23 results on '"Population status"'
Search Results
2. Assessment of the Population of the European Grayling under Limited Data.
- Author
-
Boznak, E. I., Zakharov, A. B., and Ponomarev, V. I.
- Subjects
- *
NATIONAL parks & reserves , *FISH populations , *DEATH rate - Abstract
The state of populations of European grayling Thymallus thymallus (Linnaeus, 1758) has been assessed and compared in two Ural tributaries of the Pechora River. The grayling inhabiting the Shchugor River (the territory of Yugyd Va National Park) has been satisfactorily preserved with minimal shifts in population characteristics. In the Bolshaya Synya River, protected only at the river source, the grayling population decreased mostly by the fish of the maximum age (up to 7+), the share of repeatedly spawning individuals has decreased as well (4.0–4.8%), and the overall mortality rate has increased. Deterioration of the grayling population in the Bolshaya Synya River was due to intensive illegal fishing. Under limited initial data, using a set of traditional indicators appeared a more universal assessment approach, while the length-based indicators (LBIs) method has only limited application. [ABSTRACT FROM AUTHOR] more...
- Published
- 2023
- Full Text
- View/download PDF
Catalog
3. The Critically Endangered Hainan Gibbon (Nomascus hainanus) Population Increases but not at the Maximum Possible Rate.
- Author
-
Liu, Guioqi, Lu, Xueli, Liu, Zhao, Xie, Zhi, Qi, Xuming, Zhou, Jiang, Hong, Xiaojiang, Mo, Yanni, Chan, Bosco P. L., Chapman, Colin A., and Jiang, Zhigang
- Subjects
- *
RAIN forests , *ENDANGERED species , *FOREST restoration , *NATURE reserves , *HABITATS , *CENSUS - Abstract
With the ongoing global biodiversity crisis in the Anthropocene, it is critical to understand how to save endangered species to "bend the curve" of biodiversity decline. The Hainan gibbon (Nomascus hainanus) is a Critically Endangered species that is endemic to Hainan Island. We performed two synchronized total count surveys in Hainan Tropic Rain Forest National Park in November and December of 2020 and 2021 by locating gibbon groups from their morning calls and conducting detailed counts in all potential habitat fragments. We compared our findings with existing data to model the population trend, and analyzed the potential and realized reproductive potentials. We found 5 groups with a total of 33 gibbons in 2020 and 35 in 2021, including 4 and 6 solitary individuals respectively. This is an increase of 169% since 2003, when there were 13 individuals with 2 groups and 2 solitary individuals. Logistic and linear curves fitted the 2003-2021 population census data equally well. Although the population is growing, it has not realized its full reproductive potential (when all adult females give births at 24-month intervals), suggesting that external factors like available habitat, as well as nutritional, physiological, and behavioral factors may be limiting the population. The gibbon's recovery demonstrates that establishing a nature reserve with regular patrols, banning logging, curbing poaching, and environmental education have been effective. Because the Hainan gibbon population is still extremely small, carefully planned conservation actions, including an ambitious forest restoration program, will be needed to ensure the species' continued survival. [ABSTRACT FROM AUTHOR] more...
- Published
- 2022
- Full Text
- View/download PDF
4. New and Rare Vascular Plant Species of the Kuril Islands: Distribution, Ecology, and Population Status.
- Author
-
Glazkova, E. A. and Liksakova, N. S.
- Subjects
PLANT species ,RARE plants ,ISLANDS ,DATA distribution ,VASCULAR plants ,ENDANGERED species - Abstract
Despite the long history of floristic studies of the Kuril Islands, the central part of the Kuril archipelago, particularly Urup Island, remains poorly studied. The question of the position of Urup Island in the biogeographic and floristic subdivision systems is controversial, which seems to be due to unsufficient floristic data. Studies carried out by the authors in 2019 on the islands of Urup and Iturup provided new data about the distribution, habitats, and population status of 28 indigenous species of vascular plants, including 14 species listed in the Red Data Book of the Russian Federation (2008) and the Red Data Book of the Sakhalin Oblast (2019). Myriophyllum ussuriense was first discovered in the Sakhalin Oblast and recommended for inclusion into the regional list of rare vascular plant species and the Red Data Book of the Sakhalin Oblast. Four species (Corallorhiza trifida, Pedicularis adunca, Salix arctica, and S. chamissonis) were first revealed in the southern Kuril Islands. In addition, eight species (Carex livida, Eleocharis margaritacea, Epipactis papillosa, Juncus articulatus, J. decipiens, Neottia puberula, Poa austrokurilensis, and Utricularia minor) were first found on Urup Island. Occurrence of four species (Isoëtes asiatica, Hydrangea petiolaris, Rhynchospora alba, and Salix fuscescens) on Urup Island was confirmed by new records. The data obtained confirm that Urup Island takes an intermediate position in the floristic subdivision of the Kuril archipelago and represents a transitional zone between the northern and southern Kuril Islands, which is significantly enriched by "southern" East Asian species. [ABSTRACT FROM AUTHOR] more...
