The key to the conservation of harvested species is the maintenance of reproductive success. Yet for many marine species large, old, individuals are targeted despite their disproportionate contribution to reproduction. We hypothesized that a combination of no-take marine protected areas (MPAs) and harvest slot limits (maximum and minimum size limits) would result in the conservation of large spawning individuals under heavy harvest. We tested this approach under different harvest intensities with a 2-sex, stage-structured metapopulation model for the Caribbean spiny lobster (Panulirus argus). P. argus is intensively harvested in the Caribbean, and in many localities large, mature individuals no longer exist. No-take MPAs and harvest slot limits combined, rebuilt and maintained large mature individuals even under high harvest pressure. The most conservative model (a 30% MPA and harvest slot limit of 75–105 mm) increased spawner abundance by 5.53E12 compared with the fishing status quo at the end of 30 years. Spawning stock abundance also increased by 2.76–9.56E12 individuals at a high harvest intensity over 30 years with MPAs alone. Our results demonstrate the potential of MPAs and harvest slot limits for the conservation of large breeding individuals in some marine and freshwater environments. Decisions on which management strategy best suits a fishery, however, requires balancing what is ecologically desirable with what is economically and socially feasible. 相似文献
Objective: The objective of this study was to analyze booster and rear vehicle seat dimensions to identify the most frequent compatibility problems.
Methods: Measurements were collected from 40 high-back and backless boosters and 95 left rear and center rear row seating positions in 50 modern vehicles. Dimensions were compared for 3,800 booster/vehicle seat combinations. For validation and estimation of tolerance and correction factors, 72 booster installations were physically completed and compared with measurement-based compatibility predictions. Dimensions were also compared to the International Organization for Standardization (ISO) volumetric envelopes of forward-facing child restraints and boosters.
Results: Seat belt buckles in outboard positions accommodated the width of boosters better than center positions (success rates of 85.4 and 34.7%, respectively). Adequate head restraint clearance occurred in 71.9 to 77.2% of combinations, depending on the booster's head support setting. Booster recline angles aligned properly with vehicle seat cushion angles in 71.5% of combinations. In cases of poor angle alignment, booster angles were more obtuse than the vehicle seat angles 97.7% of the time. Head restraint interference exacerbated angle alignment issues. Data indicate success rates above 90% for boosters being fully supported by the length of the seat cushion and for adequate height clearance with the vehicle roofline. Comparison to ISO envelopes indicates that most boosters on the U.S. market are taller and angled more obtusely than ISO target envelopes.
Conclusions: This study quantifies some of the common interferences between boosters and vehicles that may complicate booster usage. Data are useful for design and to prioritize specific problem areas. 相似文献
Bioassessment methods for wetlands, and other bodies of water, have been developed worldwide to measure and quantify changes in “biological integrity.” These assessments are based on a classification system, meant to ensure appropriate comparisons between wetland types. Using a local site-specific disturbance gradient, we built vegetation indices of biological integrity (Veg-IBIs) based on two commonly used wetland classification systems in the USA: One based on vegetative structure and the other based on a wetland’s position in a landscape and sources of water. The resulting class-specific Veg-IBIs were comprised of 1–5 metrics that varied in their sensitivity to the disturbance gradient (R2?=?0.14???0.65). Moreover, the sensitivity to the disturbance gradient increased as metrics from each of the two classification schemes were combined (added). Using this information to monitor natural and created wetlands will help natural resource managers track changes in biological integrity of wetlands in response to anthropogenic disturbance and allows the use of vegetative communities to set ecological performance standards for mitigation banks. 相似文献
Considerable resources are being used to develop and implement bioassessment methods for wetlands to ensure that “biological integrity” is maintained under the United States Clean Water Act. Previous research has demonstrated that avian composition is susceptible to human impairments at multiple spatial scales. Using a site-specific disturbance gradient, we built avian wetland indices of biological integrity (AW-IBI) specific to two wetland classification schemes, one based on vegetative structure and the other based on the wetland’s position in the landscape and sources of water. The resulting class-specific AW-IBI was comprised of one to four metrics that varied in their sensitivity to the disturbance gradient. Some of these metrics were specific to only one of the classification schemes, whereas others could discriminate varying levels of disturbance regardless of classification scheme. Overall, all of the derived biological indices specific to the vegetative structure-based classes of wetlands had a significant relation with the disturbance gradient; however, the biological index derived for floodplain wetlands exhibited a more consistent response to a local disturbance gradient. We suspect that the consistency of this response is due to the inherent nature of the connectivity of available habitat in floodplain wetlands. 相似文献
Shelter competition is uncommon among social animals, as is the case among normally gregarious Caribbean spiny lobsters (Panulirus argus). However, healthy lobsters avoid sheltering with conspecifics infected by a lethal pathogenic virus, PaV1. These contradictory
behaviors have implications for shelter use and survival, especially in areas where shelter is limited. In laboratory experiments,
we tested shelter competition between paired healthy and diseased juvenile lobsters in shelter-limited mesocosms. Neither
healthy nor diseased lobsters dominated access to shelters, but lobsters shared shelter less often when diseased lobsters
were present relative to controls with two healthy lobsters. We hypothesized that exclusion of juvenile lobsters from shelter
results in increased mortality from predation, especially for the more lethargic, infected individuals. Field tethering trials
revealed that predation was indeed higher on infected individuals and on all tethered lobsters deprived of shelter. We then
tested in mesocosm experiments how the contrasting risks of predation versus infection by a lethal pathogen influence shelter
use. Lobsters were offered a choice of an empty shelter or one containing a diseased lobster in the presence of a predator
(i.e., caged octopus) whose presence normally elicits shelter-seeking behavior, and these data were compared with a previous
study where the predator was absent. Lobsters selected the empty shelter significantly more often despite the threat of predation,
foregoing the protection of group defense in favor of reduced infection risk. These results offer striking evidence of how
pathogenic diseases shape not only the behavior of social animals but also their use of shelters and risk of predation. 相似文献
A radon survey has been carried out around the town of Niska Banja (Serbia) in a region partly located over travertine formations, showing an enhanced level of natural radioactivity. Outdoor and indoor radon concentrations were measured seasonally over the whole year, using CR-39 diffusion type radon detectors. Outdoor measurements were performed at 56 points distributed over both travertine and alluvium sediment formations. Indoor radon concentrations were measured in 102 living rooms and bedrooms of 65 family houses. In about 50% of all measurement sites, radon concentration was measured over each season separately, making it possible to estimate seasonal variations, which were then used to correct values measured over different periods, and to estimate annual values. The average annual indoor radon concentration was estimated at over 1500 Bq/m3 and at about 650 Bq/m3 in parts of Niska Banja located over travertine and alluvium sediment formations, respectively, with maximum values exceeding 6000 Bq/m3. The average value of outdoor annual radon concentration was 57 Bq/m3, with a maximum value of 168 Bq/m3. The high values of indoor and outdoor radon concentrations found at Niska Banja make this region a high natural background radiation area. Statistical analysis of our data confirms that the level of indoor radon concentration depends primarily on the underlying soil and building characteristics. 相似文献