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Recreational angling is a major introduction pathway for large-bodied alien fishes into freshwaters, where the fish are released to enhance angling success and increase angler satisfaction, despite this often resulting in invasive populations. There is a thus a need to understand the role of these alien species in angler catches to enable more informed risk-based decisions to be made on future releases. In England, the invasive, piscivorous pikeperch Sander lucioperca has been present in rivers since the 1960s. Anglers target invasive pikeperch in fisheries where the native piscivorous pike Esox lucius is also present; this includes two rivers in the lower Severn basin, western England (main River Severn and Warwickshire Avon). To assess the contributions of invasive pikeperch to angler catches, the aim here was to compare their catches with those of native pike in the lower Severn basin in relation to angling effort and methods, abiotic conditions, and fish size. In 307 angling sessions across 16 anglers where at least one fish was captured, 428 pike and 266 pikeperch were captured. In a sub-set of data from six anglers who submitted catch returns that included non-capture sessions, 78 % of sessions resulted in the capture of at least one pike or pikeperch. Catch rates of pike were significantly higher than pikeperch in the main River Severn but not the Avon. Captured pike were significantly larger than pikeperch, but pikeperch were larger relative to the maximum size each species reaches in England. Lures generally captured more pike than any other method, with these fish tending to be smaller than those caught on other methods; these patterns were not evident in pikeperch. Both species were captured across a broad range of river flow conditions (Q6 to Q99). Only 19 % of successful angling sessions resulted in the capture of both species, suggesting some species selectivity by anglers. These results emphasise that alien fish species can provide important angling resources in recreational fisheries, although management decisions on future introductions should still consider their ecological risks.

International audience; Populations of fishes provide valuable services for billions of people, but face diverse and interacting threats that jeopardize their sustainability. Human population growth and intensifying resource use for food, water, energy and goods are compromising fish populations through a variety of mechanisms, including overfishing, habitat degradation and declines in water quality. The important challenges raised by these issues have been recognized and have led to considerable advances over past decades in managing and mitigating threats to fishes worldwide. In this review, we identify the major threats faced by fish populations alongside recent advances that are helping to address these issues. There are very significant efforts worldwide directed towards ensuring a sustainable future for the world’s fishes and fisheries and those who rely on them. Although considerable challenges remain, by drawing attention to successful mitigation of threats to fish and fisheries we hope to provide the encouragement and direction that will allow these challenges to be overcome in the future

Variation in movement between individuals can have important ecological effects on populations and ecosystems, yet the factors driving differences in movement and their consequences remain poorly understood. Here, individual variability in the movements of juvenile (age 0 + and 1 + year) pike Esox lucius was assessed using passive integrated transponder (PIT) telemetry in off-channel nursery areas over a 26-month period. Differences in the movement patterns of individuals were tested against their body sizes, ages, growth rates and trophic positions using data collected through a combination of catch-and-release sampling and stable isotope analyses. Results revealed that variation in movement between individuals was affected by age, with 1 + individuals moving more than individuals of age 0 +, but not length. Individuals whose TP was low on their initial capture event moved significantly less than those with a higher initial TP. Individuals that moved more grew faster and achieved a higher final TP. These results suggest that higher activity (i.e., increased movement) increases resource acquisition that enhances growth rates, which could ultimately maximise individual performances.

Activities that manipulate ecosystems to support economic activities provide major introduction pathways for non-native species. As such, substantial differences in the socioeconomic conditions between countries could influence how ecosystems are manipulated and thus impact the composition of their communities of non-native species. Here, we compared the influence of freshwater fish aquaculture production and macro-socioeconomic drivers on the freshwater fish allodiversity of Europe between 1970 and 2009. A divergence in the socio-economic conditions of Europe prevailed during much of the latter half of the 20th Century as a result of the Cold War. For example, GDP and GDP per capita were significantly higher in Western bloc countries compared to the Eastern bloc. In this 39 year period, aquaculture production in Eastern bloc countries was dominated by Asian cyprinid fish whereas in Western bloc countries it was dominated by the North American rainbow trout Oncorhynchus mykiss. Analysis of a European database on introduced fish into the wild from aquaculture revealed that in entirety, there were 279 separate freshwater fish introductions in Europe associated with aquaculture (Eastern bloc 118, Western bloc 161), involving 117 species from 32 families. There was relatively low homogeneity in these introduced fishes between the two blocs; only 28 species were introduced into both. Western bloc countries also had significantly more introduced fishes and more introduction events, and less similarity in the introduced fishes between their countries. Aquaculture production was a significant predictor of the number of non-native freshwater fish across all the countries, although additional factors, especially human population size and GDP per capita, were also significant predictors. Thus, aquaculture has been a strong introduction pressure in Europe and provides a reliable predictor of fish allodiversity.

The correlation of seemingly unrelated behaviours into behavioural syndromes has been established in a wide range of species and taxa. However, most studies report on short-term behavioural correlations without insight into individual consistency or temporal stability of the behavioural syndrome. Here, we examine the individual repeatability of single behaviours, and the presence and temporal stability of a context-general behavioural syndrome in a solitary piscivorous predator, the pike (Esox lucius). Behavioural measurements on the same individuals were quantified independently through time and across three contexts: activity in the presence of a competitor, exploration of a novel environment and boldness under predation risk. There was no indication of a temporally stable behavioural syndrome, consisting of boldness, activity and exploration, nor were individuals consistent in the separate behaviours, contradicting the general assertion of its taxonomic prevalence. Furthermore, the study did not provide support for size or growth-dependent behaviour in this size-dimorphic species in conditions of limited food availability. The study highlights the importance of independent multiple observations of individual behaviour across time or contexts when measuring behavioural repeatability and covariation.

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.