Addressing the challenges posed by Non-Indigenous Species (NIS) demands coordinated efforts across terrestrial, freshwater and marine ecosystems. In this study, we engaged a diverse group of 90 Italian researchers operating within these three domains to identify and assess strategies for advancing NIS research, using a structured, interactive and expert-driven methodology. The process began with a comprehensive evaluation of ongoing activities, research methodologies and specific needs. This assessment provided information for the development of an initial set of suggestions to ameliorate NIS research, which were collectively discussed and refined, leading to the identification of six good practices identified by the acronym TRACKS and described as: i) Tracking NIS in biodiversity data collection; ii) Reference protocols for NIS data collection; iii) Active participation; iv) Collaboration and FAIR principles; v) Knowledge hub for NIS data; vi) Strategic communication. A SWOT framework was then applied to analyse the internal and external factors influencing the Strengths, Weaknesses, Opportunities and Threats associated with each good practice. Consensus-building techniques were used throughout the evaluation process to ensure the robustness of outcomes. Finally, a quantitative assessment of the SWOT analysis revealed a strong consensus amongst experts regarding the various strengths, weaknesses, opportunities and threats of the different good practices, along with a general optimism about the opportunities and strengths associated with their implementation. Developed within the Italian research community, this approach offered valuable insights to researchers worldwide working on NIS and enabled the expert assessment of six best practices that may serve as a benchmark for advancing the science of biological invasions.

Estimating ecological flows is essential in rivers to achieve the objectives defined by the EU Water Framework Directive 2000/60/EC (WFD). In the framework of an agreement with the Autorità di Bacino Distrettuale dell’Appennino Centrale, the work aims to present the results of an integrated approach developed to consider various factors affecting the river’s ecological flow (hydrological, hydrobiological, hydrogeological, hydro-morphological, and hydrochemical). The present study focuses on the Nera River, a main tributary of the Tiber River, which is primarily fed by groundwater from limestone aquifers. The river catchment hosts strategic water resources that are crucial for providing drinking water and sustaining aquatic ecosystems. Moreover, river water is utilized for hydropower generation, fish farming, and various recreational activities along the river. The ecological status was rated as good based on the New Index of the Ecological Status of Fish Communities (NISECI), along with physicochemical characterization of river water and hydromorphological characteristics as criteria for its definition. Based on a regional model specifically developed for brown trout of rivers in the Tiber River basin (thus applicable to the Nera River), the minimum ecological flow was set at approximately 2.92 m³/s. Based on flow-duration curves, the average and maximum ecological flow values were also identified as 3.71 and 5.07 m³/s, respectively. The analyses carried out by the Water Exploitation Index Plus (WEI+) revealed medium-to-high stress in the catchment; therefore, withdrawals should be carefully re-planned to minimize further impacts on water-dependent ecosystems. The approach proposed for the Nera River highlights the importance of conducting focused, multidisciplinary studies in areas where groundwater withdrawals interact with groundwater-dependent ecosystems, thereby supporting regional management plans that address the needs of both humans and aquatic ecosystems.

This is the first ultrastructural study of an adult tapeworm providing data on the morphological aspects of the pathways of lipid excretion via the tegumental surface and excretory system in the monozoic tapeworm Caryophyllaeus brachycollis (Janiszewska, 1953) from the chub Squalius tenellus (Heckel, 1843) obtained from a lake in the Bosnia-Herzegovina Federation. Our study has shown that the release of lipid droplets onto the parasite-host interface from the tegumental cytoplasm is carried out with the participation of tegumental vesicles, which clustered and fused with each other to form electron-lucent, membrane-bound sacs around lipid droplets. The ultrastructural pattern of the excretory bladder is presented for the first time for an adult tapeworm. In C. brachycollis, the syncytial epithelial lining of both the distal and proximal bladder is a derivative of the tegumental distal cytoplasm of the posterior body surface. Variations in the structural organization of both bladder parts were observed in the kinds of luminal microtriches and in the presence of large cytoplasmic protrusions in the proximal bladder. In C. brachycollis, the lipid droplets are released into the proximal bladder lumen via 10 collecting descending excretory ducts. In adult mature monozoic caryophyllidean tapeworms, an accumulation of a large number of sarcoplasmic lipid droplets is observed and their presence in the protonephridial cyrtocytes is revealed at the posterior body end, where there are the reproductive organs and ducts.