- Published
- 2021
- Full Text
- View/download PDF
5. The Current Status of the Red King Crab (Paralithodes camtschaticus) Stock and Fishery off Western Kamchatka.
- Author
-
Ivanov, P. Yu.
- Abstract
The current status of the red king crab population off western Kamchatka is considered based on data from bottom trawl surveys and fishery statistics since 2013. Some biological parameters of this crab species are provided; its commercial stock is estimated; some features of red king crab fishery and determination of total allowable catch for the past 7 years are analyzed. The red king crab fishing was resumed in 2013 after an 8-year ban imposed due to the population decline. During this period, the stock recovered and reached values greater than those recorded before the ban: the total estimated size of red king crab population in 2017 was almost 244 million ind., which is the highest value for the recent 17 years of research; the estimated number of commercial-sized males, 110 million ind., has not been recorded from the western Kamchatka shelf for at least past 4 decades. Recently, the Severny Zapretny and Khairyuzovsky areas of the shelf zone have yielded their role of main feeding grounds for pre-recruit crabs and juveniles to the Ichinsky area located south. For the 7 years of red king crab fishery, harvest values have been steadily high. In the past 3 years, the major part of the annual catch of live crabs has been exported to China and South Korea. As the analysis of size structure show, the body size of male red king crabs has been increasing each year all over the shelf. This may be explained by the strict sorting of caught crabs aboard vessels transporting live crabs with the release of the largest individuals; another possible explanation is the relatively low recorded number of pre-recruits in the past 2 years. For the 7 years past (including 2019), the fishing mortality rate is estimated within a range of 5–16% of the crab stock actually recorded from the permitted fishery areas, which is a highly cautious approach. In the nearest future, the crab commercial stock is expected to gradually decrease, which, nevertheless, should not fall below the reference target value of biomass. The current status of the red king crab population off western Kamchatka does not raise concern, and the ongoing intense harvesting of this valuable species within the recommended catch size will not have any negative effect on its commercial stock. [ABSTRACT FROM AUTHOR] more...
- Published
- 2020
- Full Text
- View/download PDF
6. Muskox status, recent variation, and uncertain future.
- Author
-
Cuyler, Christine, Rowell, Janice, Adamczewski, Jan, Anderson, Morgan, Blake, John, Bretten, Tord, Brodeur, Vincent, Campbell, Mitch, Checkley, Sylvia L., Cluff, H. Dean, Côté, Steeve D., Davison, Tracy, Dumond, Mathieu, Ford, Barrie, Gruzdev, Alexander, Gunn, Anne, Jones, Patrick, Kutz, Susan, Leclerc, Lisa-Marie, and Mallory, Conor more...
- Subjects
- *
EFFECT of human beings on climate change , *STAKEHOLDER theory , *DEMOGRAPHIC change - Abstract
Muskoxen (Ovibos moschatus) are an integral component of Arctic biodiversity. Given low genetic diversity, their ability to respond to future and rapid Arctic change is unknown, although paleontological history demonstrates adaptability within limits. We discuss status and limitations of current monitoring, and summarize circumpolar status and recent variations, delineating all 55 endemic or translocated populations. Acknowledging uncertainties, global abundance is ca 170 000 muskoxen. Not all populations are thriving. Six populations are in decline, and as recently as the turn of the century, one of these was the largest population in the world, equaling ca 41% of today's total abundance. Climate, diseases, and anthropogenic changes are likely the principal drivers of muskox population change and result in multiple stressors that vary temporally and spatially. Impacts to muskoxen are precipitated by habitat loss/degradation, altered vegetation and species associations, pollution, and harvest. Which elements are relevant for a specific population will vary, as will their cumulative interactions. Our summaries highlight the importance of harmonizing existing data, intensifying long-term monitoring efforts including demographics and health assessments, standardizing and implementing monitoring protocols, and increasing stakeholder engagement/contributions. [ABSTRACT FROM AUTHOR] more...
