Lorenzo Vilizzi

Calibration of FISK, an Invasiveness Screening Tool for Nonnative Freshwater Fishes

Adapted from the weed risk assessment (WRA) of Pheloung, Williams, and Halloy, the fish invasiveness scoring kit (FISK) was proposed as a screening tool for freshwater fishes. This article describes improvements to FISK, in particular the incorporation of confidence (certainty/uncertainty) ranking of the assessors responses, and reports on the calibration of the score system, specifically: determination of most appropriate score thresholds for classifying nonnative species into low-, medium-, and high-risk categories, assessment of the patterns of assessors confidences in their responses in the FISK assessments. Using receiver operating characteristic (ROC) curves, FISK was demonstrated to distinguish accurately (and with statistical confidence) between potentially invasive and noninvasive species of nonnative fishes, with the statistically appropriate threshold score for high-risk species scores being >/=19. Within the group of species classed as high risk using this new threshold, a higher risk category could be visually identified, at present consisting of two species (topmouth gudgeon Pseudorasbora parva and gibel carp Carassius gibelio). FISK represents a useful and viable tool to aid decision- and policymakers in assessing and classifying freshwater fishes according to their potential invasiveness.

Calibration of FI-ISK, an Invasiveness Screening Tool for Nonnative Freshwater Invertebrates

The Freshwater Invertebrate Invasiveness Scoring Kit (FI-ISK) is proposed as a screening tool for identifying potentially invasive freshwater invertebrates. FI-ISK was adapted from the Fish Invasiveness Scoring Kit (FISK) of Copp, Garthwaite, and Gozlan, which is an adapted form of the Weed Risk Assessment (WRA) of Pheloung, Williams, and Halloy. Initial assessments using FI-ISK, which include confidence (certainty/uncertainty) rankings by the assessor to each response, were calibrated to determine the most appropriate score thresholds for classifying nonnative species into low-, medium-, and high-risk categories, using both the original medium-to-high risk threshold scores for the WRA (i.e., > or = 6) and for FISK (i.e., > or = 19). Patterns of the assessors confidence, when making the responses during the FI-ISK assessments, were also examined. Using receiver operating characteristic (ROC) curves, FI-ISK was shown to distinguish accurately (and with statistical confidence) between potentially invasive and noninvasive species of nonnative crayfish (Decapoda: Astacidae, Cambaridae, Parastacidae), with the statistically appropriate threshold score for high-risk species scores being > or = 16. FI-ISK represents a useful and viable tool to aid decision- and policymakers in assessing and classifying freshwater invertebrates according to their potential invasiveness.

Experimental Evidence from Causal Criteria Analysis for the Effects of Common Carp Cyprinus carpio on Freshwater Ecosystems: A Global Perspective

As the most widely distributed freshwater fish worldwide, common carp Cyprinus carpio can be either invasive or “naturalized” in most areas of introduction. This leads to different levels of perception regarding the species role in freshwater ecosystems, with experimental research focusing either on its “middle-out” impacts or overall function in limnological processes. At the same time, the large scales at which carp dynamics operate may severely limit the validity of laboratory and, oftentimes, field experiments in extrapolating results to real-world ecosystems. In this study, 129 laboratory, field, and “natural” experiments were systematically reviewed through causal criteria analysis, and within an historical/biogeographical and risk-assessment context. Of the 19 countries where experiments were conducted, only 4 were considered as “low risk” and one as “no risk,” the other being “medium” to “high risk.” Experimental findings from 373 component-wise assessments supported the framework of effects on water quality, vegetation, invertebrates, and vertebrates, with the latter including also amphibians and waterfowl, previously unreported. Stronger evidence was provided by natural and field relative to laboratory experiments, reflecting the reductionism of the latter. Critical biomass for an impact was highly dependent on experimental setup, even though the overall threshold of ≈200 kg ha−1 under natural conditions supported recent findings. Management of carp should reflect the level of current and potential risk posed by the species in its different areas of distribution, thereby accounting for projections of further spread but also for unsuccessful colonization. Future experimentation should favor a holistic→reductionist over a reductionist→holistic approach.

Effectiveness of FISK, an invasiveness screening tool for non-native freshwater fishes, to perform risk identification assessments in the Iberian Peninsula.

