Ali Serhan Tarkan

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.

The bitterling-mussel coevolutionary relationship in areas of recent and ancient sympatry.

Host–parasite relationships are often characterized by the rapid evolution of parasite adaptations to exploit their host, and counteradaptations in the host to avoid the costs imposed by parasitism. Hence, the current coevolutionary state between a parasite and its hosts is predicted to vary according to the history of sympatry and local abundance of interacting species. We compared a unique reciprocal coevolutionary relationship of a fish, the European bitterling (Rhodeus amarus) and freshwater mussels (Unionidae) between areas of recent (Central Europe) and ancient (Turkey) sympatry. Bitterling parasitize freshwater mussels by laying their eggs in the gills of mussel and, in turn, mussel larvae (glochidia) parasitize the fish. We found that all bitterling from both regions avoided one mussel species. Preferences among other mussel species tended to be related to local mussel abundance rather than duration of sympatry. Individual fish were not consistent in their oviposition choices, precluding the evolution of host‐specific lineages. Mussels were demonstrated to have evolved strong defenses to bitterling parasitism in the area of ancient sympatry, but have no such defenses in the large areas of Europe where bitterling are currently invasive. Bitterling avoided glochidia infection irrespective of the duration of sympatry.

Evidence of threat to European economy and biodiversity following the introduction of an alien pathogen on the fungal-animal boundary.

Recent years have seen a global and rapid resurgence of fungal diseases with direct impact on biodiversity and local extinctions of amphibian, coral, or bat populations. Despite similar evidence of population extinction in European fish populations and the associated risk of food aquaculture due to the emerging rosette agent Sphaerothecum destruens, an emerging infectious eukaryotic intracellular pathogen on the fungal–animal boundary, our understanding of current threats remained limited. Long-term monitoring of population decline for the 8-year post-introduction of the fungal pathogen was coupled with seasonal molecular analyses of the 18S rDNA and histological work of native fish species organs. A phylogenetic relationship between the existing EU and US strains using the ribosomal internal transcribed spacer sequences was also carried out. Here, we provide evidence that this emerging parasite has now been introduced via Pseudorasbora parva to sea bass farms, an industry that represents over 400 Mx80 annually in a Mediterranean region that is already economically vulnerable. We also provide for the first time evidence linking S. destruens to disease and severe declines in International Union for Conservation of Nature threatened European endemic freshwater fishes (i.e. 80% to 90 % mortalities). Our findings are thus of major economic and conservation importance.Emerging Microbes & Infections (2015) 4, e52; doi:10.1038/emi.2015.52; published online 2 September 2015

DNA barcoding common non-native freshwater fish species in Turkey: Low genetic diversity but high population structuring

Negative impacts of introduced non-native freshwater species on native species have been increasingly recognized in the world as well as in Turkey. However, there has been relatively little attention on genetic characterization of alien freshwater fishes in their non-native distribution range and virtually no study has been conducted in Turkey despite its crucial importance in invasion biology. The purpose of this study was to elucidate genetic diversity of common non-native freshwater fish species (Carassius auratus, Carassius gibelio, Gambusia holbrooki, Lepomis gibbosus, and Pseudorasbora parva) using mitochondrial Cytochrome c oxidase subunit I (COI) sequences; known as DNA barcodes. Through the whole dataset, seventeen haplotypes (haplotype diversity = 0.8908) were found containing 145 COI sequences. Mean Kimura two-parameter genetic distances were calculated as 0.209 for interspecific distance and 0.009 for intraspecific variation. COI barcode diversity among populations of the same species was found to be low, especially for C. gibelio, G. holbrooki, and L. gibbosus populations which were 0.5%, 0.6%, and 0.3%, respectively. Our results clearly demonstrate the effectiveness of the DNA barcoding approach both for identifications at species level and revealing intraspecific variation among populations, which could be used for effective management measures for invasive species and conservation strategies for indigenous and endemic species.

Bioaccumulation of metals in common carp (Cyprinus carpio L.) from water bodies of Anatolia (Turkey): a review with implications for fisheries and human food consumption.