Estimating ecological flows (EFs) in rivers is crucial for meeting the Water Framework Directive (WFD) 2000/60/EC goals. To develop an EF model, it is essential to use biological indicators to reliably record the impacts of human-induced alterations on aquatic ecosystems. The adaptability of fish to annual flow variability makes them a significant biological quality element (BQE). Consequently, using fish as bioindicators is a powerful tool for assessing the impact of changes in the hydrological regime on the natural communities within a river system. The new index of the ecological status of fish communities (NISECI) is a methodology developed in Italy that uses fish communities as BQEs to assess the ecological status of rivers, as directed by the WFD. We aimed to apply the NISECI to define the transition from the minimum vital flow (MVF), currently in force in Italian legislation, to the EF, as per the WFD. Specifically, we defined NISECI values for 26 stretches of river located within the Tiber River basin hydrographic network and characterized the physicochemical and hydromorphological conditions. Fish and environmental data were collected between July 2024 and May 2025. For summer flow rates (the low-flow season), we equated the EF to the MVF at locations where WFD objectives had been met (i.e. good ecological status). In the other cases, we predicted an increase in flow rate depending on the deviation from good ecological status. In line with this holistic multidisciplinary approach, we based variation in the quantity, quality, and timing of water discharge envisioned by the EF concept on the natural flow duration curves calculated for the Tiber River basin.

The Mediterranean trout (currently referred to as Salmo ghigii for Corsican and Italian-native populations) is listed as Endangered in the IUCN Red List, due to fragmented distribution and declining populations across its whole range, and is included in Annex II of the European Habitat Directive. The widespread genome introgression from the invasive Atlantic trout (Salmo trutta), overexploitation, and habitat alterations represent major threats to the persistence of native populations. The LIFE18NAT/IT/000931 STREAMS project aims to enhance conservation status of Mediterranean trout in 6 Italian pilot areas (Maiella, Sibillini Mountains, Casentino Forests and Pollino National Parks, Montemarcello-Magra-Vara Regional Park, and Sardinia with five sites of the Natura 2000 Network), and in 19 transferability areas covering almost the whole Italian species range. To achieve this, the following conservation strategies were implemented: (i) the identification of residual native populations; (ii) eradication of entirely Atlantic-exotic populations and removal of hybrids in admixed populations; (iii) restocking/reintroduction of native populations; (iv) monitoring/improving the Mediterranean trout habitats quality; (v) production of the “Guidelines for the conservation and management of native Mediterranean trout and its habitat”; and (vi) the prevention of illegal stocking. Here, we present the project rationale, major outcomes on demographic and genetic characterization of wild populations, and summary results from conservation actions.

The signal crayfish Pacifastacus leniusculus (Dana, 1852) is one of the most ecologically impactful decapod crustaceans introduced in Europe. As a species of Union concern, early detection and rapid eradication measures are required to prevent its establishment and spread. We aimed to: i) test the effectiveness of an eradication attempt undertaken to counteract the spread and contain the demographic growth of P. leniusculus in the Clitunno River Basin (central Italy), where the species has been detected in 2020; ii) assess distribution, age structure and growth of P. leniusculus in this invaded area. The removal actions were conducted biweekly, from June 2022 to December 2024, using both traps and electrofishing. Biometric parameters were individually recorded, and the demographic features and growth of P. leniusculus population were assessed. In total, 259 removal activities were carried out and a biomass of 39.74 kg was removed. The presence of six cohorts (from 0+ to 5+), including the young-of-the-year (0+), attested to the rapid acclimatisation of P. leniusculus, which gave rise to a self-sustaining population in a short time. The greatest removal efforts have been concentrated on a small tributary, named Fosso Vecchio, where the average values of Catch Per Unit Effort (CPUE) showed a significant decreasing trend over time, suggesting the effectiveness of the removal actions. Our findings provided some evidence that early detection and eradication measures conducted on a small scale, but with high effort, represent effective management tools to limit population abundance and prevent invasive crayfish from spreading further.

