Mistrust between scientists and non-scientist stakeholders is a key challenge in fishery management. This problem is exacerbated with the use of complex models to support management: these models suffer from difficulties in communicating their results and a lack of confidence from end users. The European eel is an illustrative example; its complex life cycle raises problems of coordination and discussion among the multiple actors involved in the management of the species. The GEREM model has been proposed as a tool for estimating recruitment, but its complexity, which is essential for addressing the characteristics of the species, makes it difficult to understand and accept by all stakeholders. In the context of the SUDOANG project, we proposed a co-parametrization of this assessment model to tackle this mistrust. Through the use of various questionnaires and appropriate statistical analyses, stakeholders were involved in two important choices for the model (zone definition and prior construction). Regular workshops and presentations were organised to explain the model rationales and to gather feedback and expectations. The results show that stakeholders have very similar perceptions of the potential definitions of sub-areas of recruitment in south-western Europe, and these perceptions are consistent with the underlying environmental conditions. On the other hand, the stakeholders have contrasting opinions about the exploitation rates of fisheries in different river basins, and the use of their knowledge currently has little effect on GEREM estimates. More importantly, the overall approach of this study is thought to have reconstructed the trust and confidence among participants.

The presence of valuable bioactive compounds in European eel (Anguilla anguilla) skin was studied. For it, proximate and lipid class compositions and analysis of the fatty acid (FA) profile (individual FAs; FA groups, i.e., saturated, monounsaturated, and polyunsaturated; FA ratios, i.e., polyunsaturated/saturated, ω3/ω6) were determined and compared to the composition of the eel muscle. As a result, higher (p<0.05) levels of proteins (271.6 g·kg-1), lipids (38.0 g·kg-1), ash (27.7 g·kg-1) and ω6 FAs were observed in the skin tissue. Contrary, the muscle tissue showed higher (p<0.05) moisture, ω3 FA and ω3/ω6 values. Regarding lipid classes, a higher (p<0.05) proportion of phospholipids (111.1 g·kg-1 lipids), sterols (104.7 g·kg-1 lipids), α-tocopherol (274.0 mg·kg-1 lipids), and free fatty acids (43.6 g·kg-1 lipids) was observed in the skin tissue. No differences (p>0.05) between both tissues could be detected for triacylglycerol and FA group (saturated, monounsaturated, and polyunsaturated) values, as well as for the polyunsaturated/saturated ratio. It is concluded that eel skin, a by-product resulting from commercial processing, can be considered a valuable source to provide the food and pharmaceutical industries with useful value-added constituents such as proteins, lipids, ω3 FAs, phospholipids, and α-tocopherol.

The Matāura River is the sixth largest river system in New Zealand and has long been subject to agricultural, industrial, and residential land use activities. The catchment has geographic and economic value and is of great cultural importance for local Māori, who have concerns over potential adverse impacts that anthropogenic stressors exert on the health of the river. There is a dearth of information on the impacts of these stressors towards the health of native species such as the longfin eel Anguilla dieffenbachii. This study assessed the environmental status of the Matāura River using biological and chemical methodologies incorporating A. dieffenbachii as a bioindicator species for exposure to combined anthroprogenic stressors. A range of biomarker endpoints were measured in caged and wild-caught eels (when available) to characterize site-specific responses to combined anthropogenic stressors. While there was no clear indication of cumulative impacts moving from pristine headwaters to the lower reaches of the Matāura River biomarkers of xenobiotic metabolization were induced in A. dieffenbachia and there was evidence of chemical contamination in sediments and tissues.

Parasitic infections are often not the direct cause of death of fish but the presence of wounds in the fish's body due to parasitic attacks is a trigger factor for secondary infection. Secondary infections can be caused by fungi, bacteria or viruses, which ultimately cause the death of fish. This study aimed to determine the characteristics of parasites and fungi that infected eel (Anguilla sp.) in the waters of Poso, Buol, Toli-toli and Donggala, Central Sulawesi as an important part of the diagnosis of fish disease in the framework of teraupetic strategies. Eel were taken as many as 30 individuals / location for observation of parasites and fungi. Parasitological examination was carried out for external and internal parasites on the mucous layer of the body, gills, intestines and stomach, while fungal isolations were carried out on muscles, skin and tissues that have abnormalities. After identification, the prevalence and intensity were carried out. The results showed that the highest prevalence of parasites were Camallanus sp (70%), Proteacephalus sp (50%) and Gyrodactylus sp (40%), and the nematode Camallanus sp the tapeworm Proteocephalus sp had the highest intensity of 57.5 and 30.8 respectively. Fungal prevalence were found highest in Saprolegnia sp (36%), and Fusarium sp (32%).

The aim of the present study, was to evaluate the wild freshwater fish health status using a vast array of biomarkers as predictive factor of pollutant exposure. European eel (Anguilla anguilla) and Brown trout (Salmo trutta fario), resident in rivers with different degree of pollution in the South of Italy (Picentino river with good environmental quality and Tusciano river with low environmental quality), were examined using biometric parameters, histopathological and immunohistochemical biomarkers to evaluate the health status and a possible correlation with the water quality. Several alterations identified in the liver positively correlated with water and soil pollutants were: hemorrhage (P≤0.05), cytoplasmic vacuolization (P≤ 0.01), hemosiderosis (P≤0.05), irregular arrangement of hepatocytes (P≤ 0.01), lipid accumulation (P≤0.05), necrosis (P≤ 0.01), cellular hyperplasia (P≤0.05), leukocyte infiltration (P≤ 0.01) and melanomacrophages centers (MMC) (P≤ 0.01). In the spleen, only hemosiderosis correlated with water and soil pollutants (P≤ 0.05). The inflammatory biomarker tumor necrosis factor α (TNFα) and ciclooxigenase 2 (COX2) responded to the environmental pollution, as well as the oxidative stress biomarkers superoxide dismutase (SOD) and 8-Hydroxy-2'-deoxyguanosine (8-OHdG). Erythrocytic nuclear abnormalities and erythrocytic cellular abnormalities were found significantly higher in the blood of both Europen eel (P<0.0001) and Brown trout (P <0.001) in the Tusciano river with respect to the Picentino river. Taken together, these results outline the need to increase the number of suitable biomarkers to assess fish health and reinforce the importance to employ additional biomarkers in biomonitoring programs which can be applied to evaluate the water quality and environmental risk assessment around the world