Search

The European eel (Anguilla anguilla) is a critically endangered species. The impact of environmental contamination on this species has been highlighted as contributing to the decline in recruitment. The Mar Menor hypersaline coastal lagoon (SE Spain) is one of the most productive fisheries of European eel in Europe, making it a critical habitat for species conservation. The present study aimed to provide an initial overview of the impact of organic chemical contaminants on the European eel and the potential sublethal effects of chemical pollution on pre-migrating eels in this hypersaline habitat. We investigated muscle bioaccumulation of main persistent and hazardous organic contaminants (including some current-use pesticides) and genotoxicity, neurotoxicity, and xenobiotic detoxification system responses. The findings show that lagoon eels were exposed to high levels of legacy organochlorine contaminants, recently banned pesticides (chlorpyrifos), and some emerging chemicals. Some individuals surpassed the maximum levels of CBs authorized by the European Commission for human consumption. In this species, residuals of chlorpyrifos, pendimethalin, and chlorthal dimethyl have been reported for the first time. This field study provides relevant data to stock management and human health consumption and provides the first biomarker responses in European eel under permanent hypersaline conditions. Furthermore, the high frequency of micronuclei in peripheral erythrocytes of lagoon eels indicates sublethal genotoxic effects on the organism. Overall, the European eels growing and maturing in the Mar Menor lagoon are exposed to toxic and carcinogenic chemicals. The lack of seafood safety regulations for human consumption for some legacy chemicals that were measured in high concentrations in our study requires special action. Further biomonitoring and research are recommended to protect the animal, public, and environmental health., (© 2023. The Author(s).)

The aim of the present study was to investigate the effects on gill morphology of the explosive 2,4,6-trinitrotoluene (TNT) in a model fish, the European eel, Anguilla anguilla (Linnaeus, 1758) to assess potential detrimental effects in marine fish due to its presence in dumping areas. Juvenile specimens of A. anguilla were exposed in vivo for 6 and 24 h to 0.5, 1 and 2.5 mg/l nominal concentrations of TNT using dimethyl sulfoxide (0.1 per thousand) as solvent carrier. Histological analysis of gills indicated that TNT induced several structural lesions. After 6h of exposure at 0.5 and 1 mg/l TNT, oedema of some secondary lamellae was evident: this change at the highest dose of 2.5 mg/l led to epithelial lifting and detachment from the endothelium and rupture of the branchial membrane and vascular congestion. After 24 h at 0.5 mg/l, increased oedema in secondary lamellae, extensive epithelial detachment and vascular congestion and dilation of lamellar capillaries and pooling of blood at 1 mg/l were observed. At 2.5 mg/l, epithelial hyperplasia, fusion of adjacent lamellae, obliteration of interlamellar spaces by means of tight junctions were also observed. Moreover, chloride cells proliferated along secondary lamellae, and mucus hypersecretion was evident. The overall results clearly indicate that gills are sensitive targets of TNT.

Freshwater mussels and crayfish provide important ecosystem functions and services. In both groups, global declines of native species are paralleled by invasions of non‐native species. Knowledge on differences in predation susceptibility of native and invasive freshwater mussels exposed to native and invasive crayfish is essential for understanding their ecological interactions and for conservation management.In this study, we compared the predation impact of the native European noble crayfish (Astacus astacus) and the invasive signal crayfish (Pacifastacus leniusculus) on three native (Anodonta anatina, Anodonta cygnea, and Unio pictorum) and one invasive (Sinanodonta woodiana) mussel species in controlled laboratory experiments. We repeated the same experiments with the same crayfish specimens to investigate a potential learning effect of crayfish and assessed the in situ impacts in a natural stream.Mussel predation and damage caused by P. leniusculus was significantly higher than by A. astacus. Irrespective of the crayfish species, susceptibility was greater in native mussel species compared to invasive S. woodiana. Predation and damage was greatest in the thick‐shelled U. pictorum, suggesting that other factors such as shell shape are more important in explaining susceptibility than shell thickness. A predation learning effect from previous co‐exposure was evident, being most pronounced for A. astacus.Even if our experimental findings could not be confirmed in the field, the experimental results suggest that crayfish may have a negative impact on mussels and this impact will likely increase with the ongoing spread of P. leniusculus replacing A. astacus populations in Europe. The co‐occurrence of invasive P. leniusculus with the invasive S. woodiana could potentially exacerbate declines of endangered native mussel populations. [ABSTRACT FROM AUTHOR]

