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Although dam removal has been considered a viable strategy to mitigate habitat fragmentation within a stream, long-term ecosystem effects after dam removal have rarely been discussed. In an effort to enhance the resilience of the critically endangered Formosan salmon (Oncorhynchus masou formosanus) in response to climate change, a 15-m-high check dam in a subtropical high-mountain stream was half-removed. The aim of this study was to analyze the long-term response of trophic structure and function to dam removal by constructing Ecopath models upstream and downstream of the removed dam at different times. Field surveys for model parameters were conducted for a complete seasonal cycle 1 year before dam removal, 1 and 2 years (short-term) after dam removal and 7 and 8 years (long-term) after dam removal. Both upstream and downstream systems moved toward maturity after dam removal. In the short term after dam removal, more energy can be transferred further up in the food webs. The vitality and diversity of both systems also increased. In the long term after dam removal, although the transfer efficiencies of both systems generally showed a decreasing pattern, the resilience increased. Compared to the upstream system, the effects of dam removal on the downstream system were more evident. In the downstream system, dam removal enhanced the vitality of the Formosan salmon and thus the top-down control. The dominance of detritivory flow in the food web also shifted toward the dominance of herbivory flow. Consequently, the downstream system reached more maturity, and the food web was more closely linked. The ecosystem attributes of the upstream and downstream systems converged, suggesting that the decoupling between upstream and downstream systems resulting from damming disappeared 8 years after dam removal.

Wetlands are recognized as one of the most productive aquatic ecosystems. This high productivity supports its enormous biodiversity, aiding a scope for the small scale fisheries within it. Basically, these wetlands act as platforms for culture-based fisheries (CBF) i.e practice of stocking fish seeds and harvesting the grow out fishes at later. Often in tropical wetlands, the high nutrient load and high temperature enable the luxurious growth of macrophytes. Moreover, this macrophyte infestation is considered as a bottleneck for wetland managers. Facing a similar situation our studied Beledanga wetland is a macrophyte-infested wetland and the invasive Eichhornia crassipes is the most dominant macrophyte species. Owing to the macrophyte problem, Grass carp have been stocked in it as a biocontrol agent, as grass carp is a known biocontrol agent for the macrophyte infestation situation and simultaneously it will raise the fish production. To ensure maximum sustainable production from the wetland by harnessing with the available resources, it is necessary to acquire knowledge about the system’s ecological status and its ecological networks. Thus, the Ecopath based mass-balanced model is one of the best suitable tools to know about the ecological organization of this Beledanga wetland. Considering the available data (observational and literature data), this study has constructed a mass-balanced Ecopath model with 14 functional groups including all fish groups, birds, plankton, benthos and detritus. It has been found that the zooplankton and benthos are the most utilized group and the birds are the keystone group in this wetland system. This wetland possesses a lower transfer efficiency as well as a low Finn’s cycling index (0.224%). The system is found as an immature system with moderate ascendancy and system reserve (overhead). Moreover, concerning the ecologically sustainable production from this wetland more virtual mass-balanced models were developed (i) to evaluate the optimum grass carp stocking to manage the macrophyte population and (ii) to assess the impact of the Eichhornia on the system functioning. The results show that the system can harbour 1.5 times more grass carp biomass than the present without hampering sustainability. Concerning the impact of Eichhornia, it has been noticed that this macrophyte affects the maturity and transfer process of the system. Moreover, its huge biomass only accumulates more detritus in the ecosystem.