- Published
- 2020
- Full Text
- View/download PDF
7. Concise review of the genus Durvillaea Bory de Saint-Vincent, 1825.
- Author
-
Velásquez, Marcel, Fraser, Ceridwen I., Nelson, Wendy A., Tala, Fadia, and Macaya, Erasmo C.
- Abstract
The genus Durvillaea includes six currently accepted species, as well as two newly proposed species. Durvillaea spp. have a diplontic life cycle, lack a free-living gametophyte and have oogamous reproduction. All Durvillaea species require rocky substrate for attachment and wave-exposed environments. These "southern bull kelps" occur exclusively in the Southern Hemisphere and are important foundation species, in most cases controlling local community structure, influencing biodiversity, and providing food and habitat for other culturally and economically important species. Most species are non-buoyant and these have restricted geographic ranges, in some cases endemic to small oceanic islands. Buoyant members of the genus are more widespread, with one species (Durvillaea antarctica) found throughout the subantarctic, Chile, and New Zealand. This chapter summarizes the taxonomy, biology, and economic importance of Durvillaea species, with a focus on aspects relevant to their availability and productivity as crop plants. Systematics, distribution, ecology, life histories, population status, harvesting times, protection, management and chemical composition are covered. Much of the available data are for the species Durvillaea antarctica, D. willana, and D. potatorum. The techniques used in harvesting and the human uses of Durvillaea spp. (e.g., as food) are described, along with recommendations for harvest timing and methods. [ABSTRACT FROM AUTHOR] more...
- Published
- 2020
- Full Text
- View/download PDF
8. Tengmalm's Owl (Aegolius funereus) (Strigidae, Aves) in the North Caucasus.
- Author
-
Belik, V. P. and Akkiev, M. I.
- Subjects
- *
DECIDUOUS forests , *OLD growth forests , *MIXED forests , *CONIFEROUS forests , *MOUNTAIN forests , *PINACEAE - Abstract
Abstract—Tengmalm's Owl (Aegolius funereus caucasicus But.) inhabits dark coniferous, pine, and deciduous forests in the mountains of the North Caucasus in the range from the city of Tuapse in the west to Inner Dagestan in the east, rising to pine forests to a height of 1900–2000 m above sea level. During its winter wanderings, it occasionally occurs in the foothills, but almost does not go out to the piedmont plains. Winter records in the steppe regions of Ciscaucasia may refer to nomadic specimens of a nominate subspecies (A. f. funereus L.), which is common in Voronezh oblast and in northern Rostov oblast. The bird finds the most optimal conditions in old dark coniferous and mixed forests of the Western Caucasus, and its maximum abundance is noted in the Teberda Nature Reserve (1 pair/10 km2). In the Central and Eastern Caucasus, it lives in old deciduous forests (mountains with a low elevation) and in pine forests (mountains of average height). The population of Tengmalm's Owl in the North Caucasus is considered relatively stable, and its total number is now estimated at 1000–2000 pairs, including 200–400 pairs living in Karachaevo-Cherkessia and 20–30 pairs living in Adygea. Tengmalm's Owl is ecologically closely connected with the Black Woodpecker (Dryocopus martius), whose old hollows it usually nests in. The birds display from January to May, but most actively in mid-April. In late April, they lay eggs and fledglings appear in June–July. [ABSTRACT FROM AUTHOR] more...
- Published
- 2019
- Full Text
- View/download PDF
9. Distribution, population density and conservation of the critically endangered brown spider monkey (Ateles hybridus) and other primates of the inter-Andean forests of Colombia.
