Integrating Economic and Ecological Benchmarking for a Sustainable Development of Hydropower

Hydropower reservoirs play an increasingly important role for the global electricity supply. Reservoirs are anthropogenically-dominated ecosystems because hydropower operations induce artificial water level fluctuations (WLF) that exceed natural fluctuations in frequency and amplitude. These WLF have detrimental ecological effects, which can be quantified as losses to ecosystem primary production due to lake bottoms that fall dry. To allow for a sustainable development of hydropower, these “ecological costs” of WLF need to be weighed against the “economic benefits” of hydropower that can balance and store intermittent renewable energy. We designed an economic hydropower operation model to derive WLF in large and small reservoirs for three different future energy market scenarios and quantified the according losses in ecosystem primary production in semi-natural outdoor experiments. Our results show that variations in market conditions affect WLF differently in small and large hydropower reservoirs and that increasing price volatility magnified WLF and reduced primary production. Our model allows an assessment of the trade-off between the objectives of preserving environmental resources and economic development, which lies at the core of emerging sustainability issues

Flow field-induced drag forces and swimming behavior of three benthic fish species

Modern ethohydraulics is the study of the behavioral responses of swimming fish to flow fields. However, the exact drag forces experienced by fish remain poorly studied; this information is required to obtain a better understanding of the behavioral responses of fish and their current resistance strategies. We measured near-ground frontal drag forces on preserved individuals of three benthic fish species, round goby ( Neogobius melanstomus ), gudgeon ( Gobio gobio ) and bullhead ( Cottus gobio ), in a flow channel. The forces were compared to acoustic Doppler velocity (ADV) measurements and fish tracking data based on video observations of live fish in the flow channel. Overall, we observed drag coefficients (C D ) of ∼10 −3 at Reynolds numbers ∼10 5 . The frontal drag forces acting on preserved fish with non-spread fins ranged from -1.96 mN*g -1 (force per fish wet weight, velocity 0.55 m*s -1 ) to 11.01 mN*g -1 (velocity 0.85 m*s -1 ). Spreading the fins strongly increased the drag forces for bullhead and round goby. In contrast, the drag forces were similar for gudgeon with spread fins and all fish with non-spread fins. Video tracking revealed no clear relationship between the position of the fish in the flow field and the forces experienced by the preserved fish at these positions. Collectively, these results suggest that i) the differences in frontal drag forces between species are small in homogenous flow, ii) individuals chose their position in the flow field based on factors other than the drag forces experienced, and iii) whether fins are spread or non-spread is an essential quality that modulates species-specific differences. The methodology and results of this study will enable integration of flow measurements, fish behavior and force measurements and inform ethohydraulics research. More advanced force measurements will lead to a detailed understanding of the current resistance strategies of benthic fish and improve the design of fish passes

Comparative swimming performance and behaviour of three benthic fish species: The invasive round goby (Neogobius melanostomus), the native bullhead (Cottus gobio), and the native gudgeon (Gobio gobio)

Efforts to restore river ecosystem connectivity focus predominantly on diadromous, economically important fish species, and less attention is given to nonmigratory, small‐bodied, benthic fish species. Data on benthic fish swimming performance and behaviour in comparison with ecologically similar native species are especially relevant for the study of one of the most successful invaders in the last decades: the Ponto‐Caspian gobiid species Neogobius melanostomus. To evaluate future measures against its further upstream dispersal, we conducted comparative swimming performance and behaviour experiments with round goby and two native species: the European bullhead (Cottus gobio) and the gudgeon (Gobio gobio). Experiments in a swim tunnel revealed a high variation in the swimming performance and behaviour within and among the three species. Gudgeon performed best in both U$_{crit}$ and U$_{sprint}$ experiments and displayed a rather continuous, subcarangiform swimming mode, whereas bullhead and round goby displayed a burst‐and‐hold swimming mode. Experiments in a vertical slot pass model, which contained a hydraulic barrier as a challenge to upstream movement, confirmed the high swimming performance of gudgeon. Gudgeon dispersed upstream even across the hydraulic barrier at the highest flow velocities. Round goby showed a higher capability to disperse upstream than bullhead, but failed to pass the hydraulic barrier. Our results on comparative swimming performance and behaviour can inform predictive distribution modelling and range expansion models, and also inform the design of selective barriers to prevent the round goby from dispersing farther upstream