Risk assessments are crucial for identifying and mitigating impacts from biological invasions. The Fish Invasiveness Scoring Kit (FISK) is a risk identification (screening) tool for freshwater fishes consisting of two subject areas: biogeography/history and biology/ecology. According to the outcomes, species can be classified under particular risk categories. The aim of this study was to apply FISK to the Iberian Peninsula, a Mediterranean climate region highly important for freshwater fish conservation due to a high level of endemism. In total, 89 fish species were assessed by three independent assessors. Results from receiver operating characteristic analysis showed that FISK can discriminate reliably between noninvasive and invasive fishes for Iberia, with a threshold of 20.25, similar to those obtained in several regions around the world. Based on mean scores, no species was categorized as low risk, 50 species as medium risk, 17 as moderately high risk, 11 as high risk, and 11 as very high risk. The highest scoring species was goldfish Carassius auratus. Mean certainty in response was above the category mostly certain, ranging from tinfoil barb Barbonymus schwanenfeldii with the lowest certainty to eastern mosquitofish Gambusia holbrooki with the highest level. Pair-wise comparison showed significant differences between one assessor and the other two on mean certainty, with these two assessors showing a high coincidence rate for the species categorization. Overall, the results suggest that FISK is a useful and viable tool for assessing risks posed by non-native fish in the Iberian Peninsula and contributes to a watch list in this region.

Revisions of the Fish Invasiveness Screening Kit (FISK) for its application in warmer climatic zones, with particular reference to peninsular Florida.

The initial version (v1) of the Fish Invasiveness Scoring Kit (FISK) was adapted from the Weed Risk Assessment of Pheloung, Williams, and Halloy to assess the potential invasiveness of nonnative freshwater fishes in the United Kingdom. Published applications of FISK v1 have been primarily in temperate-zone countries (Belgium, Belarus, and Japan), so the specificity of this screening tool to that climatic zone was not noted until attempts were made to apply it in peninsular Florida. To remedy this shortcoming, the questions and guidance notes of FISK v1 were reviewed and revised to improve clarity and extend its applicability to broader climatic regions, resulting in changes to 36 of the 49 questions. In addition, upgrades were made to the software architecture of FISK to improve overall computational speed as well as graphical user interface flexibility and friendliness. We demonstrate the process of screening a fish species using FISK v2 in a realistic management scenario by assessing the Barcoo grunter Scortum barcoo (Terapontidae), a species whose management concerns are related to its potential use for aquaponics in Florida. The FISK v2 screening of Barcoo grunter placed the species into the lower range of medium risk (score = 5), suggesting it is a permissible species for use in Florida under current nonnative species regulations. Screening of the Barcoo grunter illustrates the usefulness of FISK v2 as a proactive tool serving to inform risk management decisions, but the low level of confidence associated with the assessment highlighted a dearth of critical information on this species.

Trophic consequences of non-native pumpkinseed Lepomis gibbosus for native pond fishes

Introduced non-native fishes can cause considerable adverse impacts on freshwater ecosystems. The pumpkinseed Lepomis gibbosus, a North American centrarchid, is one of the most widely distributed non-native fishes in Europe, having established self-sustaining populations in at least 28 countries, including the U.K. where it is predicted to become invasive under warmer climate conditions. To predict the consequences of increased invasiveness, a field experiment was completed over a summer period using a Control comprising of an assemblage of native fishes of known starting abundance and a Treatment using the same assemblage but with elevated L. gibbosus densities. The trophic consequences of L. gibbosus invasion were assessed with stable isotope analysis and associated metrics including the isotopic niche, measured as standard ellipse area. The isotopic niches of native gudgeon Gobio gobio and roach Rutilus rutilus overlapped substantially with that of non-native L. gibbosus, and were also substantially reduced in size compared to ponds where L. gibbosus were absent. This suggests these native fishes shifted to a more specialized diet in L. gibbosus presence. Both of these native fishes also demonstrated a concomitant and significant reduction in their trophic position in L. gibbosus presence, with a significant decrease also evident in the somatic growth rate and body condition of G. gobio. Thus, there were marked changes detected in the isotopic ecology and growth rates of the native fish in the presence of non-native L. gibbosus. The implications of these results for present and future invaded pond communities are discussed.

