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- To facilitate conservation planning, there is a need for improved confidence in forecasts of climate change impacts on species distributions. Towards that end, there have been calls for the development of process-based models to test hypotheses concerning the mechanisms by which temperature shapes distribution and to corroborate forecasts of correlative models.
- Models of temperature-dependent growth (TDG) were developed for two Australian riverine blackfishes with disjunct longitudinal distributions: Gadopsis marmoratus (occupies lower, warmer elevations) and Gadopsis bispinosus (occupies higher, cooler elevations). The models were used to (a) predict blackfish monthly and annual growth dynamics under current and future climate scenarios within different elevation bands of their current distribution, and (b) test the hypothesis that, under the current climate, the distributions of each species would be positively correlated with predicted TDG.
- Increases in mean annual growth were forecast for both species under all warming scenarios, across all elevation bands. Both species currently occupy annual habitat temperatures below those optimal for growth. Under certain warming scenarios, the predicted increases in annual growth belie forecasts of within-year dynamics that may interact with the phenology of blackfish to impair recruitment.
- There was not a significant positive linear relationship between predicted TDG and observed abundance among river segments for either species. Both species were strongly under-represented where annual growth rates were forecast to be optimal and over-represented where growth rates were forecast to be intermediate.
- Confidence in forecasts of climate change impacts based on correlative models will increase when those forecasts are consistent with a mechanistic understanding of how specific drivers (e.g. water temperature) affect processes (e.g. growth). This process-based study revealed surprises concerning how future climates may affect fish growth dynamics, showing that although the blackfish distributions are correlated with temperature the temperature-dependent mechanisms underpinning that correlation require further investigation.
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Biodiversity values of remnant freshwater floodplain lagoons in agricultural catchments: evidence for fish of the Wet Tropics bioregion,northern Australia 总被引：1，自引：0，他引：1 
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下载免费PDF全文 Angela H. Arthington Paul C. Godfrey Richard G. Pearson Fazlul Karim Jim Wallace 《水产资源保护:海洋与淡水生态系统》2015,25(3):336-352
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Yik-Hei Sung Jia Huan Liew Hoi Kin Chan Wing-Ho Lee Billy Ho-Fung Wong Caroline Dingle Nancy E. Karraker Ricky-John Spencer Jonathan J. Fong 《水产资源保护:海洋与淡水生态系统》2021,31(10):2804-2813
- Turtles from Asia are on the brink of extinction with 53% of species considered endangered or critically endangered. Unfortunately, the ecology of many threatened species remains largely unknown.
- In this study, the diet of the endangered Beale’s eyed turtle (Sacalia bealei) was investigated using two methods, visual faecal content analysis and stable isotope analysis.
- Results from both methods indicated that S. bealei is highly reliant on riparian resources, especially fruits and terrestrial insects. Stable isotope data indicated that terrestrial resources made up around half (47–53%) of all assimilated food resources. These findings suggest that S. bealei facilitates energy flow from riparian forests to stream ecosystems. Moreover, S. bealei is likely to be a seed disperser for riparian plants.
- This study represents the first application of stable isotope methods to examine the diet of Asian freshwater turtles and their resource use. We stress the importance of similar studies to improve our understanding of remnant turtle populations before they disappear as a result of human activities.
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- 1. Allochthonous carbon is the basis of the detrital food web in low‐order, warmwater stream ecosystems, and stream‐bed sediments typically function as carbon reservoirs. Many of the same factors that govern carbon input and storage to streams (e.g. riparian vegetation, large wood, heterogeneous boundaries) have also been identified as key attributes of stream fish habitat.
- 2. Effects of channel incision on sand‐bed stream carbon reservoirs and indices of biological integrity (IBIs) based on fish collections were examined for four streams exhibiting a range of incisement in northern Mississippi. Observed mean C concentrations (mass percentage) ranged from 0.24±0.36% for a non‐incised stream to only 0.01±0.02% for a severely incised channel, and were not correlated with large wood (LW) density, perhaps because LW density at one site was elevated by a habitat rehabilitation project and at another site by accelerated inputs from incision‐related riparian tree fall. Fish IBI was positively correlated with bed C (r=0.70, p=0.003), and IBIs for reference streams were more than 50% greater than those computed for the most severely degraded sites.
- 3. More testing is needed to determine the efficacy of stream bed C as an indicator, but its importance to warmwater stream ecosystems, and the importance of covarying physical and hydrologic conditions seems evident.
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- 1. Projected sea‐level rise (SLR) is expected to cause shoreline erosion, saline intrusion into the water table and inundation and flooding of beaches and coastal areas. Areas most vulnerable to these physical impacts include small, tropical low‐lying islands, which are often key habitat for threatened and endemic species, such as sea turtles.
