Valencia Letourneuxi Research Articles

Designing, implementing and monitoring the translocation of a highly threatened freshwater fish

Abstract Conservation translocations are increasingly applied for the protection of threatened species, but their success depends strongly on pre‐release preparatory work and strict implementation methodology, followed by post‐release monitoring. The aim of this work was to implement a conservation translocation that involved (a) the design and application of a pre‐release feasibility assessment tool for the selection of the translocation water bodies; (b) the translocation of 77 individuals of the highly threatened freshwater Corfu killifish Valencia letourneuxi in 2015, 2016 and 2017; and (c) a 5‐year post‐release monitoring with multiple methods. After initial pre‐screening, a feasibility assessment was conducted on two potential release water bodies (R‐WBs) and on four potential source water bodies (S‐WBs), using a custom‐made feasibility assessment tool that incorporated 14 criteria for the potential R‐WBs, related to the species' habitat requirements, human pressures and technical issues. Two criteria were applied to the potential S‐WBs, on source population availability and on its genetic compatibility to the release area. Post‐release monitoring (2017–2022) was conducted with fish sampling methods, underwater video recording and/or using environmental DNA (eDNA). The feasibility assessment tool gave one R‐WB high, positive score, and one S‐WB met both criteria, thus these selected as the translocation water bodies. Despite the low number of founders, the establishment of a self‐reproducing population was finally confirmed in 2022 in the R‐WB, initially with video recording and subsequently by fish sampling and eDNA. This study highlights the importance of pre‐release feasibility assessment, the use of multiple post‐release monitoring methods and actions to secure the long‐term viability of the translocated population. The feasibility assessment tool and the methodological protocol can easily be modified for successful application to other freshwater fish species, with different habitat requirements, current and future human pressures and genetic constraints.

Dramatic decline of two freshwater killifishes, main anthropogenic drivers and appropriate conservation actions

Freshwater fish biodiversity loss in the Mediterranean Basin is regarded as among the highest globally, with long-term population data sets required to discern long-term population trends of threatened species, in order to design appropriate conservation interventions. In this study, we assessed the population trends of two threatened freshwater fishes, Valencia letourneuxi and Valencia robertae, employing the most recent and largest compiled database to date (16 populations over 14 years). We applied the innovative methodology of the Living Planet Index (LPI) to assess the average rate of change over time across a set of V. letourneuxi and V. robertae populations in Greece. The LPI application revealed a dramatic decline of both species, with V. letourneuxi declining by 97.7% and V. robertae by 91.0%. Beta regression showed that water pollution, eutrophication and alien Eastern mosquitofish Gambusia holbrooki’ presence were the three best fitting predictors of the decline of V. letourneuxi and V. robertae populations. Based on the above, we outline the conservation measures urgently required to revert the near collapse of the populations of the two species. Conservation actions include the strict protection of the their lowland spring habitats, habitat improvement through changes in water management and agricultural practices, mosquitofish invasion prevention and mosquitofish impact mitigation measures, as well as translocation actions and captive breeding. Lastly, the association patterns of the proposed conservation actions with anthropogenic pressures and their expected outcomes were analysed through an alluvial diagram, providing insights on the scale of pressures mitigated by conservation actions and on their conservation benefits.

EDNA‐based monitoring: Advancement in management and conservation of critically endangered killifish species

AbstractEcosystems are currently changing at unprecedented rates due to anthropogenic influences. Application of appropriate management regimes and mitigation measures requires knowledge of ecological community composition and monitoring of any changes that occur. Environmental DNA‐based monitoring is becoming increasingly common and offers substantial potential as a noninvasive method associated with highly repeatable and reliable results. In this study, we monitored river systems in Western Greece that have been strongly impacted by anthropogenic activities and the spread of an alien invasive fish species, the Eastern mosquitofish (Gambusia holbrooki). This invasive species has been credited as the major cause for the drastic decline of two endemic killifish species (Valencia letourneuxi and Valencia robertae). Here, we investigated the efficacy of an environmental DNA (eDNA‐based) method of detection for all three species, as an alternative to conventional monitoring methods. Initially, a mesocosm experiment provided material for the design and validation of the sampling protocol. This was followed by two sampling periods in the field conducted in autumn 2017 and 2018, comparing the novel eDNA assays with the conventional surveying methods in six and 20 systems, respectively. eDNA detection consistently outperformed the traditional monitoring methods for both V. letourneuxi and V. robertae and was comparable for the invasive G. holbrooki. This supports the now increasing body of literature, highlighting the benefits of species‐specific, targeted eDNA assays for the assessment of threatened and/or invasive species, one which can be utilized by conservation organizations and government bodies alike. However, we note that care should always be taken when designing such tools and strict validation steps should be adhered to, particularly with respect to minimizing the probability of false positives and negatives.