- Author
-
de Luna, Ana Gabriela and Link, Andrés
- Subjects
POPULATION density ,POPULATION geography ,SPIDER monkeys ,PRIMATES ,FORESTS & forestry - Abstract
The inter-Andean tropical rainforests and dry forests of the Magdalena river basin (Tumbes-Choco-Magdalena biodiversity hotspot) in northern Colombia have undergone significant forest loss and degradation in recent decades. Six primate species inhabit this region, five of which are currently threatened with extinction and one of which—the brown spider monkey, Ateles hybridus—is considered critically endangered. Accurate and recent information on the distribution and conservation status of these threatened primate populations is scarce or nonexistent, even though such data are needed to implement successful conservation actions and management plans. Between 2006 and 2016, we evaluated the status and distribution of primates across inter-Andean lowland forests in northern Colombia. We visited 30 sites to evaluate the presence/absence of brown spider monkeys and other primate taxa in the region. We also carried out surveys at 10 of these sites to obtain estimates of primate population densities and demographic information from forests with different levels of anthropogenic disturbance. Novel data on primate presence/absence were obtained for 27 sites, and 136 records were collected in total. Only 33% of the sites visited were large forest fragments (> 500 Ha). This study confirms that at least six primate species are still present in the Rio Magdalena region, which represents the highest platyrrhine diversity west of the Andes. This study also confirms the persistence of a wild population of Colombian woolly monkeys (Lagothrix lagotricha lugens) in the Serranía de San Lucas. Assigning formal protected status to this region is an urgent priority for the conservation of primates in the Rio Magdalena region. [ABSTRACT FROM AUTHOR] more...
- Published
- 2018
- Full Text
- View/download PDF
10. The Current Status of Populations of the Sea Cucumber <italic>Apostichopus japonicus</italic> (Selenka, 1867) in the Far Eastern Marine Reserve.
- Author
-
Lysenko, V. N., Zharikov, V. V., and Lebedev, A. M.
- Abstract
The spatial distribution of the sea cucumber
Apostichopus japonicus (Selenka, 1867) in the Far Eastern Marine Reserve was studied using scuba. The abundance, size composition, population density, and distribution ofA. japonicus were determined. The population density of this species at the mainland coast was higher than in waters around islands in the reserve. Seasonal movements of sea cucumber were observed: in autumn large individuals migrate to greater depths, but at the beginning of summer they move to shallow water. The average sizes of individuals and population density of sea cucumber in the reserve do not differ from those in unprotected areas of Peter the Great Bay. A comparative analysis of our own and literature data showed that the current estimates of sea cucumber population density in the reserve are 5−7 times lower than estimates for the period before the illegal fishing of sea cucumber began in Primorye. [ABSTRACT FROM AUTHOR] more...- Published
- 2018
- Full Text
- View/download PDF
11. Diversity, regeneration status and population structure of gum- and resin-bearing woody species in south Omo zone, southern Ethiopia.
- Author
-
Adem, Muhamed, Worku, Adefires, Lemenih, Mulugeta, Tadesse, Wubalem, and Pretzsch, Jürgen
- Abstract
South Omo Administrative Zone in Ethiopia is home to 18 indigenous ethnic groups whose livelihood is vulnerable due to recurrent drought and degradation. Despite the preliminary observation showing the rich dry-forest resource base that, if sustainably managed could enhance livelihoods and biodiversity conservation, there is lack of empirical data on its current status. We conducted a study aiming at quantifying the population status of gum- and resin-bearing species in two randomly selected districts, Hamer and Bena-Tsemay. Seventy-five quadrats (35 at Hamer and 40 at Bena-Tsemay) each measuring 400 m2 were established along line transects to assess species diversity and equitability, density, frequency, dominance, importance value and population structure. We recorded a total of 27 woody species of 12 families and 14 genera. Fifteen species (9 at Hamer and 14 at Bena-Tsemay) of the genera Acacia, Boswellia, Commiphora and Sterculia, were identified as either major sources of commercial gums and resins or their adulterants. Gum- and resin-bearing species comprised 56% and 57% of species richness, 48% and 50% of total density per ha, 95% and 98% of basal area, and 64% and 56% of importance values at Hamer and Bena-Tsemay, respectively. Diversity of the entire woody species assemblage and of the gum- and resin-bearing species was slightly higher at Bena-Tsemay (H= 2.61, 1.4) than at Hamer (H′= 2.48, 1.28), respectively. The diversity and abundance of the resource base suggest potential for development of value-added commercialization of gum and resins to enhance livelihoods and encourage sustainable management of the forest at these study areas. We recorded, however, declining natural regeneration of most gum- and resin-bearing species, and this calls for integrated and participatory species management and landscape rehabilitation. [ABSTRACT FROM AUTHOR] more...
- Published
- 2014
- Full Text
- View/download PDF
12. The relative impact of forest patch and landscape attributes on black howler monkey populations in the fragmented Lacandona rainforest, Mexico.