In the southern Gulf of California, the Cabo Pulmo reef has been the focus of many studies because it is the northern-most coral reef in the eastern Pacific. It is a paragon of a well-managed marine protected area. Under the assumption that fishing mortality is negligible, we want to identify and quantify major energy flows in an ecosystem without human intervention and describe the ecosystem resources and their interactions among species, to provide a tool for ecosystem-based management. We built a trophodynamic model using Ecopath to perform network analysis. Based on fieldwork (October 2017 – May 2018) and literature review, we identified 57 functional groups comprising 51 consumers (including 15 top predators), five primary producers plus detritus, and cluster analysis of trait profiles. The connectance index (0.17) and the system omnivory index (0.22) are low, suggesting that consumers feed on a few discrete trophic levels. Biomass of primary producers (grazing food chain; 186.8 t km−2) provides 9,813 t km−2 y−1, whereas flow from detritus supply 344.9 t km−2 y−1. The transfer efficiency decreases as flows go up the food web, from 12% at TL II to 4% at TL X, and throughput cycled (including detritus) = 118.7 t km−2 y−1. In comparison with other coral reefs, we found that Cabo Pulmo complies with the attributes to resist disturbances, with an estimated total system throughput = 95,789 t km−2 y−1, a net system production = 38,535 t km−2 y−1, a large mean path length = 12.11, ascendency = 123,662 (52%) flowbits and overhead = 116,164 (48%) flowbits. The high quality of the ecosystem services provided by Cabo Pulmo and the scenic beauty appeals to developers. Although the system is resilient, unregulated human activities may impact the reef condition and decrease the residents' quality of life and that of all the people who make a living from the low impact activities currently in effect. The trophic web model presented here may help to improve the response capacity of the coalition of residents, authorities, diving companies, and NGO's to preserve the reef and be a key element to conserve the system by contributing to its best management.

[Display omitted] Channel evolution before and after dam removal on 26 May 2011. • Long-term ecosystem effects after dam removal have rarely been discussed. • More energy was transferred further up in the food webs after short-term dam removal. • Both upstream and downstream resilience increased after long-term dam removal. • Effects of dam removal on downstream ecosystem were more evident. • Upstream and downstream ecosystems converged 8 years after dam removal. Although dam removal has been considered a viable strategy to mitigate habitat fragmentation within a stream, long-term ecosystem effects after dam removal have rarely been discussed. In an effort to enhance the resilience of the critically endangered Formosan salmon (Oncorhynchus masou formosanus) in response to climate change, a 15-m-high check dam in a subtropical high-mountain stream was half-removed. The aim of this study was to analyze the long-term response of trophic structure and function to dam removal by constructing Ecopath models upstream and downstream of the removed dam at different times. Field surveys for model parameters were conducted for a complete seasonal cycle 1 year before dam removal, 1 and 2 years (short-term) after dam removal and 7 and 8 years (long-term) after dam removal. Both upstream and downstream systems moved toward maturity after dam removal. In the short term after dam removal, more energy can be transferred further up in the food webs. The vitality and diversity of both systems also increased. In the long term after dam removal, although the transfer efficiencies of both systems generally showed a decreasing pattern, the resilience increased. Compared to the upstream system, the effects of dam removal on the downstream system were more evident. In the downstream system, dam removal enhanced the vitality of the Formosan salmon and thus the top-down control. The dominance of detritivory flow in the food web also shifted toward the dominance of herbivory flow. Consequently, the downstream system reached more maturity, and the food web was more closely linked. The ecosystem attributes of the upstream and downstream systems converged, suggesting that the decoupling between upstream and downstream systems resulting from damming disappeared 8 years after dam removal. [ABSTRACT FROM AUTHOR]