Ecological particularities of the critically endangered killifish Valencia letourneuxi and its spring-fed habitats: a long-lost endemic species of south Albania

The southernmost part of Albania, the Butrinti Lake area is characterised by a highly diverse freshwater fish community with a high degree of regional endemism. This study focuses on the Corfu killifish (or toothcarp) Valencia letourneuxi (Sauvage, 1880) that is endemic to the western part of the Ionian Ecoregion, and reported in Albania in the past from a single location, Lake Butrinti. Recently, in June 2019, the species has been rediscovered at a very low population density (only 11 individuals collected) in a spring-fed stream in the vicinity of Lake Butrinti. Other fish present together with V. letourneuxi were the native Telestes pleurobipunctatus, Barbus peloponnesius, Anguilla anguilla and Pelasgus thesproticus and the translocated Alburnus sp. Our findings provide useful insights into the ecology and conservation of a Critically Endangered, range-restricted species and its habitats. The Corfu killifish presence correlated negatively with water depth and positively with aquatic vegetation coverage. The conservation implications of our findings both for the target species and the co-occurring fish fauna in its spring-fed habitats are discussed.

Impacts of the alien mosquitofish on the abundance and condition of two Mediterranean native fish

The rapid decline of the Greek native Valencia letourneuxi, and its recently described sister species Valencia robertae, has been often attributed to habitat degradation, as well as aggression from or resource competition with the alien mosquitofish Gambusia holbrooki. The mosquitofish is extremely wide-spread in Mediterranean freshwater ecosystems, however, documentation on its presumed negative impacts on native freshwater fishes is limited. In this study, we compared abundance, condition and gonad weight of Valencia spp. in no co-occurrence versus co-occurrence to the mosquitofish, using data collected from eight aquatic systems of Greece, over a five year period (2005 to 2009). Our results show that Valencia abundance is significantly lower in co-occurrence to the Eastern mosquitofish. Furthermore, female Valencia spp. individuals in co-occurrence to the mosquitofish were smaller in length and had poorer somatic condition compared to females in habitats not invaded by the mosquitofish. The mechanisms responsible for these effects of the alien mosquitofish as well as the conservation implications for native Valencia populations are discussed.

New Red List assessments proposed for the recently described freshwater fish species in Greece

New Red List assessments proposed for the recently described freshwater fish species in Greece

Ecomorphological diversity of freshwater fishes as a tool for conservation priority setting: a case study from a Balkan hotspot

Biodiversity studies commonly focus on taxonomic diversity measures such as species richness and abundance. However, alternative measures based on ecomorphological traits are also critical for unveiling the processes shaping biodiversity and community assembly along environmental gradients. Our study presents the first analysis of habitat-trait-community structure in a Balkan biodiversity hotspot (Louros river, NW Greece), through the investigation of the relationships among freshwater fish assemblages’ composition, morphological traits and habitat features. In order to provide a hierarchical classification of species’ priority to protection measures, we highlight the most ecomorphologically distinct species using originality analysis. Our results suggest that the longitudinal changes of habitat variables (water temperature, depth, substrate, altitude) drive the local fish assemblages’ structure highlighting the upstream-downstream gradient. We also present evidence for environmental filtering, establishing fish assemblages according to their ecomorphological traits. The calculation of the seven available indices of ecomorphological originality indicates that Valencia letourneuxi and Cobitis hellenica, which are endemic to Louros and threatened with extinction, exhibited the highest distinctiveness; thus their protection is of great importance. The methodological approach followed and the patterns described herein can contribute further to the application of community ecology theory to conservation, highlighting the need to use ecomorphological traits as a useful ‘tool’.

Occurrence and effect of trematode metacercariae in two endangered killifishes from Greece