The early Pleistocene whale fall events recognized at the Bargiano site (southwestern Umbria, central Italy) provided the opportunity to document and reconstruct the community of scavengers and opportunists, vertebrates and invertebrates that gathered around cetacean remains. A rich fauna of ghost shrimps and brachyuran crustaceans (the most represented ones), teleost fish and other osteichthyes (i.e., Ophidiiformes and Sciaenidae), sharks, as well as some specimens of irregular echinoids, have been analysed. The occurrence of otoliths of the rare ophidiid fish Hoplobrotula orcianensis Schwarzhans, 1994 and the irregular echinoid Ova canalifera (Lamarck, 1816) are herein reported for the first time in early Pleistocene marine deposits from Umbria. Among the decapods, Jaxea nocturna Nardo, 1847, Goneplax rhomboides (Linnaeus, 1758), and Asthenognathus alleronensis Pasini, Garassino and De Angeli, 2017 are herein recorded, together with some additional well-preserved specimens of the previously reported Albaidaplax ispalensis Garassino, Pasini and Castro, 2013 and Chlinocephalus demissifrons Ristori, 1886. A shark teeth assemblage related to whale fall events is here documented. Moreover, the common tracks of burrowing organisms, referable to activity of crustaceans and echinoids, have been documented, allowing to reconstruct the life on the shallow seabed (maximum depth of about 150m) of scavengers and opportunists, which developed around a whale carcass. The identification of a specialized community (biome) of benthonics and nectonics, contributes to best define this peculiar bioenvironment, confirming the gers, Opportunists, Sulphophilic and Reef stages) linked to the whale fall events.

The signal crayfish Pacifastacus leniusculus (Dana, 1852) is one of the most ecologically impactful decapod crustaceans introduced in Europe. As a species of Union concern, early detection and rapid eradication measures are required to prevent its establishment and spread. We aimed to: i) test the effectiveness of the control plan prepared within the LIFE IMAGINE IPE/IT/000015 project to contrast the diffusion and contain demographic growth of P. leniusculus in the Clitunno River basin (Central Italy), where the species has been detected in 2020; ii) assess distribution, age structure and growth of P. leniusculus in this invaded area. The removal actions were conducted biweekly, from June 2022 to December 2024, using both traps and electrofishing. Biometric parameters were individually recorded, and the demographic features and growth of P. leniusculus population were assessed. In total, 259 removal actions were carried out and a biomass of 39.74 Kg has been removed. Maximum size (Total Length = 14.8 cm) was consistent with what has been reported for another Italian population, but greater than some native Californian ones. The presence of six cohorts (from 0+ to 5+), including the young-of-the-year (0+), attested the quick acclimatization of P. leniusculus, which gave rise to a self-sustaining population in a short time. The greatest removal efforts have been concentrated on a small tributary, named Fosso Vecchio, where the average values of Catch Per Unit Effort (CPUE) showed a significant decreasing trend over time, arguing in favour of the removal actions' effectiveness. Our findings provided some evidence that early detection and control measures conducted at a small scale, applying strong catching efforts, represent effective management tools to limit population abundance and prevent invasive crayfish from spreading further.

In this study the reproduction of the southernmost Italian population of the invasive Pacifastacus leniusculus (Dana, 1852) was analyzed. The species was recorded for the first time in the Clitunno River in 2020, an eradication plan started in June 2022 as part of the LIFE IMAGINE 19 IPE/IT/000015 project and aspects of the reproductive biology were examined from individuals captured. In this population, gonad maturation starts in February in females and in May in males. Spawning begins in October and the incubation lasts approximately four-five months. The smallest ovigerous female recorded had a cephalothorax length (CL) of 3.3 cm at an estimate age of 2+. Ovarian eggs and pleopodal eggs number ranged from 142 to 726 and from one to 481, respectively. A positive significant linear correlation between ovarian egg number and female CL was observed. Pleopodal egg diameter was positively correlated with female CL, indicating that bigger females produce larger eggs. This study shows the species is well adapted to the environmental conditions of the new habitat, exhibiting early sexual maturity, and a high potential fecundity but with a high percentage of egg loss. The reproductive characteristics highlighted in this study could help optimize containment efforts for the signal crayfish. Copyright (c) 2025 by The Author(s). Published by the International Association of Astacology This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