Although fish is widely consumed by humans for its nutritional properties, accumulation of heavy metals can pose serious health hazards. Widespread common carp Cyprinus carpio is cultured worldwide and represents an economically important species for fisheries in several countries. These include Turkey, where C. carpio often makes for a large part of the sales of the locally marketed fish and also for a traditional dish. This study provides a review of bioaccumulation of metals in tissues of C. carpio from water bodies of Anatolia and also includes reference to worldwide studies. From 42 water bodies across the region, 27 metals in total were studied, of which Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn were the most widely analysed, mainly in the muscle, liver and gill tissues. Amongst the potentially toxic metals, Cd, Cr and Pb occurred in several water bodies at concentrations not only above maximum allowed limits but also higher relative to other water bodies worldwide, even though As, Hg and Ni were also sometimes present at potentially hazardous concentrations. The essential metals Cu, Fe, Mn, Se and Zn were detected at various concentrations, with the latter two occasionally above limit. All water bodies flagged as having especially critical (i.e. above limit) concentrations of toxic metals supported C. carpio fisheries from highly populated regions, raising concern about food safety and calling for preventative measures. Given the significantly lower bioaccumulation levels in the muscle relative to the liver and gill tissues, it is suggested that consumption of C. carpio as fillets may be safer than after processing into e.g. meat balls and sausages. The limits of 1.0xa0μg/g for Cr and 1.15xa0μg/g for Se, currently lacking from the Turkish food safety legislation, are proposed, and it is suggested that a similar meta-analytical approach as adopted in this study may benefit other countries where C. carpio represents an important fisheries resource.

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.

A review of growth and life-history traits of native and non-native European populations of black bullhead Ameiurus melas

Abstract North American black bullhead, Ameiurus melas, which were introduced to Europe in the nineteenth and twentieth centuries, have received relatively little study. With focus on growth and reproduction, this extensive review, which includes new European data, aims to inform the risk analysis process concerning this non-native species in Europe. Surprisingly, the new data for Europe were more comprehensive than for native populations, with data available mainly from Oklahoma, and North and South Dakota (USA). In terms of relative growth, juvenile A. melas were found to have a relatively uniform body shape regardless of the population’s origin, whereas adults developed different phenotypes depending upon location. Overall growth trajectory was significantly faster for native than for non-native populations. Growth index values decreased significantly with increasing latitude in non-native but not native populations—the latter decreasing weakly with increasing altitude in the populations located at latitudesxa0<40°. Mean general condition (slope ‘b’), mean sex ratio and mean egg diameter did not differ significantly between native and non-native populations. Absolute fecundity was slightly (but not significantly) higher in non-native than native populations. GSI data, which were very scarce for native populations, suggest gonad production may be slightly higher in native than in non-native populations. Precise data on age at maturity (AaM) are lacking for the native range, where 2–5xa0years is reported. Whereas, in the introduced range the greatest AaM was 3.5xa0years, and AaM decreases with increasing juvenile growth (TL at age 3). The populations with fastest juvenile growth tended to be from warmer water bodies where they are considered to be invasive. The great growth and life-history plasticity of black bullhead affords the species great potential to invade and establish viable populations in new areas.

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.

Origin and invasion of the emerging infectious pathogen Sphaerothecum destruens

Non-native species are often linked to the introduction of novel pathogens with detrimental effects on native biodiversity. Since Sphaerothecum destruens was first discovered as a fish pathogen in the United Kingdom, it has been identified as a potential threat to European fish biodiversity. Despite this parasite’s emergence and associated disease risk, there is still a poor understanding of its origin in Europe. Here, we provide the first evidence to support the hypothesis that S. destruens was accidentally introduced to Europe from China along with its reservoir host Pseudorasbora parva via the aquaculture trade. This is the first study to confirm the presence of S. destruens in China, and it has expanded the confirmed range of S. destruens to additional locations in Europe. The demographic analysis of S. destruens and its host P. parva in their native and invasive range further supported the close association of both species. This research has direct significance and management implications for S. destruens in Europe as a non-native parasite.

Mitochondrial genetic variations of an introduced freshwater fish, goldfish Carassius auratus at the frontier between Europe and Asia (western Anatolia, Turkey): proximity to Europe rather than East Asia?

Abstract Carassius auratus is one of the most significant ornamental and food fishes of the world that is globally distributed and well known. Although it is known to have existed at least for six decades and expanding its distribution range in Turkish waters, there is a dearth of information on genetic structure and variations of goldfish in Turkey. In this study, four mitochondrial genes (Cytochrome b, cytochrome oxidase II, 12S ribosomal RNA, and 16S ribosomal RNA) were used to infer the genetic variations of goldfish populations sampled from western part of Anatolia, Turkey. Three populations were clustered under three haplotypes for each gene and all haplotypes were special. Cytochrome b was found to have more variable sites and higher genetic diversity than other genes. According to the haplotype networks, goldfish populations in Turkey showed high level of genetic structuring and originated from the common haplotype known in native East Asian populations of the species. Extensive sampling scheme covering whole Anatolia should provide better understanding on the dispersal pattern of the species.