- 2. Successful conservation of threatened species relies upon the ability of managers to understand current threats and to quantify and mitigate future threats to these species. This study investigated how sea‐level rise might affect key rookeries (nesting grounds) (n=8) for the northern Great Barrier Reef (nGBR) green turtle population, the largest green turtle population in the world.
- 3. 3‐D elevation models were developed and applied to three SLR scenarios projected by the IPCC 2007 and an additional scenario that incorporates ice melting. Results indicate that up to 38% of available nesting area across all the rookeries may be inundated as a result of SLR.
- 4. Flooding, as a result of higher wave run‐up during storms, will increase egg mortality at these rookeries affecting the overall reproductive success of the nGBR green turtle population. Information provided will aid managers to prioritize conservation efforts and to use realistic measures to mitigate potential SLR threats to the nGBR green turtle population. Copyright © 2009 John Wiley & Sons, Ltd.
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Mario Brauns Thomas Berendonk Sina Berg Felix Grunicke David Kneis Sascha Krenek Thomas Schiller Jana Schneider Annekatrin Wagner Markus Weitere 《水产资源保护:海洋与淡水生态系统》2021,31(9):2496-2505
- The freshwater pearl mussel (FPM) is among the most endangered freshwater species worldwide. The few remaining populations suffer from low recruitment rates and are subject to habitat fragmentation, pollution, siltation, decline or loss of host fish populations, and climate change.
- Successful conservation strategies for FPM require a holistic understanding of its ecological requirements, life history, population dynamics, and habitat prerequisites. Although habitat requirements are well described, food requirements at different life stages have received less attention.
- Stable isotope analyses of FPM and potential food resources in three German streams were combined with mixing model analysis to quantify organic matter resources assimilated by juvenile (first year after encystment from host fish) and semi-adult (10 years old, immature) individuals.
- There were only slight differences in dietary contributions between the two life stages, and terrestrial particulate organic matter and benthic organic matter contributed substantially to the diet. Tissue type was more important in explaining variation in dietary contributions than individual variation for semi-adult FPM. The strong reliance on terrestrial resources sheds new light on the functional role of unionid mussels and the connection of streams to their riparian area.
- The dependence of FPM on terrestrial resources also emphasizes the need for a stronger focus on the restoration and protection of intact riparian areas, including wetlands with their specific vegetation, when planning conservation and management strategies for threatened FPM populations.
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Suresh A. Sethi Joshua Ashline Bradley P. Harris Jonathon Gerken Felipe Restrepo 《水产资源保护:海洋与淡水生态系统》2021,31(7):1791-1801
- Juvenile Pacific salmon exhibit diverse habitat use and migration strategies to navigate high environmental variability and predation risk during freshwater residency. Increasingly, urbanization and climate-driven hydrological alterations are affecting the availability and quality of aquatic habitats in salmon catchments. Thus, conservation of freshwater habitat integrity has emerged as an important challenge in supporting salmon life-history diversity as a buffer against continuing ecosystem changes.
- To inform catchment management for salmon, information on the distribution and movement dynamics of juvenile fish throughout the annual seasonal cycle is needed. A number of studies have assessed the ecology of juvenile coho salmon (Oncorhynchus kisutch) during summer and autumn seasons; catchment use by this species throughout the annual cycle is less well characterized, particularly in high-latitude systems.
- Here, n = 3,792 tagged juvenile coho salmon were tracked throughout two complete annual cycles to assess basin-wide distribution and movement behaviour of this species in a subarctic, ice-bearing catchment.
- Juvenile coho salmon in the Big Lake basin, Alaska, exhibited multiple habitat use and movement strategies across seasons; however, summer rearing in lotic mainstem environments followed by migration to lentic overwinter habitats was identified as a prominent behaviour, with two-thirds of tracked fish migrating en masse to concentrate in a small subset of upper catchment lakes for the winter. In contrast, the most significant tributary overwintering site (8% of tracked fish) occurred below a culvert and dam, blocking juvenile fish passage to a headwater lake, indicating that these fish may have been restricted from reaching preferred lentic overwinter habitats.
- These findings emphasize the importance of maintaining aquatic connectivity to lentic habitats as a conservation priority for coho salmon during freshwater residency.
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M. Worth Pugh Gary Pandolfi Thomas Franklin Michael M. Gangloff 《水产资源保护:海洋与淡水生态系统》2021,31(3):494-503
- Freshwater communities are threatened by the conversion of natural landscapes for urban and agricultural purposes. Changes to land use may disrupt stream nutrient and geomorphological processes and reduce water quality, increase sedimentation, and decrease habitat heterogeneity eventually leading to species loss and decreases in ecosystem productivity. Endemic species are frequently at greater risk of habitat-mediated fragmentation and extirpation due to their constrained distributions.