Highlights • Hooghly estuarine system is divided into 22 functional groups. • Flow of material among compartments is quantified. • Assessment of the ecosystem health using ecological network analysis is done. • The system is a maturing one with moderate stress level. Abstract The structure and function of food web of Hooghly-Matla estuarine system (HMES) including Sundarban mangroves is studied to assess the health of the system. HMES, provides shelter and make a home to many economically important shell and fin fishes. This estuary is exposed to various threats such as increasing salinity, deterioration of soil fertility and productivity, pollution and loss of biodiversity. Ecological network analysis (ENA) is applied for the HMES to model the trophic flows in 22 ecological compartments using Ecopath (a software for network analysis), integrating ecological data for the 2013–2015. ENA is performed, including a set of indices, keystoneness and trophic spectrum analysis to describe the contribution of the 22 groups to the HMES functioning. Results show that 22 compartments of the HMES including primary producers (trophic level TL 1) to the top consumers (elasmobranch, TL 3.5), the ecotrophic efficiency ranges from 0.016 to 0.989. Small demersal fishes, prawns, shrimps and crabs are the most exploited groups of this ecosystem. Herbivory and detritivory ratio is 1:1 indicating relative absence of top predators and low maturation level. Maturity of the system, organization, relative order and disorder within the system, diversity of flow of material among compartments and overhead of the system has been assessed. Biomass over Total system throughput ratio (TB / TST), Total primary production over total respiration ratio (TPP / TR), Total primary production over biomass (TPP / TB) and system omnivory index (SOI) indicate the moderate maturity level of the system. The HMES trophic network has a moderate recycling level (FCI = 12.99%), a high total system throughput (TST = 22976.03 tonnes km−2 yr−1) and a low ascendency (A = 25799 tonnes km−2 yr−1), but a relatively low connectance (CI = 0.27), high internal relative ascendency (A = 29.6%) and a high omnivory index (OI = 0.203), indicating that this estuary is immature but relatively organized and complex, with strong production. HMES has some unique features in comparison to similar functioning geographically close estuaries or estuaries with similar environmental characteristics. System robustness and exergy are also estimated to assess ecosystem health and compared with other tropical systems. From a holistic point of view, present study conveys fundamental information and categorizes the status of the system. [ABSTRACT FROM AUTHOR]

Highlights • We investigate how dietary uncertainty data can strengthen model-derived ENA indicators. • 10,000 parameterisations for the Irish Sea food web reveal plausible indicator distributions. • Higher trophic levels are controlled by mid-to-low trophic levels. • Fisheries discards control the flow of energy to seabirds, Nephrops , and crabs and lobsters. • Uncertainty analyses for ENA enabled stronger ecological inferences which are crucial for management. Abstract Ecological Network Analysis (ENA) can inform marine management decisions by producing indicators that describe ecosystem health and function. Reporting ENA indicators with uncertainty boundaries lets end-users draw stronger inferences and can increase confidence in model results. However, few studies developing these indicators have estimated uncertainty due to data limitations and computational challenges. In this study, we used Linear Inverse Modelling with an Ecopath model of the Irish Sea to investigate how the incorporation of uncertainty in dietary data can strengthen inferences based on model-derived ENA indicators. A Monte Carlo approach was used to generate ten thousand data-bound parameterisations for the Irish Sea food web and provide plausible distribution estimates for functional group diets. ENA results captured the plausible range of state-indicators and provided robust estimates of the control exerted by components within the food web. Results suggest that, higher trophic components, such as mammals, birds, and elasmobranchs in the Irish Sea are controlled by mid-to-low trophic components, such as small pelagic fish, invertebrates, and plankton. Fisheries discards also played an important role in the flow of energy to groups such as Nephrops (Norway lobster), crabs and lobsters, and seabirds. These results bolster our understanding of food web dynamics in the Irish Sea and demonstrate how information derived from ENA indicators can have implications for effective and sustainable ecosystem based management. Finally, the methods established here represent an important step in the maturation of marine ecosystem modelling and ENA for management purposes. [ABSTRACT FROM AUTHOR]