We report digeneans (Diplostomidae, Crassiphialinae) in the endangered freshwater fishes Valencia letourneuxi and Valencia robertae, endemics of Western Greece. Digenean metacercariae occurred in two forms in the abdominal cavity, excysted and encysted, the latter attached to the gonads, liver and alimentary tract. Parasites were, using morphological and molecular techniques, identified as two representatives of Crassiphialinae, specifically part of the Posthodiplostomum-Ornithodiplostomum clade. The spatial, seasonal, and age class variation in parasite prevalence was examined. Autumn parasite prevalence varied between the six populations sampled (18.2 to 100%). Seasonal prevalence at the two sites sampled quadannually peaked in autumn and reached its lowest value in spring; prevalence increased with size to 100% in young adult fish. We did not find a correlation between prevalence and host sex. Overall parasites' weight averaged 0.64% of the host's, while parasite weight increased with host weight. A comparison of relative condition and hepatosomatic and gonadosomatic indices of infected and metacercariae-free specimens showed that infection did not have a significant effect on host body condition and reproduction. Regarding the parasite's life cycle, planorbid gastropods are proposed as potential first intermediate hosts in view of the host's diet and occurrence data of molluscs in the ecosystem. This is the first record of a diplostomid digenean in valenciid fishes and of representatives of the Posthodiplostomum-Ornithodiplostomum clade in a native Greek freshwater fish. Our findings are discussed in conjunction to fish conservation interventions, since parasites may contribute to the decline of endangered species.

Length–weight relations of seven native fish species (Actinopterygii) from the Louros River, Greece

Length–weight relations were estimated for 7 native fish species of the Louros River in north-western Greece, 6 of them being endemic to the Ionian Sea ecoregion. The b values ranged from 3.05 to 3.21. Five species, namely Cobitis hellenica Economidis et Nalbant, 1996; Pelasgus thesproticus (Stephanidis, 1939); Gasterosteus gymnurus Cuvier, 1829; Economidichthys pygmaeus (Holly, 1929); and Valencia letourneuxi (Sauvage, 1880) displayed an isometric growth pattern (b = 3) while the remaining two species—Salmo lourosensis Delling, 2011 and Telestes pleurobipunctatus (Stephanidis, 1939)—showed a positive allometric growth (b > 3). New maximum lengths are given for three species. Moreover, this study constitutes the first world report on the length–weight relations for 5 species and the first report for the Ionian Sea ecoregion for two other species.

Prey utilisation and trophic overlap between the non native mosquitofish and a native fish in two Mediterranean rivers

Non native freshwater fish species have been long implicated in the decline of native Mediterranean ichthyofauna, through hybridization, disease transmission, competition for food and habitat, predation and/or ecosystem alteration; our knowledge, however, on the underlying mechanisms of these ecological impacts remains very limited. To explore the potential for trophic competition between the widespread Eastern mosquitofish Gambusia holbrooki and its co-occurring native toothcarp Valencia letourneuxi we compared resource use, feeding strategies, trophic selectivities and diet niche overlap. For this purpose, we studied two populations of the two species from a freshwater and a brackish habitat respectively, characterized by different food resource availabilities. In both habitats, the mosquitofish consumed a greater diversity of invertebrates and preyed on terrestrial invertebrates more frequently than the native toothcarp. Furthermore, in the less diverse and less rich brackish habitat, the non native relied heavily on plant material to balance a decrease in animal prey consumption and modified its individual feeding strategy, whereas these adaptive changes were not apparent in the native species. Their diet overlapped, indicating trophic competition, but this overlap was affected by resource availability variation; in the freshwater habitat, there was limited overlap in their diet, whereas in the brackish habitat, their diets and prey selectivities converged and there was high overlap in resource use, indicative of intense interspecific trophic competition. Overall, it appears that the underlying mechanism of the putative negative impacts of the mosquitofish on the declining Corfu toothcarp is mainly trophic competition, regulated by resource variability, though there is also evidence of larvae predation by the mosquitofish.

Reduced genetic variation and strong genetic population structure in the freshwater killifishValencia letourneuxi(Valenciidae) based on nuclear and mitochondrial markers

The genetic variation of the critically endangered Corfu killifish (Valencia letourneuxi), an endemic freshwater fish species of the western Balkans, was assessed for nine populations sampled in eight water systems in western continental Greece, the Peloponnese and the Ionian Island of Corfu, using mitochondrial and microsatellite markers. The analyses were based on data from three mtDNA regions (D-loop, COI and 16S rRNA sequences) and 14 microsatellite loci. Samples from the congeneric species Valencia hispanica and the phylogenetically closely related species Aphanius fasciatus were also used in the study as outgroups. Both the mitochondrial and the microsatellite analyses revealed three distinct population groupings associated with the geographical distribution of the populations: one southern group occupying rivers draining to the Patraikos Gulf, the second one including the populations flowing into the Amvrakikos Gulf and the third, more northern group, including the other populations from rivers in Corfu Island and Epirus flowing into the Ionian Sea. Within these groupings there is limited genetic differentiation between populations; in addition, there is reduced intrapopulation genetic variation, evidenced by low heterozygosity values, number of alleles and haplotype diversity. In terms of taxonomic implications and appropriate management actions for conservation, our data suggest that the major population groups should be regarded at least as three distinct conservation units (CUs), with translocation and restocking actions to take place only within the geographical range of the CU concerned. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111, 334–349.