Flow field-induced drag forces and swimming behavior of three benthic fish species

Modern ethohydraulics is the study of the behavioral responses of swimming fish to flow fields. However, the exact drag forces experienced by fish remain poorly studied; this information is required to obtain a better understanding of the behavioral responses of fish and their current resistance strategies. We measured near-ground frontal drag forces on preserved individuals of three benthic fish species, round goby ( Neogobius melanstomus ), gudgeon ( Gobio gobio ) and bullhead ( Cottus gobio ), in a flow channel. The forces were compared to acoustic Doppler velocity (ADV) measurements and fish tracking data based on video observations of live fish in the flow channel. Overall, we observed drag coefficients (C D ) of ∼10 −3 at Reynolds numbers ∼10 5 . The frontal drag forces acting on preserved fish with non-spread fins ranged from -1.96 mN*g -1 (force per fish wet weight, velocity 0.55 m*s -1 ) to 11.01 mN*g -1 (velocity 0.85 m*s -1 ). Spreading the fins strongly increased the drag forces for bullhead and round goby. In contrast, the drag forces were similar for gudgeon with spread fins and all fish with non-spread fins. Video tracking revealed no clear relationship between the position of the fish in the flow field and the forces experienced by the preserved fish at these positions. Collectively, these results suggest that i) the differences in frontal drag forces between species are small in homogenous flow, ii) individuals chose their position in the flow field based on factors other than the drag forces experienced, and iii) whether fins are spread or non-spread is an essential quality that modulates species-specific differences. The methodology and results of this study will enable integration of flow measurements, fish behavior and force measurements and inform ethohydraulics research. More advanced force measurements will lead to a detailed understanding of the current resistance strategies of benthic fish and improve the design of fish passes

Environmental flows or economic woes - Hydropower under global energy market changes

The global energy system changes towards renewables-dominated and liberalized markets. This requires making novel trade-offs between the profitable development of hydropower and its environmental effects on the natural flow regime. Here, we used a pristine river as a model for how these future changes will affect the natural flow regime and identify future changes on previously overlooked levels. We found that damming and discharging based on market prices leads to first- and second-level deviation from natural flows. Beyond these effects, we identified a third level of distance from natural flow. This third level is created by the transition towards a renewables-dominated energy system. The volatile energy input from renewables incentivizes hydropower plant operators to discharge based on more flexible trading behavior. We conclude that novel economic models be combined with tailored implementations of environmental flows. This will allow to find novel solutions for the trade-off between market liberalization and sustainable hydropower development

hobbyists acting simultaneously as anglers and aquarists: Novel pathways for non-native fish and impacts on native fish

Abstract 1. Human translocations of non-native aquatic species are a global conservation challenge. Aquarists and anglers are two hobbyist groups whose practices are par- ticularly likely to translocate non-native aquatic species, especially fish. 2. This article aims to stipulate a change of perspective among these hobbyists, who - by acting simultaneously as anglers and aquarists - establish novel pathways for non-native fish. 3. This study showed that: (i) 51 of 226 respondents to a questionnaire act simulta- neously as anglers and aquarists; (ii) 53 of 237 non-native fish species in the European Union are used for both angling and aquarium hobbies; and (iii) hobbyists write online reports on the catch and exchange of a particularly invasive fish, the round goby ( Neogobius melanostomus ). 4. This combination of knowledge on how hobbyists use non-native fish and the ecological impacts of round goby demonstrates how the impact of an invasive species can be influenced by the combined behaviours of anglers and aquarists. 5. We suggest that future research in aquatic conservation should move beyond considering the commercial aquarium trade and angling as separate pathways for translocating non-native fish, and instead consider these hobbyist groups as interconnected

