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11.
KIRSTIN K. HOLSMAN MARK D. SCHEUERELL ERIC BUHLE ROBERT EMMETT 《Conservation biology》2012,26(5):912-922
Abstract: Captive rearing and translocation are often used concurrently for species conservation, yet the effects of these practices can interact and lead to unintended outcomes that may undermine species’ recovery efforts. Controls in translocation or artificial‐propagation programs are uncommon; thus, there have been few studies on the interacting effects of these actions and environmental conditions on survival. The Columbia River basin, which drains 668,000 km2 of the western United States and Canada, has an extensive network of hydroelectric and other dams, which impede and slow migration of anadromous Pacific salmon (Oncorhynchus spp.) and can increase mortality rates. To mitigate for hydrosystem‐induced mortality during juvenile downriver migration, tens of millions of hatchery fish are released each year and a subset of wild‐ and hatchery‐origin juveniles are translocated downstream beyond the hydropower system. We considered how the results of these practices interact with marine environmental conditions to affect the marine survival of Chinook salmon (O. tshawytscha). We analyzed data from more than 1 million individually tagged fish from 1998 through 2006 to evaluate the probability of an individual fish returning as an adult relative to its rearing (hatchery vs. wild) and translocation histories (translocated vs. in‐river migrating fish that traveled downriver through the hydropower system) and a suite of environmental variables. Except during select periods of very low river flow, marine survival of wild translocated fish was approximately two‐thirds less than survival of wild in‐river migrating fish. For hatchery fish, however, survival was roughly two times higher for translocated fish than for in‐river migrants. Competition and predator aggregation negatively affected marine survival, and the magnitude of survival depended on rearing and translocation histories and biological and physical conditions encountered during their first few weeks of residence in the ocean. Our results highlight the importance of considering the interacting effects of translocation, artificial propagation, and environmental variables on the long‐term viability of species. 相似文献
12.
Salmon farming is a rapidly expanding industry. In order for it to develop in an ethical manner, many ethical issues must be confronted. Among these are questions regarding the quality of life of salmon on farms. To develop reasonable answers to these questions considerable thought must be devoted to developing appropriate standards of care for salmon. If these questions are not addressed the results could be bad both for salmon and for salmon farmers. 相似文献
13.
A hierarchical approach to fisheries planning and modeling in the Columbia River Basin 总被引:1,自引:0,他引:1
The Columbia River Basin is the scene of a massive effort to restore populations of Pacific salmon (Oncorhynchus spp.) and steelhead (O. mykiss). Efficient restoration is confounded by a high level of complexity, competing sociopolitical goals and values, and uncertainty
about key system properties. Simulation models and other tools of systems analysis are important to development of a comprehensive,
regionally acceptable strategy. Hierarchy theory provides a useful paradigm for organized complexity within the Columbia Basin
and the basis for a trilevel hierarchical structure for organizing and integrating models. Life-stage models compose the most
basic simulation units at the lowest level in the proposed hierarchical modeling structure. Each life-stage model simulates
a distinct period in the life cycle of anadromous salmonids. Population models at the intermediate level simulate the complete
life cycles of salmon and steelhead populations. At the highest level in the hierarchy, interpopulation models simulate extensive,
long-term processes that affect multiple species and stocks. A hierarchical system of models is preferable to a single model
or to a group of models lacking formal structure. A principal advantage is that models have the correct spatial and temporal
resolution for analyzing questions at different scales. A hierarchical structure also facilitates the flow of information
among models, and aids in understanding the impacts of uncertainty. Constructing a hierarchy of models should involve both
bottom-up and top-down perspectives that maintain logical consistency among models, while allowing unique model structures
appropriate for each level in the hierarchy. 相似文献
14.
To evaluate the accounts of local fishermen, Landsat TM images (1986, 1993, 1999) were examined to assess potential losses
in the mangrove forests of the Teacapán–Agua Brava lagoon system, Mexico. A binary change mask derived from image differencing
of a band 4/3 ratio was employed to calculate any changes within this forested wetland. The results indicate that by 1986
approximately 18% (or 86 km2) of the mangrove area under study was either dead or in poor condition. The majority of this damage had occurred in the eastern
section of the Agua Brava basin, which coincides, with the reports of the elderly fishermen. Examination of aerial photographs
from 1970 revealed no adverse impacts in this area and would suggest, as postulated by the fishermen and other scientists,
that modifications in environmental conditions following the opening of a canal, Cuautlá canal, in 1972 may have initiated
the large-scale mortality. Although these areas of impact are still developing, the results from the satellite data indicate
that the majority of the more recent changes are occurring elsewhere in the system. Obvious in the 1999 satellite data, but
not so in the 1993, are large areas of mangrove degradation in the northern section of the Teacapán region. In the Agua Brava
basin, the more recent transformations are appearing on the western side of the basin. Since long-term records of environmental
conditions are absent, it is difficult to determine why these latest changes are occurring or even if the earlier losses were
the result of the canal. Potential agents of change that have recently been observed include a hurricane, a second canal,
and the uncontrolled expansion of the Cuautlá canal since 1994. 相似文献
15.