Current distribution and ecology of the critically endangered Valencia letourneuxi in Greece

AbstractThe current population status of the critically endangered Greek valencia Valencia letourneuxi (Sauvage, 1880), is presented, based on a thorough survey of low-altitude aquatic systems of Western Greece. The species’ historical geographical range appears to have been reduced, with the westernmost and southernmost populations being currently extinct or near extinction respectively, and the remaining ones in a vulnerable state. According to univariate and multivariate analysis, V. letourneuxi exhibits habitat specificity, with a strong affinity towards spring-fed wetlands with clear waters and rich surface vegetation, being thus vulnerable to human-induced habitat modifications and hydrological changes. The impact of the above threats, as well as of the introduction of alien species such as the mosquitofish Gambusia holbrooki is discussed.

Feeding ecology of the critically endangered Valencia letourneuxi (Valenciidae)

Valencia letourneuxi is a critically endangered freshwater fish in urgent need of targeted conservation. Little information is however available on its life history and feeding ecology; therefore, food resource utilization by V. letourneuxi was studied in its most abundant known Greek population of Chiliadou stream. The diet of this population appears to be dominated by microcrustaceans, Dipteran larvae, Acari, and Mollusca. Its feeding is highly dependent on seasonal prey availability and diversity, with niche overlap being low only between winter and the rest of the seasons, indicating that only during winter its diet differs significantly in relation to the other seasons. There are no significant sex- and size-related dietary shifts. This V. letourneuxi population is characterized by a generalist feeding strategy and appears to consist mostly of individuals with broad niches. Its generalist feeding pattern and dietary flexibility permits it to fully exploit this very diverse and rich habitat and may account for the high local abundance of this population.

Characterization of polymorphic microsatellite markers in Valencia letourneuxi (Valenciidae) and cross-amplification in two other cyprinodontiform species

Fourteen microsatellite loci were isolated from the critically endangered Corfu toothcarp Valencia letourneuxi using a microsatellite enrichment protocol and selective hybridization with a biotinylated (AC) probe. Nine of these loci were polymorphic in a V. letourneuxi population of 20 individuals (Vlychos stream) with mean number of alleles per locus = 2.55 and mean observed heterozygosity = 0.3447. Moreover, some of these 9 microsatellite markers and the remaining five loci, monomorphic in V. letourneuxi, were found to be polymorphic in the Spanish samaruc Valencia hispanica and the Mediterranean toothcarp Aphanius fasciatus. These microsatellite loci are expected to be used for population genetic analysis as well as studying the genetic diversity of this endangered species.

The salinity tolerance of Pseudophoxinus stymphalicus (Cyprinidae) and Valencia letourneuxi (Valenciidae) from western Greece suggests a revision of the ecological categories of freshwater fishes

The salinity tolerance of two common teleosts from Greece, one a primary division species, Pseudophoxinus stymphalicus, the other a secondary division species, Valencia letourneuxi, was evaluated in laboratory studies. Experimental subjects were acclimated to a salinity of 6 ppt. Through gradual increases, individuals of P. stymphalicus were able to tolerate salinities up to 12–13 ppt, while individuals of V. letourneuxi survived in normal seawater (33 ppt) and had an upper lethal limit of ca. 46 ppt. Valencia letourneuxi, one of two species of the Mediterranean family Valenciidae, is one of the least euryhaline of secondary division teleost fishes. Its distribution matches that of P. stymphalicus, suggesting that its dispersion was not by way of marine waters but by mechanisms used by primary and primary‐like freshwater fishes. We reconsider the primary and secondary division and primary‐like categories and propose that five basic groups be recognized: primary, primary‐like, secondary low salt tolerant, secondary high salt tolerant, and peripheral.

Identification of endangered Mediterranean cyprinodontiform fish by means of DNA inter-simple sequence repeats (ISSRs)

We used inter-simple sequence repeat (ISSR) technique to obtain species-specific molecular markers for the cyprinodontiform fish Valencia hispanica, Valencia letourneuxi and Aphanius fasciatus. The aims were (i) to assess the effectiveness of ISSRs in discriminating the three species and (ii) to identify tissues of two unidentified fish suspected to belong to one of the three above species by comparing ISSR genotypes. Nine ISSR primers produced 101 scorable polymorphic loci with a large number of species-specific bands. UPGMA cluster analysis and nonmetric multidimensional scaling of inter-individual genetic dissimilarities were consistent in separating the three species and attributing the unidentified individuals to V. hispanica. This result was corroborated by the assignment test. ISSRs represent an attractive tool for specimen and species identification. We recommend their use, coupled with appropriate statistical analyses, in species identification when only small portions of the organisms are available.

