Aquatic Conservation-Marine and Freshwater Ecosystems最新文献

The Mediterranean basin is a hotspot of freshwater endemisms and restricted-range species, which are among the most threatened worldwide. The Adriatic brook lamprey Lampetra zanandreai is a non-parasitic, freshwater-resident lamprey whose core distribution lies in the Po River basin (Northern Italy). This species is highly sensitive to anthropogenic pressures: it has historically been threatened by river alterations, and climate change is now emerging as an additional threat. In this study, we compiled and updated the distribution of L. zanandreai and applied species distribution models to project its current and future potential distribution under different climate models for 2050. We further performed a river network-level analysis to assess the relevance of human stressors and the effectiveness of the EU Natura 2000 network in representing highly suitable areas. Our outcomes indicate a substantial range contraction coupled with an upward altitudinal shift. Areas of overlap between the current and future suitable areas highlight potential climatic and environmental refuges, although limited and fragmented. Highly suitable riverine cells largely overlap with cells under a higher human footprint, showing how the species is caught between multiple pressures that exacerbate its vulnerability. In addition, protected areas perform poorly in covering both current occurrences and predicted suitable habitats. These findings provide crucial insights to support conservation planning, suggesting potential areas for the protection, management and monitoring of this threatened species. The long-term persistence of L. zanandreai requires urgent mitigation of human pressures, particularly through the restoration of river connectivity to facilitate population exchange and access to future refuges.

The Mediterranean basin is a hotspot of freshwater endemisms and restricted-range species, which are among the most threatened worldwide. The Adriatic brook lamprey Lampetra zanandreai is a non-parasitic, freshwater-resident lamprey whose core distribution lies in the Po River basin (Northern Italy). This species is highly sensitive to anthropogenic pressures: it has historically been threatened by river alterations, and climate change is now emerging as an additional threat. In this study, we compiled and updated the distribution of L. zanandreai and applied species distribution models to project its current and future potential distribution under different climate models for 2050. We further performed a river network-level analysis to assess the relevance of human stressors and the effectiveness of the EU Natura 2000 network in representing highly suitable areas. Our outcomes indicate a substantial range contraction coupled with an upward altitudinal shift. Areas of overlap between the current and future suitable areas highlight potential climatic and environmental refuges, although limited and fragmented. Highly suitable riverine cells largely overlap with cells under a higher human footprint, showing how the species is caught between multiple pressures that exacerbate its vulnerability. In addition, protected areas perform poorly in covering both current occurrences and predicted suitable habitats. These findings provide crucial insights to support conservation planning, suggesting potential areas for the protection, management and monitoring of this threatened species. The long-term persistence of L. zanandreai requires urgent mitigation of human pressures, particularly through the restoration of river connectivity to facilitate population exchange and access to future refuges.

Dams and deforestation are key drivers of freshwater biodiversity loss in the Amazon, as they alter river connectivity, water quality and habitat structure. This study investigates how connectivity (Reach Connectivity Index—RCI), elevation and natural land cover influence the diversity and composition of fish assemblages in a highly fragmented Amazonian river network. Based on their distinct life-history traits, we analysed migratory and non-migratory species separately, hypothesizing differential responses to these environmental gradients. Generalized linear models (GLMs) were used to evaluate the effects of RCI, elevation and land cover on species richness (alpha diversity) and the Local Contribution to Beta Diversity (LCBD, a measure of community uniqueness). Additionally, we examined the influence of these variables on community composition using distance-based RDA and hierarchical partitioning. We found that species richness for both groups was higher at lower elevations. However, only non-migratory species richness increased with greater connectivity (RCI), whereas migratory species richness was unaffected by RCI. For community uniqueness (LCBD), values for migratory species were higher in areas with more conserved land cover. In contrast, non-migratory species had higher LCBD at less connected sites. Community composition analysis revealed that non-migratory species were strongly influenced by elevation, while migratory species composition showed no significant relationship with the environmental variables analysed. Our results confirm distinct ecological responses between migratory and non-migratory species to fragmentation, supporting our initial hypothesis. These findings underscore the critical importance of considering species' life-history traits when planning conservation strategies and river connectivity restoration in the Amazon.