- The Kanawha darter (Etheostoma kanawhae) is an understudied fish endemic to the New River Drainage in North Carolina and Virginia, USA. To investigate the potential effect(s) of land-use change on Kanawha darters, naïve occupancy was modelled using instream habitat characteristics and upstream forest cover.
- Generalized linear models revealed that instream habitat and forest cover are reliable predictors of Kanawha darter site occupancy. Specifically, models demonstrated that occupancy increased in reaches with reduced stream width, velocity, and bedrock substrate but higher concentrations of coarse woody material. Kanawha darter occupancy was also positively associated with the extent of forest cover in upstream catchments.
- Although Kanawha darters are not currently considered imperilled, most populations occurred in isolated reaches separated by large sections of unoccupied habitat. Continuing ex-urban development in riparian zones is likely to be the primary threat to Kanawha darters and other endemic species in this catchment. Resource managers and stakeholders should preserve forest cover in headwaters and occupied tributaries and protect or restore riparian zones along the main-stem South and North Forks of the New River to preserve high-quality habitat and enhance connectivity among isolated Kanawha darter populations.
- As human populations in montane regions continue to grow, there is a need to understand how land-use change affects endemic freshwater species. This study further supports the importance of retaining forest cover as an effective strategy for protecting and restoring populations of endemic fishes in high-gradient streams.
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Carolina Bezamat Philip S. Hammond Pedro V. Castilho Paulo C. Simões-Lopes Fábio G. Daura-Jorge 《水产资源保护:海洋与淡水生态系统》2021,31(11):3133-3145
- The small population paradigm assumes that populations with low numbers of individuals intrinsically have a high probability of extinction. The small population of Lahille’s bottlenose dolphins Tursiops truncatus gephyreus that specializes in foraging with artisanal fishers in Laguna, southern Brazil, faces human pressures including bycatch in fishing gear. The viability of this population was modelled over 30 and 100 years under different levels of bycatch, including the current scenario of two bycatches every year, two scenarios with higher incidence of bycatches and three management scenarios. The sensitivity of predicted growth rates to fixed-proportion and observed-variation changes in life history parameters was explored.
- The current scenario predicted a declining population (r = −0.014; λ = 0.986) with a high probability of extinction in the long term (PE = 0.71). A small increase in bycatches would result in a marked increase in the probability of extinction. Management scenarios seem promising, but only the zero-bycatch management scenario would make the difference between a declining and an increasing population.
- As expected for slow-growing species, population growth rate was most sensitive to proportional changes in adult female and juvenile survival. However, considering observed variation in vital rates, population dynamics were most influenced by variation in reproductive rates.
- To determine the highest priority for management action, another simulation was made of how additional threat scenarios of recognized human activities (i.e. bycatch influencing adult survival and increased underwater noise or pollution influencing calf survival) would affect population dynamics. Population growth rate was very sensitive to changes in adult bycatch (especially females), as expected, and only subtly sensitive to a reduction in calf survival.
- The current level of bycatch is unsustainable. Bycatch needs to be eliminated to maximize the probability of long-term persistence of this dolphin population. However, this population’s persistence could be threatened by natural variation in reproductive rates.
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- 1. The Hawkesbury‐Nepean River provides potable water for 5 million people living in the Sydney basin, and water for agricultural and horticultural production that meets most of Sydney's daily needs for fresh food. Anecdotal evidence indicated that numbers of freshwater mussels have seriously declined in much of the river over recent decades.
- 2. A field survey revealed the presence of populations of three species of mussels, Hyridella depressa, Hyridella australis and Velesunio ambiguus in the river. Higher density mussel populations were most common in catchment areas with little human modification to the channel bed or adjacent vegetation communities.
- 3. Levels of disturbance of riparian vegetation and, to a lesser degree, land use, were identified as being strongly associated with the absence of mussels from some reaches.
- 4. Catchment geomorphology was also shown to be relevant to the abundance, population structure and suite of mussel species present in different geomorphic reaches of the river. Absence of mussels was noted from areas where they had been recorded in previous studies. These results demonstrate that mussel species are under threat in the catchment.
- 5. As filter feeders with the ability to remove excess nutrients and bioaccumulate toxic substances, freshwater mussels play an important role in natural remediation processes in freshwater systems.
- 6. The decline in mussel populations in the Hawkesbury‐Nepean River highlights concerns for the overall health of the river system, and supports the need to identify the subsidiary impacts of physical habitat modification in developing both riverine and riparian management strategies.