Reproductive potential of silver European eels (Anguilla anguilla) migrating from Vistonis Lake (Northern Aegean Sea, Greece)

The European eel (Anguilla anguilla), once abundant throughout much of Europe and North Africa, has recently been classified as critically endangered. Information on its biology from the eastern Mediterranean is lacking, especially in relation to spawner quality. Therefore, silver eels were sampled during their seaward spawning migration from Vistonis Lake in Greece. Characteristics linked to reproductive output and success (i.e. body size and condition, sex ratio, silvering, Anguillicola crassus infection, fecundity and oocyte diameter) were examined. The lake produced large (687–1138 mm), exclusively female silver eels, 61.7% of which were infected by A. crassus. Silver eel fecundity, the first estimates from the southern part of the species range, was positively related to body length (R2 = 0.693; P < 0.001) and body weight (R2 = 0.731; P < 0.001). Fecundity did not differ between A. crassus infected and uninfected silver eels, but Greek silver eels were significantly more fecund than those in north-west Europe. The reproductive potential of Vistonis Lake silver eels and their contribution to the A. anguilla spawning stock is discussed.

Visitors' awareness of ICZM and WTP for beach preservation in four European Mediterranean regions.

This paper discusses the results of a multi-country survey about private stakeholders' contribution to coastal preservation. It was conducted in four coastal sites of Greece, Italy and France, in order to collect information about beach visitors' perception of Integrated Coastal Zone Management (ICZM) and their willingness to pay (WTP) for beach preservation, intended here as defence from erosion. In order to find out whether ICZM perception is a determinant of WTP, regression analysis is applied. Results show that in these sites respondents have a low level of information about the nature of ICZM, despite local authorities having implemented some ICZM strategies for preserving the coast. Nevertheless, those who are informed about ICZM have a higher probability of paying for beach preservation. This suggests to policymakers that promoting public awareness about ICZM may increase the probability of paying. Finally, some categories of visitors, such as women and young and middle-aged people, have a higher probability of paying than men and older people, thus suggesting a more sensitive attitude to beach preservation. Therefore, policy-makers should also pay attention to the categories of visitors less likely to pay

Visitors' awareness of ICZM and WTP for beach preservation in four European Mediterranean regions

This paper discusses the results of a multi-country survey about private stakeholders' contribution to coastal preservation. It was conducted in four coastal sites of Greece, Italy and France, in order to collect information about beach visitors' perception of Integrated Coastal Zone Management (ICZM) and their willingness to pay (WTP) for beach preservation, intended here as defence from erosion. In order to find out whether ICZM perception is a determinant of WTP, regression analysis is applied. Results show that in these sites respondents have a low level of information about the nature of ICZM, despite local authorities having implemented some ICZM strategies for preserving the coast. Nevertheless, those who are informed about ICZM have a higher probability of paying for beach preservation. This suggests to policymakers that promoting public awareness about ICZM may increase the probability of paying. Finally, some categories of visitors, such as women and young and middle-aged people, have a higher probability of paying than men and older people, thus suggesting a more sensitive attitude to beach preservation. Therefore, policy-makers should also pay attention to the categories of visitors less likely to pay

Anguillicola (Anguillicoides) crassus: Morphometric characteristics and pathogenicity in eels (Anguilla anguilla) in Greece

Anguillicola (Anguillicoides) crassus is a swimbladder nematode parasite of Anguilla anguilla (Linnaeus, 1758). The present study investigates the morphology and pathogenicity of A. crassus in European eel, as well as, the effects of different aquatic environments on the infection of A. crassus, in Greece. A total of 268 nematodes were collected from four estuarine systems in Greece. In all collected parasites, measurements carried out to define the morphological characteristics of parasites: parasite length and width, oesophagus max length and max width. Τhe mean parasite length was 23.50 mm (95% CI: 22.42–24.58) for females, 12.95 mm (95% CI: 12.25–13.64) for the males and 6.39 mm (95% CI: 5.27–7.50) for the juveniles. The mean parasite width was 1.99 mm (95% CI: 1.88–2.10) for females, 0.93 mm (95% CI: 0.86–1.00) for males and 0.51 mm (95% CI: 0.39–0.64) for juveniles. In total, the mean intensity was found 3.15 (95% CI: 2.53–3.78), while the highest mean intensity per eel was 8.00 (95% CI: 0.00–29.51) in Tholi Lagoon and the lowest was 2.20 (95% CI: 0.36–4.04) in Amvrakikos Gulf. Longitudinal and transverse histological sections of two adults A. crassus and two swimbladders were carried out. Multiple granules were observed, as a tissue reaction of the organism to swath around the 4th stage larvae (L4) that have entered the swimbladder. Molecular analysis was performed on three female adults A. crassus derived from eel specimens coming from the Vistonis estuarine system. The high reproductive capacity of the parasite reveals that A. anguilla has low effective defense mechanisms against the parasite. Also, the morphometric variations of the A. crassus seems to have a plastic feature which is being differently expressed when exposed to various environments. © 202