The caryophyllidean tapeworm Caryophyllaeus brachycollis (Janiszewska, 1953) is indigenous to the Lake Blidinje in the west-central part of Bosnia-Herzegovina where it infects chub Squalius tenellus (Heckel, 1843). Of 22 chubs examined, 45% were infected with C. brachycollis and a total of 912 specimens of this worm were counted. Histopathological and ultrastructural investigations were conducted on interface region between chub intestine and cestode scolex. Different sizes of lipid droplets in cestode tegument, in interface region and in chub enterocytes were observed. C. brachycollis lacks any specialized attachment organs and with an expanded, flattened scolex goes deep in mucosal folds and firmly attaches to them. In the epithelium of fish intestine, near the site of worm attachment, a high number of mucous cells and several rodlet cells were noticed. Indeed, within the intestinal tunica propria-submucosa, beneath the site of scolex attachment, numerous neutrophils and mast cells were encountered. Transmission electron microscopy of the apical part of the scolex of C. brachycollis showed the occurrence of a multicellular, syncytial glandular complex, the scolex produced membrane-bound secretory granules and their fibrillar contents discharged by merocrine and apocrine secretion onto the host-parasite interface. Our results are among the first to provide evidence on the sophisticated relationship between fish intestine and amorphous-undefinable substance produced by scolex glandular complex.

Freshwaters of the Balkan Peninsula show high levels of endemism and relict species, which are still little studied and are threatened by numerous anthropogenic stressors. Protected areas could give special opportunities to improve knowledge of their biodiversity and develop proper conservation measures for the most at-extinction risk species. The aims of this research were to: i) fill the knowledge gap regarding fish and crustaceans occurring in the main water bodies of the Blidinje Nature Park (Southwestern Bosnia-Herzegovina); ii) assess the population abundance and growth, for the species of conservational interest; iii) identify fish biodiversity hotspots in Bosnia-Herzegovina; iv) identify anthropogenic pressures and suggest proper conservation measures. Fish and crayfish data were collected in four sampling sites located on the main water bodies, using electrofishing and gillnets, in three sampling phases over the period July 2022-August 2023. The presence of three species at high extinction risk has been detected: Squalius tenellus, Aulopyge huegelii and Astacus astacus. Their populations were abundant, with balanced age structure and good growth performance. A spatial analysis allowed to quantify the fractions of the endemic species range covered by the Blidinje Nature Park, which were 6.1% and 2.3% for S. tenellus and A. huegelii, respectively. The presence of invasive Atlantic trout and overharvesting of crayfish seem to represent the main anthropogenic pressures on freshwater biota. The obtained information allowed to expand the knowledge on the distribution and population status of threatened species and to highlight diversity hotspots as valuable tools for their conservation and management.

To complete their life cycle, freshwater mussels of the order Unionida depend on fishes as hosts for their obligatory parasitic larval phase, the glochidium. Here we report the first documentation of gobioid fishes as hosts of glochidia of unionid mussels in the wild in Italy and in southern Europe (outside of the Danube drainage area). We also examined the pattern of the attached glochidia. A recent review reported 326 fish species as suitable hosts for unionids, but only eight (2.5%) of these were Gobioidei. Host identification and the documentation of their benefits or threats for the interaction of the mussels with their hosts is important for conservation of freshwater mussels. But the co-existence of mussels with non-native fish species is only poorly understood, including the compatibility of these two groups. Knipowitschia panizzae and Pomatoschistus canestrinii, two translocated sand gobies, were sampled in 2022 at the east shore of Lake Trasimeno (Italy). Two species of anodontine mussels were present at this locality, the native Anodonta anatina and the translocated Sinanodonta woodiana. Genetic data revealed that both sand gobies hosted glochidia only of A. anatina but not of S. woodiana, possibly because of seasonal bias. About 50% of the specimens of both fish species were infested. The paired fins were the most prominent targets. The examined individuals of both sand gobies carried only few glochidia (max. 5). Nevertheless, the two species showed a divergent pattern of glochidia attachment.