Dams and deforestation are key drivers of freshwater biodiversity loss in the Amazon, as they alter river connectivity, water quality and habitat structure. This study investigates how connectivity (Reach Connectivity Index—RCI), elevation and natural land cover influence the diversity and composition of fish assemblages in a highly fragmented Amazonian river network. Based on their distinct life-history traits, we analysed migratory and non-migratory species separately, hypothesizing differential responses to these environmental gradients. Generalized linear models (GLMs) were used to evaluate the effects of RCI, elevation and land cover on species richness (alpha diversity) and the Local Contribution to Beta Diversity (LCBD, a measure of community uniqueness). Additionally, we examined the influence of these variables on community composition using distance-based RDA and hierarchical partitioning. We found that species richness for both groups was higher at lower elevations. However, only non-migratory species richness increased with greater connectivity (RCI), whereas migratory species richness was unaffected by RCI. For community uniqueness (LCBD), values for migratory species were higher in areas with more conserved land cover. In contrast, non-migratory species had higher LCBD at less connected sites. Community composition analysis revealed that non-migratory species were strongly influenced by elevation, while migratory species composition showed no significant relationship with the environmental variables analysed. Our results confirm distinct ecological responses between migratory and non-migratory species to fragmentation, supporting our initial hypothesis. These findings underscore the critical importance of considering species' life-history traits when planning conservation strategies and river connectivity restoration in the Amazon.

Monitoring and understanding the population structure of anadromous fishes is vital to their conservation. The southern distinct population segment of green sturgeon (Acipenser medirostris) is a threatened long-lived anadromous fish, for which we have insufficient information about fundamental aspects of population structure. To gather these data, we began monitoring the population in 2010 with annual surveys using acoustic imagery, and we have recently updated the field and analytical methods. In this work we (1) examine the transition between the two methods using both Dual-frequency Identification Sonar (DIDSON) and consumer-grade side-scan sonar products, (2) use underwater videography to test methodological assumptions about sturgeon species identification, (3) confirm the spatial extent of the spawning grounds with side-scan sonar and publicly available acoustic telemetry data and (4) update the population estimates. We find the following: there is a consistent detectability relationship between the two acoustic imagery methods, the species we are detecting is indeed green sturgeon rather than a sympatric congener, and the extent of the historical survey covers the entire spawning ground. Through our population estimate update, we find potential evidence for a 4-year spawning cyclic dominance where one spawning line is significantly larger than the others. The larger line is expected to spawn again in 2026. We believe that this information will be useful to those attempting to recover this species.

Invasive species severely threaten biodiversity, ecosystem stability and local livelihoods, especially in vulnerable areas. Therefore, understanding community perceptions is vital for creating effective and inclusive management strategies. This study investigated perceived environmental and economic impacts of the invasive, Redclaw crayfish (Cherax quadricarinatus) in Lake Itezhi-Tezhi, Zambia, using structured surveys of 325 local fishers. Descriptive statistics and frequency analyses summarised respondent perception, and multiple linear regression models tested predictors of fishers' environmental and economic perceptions. Results revealed that 38% of the respondents first encountered the species within 1–5 years, 55.1% reported harvesting < 250 g per trip and 61.5% encountered crayfish only 1–2 times per seven trips. Most respondents reported negative environmental effects (77.98%), specifically competition with native fish and gear damage, and 62.4% attributed decreased household income to the invasion, though 45.0% expressed positive attitudes, seeing crayfish as a food and income resource. The regression predicting environmental perceptions was significant (F(9,94) = 2.75, p = 0.007, R² = 0.21), with younger fishers perceiving greater environmental impacts (β = −0.31, p = 0.005). The model for economic perceptions was not significant (F(9,94) = 0.54, p = 0.839, R² = 0.05). There was strong support emerged for community participation (80.7%), along with a notable preference for government-led action (54.1%). Our findings highlight the need for integrated co-management that mitigates environmental harm while exploring sustainable crayfish-based livelihoods.