Risk assessment of non-native fishes in the catchment of the largest Central-European shallow lake (Lake Balaton, Hungary)

The Fish Invasiveness Screening Kit (FISK) has proved to be a useful tool for assessing and screening the risk posed by potentially invasive fish species in larger risk assessment (RA) areas (i.e. country or multi-country level). In the present study, non-native freshwater fishes were screened for a smaller RA area, the closed and vulnerable but economically important drainage basin of Lake Balaton (Hungary). Receiver operator characteristic analysis of FISK scores for 26 fish species screened by four assessors identified 21 species with scores of ≥11.4 to pose a ‘high risk’ of being invasive, with five species ranked as ‘medium risk’ and none as ‘low risk’. The highest scoring species were gibel carp Carassius gibelio and black bullhead Ameiurus melas, with three Ponto-Caspian Gobiidae identified as amongst the species posing the potentially greatest threat to the catchment. The results of the present study indicate that FISK can be applied to risk assessment areas of smaller geographical scale.

Patterns, latitudinal clines and countergradient variation in the growth of roach Rutilus rutilus (Cyprinidae) in its Eurasian area of distribution

The roach Rutilus rutilus is a eurythermal generalist that has been translocated and introduced mainly beyond the southern limits of its native Eurasian range of distribution. Although largely studied in most aspects of its ecology, no global assessment is available on its growth. Such information is critical for management purposes, especially in view of further dispersal of this ‘potential pest’ and climate change predictions. To address this knowledge gap, a meta-analysis was carried out of the age and growth of 301 roach populations from 231 water bodies across the species’ native and translocated/introduced Eurasian range of distribution with the aim to identify habitat and climate-related differences in growth patterns, latitudinal clines, and the possible presence of countergradient growth variation (CGV). Faster growth rates were identified under warm relative to temperate and cold climates, and these were related to optimised resource allocation. Latitudinal clines indicated decreasing trends with increasing latitude in growth and body size, in line with life-history theory. However, the presence of thresholds encompassing the previously-reported 50°N latitude value suggested a ‘plateau’ or decrease in growth at lower latitudes, and CGV was identified for 1+ to 10+ fish. It is argued that increased water temperatures are likely to cause a northern shift in the observed thresholds and a ‘homogenisation’ of the species’ population dynamics resulting in faster growth rates, but with more pronounced effects in continental Eurasia.

Risk screening of non-native and translocated freshwater fish species in a Mediterranean-type shallow lake: Lake Marmara (West Anatolia)

Risk screening tools to identify species with a high or low risk of invasiveness are being increasingly used for effective management purposes. Amongst the available tools, the Fish Invasiveness Screening Kit (FISK) has been used extensively and successfully in large risk assessment (RA) areas, and was recently upgraded to the new generic tool Aquatic Species Invasiveness Screening Kit (AS-ISK). The aim of the present study was to assess with AS-ISK the invasive potential of introduced non-native and translocated fishes in a Mediterranean-type shallow lake (Lake Marmara) located in west Anatolia (Turkey). Based on independent evaluations of 35 species by two assessors, calibration of AS-ISK resulted in a threshold score of -3.65, which reliably distinguished between potentially invasive (high risk) and potentially non-invasive (medium to low risk) fishes. Of the 35 species assessed, 17 were categorised as ‘low risk’ and included native/endemic and translocated natives, and the remaining 18 as ‘high risk’ and comprised non-natives and translocated natives. Carassius gibelio had the highest score in the Climate Change Assessment section, suggesting that it might potentially impact on the native fish fauna under likely climate change scenarios for the RA area. Some cool water non-native (Oncorhynchus mykiss, Salvelinus fontinalis), translocated native (Luciobarbus lydianus) and endemic species (Ladigesocypris mermere) in the catchment will likely be affected negatively by predicted climate change conditions.

The common carp Cyprinus carpio in Croatia (Danube and Adriatic basins): a historical review

This review provides the first historical account of the ecology and biology of common carp Cyprinus carpio in the Danube and Adriatic basins of Croatia, and emphasises the species’ economic relevance and management implications. As a semi-native species that is native to the Danube but translocated across the Adriatic Basin, carp plays an important role for aquaculture, recreational and artisanal fisheries. However, original strains have now disappeared, and because of genetic pollution in inland waters there is an increasing demand for restoring populations of the now rare and threatened wild carp, making conservation measures a priority. Translocations of carp across water bodies of the Adriatic Basin mostly for food supply did not prove successful in the long term, as the resulting ecological impacts may have been higher than the expected economic advantages. Measures for the prevention of further (uncontrolled) carp re-stocking are therefore necessary and this will require closer collaboration between scientists and environmental managers.