Invasive goby larvae: first evidence as stowaways in small watercraft motors

Aquatic invasive species (AIS) are a major threat to aquatic ecosystems worldwide. Despite management efforts, human assisted dispersal continues to distribute AIS within and across waterbodies. An understudied translocation vector for AIS, especially for invasive fish, are the cooling systems of small watercraft motors. Here, we investigate the contents of boat motor cooling systems for the presence of invasive goby larvae in a collaboration with local boat owners. Because of the exclusively nocturnal drift activity of goby larvae, to collect samples we drove boats in the first hours after sunset. For an estimate of the translocation potential, we quantified drift density of goby larvae as well as boat traffic after sunset. We found a goby larva in a boat motor once in 30 boat drives of 1-2 hours duration each. Peak drift densities of goby larvae were 2.5 per 100 m3, which is comparable to previously reported data. Recreational boats were active after sunset throughout the reproductive season of invasive gobies and are therefore a realistic translocation vector for goby larvae. Additionally, evidence of fish and other animals inside boat motor cooling systems, gathered from online boating forums, demonstrates the potential of AIS transport in small watercraft. Translocation inside motors is especially likely for in-water transport of boats, which should be a management focus in interconnected aquatic systems

Differential habitat use of a notorious invasive fish, the round goby, in a translocation-relevant system

Anthropogenic structures can form novel ecosystem niches. Invasive species are often particularly successful in occupying these habitats and utilize them as beachheads for further spread. The invasive round goby (Neogobius melanostomus, Pallas 1814), an inherently bottom-dwelling fish, uses vertical harbor walls as habitat, enabling them to reach boats (i.e., potential translocation vectors). To evaluate the relevance of vertical habitat use for population dynamics and translocation, we exemplary investigated a population of round gobies in a harbor ecosystem. Specifically, we investigated differences in trophic niche characteristics, individual trophic specialization, phenotypic traits, and breeding frequency in wall versus bottom-dwelling round gobies. Habitat-characteristic dietary signatures indicated habitat partitioning during the breeding season. Trophic niches overlapped but were clearly distinguishable between the habitats: Walls were inhabited by 1.4 times more trophic generalists than specialists, while the bottom was inhabited by 2.1 times more trophic specialists. Breeding frequency was 24 times higher on the walls than on the bottom. After the reproductive season, we found a higher similarity in trophic ecology of gobies inhabiting the two habitats, and differences in abundance, size, and condition. These results are in line with winter migrations to deeper habitats, which are common in round gobies in lentic and marine ecosystems. Our results suggest a high potential for microgeographic adaptation to either horizontal or vertical habitat use in invasive round gobies. We demonstrated that male gobies using the walls during the breeding season are larger and heavier, suggesting that wall climbing may select for more competitive individuals. Additionally, the overall abundance of round gobies likely increases with the additional use of vertical habitat space, which may lead to higher propagule pressure. The ability to exploit anthropogenic habitats, and a higher translocation probability of competitive individuals, can contribute to the invasion success of round gobies in anthropogenically influenced aquatic systems

Shell shape and growth are correlated in zebra mussels.

<p><b>A</b>: experimental data as mean growth (measured in mm increase in the 3 shell dimensions length, height, and width) in relation to the corresponding shell shape as means from the 28 experimental tanks with 16 mussels each. <b>B</b>: field data as individual growth in the first year post settlement in relation to individual shape of 556 mussels. The contours on the y-axis depict ±2SD of the mean of PC1. Dashed lines denote 95% confidence intervals for the fit.</p

Shell shape and shell strength are correlated in zebra mussels.

<p><b>A</b>: experimental data from 448 mussels. <b>B</b>: field data from 756 mussels. The contours on the y-axis depict ±2SD of the mean of PC1. Dashed lines denote 95% confidence intervals for the fit. Note that we here present individual values for the experimental mussels since we obtained both a shape and strength measure for each mussel separately.</p