A subpopulation of 97 European eels, Anguilla anguilla, was obtained from a local consortium of Lake Trasimeno. The fish were examined for parasites in the swimbladder (SB) and intestine; the SBs of 66 (68%) of the 97 eels contained 480 adult specimens of the nematode Anguillicoloides crassus (Kuwahara, Niimi and Itagaki, 1974) and the intensity of infection ranged from 1 to 18 adult worms per SB (7.27 ± 0.43, mean ± SE). In heavily infected SB, the wall was thicker; upon excision, black-brownish adult nematodes were noticed inside the lumen. The infected SBs showed a papillose aspect of the epithelium and frequent erosion, inflammation, hemorrhages, and dilation of blood vessels. In parasitized SBs, mast cells and macrophages were encountered in the mucosal layer; in several heavily infected SB, rodlet cells were the sole fish immune cells noticed in the epithelium and in close contact with the A. crassus. With reference to the eel intestinal epithelium, in fifteen eels, two developmental stages of coccidian were close to clusters of rodlet cells, the coccidian induced erosion of the epithelium. The results of a panel of 12 antibodies in the European eel infected tissues will be presented.

The interaction between climate warming and alien fish invasions could have severe consequences in inland waters, which represent isolated environments with high biodiversity richness. Due to the current climatic trend, increasing water temperatures and salinization, shorter ice cover period, and altered flow regimes are predicted for these environments. The aim of this review is to offer a comprehensive analysis at a global scale of the recent studies available in the literature, focused on the responses of invasive freshwater fish to the effects of climate change in both lotic and lentic environments. To achieve this purpose, we selected 34 relevant papers, using the Scopus and Google Scholar database. New alien species establishment, distribution range expansion of species already introduced, and exacerbating impacts on freshwater ecosystems and the native fish communities they host were included in the topics covered by the analyzed papers. Despite the uncertainties related to the unpredictability with which the effects of global warming will occur, the findings of the selected studies served as a support to evaluate conservation and management implications, with particular reference to possible mitigation strategies.

Fish, comprising over 27,000 species, represent the oldest vertebrate group and possess both innate and adaptive immune systems. The susceptibility of most wild fish to parasitic infections and related diseases is well-established. Among all vertebrates, the digestive tract creates a remarkably favorable and nutrient-rich environment, which, in turn, renders it susceptible to microparasites and macroparasites. Consequently, metazoan parasites emerge as important disease agents, impacting both wild and farmed fish and resulting in substantial economic losses. Given their status as pathogenic organisms, these parasites warrant considerable attention. Helminths, a general term encompassing worms, constitute one of the most important groups of metazoan parasites in fish. This group includes various species of platyhelminthes (digeneans, cestodes), nematodes, and acanthocephalans. In addition, myxozoans, microscopic metazoan endoparasites, are found in water-dwelling invertebrates and vertebrate hosts. It is worth noting that several innate immune cells within the fish alimentary canal and certain visceral organs (e.g., liver, spleen, and gonads) play active roles in the immune response against parasites. These immune cells include macrophages, neutrophils, rodlet cells, and mast cells also known as eosinophilic granular cells. At the site of intestinal infection, helminths often impact mucous cells number and alter mucus composition. This paper presents an overview of the state of the art on the occurrence and characteristics of innate immune cells in the digestive tract and other visceral organs in different fish-parasite systems. The data, coming especially from studies employed immunohistochemical, histopathological, and ultrastructural analyses, provide evidence supporting the involvement of teleost innate immune cells in modulating inflammatory responses to metazoan and protozoan parasitic infections.

The endemic chub Squalius tenellus (Heckel, 1843) was introduced more than 100 years ago to Lake Blidinje (Bosnia-Herzegovina). Only 1 species of enteric helminth was found in a sample of 35 chubs, the tapeworm Caryophyllaeus brachycollis (Janiszewska, 1953). The paper includes histopathological investigation with identification of innate immune cells involved in host reaction and molecular data allowed correct designation of the cestode species. Of 35 specimens of chub examined, 21 (60%) harboured individuals of C. brachycollis and a total of 1619 tapeworms were counted, the intensity of infection ranged from 1 to 390 worms per fish (46.2 ± 15.3, mean ± s.e.). Histopathological and ultrastructural investigations showed strict contact between the worm's body and the epithelia and increase in the number of mucous cells, rodlet cells among the epithelial cells. Within the tunica propria-submucosa, beneath the site of scolex attachment, numerous neutrophils and mast cells were noticed. This is the first study of the occurrence of C. brachycollis in chub from Lake Blidinje and on the response of the innate immune cells of S. tenellus to this tapeworm. Interestingly, in 3 very heavily infected chubs, perforation of the intestinal wall was documented; this is uncommon among cestodes which use fish as a definitive host.

