batch of model native fish ( Rutilus rutilus). It was tested in relation to different P. parva contamination levels (1, 5, 10, 20%), auditor expertise (Expert, Intermediate, Novice) and search effort., There was considerable variability in the detection thresholds among contamination levels, auditor experience and search effort; false-negative recordings reduced as all these parameters increased. Probability of P. parva detection (POD, 0 to 1) showed that at the lowest search effort, POD was greater than 0.80 for Expert auditors only when contamination levels exceeded 10%. At the highest search effort, POD was greater than 0.80 at the 1% contamination level for Experts, but was at 3 and 8% contamination for Intermediates and Novices., Thus, while small non-native fishes are at risk of being accidentally introduced owing to their difficulty of detection in stocking consignments, an effective audit procedure using experienced auditors and high search effort reduces this risk. Implementation should help prevent subsequent invasions, protecting native species from their adverse ecological consequences., Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The European barbel Barbus barbus is threatened in areas of its range because of its sensitivity to anthropogenic disturbance in riverine habitats and, in the UK, is indigenous to a relatively small number of east-flowing rivers, with nonindigenous populations present in other rivers following introductions for angling enhancement. Fish stock assessment surveys completed between 2002 and 2010 collated age and growth data from 20 rivers across their indigenous and nonindigenous UK range. Analyses revealed that individuals present in samples are of 21 years old, with growth rates highly variable between rivers. There was no relationship between growth rates and the maximum age of fish per river, and there was no difference in growth rates between their indigenous and nonindigenous ranges. A range of abiotic data were collated and analysed against the growth data; these analyses suggested higher mean growth rates were evident in rivers of higher biological water quality (expressed as British Monitoring Working Party Score) and higher mean air temperatures (used as a surrogate of water temperature). That growth of B. barbus was significantly and positively enhanced by increased biological water quality was in contrast to cyprinid fishes such as roach Rutilus rutilus and suggests that as river water quality continues to improve through reduced nutrient inputs, further ecological changes are likely in riverine fish communities. [ABSTRACT FROM AUTHOR]