Monitoring and understanding the population structure of anadromous fishes is vital to their conservation. The southern distinct population segment of green sturgeon (Acipenser medirostris) is a threatened long-lived anadromous fish, for which we have insufficient information about fundamental aspects of population structure. To gather these data, we began monitoring the population in 2010 with annual surveys using acoustic imagery, and we have recently updated the field and analytical methods. In this work we (1) examine the transition between the two methods using both Dual-frequency Identification Sonar (DIDSON) and consumer-grade side-scan sonar products, (2) use underwater videography to test methodological assumptions about sturgeon species identification, (3) confirm the spatial extent of the spawning grounds with side-scan sonar and publicly available acoustic telemetry data and (4) update the population estimates. We find the following: there is a consistent detectability relationship between the two acoustic imagery methods, the species we are detecting is indeed green sturgeon rather than a sympatric congener, and the extent of the historical survey covers the entire spawning ground. Through our population estimate update, we find potential evidence for a 4-year spawning cyclic dominance where one spawning line is significantly larger than the others. The larger line is expected to spawn again in 2026. We believe that this information will be useful to those attempting to recover this species.

Aquatic ecosystems and species are under threat due to anthropogenic impacts, prompting implementation of conservation strategies. Headstarting is a strategy that involves rearing vulnerable life stages (e.g., eggs and hatchlings) in human care until they are large enough to reduce mortality risk after release. Many reintroductions fail because animals released into new environments often experience an acclimation period manifesting as short-term increases in mortality or dispersal. To improve reintroduction outcomes, additional support (e.g., use of soft release) could be provided to headstarted animals in the release environment. Using data collected from a headstarting programme on the globally endangered Blanding's turtle (Emydoidea blandingii) in Toronto, Ontario, Canada, we tested whether headstarted turtles experienced an acclimation period and whether release types affected movement patterns and home-range sizes. We used two release types: a hard release, where headstarted turtles were released directly into the wetland, and a type of soft release, where headstarted turtles were penned for 7 days without supplemental food or protection from predators and then released (i.e., delayed-release). From 2014 to 2020, the mean daily distance travelled (m) by headstarted turtles ranged 0.61–19.62 m, and the annual home-range size ranged 0.002–6.77 ha. Headstarted turtles in both release groups had similar mean daily distance travelled and home-range size at release and 6 years post-release. Furthermore, there was no evidence of an acclimation period in either metric, indicating that release type did not influence movement patterns. Our study highlights the need for long-term monitoring of headstarted animals and the importance of testing common assumptions of release types in the context of reintroductions.

The tufted ghost crab, Ocypode cursor, native to the southeastern Mediterranean and subtropical Atlantic Ocean, is a key bioindicator species, providing valuable insights into the health and stability of sandy beach ecosystems through its population dynamics, behaviour and interactions with the environment. Sandy shores along the Mediterranean coast of Israel have been excluded from the national terrestrial monitoring and conservation programs; yet, occasional observations indicated that its once plentiful population in this region suffered a steep decline. We assessed the effects of recreational disturbance on abundance, spatio-temporal distribution patterns and population size structure in four authorized exurban bathing beaches and four adjacent nature reserves in 2020–2021. We employed burrow count censusing and burrow opening diameter surveys as proxies for population abundance and population size structure. A total of 8555 burrows were surveyed. A well-defined post-weekend reduction in the number of burrows was apparent in both bathing beaches and nature reserves during high summer, though burrows in bathing beaches were generally fewer than in nature reserves. The survival of the local population of O. cursor, an endangered iconic species and a protected natural asset, depends on elimination, or at least scaling back, destructive activities (such as mechanical beach cleaning and off-road vehicular traffic) along open sandy beaches, as well as reducing public access to the 10 sandy-shore nature reserves along the Israeli Mediterranean, so as to provide spillover and recruitment subsidies to adjacent beaches, enhancing the long-term sustainability of their biota.