Welfare in farmed fish got particular attention during the last decades from both governmental and public sides. In aquaculture context, welfare concerns are mainly related to handling procedures, water quality and stoking densities. In Europe, authorities had to clarify the threshold limits of stocking densities to maintain fish good welfare, including for organics aquaculture through the EC regulation 710/2009. However, effects of stocking density on fish welfare are complex and sometimes contradictory. Moreover, there is a lack of knowledge about the impact of density on fish welfare in organic aquaculture. Thus, the aim of the study is to asses welfare state of rainbow trout (Oncorhynchus mykiss) at two initial stocking densities (low density, LD: 12 kg/m3 and high density, HD: 17 kg/m3) fed using organic feed by combining the monitoring of growth performances, behaviour (swimming activity) and physiological indicators (i.e. cortisol, glucose, lactate, hematocrit, red blood cellule count and lysozyme). At the end of experiment, the stocking density reached 21 kg/m3 and 30 kg/m3 for the LD and HD respectively. Overall, growth performances, swimming activity and level of physiological indicators of stress and welfare were similar between HD and LD over the experiment duration. To conclude, we observed no alteration of fish welfare between the two stocking densities monitored. This study suggests that a final stocking density of 30 kg/m3 can be considered for organic aquaculture of rainbow trout respecting welfare. [ABSTRACT FROM AUTHOR]

The explosive global spread of Sinadonta woodiana, a large‐bodied unionid mussel of East Asian origin, potentially affects the functioning of freshwater habitats and threatens native mussels. Molecular data indicate that its invasion in Europe started with a single colonization event, followed by in situ adaptation. This study traces one of the possible routes of such adaptation. It documents a population of S. woodiana with a known history of a two‐stage introduction: first, from a heated water source to a production fish pond in northern Poland, and subsequently from that pond to the study site. As the latest local transfer occurred more than 15 years before the study, the abundance of young S. woodiana in various age classes provides proof of ongoing in situ reproduction and resolves the question of the ability of S. woodiana to permanently colonize thermally unpolluted water bodies in areas with prolonged and cold winters. The study also shows that translocations of glochidia‐infested fish and/or adult mussels between water bodies in such areas result in the establishment of new self‐recruiting populations. Together, these findings show that further expansion of S. woodiana into colder regions and establishment of new populations in already invaded areas are to be expected. The relative abundance of S. woodiana and the native unionids: Anodonta anatina and A. cygnea was 40%, 18%, and 42%, respectively. S. woodiana contributed to 65% of the total mussel biomass. Individuals in the first three size classes, corresponding to the 2‐ to 4 year age classes, composed 50% of S. woodiana, 37% of A. anatina, and 26% of A. cygnea. The high proportion of young individuals in S. woodiana indicates population trajectories toward a gradually increasing dominance of this species and possibly reflects its negative impacts via interactions with host fish and competition for resources. [ABSTRACT FROM AUTHOR]

In recent years, EU countries have recognized national policies to authorize dispersant use to mitigate the petroleum hydrocarbon contamination in case of unintentional oil spills at sea. A harmonization of dispersant approval procedures is needed because the application of different methodologies agrees on dissimilar toxic responses for the same dispersant in different European countries. Actually, different dispersant approval procedures are applied in France and Italy with one French mandatory toxicity test and three Italian bioassays accompanied with different criteria of toxicity classification. In this paper, a harmonized tiered approach is proposed to address the dispersant ecotoxicological assessment in these two nations. Our approach, applicable at the European level, introduces two mandatory tests (algal growth inhibition test and mortality test with crustaceans) and one discretionary test (fish mortality test), by reducing use of vertebrates as much as possible in accordance with humane principles and animal welfare.