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Desiccation resistance is a key trait determining the distribution of aquatic insects, their potential for overland dispersal, and survival during drought periods in temporary waterbodies, as well as the spread of invasive species. Passive dispersal by waterbirds is considered to be a key process favouring the spread of invasive species and is more likely to occur for insects with eggs that are resistant to desiccation or gut passage. We investigated the hypothesis that the eggs of the alien boatman Trichocorixa verticalis verticalis are resistant to desiccation and digestion and thus able to disperse via waterbirds. We conducted experiments to test for egg resistance to desiccation in still air and under moving air conditions, to simulate bird flight. Oviposition on greater flamingo (Phoenicopterus roseus) legs and wetland plants was tested in the laboratory and in the field. Resistance of eggs to simulated gut passage was studied, as was the viability of eggs recovered from Eurasian coot (Fulica atra) droppings in the field. Only a fraction of eggs hatched after 8 hr of exposure to still air at 15°C (4% of exposed eggs), and after 2 hr exposure to air flow conditions at 20°C (8%). Oviposition on flamingo legs was confirmed in the laboratory but not in the field. However, oviposition rates were higher on plant stems than on flamingo legs. Digestion simulations showed very low resistance to chemical treatment and no resistance to scarification, and eggs recovered from coot droppings did not hatch. Our experiments demonstrated that T. v. verticalis cannot be considered to have eggs resistant to desiccation or gut passage. However, the dispersal of eggs on legs of flamingos or other waterbirds may occur as rare events. This epizoochory of eggs could potentially contribute to the expansion and gene flow of T. v. verticalis around the Mediterranean region.

There is a risk of ‘ecological surprises’ if multiple potentially interacting stressors are managed individually, which is a question attracting significant current interest. Habitat degradation and species introductions are major threats to global biodiversity, and riverine fish are among the most threatened taxa in the world. Our interest was whether the presence of non-native species can affect native fish sensitivity to water quality deterioration in a large region in northeastern Spain (99,700 km, 15 catchments, 530 sites). We used a ‘base model’ with geographical and hydro-morphological variables, which are the major shaping factors in rivers. We tested whether water pollution, non-native species, or their interaction provided an improved understanding of patterns of distributions and health measurements of the twelve most common native species. There was little evidence that variation in native species abundance, where they occurred, the presence of diseases and changes in mean fish length or body condition was affected by water deterioration, the presence of non-native species, or their interaction. The disease rate and occurrence of native species might be affected, to a minor degree, by water quality changes and the presence of non-native species. Environmental conditions between sites with and without non-native fish differed in the condition of riparian areas and in water quality. Based on presence-absence data and changes in abundances through weighted average equations we also derived potential safe levels of salinization, nutrient pollution, and pH for the native fish. Overall, additive effects of stressors prevail over interactions, and the restoration of natural hydro-morphology in rivers is likely to be the most effective management approach to improving the prospects for the native fish fauna.

There is a risk of ‘ecological surprises’ if multiple potentially interacting stressors are managed individually, which is a question attracting significant current interest. Habitat degradation and species introductions are major threats to global biodiversity, and riverine fish are among the most threatened taxa in the world. Our interest was whether the presence of non-native species can affect native fish sensitivity to water quality deterioration in a large region in northeastern Spain (99,700 km, 15 catchments, 530 sites). We used a ‘base model’ with geographical and hydro-morphological variables, which are the major shaping factors in rivers. We tested whether water pollution, non-native species, or their interaction provided an improved understanding of patterns of distributions and health measurements of the twelve most common native species. There was little evidence that variation in native species abundance, where they occurred, the presence of diseases and changes in mean fish length or body condition was affected by water deterioration, the presence of non-native species, or their interaction. The disease rate and occurrence of native species might be affected, to a minor degree, by water quality changes and the presence of non-native species. Environmental conditions between sites with and without non-native fish differed in the condition of riparian areas and in water quality. Based on presence-absence data and changes in abundances through weighted average equations we also derived potential safe levels of salinization, nutrient pollution, and pH for the native fish. Overall, additive effects of stressors prevail over interactions, and the restoration of natural hydro-morphology in rivers is likely to be the most effective management approach to improving the prospects for the native fish fauna.

One of the most influential mechanisms for the introduction of aquatic nuisance species is transport in ship ballast waters. Although several ballast tank treatments to prevent transport of aquatic or organisms appear promising, all existing approaches will result in significant costs to the shipping industry. The implementation of ballast water treatment measures would be hastened by providing the shipping industry with economic incentives for doing so. Our previous work suggests that deoxygenation may be such a treatment with benefit for ship owners by reducing corrosion, while simultaneously limiting the number of aquatic organisms surviving transport in ballast tanks. Our current investigations are providing the critical information required to evaluate the efficacy and feasibility of deoxygenation as a ballast water treatment to prevent aquatic invasions and tank corrosion. These results will ultimately lead to a fall-scale shipboard evaluation of deoxygenation as a cost-saving ballast water treatment.