- Author
-
Arroyo-Rodríguez, Víctor, González-Perez, Iraida M., Garmendia, Adriana, Solà, Mireia, and Estrada, Alejandro
- Subjects
BLACK howler monkey ,RAIN forests ,HABITATS ,ANIMAL population density - Abstract
Land-use change is forcing many animal populations to inhabit forest patches in which different processes can threaten their survival. Some threatening processes are mainly related to forest patch characteristics, but others depend principally on the landscape spatial context. Thus, the impact of both patch and landscape spatial attributes needs to be assessed to have a better understanding of the habitat spatial attributes that constraint the maintenance of populations in fragmented landscapes. Here, we evaluated the relative effect of three patch-scale (i.e., patch size, shape, and isolation) and five landscape-scale metrics (i.e., forest cover, fragmentation, edge density, mean inter-patch isolation distance, and matrix permeability) on population composition and structure of black howler monkeys ( Alouatta pigra) in the Lacandona rainforest, Mexico. We measured the landscape-scale metrics at two spatial scales: within 100 and 500 ha landscapes. Our findings revealed that howler monkeys were more strongly affected by local-scale metrics. Smaller and more isolated forest patches showed a lower number of individuals but at higher densities. Population density also tended to be positively associated to matrices with higher proportion of secondary forests and arboreal crops (i.e. with greater permeability), most probably because these matrices can offer supplementary foods. The immature-to-female ratio also increased with matrix permeability, shape complexity, and edge density; habitat characteristics that can increase landscape connectivity and sources availability. The prevention of habitat loss and isolation, and the increment of matrix permeability are therefore needed for the conservation of this endangered Neotropical mammal. [ABSTRACT FROM AUTHOR] more...
- Published
- 2013
- Full Text
- View/download PDF
13. Population status, habitat associations, and distribution of the steppe polecat Mustela eversmanii in Europe.
- Author
-
Šálek, Martin, Spassov, Nikolai, Anděra, Miloš, Enzinger, Karin, Ottlecz, Barnabás, and Hegyeli, Zsolt
- Abstract
The steppe polecat Mustela eversmanii is a medium-sized mustelid species whose European population has significantly declined over the past century. However, due to the lack of systematic surveys, little is known about its status and distribution. In this paper, we review the current distribution, habitat associations, and population trends of steppe polecats in Europe and assess the main factors associated with these trends. Our results reveal ongoing population declines in most of the studied countries, which led to fragmentation and local population extinctions at the beginning of the twenty-first century. The species was assessed as rapidly declining in Austria, Czech Republic, Moldova, Slovakia, and Ukraine; declining in Bulgaria; and stable in Hungary. Due to insufficient data, its status was not evaluated for Romania, Poland, and Serbia. M. eversmanii naturally occurs in steppe habitats, but recently seems to have adopted open agricultural landscapes consisting of a mosaic of grasslands, small fields with hedges, and dry embankments. Its distribution often coincides with populations of ground squirrels and hamsters. However, in intensively used agricultural landscapes, smaller rodents (especially voles) could also be an important dietary component. Intensive agricultural production, habitat loss, the degradation of steppe and grassland habitats, and significant declines in the availability of its main prey are the crucial factors for the species' current population decline. Further research is urgently needed to fill the gaps in our knowledge of its distribution, population densities, feeding ecology, habitat associations, and population genetics. This would enable first steps towards its effective conservation and management strategies. [ABSTRACT FROM AUTHOR] more...
- Published
- 2013
- Full Text
- View/download PDF
14. Marked population increase in Pale-headed Brush-finch Atlapetes pallidiceps in response to cowbird control.
- Author
-
Krabbe, Niels, Juiña, Mery, and Sornoza, Aldo Fernando
- Subjects
- *
FINCHES , *ENDANGERED species , *BIRD conservation , *COWBIRDS , *PARASITISM , *ANIMAL behavior - Abstract
The Pale-headed Brush-finch Atlapetes pallidiceps is an emberizine finch that is confined to south-central Ecuador and critically endangered owing to cowbird parasitism and habitat loss. We report a marked increase in numbers of brush-finches after seven years of cowbird control, confirming that brood parasitism had been an important limiting factor, and that shooting with firearms can be an effective method of controlling local cowbird parasitism. [ABSTRACT FROM AUTHOR] more...
- Published
- 2011
- Full Text
- View/download PDF
15. Regeneration ecology and population status of a critically endangered and endemic tree species ( Ilex khasiana Purk.) in north-eastern India.