• The ecological status of the Beledanga wetland was found to be immature in Ecopath. • Optimum stocking density of Grass carp was calculated using the ECOPATH model for macrophyte management in the wetland. • The huge biomass of Eichhornia is negatively impacting the ecosystem functioning and maturity of the Beledanga wetland. • Maximization of sustainable fish production for improving the livelihood of the wetland fisher and in achieving the SDGs. Wetlands are recognized as one of the most productive aquatic ecosystems. This high productivity supports its enormous biodiversity, aiding a scope for the small scale fisheries within it. Basically, these wetlands act as platforms for culture-based fisheries (CBF) i.e practice of stocking fish seeds and harvesting the grow out fishes at later. Often in tropical wetlands, the high nutrient load and high temperature enable the luxurious growth of macrophytes. Moreover, this macrophyte infestation is considered as a bottleneck for wetland managers. Facing a similar situation our studied Beledanga wetland is a macrophyte-infested wetland and the invasive Eichhornia crassipes is the most dominant macrophyte species. Owing to the macrophyte problem, Grass carp have been stocked in it as a biocontrol agent, as grass carp is a known biocontrol agent for the macrophyte infestation situation and simultaneously it will raise the fish production. To ensure maximum sustainable production from the wetland by harnessing with the available resources, it is necessary to acquire knowledge about the system's ecological status and its ecological networks. Thus, the Ecopath based mass-balanced model is one of the best suitable tools to know about the ecological organization of this Beledanga wetland. Considering the available data (observational and literature data), this study has constructed a mass-balanced Ecopath model with 14 functional groups including all fish groups, birds, plankton, benthos and detritus. It has been found that the zooplankton and benthos are the most utilized group and the birds are the keystone group in this wetland system. This wetland possesses a lower transfer efficiency as well as a low Finn's cycling index (0.224%). The system is found as an immature system with moderate ascendancy and system reserve (overhead). Moreover, concerning the ecologically sustainable production from this wetland more virtual mass-balanced models were developed (i) to evaluate the optimum grass carp stocking to manage the macrophyte population and (ii) to assess the impact of the Eichhornia on the system functioning. The results show that the system can harbour 1.5 times more grass carp biomass than the present without hampering sustainability. Concerning the impact of Eichhornia , it has been noticed that this macrophyte affects the maturity and transfer process of the system. Moreover, its huge biomass only accumulates more detritus in the ecosystem. [ABSTRACT FROM AUTHOR]

Abstract: Commercial harbors are commonly considered as definitively lost environment sacrificed in the name of economic development, but, recently, a growing attention has been addressed to harbor ecology and harbor ecological state. The objective of this research is to identify the adaptation strategy carried out by the benthic community of Voltri harbor (NW Italy) by means of the application of a set of whole system metrics. Thermodynamic and network analysis revealed harbor benthic community characterized by an efficient and active network but also scarcely able to maintain complex structures and organisms. These results can be interpreted as evidences of adaptations carried out by the harbor benthic community that revealed itself healthy even if poorly resilient and thus not able to face further disturbances. [Copyright &y& Elsevier]

• Trophic model includes 19 top predators: mammals, birds, turtles, and 15 shark species. • Network analysis suggests Cabo Pulmo reef is in an advance developing stage. • Large overhead (116,164 fb) provides a reserve to meet unexpected perturbations. • The claim of this MPA successful management is shaded by external threats. In the southern Gulf of California, the Cabo Pulmo reef has been the focus of many studies because it is the northern-most coral reef in the eastern Pacific. It is a paragon of a well-managed marine protected area. Under the assumption that fishing mortality is negligible, we want to identify and quantify major energy flows in an ecosystem without human intervention and describe the ecosystem resources and their interactions among species, to provide a tool for ecosystem-based management. We built a trophodynamic model using Ecopath to perform network analysis. Based on fieldwork (October 2017 – May 2018) and literature review, we identified 57 functional groups comprising 51 consumers (including 15 top predators), five primary producers plus detritus, and cluster analysis of trait profiles. The connectance index (0.17) and the system omnivory index (0.22) are low, suggesting that consumers feed on a few discrete trophic levels. Biomass of primary producers (grazing food chain; 186.8 t km−2) provides 9,813 t km−2 y−1, whereas flow from detritus supply 344.9 t km−2 y−1. The transfer efficiency decreases as flows go up the food web, from 12% at TL II to 4% at TL X, and throughput cycled (including detritus) = 118.7 t km−2 y−1. In comparison with other coral reefs, we found that Cabo Pulmo complies with the attributes to resist disturbances, with an estimated total system throughput = 95,789 t km−2 y−1, a net system production = 38,535 t km−2 y−1, a large mean path length = 12.11, ascendency = 123,662 (52%) flowbits and overhead = 116,164 (48%) flowbits. The high quality of the ecosystem services provided by Cabo Pulmo and the scenic beauty appeals to developers. Although the system is resilient, unregulated human activities may impact the reef condition and decrease the residents' quality of life and that of all the people who make a living from the low impact activities currently in effect. The trophic web model presented here may help to improve the response capacity of the coalition of residents, authorities, diving companies, and NGO's to preserve the reef and be a key element to conserve the system by contributing to its best management. [ABSTRACT FROM AUTHOR]