Cleo Woelfle-Erskine 《Local Environment》2015,20(5):581-599
The construction of California's large waterworks was inextricably entangled with a discourse of progress through technoscientific control over unruly rivers. In recent years, a turn towards decentralised governance and diversified infrastructure has produced alternate discourses of human–ecological collaboration and water as a commons. I investigate how water is understood by residents along Salmon Creek (Sonoma Co., CA) engaged in efforts to increase streamflow and restore salmon runs. Drawing on Barad's theory of agential realism, I find that living with springs and rainwater harvesting cisterns enacts intra-actions that increase residents' sense of interdependence with other human and nonhuman watershed residents. I argue that commons frameworks represent a coherent alternative to state and market frameworks of water governance. 相似文献
16.
17.
Shifting elasmobranch community assemblage at Cocos Island—an isolated marine protected area
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Easton R. White Mark C. Myers Joanna Mills Flemming Julia K. Baum 《Conservation biology》2015,29(4):1186-1197
Fishing pressure has increased the extinction risk of many elasmobranch (shark and ray) species. Although many countries have established no‐take marine reserves, a paucity of monitoring data means it is still unclear if reserves are effectively protecting these species. We examined data collected by a small group of divers over the past 21 years at one of the world's oldest marine protected areas (MPAs), Cocos Island National Park, Costa Rica. We used mixed effects models to determine trends in relative abundance, or probability of occurrence, of 12 monitored elasmobranch species while accounting for variation among observers and from abiotic factors. Eight of 12 species declined significantly over the past 2 decades. We documented decreases in relative abundance for 6 species, including the iconic scalloped hammerhead shark (Sphyrna lewini) (?45%), whitetip reef shark (Triaenodon obesus) (?77%), mobula ray (Mobula spp.) (?78%), and manta ray (Manta birostris) (?89%), and decreases in the probability of occurrence for 2 other species. Several of these species have small home ranges and should be better protected by an MPA, which underscores the notion that declines of marine megafauna will continue unabated in MPAs unless there is adequate enforcement effort to control fishing. In addition, probability of occurrence at Cocos Island of tiger (Galeocerdo cuvier), Galapagos (Carcharhinus galapagensis), blacktip (Carcharhinus limbatus), and whale (Rhincodon typus) sharks increased significantly. The effectiveness of MPAs cannot be evaluated by examining single species because population responses can vary depending on life history traits and vulnerability to fishing pressure. 相似文献
18.
Research priorities for conservation and natural resource management in Oceania's small‐island developing states
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For conservation science to effectively inform management, research must focus on creating the scientific knowledge required to solve conservation problems. We identified research questions that, if answered, would increase the effectiveness of conservation and natural resource management practice and policy in Oceania's small‐island developing states. We asked conservation professionals from academia, governmental, and nongovernmental organizations across the region to propose such questions and then identify which were of high priority in an online survey. We compared the high‐priority questions with research questions identified globally and for other regions. Of 270 questions proposed by respondents, 38 were considered high priority, including: What are the highest priority areas for conservation in the face of increasing resource demand and climate change? How should marine protected areas be networked to account for connectivity and climate change? What are the most effective fisheries management policies that contribute to sustainable coral reef fisheries? High‐priority questions related to the particular challenges of undertaking conservation on small‐island developing states and the need for a research agenda that is responsive to the sociocultural context of Oceania. Research priorities for Oceania relative to elsewhere were broadly similar but differed in specific issues relevant to particular conservation contexts. These differences emphasize the importance of involving local practitioners in the identification of research priorities. Priorities were reasonably well aligned among sectoral groups. Only a few questions were widely considered answered, which may indicate a smaller‐than‐expected knowledge‐action gap. We believe these questions can be used to strengthen research collaborations between scientists and practitioners working to further conservation and natural resource management in this region. 相似文献
19.
Abstract: Anadromous salmonids have been particularly successful at establishing wild populations in southern Patagonia, in contrast to their limited success elsewhere outside their native ranges. The most recent such discovery is a spawning population of Chinook salmon in the Santa Cruz River, which flows into the Atlantic Ocean from Argentina. We used mitochondrial DNA analysis to discriminate between alternative potential sources of this population and were able to discard in situ introductions of fish imported directly from California in the early twentieth century. Our results showed that the fish most likely came from Puget Sound, Washington, imported into southern Chile for salmon-ranching experiments in the 1980s. This finding provides concrete evidence of colonization of Atlantic rivers from Pacific locations. The southern Pacific and Atlantic oceans provide a favorable marine environment for the success of invading salmon. In particular, the waters associated with fjords, southern channels, and the inshore portion of the Patagonian shelf provide a rather bounded, continuous waterway for exotic anadromous salmonids, rich in diverse forage species. 相似文献
20.
Arsenic, cadmium, chromium, and copper concentrations of the Pacific oyster,Crassostrea gigas, purchased from four different markets were determined in this project. In general, gill tissue had the highest proportion
of metal contents (34%–67%) when compared with other tissue parts (mantle, viscera, and adductor muscle), except for arsenic,
which showed the highest level in adductor muscle (44%). Smaller oysters (longitudinal length of soft body part less than
6 cm) had higher metal levels than larger ones (longitudinal length of soft body part more than 6 cm), except copper. None
of the four metals examined showed an obvious seasonal trend, although cadmium levels seemed to be higher in autumn and winter
months. Arsenic, cadmium, and copper levels in oysters purchased from different markets and different months obtained in the
present study were higher when compared with past reports. Cadmium levels, as high as 10.98 mg/kg (dry weight basis) have
been obtained. This approaches the safety limit that may be hazardous to human health. Continual monitoring of cadmium and
other trace metals of toxicological significance to man in Hong Kong seafood is recommended. 相似文献