Reproductive potential of silver european eels (anguilla anguilla) migrating from vistonis lake (northern aegean sea, greece)

The European eel (Anguilla anguilla), once abundant throughout much of Europe and North Africa, has recently been classified as critically endangered. Information on its biology from the eastern Mediterranean is lacking, especially in relation to spawner quality. Therefore, silver eels were sampled during their seaward spawning migration from Vistonis Lake in Greece. Characteristics linked to reproductive output and success (i.e. body size and condition, sex ratio, silvering, Anguillicola crassus infection, fecundity and oocyte diameter) were examined. The lake produced large (687-1138 mm), exclusively female silver eels, 61.7% of which were infected by A. crassus. Silver eel fecundity, the first estimates from the southern part of the species range, was positively related to body length (R-2 = 0.693; P &amp;lt; 0.001) and body weight (R-2 = 0.731; P &amp;lt; 0.001). Fecundity did not differ between A. crassus infected and uninfected silver eels, but Greek silver eels were significantly more fecund than those in northwest Europe. The reproductive potential of Vistonis Lake silver eels and their contribution to the A. anguilla spawning stock is discussed

Evaluation of ecological flows in highly regulated rivers using the mesohabitat approach: A case study on the Nestos River, N. Greece

Preservation of a good ecological status in riverine habitats emerged as a priority for water management policies in Europe since the negative impact caused by the construction and operation of dams on the ecohydrology and habitat availability became more evident. Ecological flows, as reported in the recently published European guidance, represent a link between water and habitat EU Directives. This study presents the application of a mesohabitat simulation model (MesoHABSIM) to evaluate and quantify ecological flows in a highly regulated Mediterranean watershed (Nestos River, Northern Greece). Data collection was performed through GIS/GPS mapping surveys, hydro-morphological measurements (water depth, flow, substratum type, etc.) and electrofishing samplings at mesohabitat scale under different discharge conditions. In total, 81 hydromorphological units were surveyed and 7532 fish samples were collected to develop habitat suitability predictions. Ecological flows were calculated in the range 10–15 m3/s as the required discharge which assures the welfare and sustainability of protected fish species populations. In the lower course of the Nestos River habitat time-series indicated irrigation abstractions as a major stressor since summer was the period where habitat availability thresholds were mostly violated. Application of a revised water management plan is required for the downstream part of the Nestos River in order to maintain high ecological standards in the Natura 2000 sites of the Delta

Reproductive potential of silver european eels (anguilla anguilla) migrating from vistonis lake (northern aegean sea, greece)

The European eel (Anguilla anguilla), once abundant throughout much of Europe and North Africa, has recently been classified as critically endangered. Information on its biology from the eastern Mediterranean is lacking, especially in relation to spawner quality. Therefore, silver eels were sampled during their seaward spawning migration from Vistonis Lake in Greece. Characteristics linked to reproductive output and success (i.e. body size and condition, sex ratio, silvering, Anguillicola crassus infection, fecundity and oocyte diameter) were examined. The lake produced large (687-1138 mm), exclusively female silver eels, 61.7% of which were infected by A. crassus. Silver eel fecundity, the first estimates from the southern part of the species range, was positively related to body length (R-2 = 0.693; P &amp;lt; 0.001) and body weight (R-2 = 0.731; P &amp;lt; 0.001). Fecundity did not differ between A. crassus infected and uninfected silver eels, but Greek silver eels were significantly more fecund than those in northwest Europe. The reproductive potential of Vistonis Lake silver eels and their contribution to the A. anguilla spawning stock is discussed

fshr: a fish sex-determining locus shows variable incomplete penetrance across flathead grey mullet populations

Whole-genome sequencing data were produced from a single flathead grey mullet female and assembled into a draft genome sequence, whereas publicly available sequence data were used to obtain a male draft sequence. Two pools, each consisting of 60 unrelated individuals, respectively, of male and female fish were analyzed using Pool-Sequencing. Mapping and analysis of Pool-Seq data against the draft genome(s) revealed >30 loci potentially associated with sex, the most promising locus of which, encoding the follicle-stimulating hormone receptor (fshr) and harboring two missense variants, was genotyped on 245 fish from four Mediterranean populations. Genotype data showed that fshr represents a previously unknown sex-determining locus, although the incomplete association pattern between fshr genotype and sex-phenotype, the variability of such pattern across different populations, and the presence of other candidate loci reveal that a greater complexity underlies sex determination in the flathead grey mullet