The Italian-native Mediterranean brown trout (Salmo ghigii) is a seriously threatened freshwater fish, especially by anthropogenic hybridisation with the domestic strains of Atlantic origin that have been repeatedly released into the wild for angling. A PCR-restriction fragment length polymorphism (RFLP) assay of the diagnostic lactate dehydrogenase chain-1 (LDH-C1) gene sequences has been routinely applied to distinguish exotic from native brown trout lineages and detect Atlantic introgression signals in the Mediterranean wild populations. Here, we used dermal swab DNA obtained from 28 wild trout to improve laboratory procedures to genetically characterise trout samples at the LDH-C1gene through (1) a capillary electrophoresis analysis of the RFLP fragments and (2) the optimisation of a diagnostic single nucleotide polymorphism analysable through mini-sequencing approaches. The developed methods were fully consistent with those obtained through the traditional approach, but their analytical process is almost entirely automated and digitalised, thus improving result readability and accuracy in the detection of alien introgressed traces in wild Mediterranean brown trout populations.

The Salmo trutta species complex includes threatened or intensively managed taxa. Domestic-Atlantic strains are widely farmed and massively introduced into the wild to support fisheries, although such practices seriously threaten native populations of Mediterranean brown trout through anthropogenic hybridization. Characterizing the distribution and genetic composition of wild populations across river catchments is crucial to identify conservation priorities and define appropriate management strategies. Here, we genotyped 586 brown trout at the diagnostic nuclear LDH-C1 gene and the mitochondrial D-loop fragment, to assess the conservation status of 33 sites in a protected area spanning river catchments from both the Adriatic and Tyrrhenian slopes in the northern Apennines (Italy). The results indicated a critical situation of widespread domestic-Atlantic introgression. Further analyses at 15 microsatellite loci on 159 individuals from 12 natural sites (along with 113 references from hatcheries) revealed similarity to hatchery stocks, higher genetic diversity and bottleneck signals in introgressed/exotic populations, consistently with relatively recent introductions of domestic-Atlantic individuals into wild sites. Conversely, the only native sites from a single river catchment on the Adriatic slope showed genetic distinctiveness, reduced diversity and demographic stability. We also found genetic evidence of a human-mediated introduction of allochthonous Mediterranean trout in a single wild site, as well as of a putative between-slopes translocation. We provide further insight into the occurrence and consequences of human manipulations on wild Mediterranean brown trout populations, contextually offering a reliable baseline for an ongoing conservation project aiming at preserving native populations of this endangered taxon.

Local adaptation and phenotypic plasticity can lead to environment-related morphological and genetic variations in freshwater fish. Studying the responses of fish to environmental changes is crucial to understand their vulnerability to human-induced changes. Here, we used a latitudinal gradient as a proxy for past and present environmental factors and tested its influences on both genetic and morphological patterns. We selected as a suitable biogeographic model, the barbels, which inhabit 17 Adriatic basins of the central-southern Italian Peninsula, and explored association among attributes from genetic, morphological, and environmental analyses. The analysis of the mitochondrial DNA control region evidenced a southward significant increase in the number of private haplotypes, supporting the isolation of the southernmost populations related to the Mio-Pleistocene events. In contrast, morphology was mainly affected by changes in the present environmental conditions. Particularly, the number of scales and fish coloration were clearly associated to latitude, and thus thermal and hydrological conditions. Other morphometric and functional traits varied under the selective pressure of other environmental factors like elevation and distance from headwater. These results highlight the sensitivity of barbels to climate changes, which can serve as a basis for future eco-evolutionary and conservation studies.