The biology and ecology of Valencia letourneuxi Sauvage 1880 (Valenciidae) - Prospects for conservation

Data are provided on the distribution, abundance, early development and biology of the endangered Greek endemic species Valencia letourneuxi Sauvage 1880, along with a record of its occurrence at new localities. V. letourneuxi is a small-bodied and short-lived insectivorous species, exhibiting cryptic colouration and sexual dimorphism. It matures in the first year of life, reproduces serially in late spring and summer, and deposits spherical eggs, around 2 mm, on aquatic plants. Most morphometric characters show size-specific trends, which complicate comparisons among populations or with other species. Of specific systematic importance is the relative position of the anal and dorsal fins, which remains almost unaltered throughout development, and allows safe distinction from A. fasciatus. The species was found mostly in deep areas with clean and slow running water, usually associated with freshwater springs. Rich submerged vegetation is the prominent ecological feature of all sites in which the species was found. Using as criteria of rarity the limited geographic distribution, the confinement of the species in few localities of each aquatic system and the low local densities, V. letourneuxi can be characterised as a "restricted and locally rare species". The restricted distribution, coupled with the narrow ecological requirements, makes the species vulnerable to extinction. Its disappearance from at least four aquatic systems and the serious population decline in a number of other systems seems to be connected with habitat loss or degradation caused by human activities. The prospects of conservation are discussed.

Introduced and translocated fish species in the inland waters of Greece

Over the last 7 decades, 23 exotic fish species have been introduced into the inland waters of Greece. Some introductions were deliberately planned to take advantage of particular ecological or economic qualities of the species concerned. These include rainbow trout, Oncorhynchus mykiss (Walbaum), Pacific salmon, Oncorhynchus sp., vendace, Coregonus lavaretus (L.), grass carp, Ctenopharyngodon idella (Valenciennes), and silver carp, Hypophthalmichthys molitrix (Valenciennes). Other introductions, such as that of pumpkinseed, Lepomis gibbosus (L.), and false rasbora, Pseudorasbora parva (Temminck & Schlegel), were unintentional. Further transfers were made of species between various basins within the country, including common carp, Cyprinus carpio L., tench, Tinca tinca (L.), crucian carp, Carassius auratus gibelio (Bloch), bitterling, Rhodeus amarus (Bloch), and Aristotle's catfish, Silurus aristotelis Garman. Some species have become fully acclimatized and have built up important populations. In other cases, the transfers and introductions have had considerable negative impacts, particularly where introduced species have outcompeted native forms, as in the cases of the mosquito fish, Gambusia affinis (Baird & Girard), versus Greek toothcarp, Valencia letourneuxi (Sauvage), in the western Greek marshes, and of Aristotle's catfish versus the wels, Silurus glanis L., in Lake Volvi.

Endangered freshwater fishes of Greece

The freshwater fish fauna of Greece includes 106 species of which 79 are native primary species. Of these 38 species are endemic to Greece and southern parts of neighbouring countries. Endangered species are divided into three groups: wholly endangered, locally endangered and rare and threatened. In the first group are eight taxa, usually found in a very restricted area ( Eudontomyzon hellenicus, Alosa caspia vistonica, Pseudophoxinus beoticus, Ladigesocypris ghigii ghigii, Barbus euboicus, Barbus cyclolepis cholorematicus, Pungitius hellenicus and Knipowitschia goerneri). The second group includes five species with a wide area of distribution but some local populations which are extinct or in obvious decline ( Salmo trutta, Pseudophoxinus stymphalicus, Vimba melanops, Valencia letourneuxi, Proterorhinus marmoratus). The third group comprises nine endemic taxa, mainly with a wide distribution in Greece, or widely distributed in Europe but represented in Greece by local populations, sometimes recognized as subspecies ( Phoxinellus pleurobipunctatus, Barbus prespensis, Gobio kessleri banarescui, Gobio uranoscopus elimeius, Carassius carassius, Orthrias barbatulus vardarensis, Pungitius platygaster, Knipowitschia thessala, Economidichthys pygmaeus). These taxa often have rare or threatened local populations. The main reasons for the decline of fish species are: agricultural and industrial activity, overfishing, partial or total destruction of many karstic springs, public and private works abstracting water, drainage, irrigation, tourist and industrial installations, dams, mixing of fish faunas of different origin and introduction of exotic species.