- Author
-
Krishna, Upadhaya, Kanta, Barik, Dibyendu, Adhikari, Ratul, Baishya, and John, Lakadong
- Abstract
Detailed studies on population structure and regeneration ecology of Ilex khasiana were carried out at five representative natural populations i.e. Mylliem (Population - I), Upper Shillong (Population - II), Shillong Peak (Population - III), Laitkor (Population - IV) and Nongpiyur (Population - V) to probe into the responsible affecting factors for its population structure and regeneration ability in these populations. Experimental observation under three controlled light conditions (full sunlight (100%), intermediate sunlight (50%) and low sunlight (30%)) showed that the growth status and survival rates of seedlings under intermediate and low light were better than those under the high light condition. The density-diameter distribution in population of adult trees (≥5cm dbh) exhibited a typical character of a regenerating population. A higher seedling mortality rate in natural populations of I. khasiana was most probably due to increase in light intensity following vegetation destruction and other anthropogenic disturbances that cause opening of forest canopy. The findings of the present study would be of immense value in formulating appropriate conservation measures for the species. [ABSTRACT FROM AUTHOR] more...
- Published
- 2009
- Full Text
- View/download PDF
16. STATUS AND HABITAT USE OF THE CALIFORNIA BLACK RAIL IN THE SOUTHWESTERN USA.
- Author
-
Conway, Courtney J. and Sulzman, Christina
- Abstract
California black rails (Laterallus jamaicensis coturniculus) occur in two disjunct regions: the southwestern USA (western Arizona and southern California) and northern California (Sacramento Valley and the San Francisco Bay area). We examined current status of black rails in the southwestern USA by repeating survey efforts first conducted in 1973 1974 and again in 1989, and also examined wetland plant species associated with black rail distribution and abundance. We detected 136 black rails in Arizona and southern California. Black rail numbers detected during past survey efforts were much higher than the numbers detected during our more intensive survey effort, and hence, populations have obviously declined. Plants that were more common at points with black rails included common threesquare (Schoenoplectus pungens), arrowweed (Pluchea sericea), Fremont cottonwood (Populus fremontii), seepwillow (Baccharis salicifolia), and mixed shrubs, with common threesquare showing the strongest association with black rail presence. Plant species and non-vegetative communities that were less common at points with black rails included California bulrush (Schoenoplectus californicus), southern cattail (Typha domingensis), upland vegetation, and open water. Black rails were often present at sites that had some saltcedar (Tamarix ramosissima), but were rarely detected in areas dominated by saltcedar. We recommend that a standardized black rail survey effort be repeated annually to obtain estimates of black rail population trends. Management of existing emergent marshes with black rails is needed to maintain stands of common threesquare in early successional stages. Moreover, wetland restoration efforts that produce diverse wetland vegetation including common threesquare should be implemented to ensure that black rail populations persist in the southwestern USA. [ABSTRACT FROM AUTHOR] more...
- Published
- 2007
- Full Text
- View/download PDF
17. Population Status of North American Green Sturgeon, Acipenser medirostris.
- Author
-
Adams, Peter, Grimes, Churchill, Hightower, Joseph, Lindley, Steven, Moser, Mary, and Parsley, Michael
- Subjects
GREEN sturgeon ,ACIPENSER ,STURGEONS ,ENDANGERED species ,ANIMALS ,NATURE conservation ,WILDLIFE conservation - Abstract
North American green sturgeon, Acipenser medirostris, was petitioned for listing under the Endangered Species Act (ESA). The two questions that need to be answered when considering an ESA listing are; (1) Is the entity a species under the ESA and if so (2) is the “species” in danger of extinction or likely to become an endangered species in the foreseeable future throughout all or a significant portion of its range? Green sturgeon genetic analyses showed strong differentiation between northern and southern populations, and therefore, the species was divided into Northern and Southern Distinct Population Segments (DPSs). The Northern DPS includes populations in the Rogue, Klamath-Trinity, and Eel rivers, while the Southern DPS only includes a single population in the Sacramento River. The principal risk factors for green sturgeon include loss of spawning habitat, harvest, and entrainment. The Northern DPS is not considered to be in danger of extinction or likely to become an endangered species in the foreseeable future. The loss of spawning habitat is not large enough to threaten this DPS, although the Eel River has been severely impacted by sedimentation due to poor land use practices and floods. The two main spawning populations in the Rogue and Klamath-Trinity rivers occupy separate basins reducing the potential for loss of the DPS through catastrophic events. Harvest has been substantially reduced and green sturgeon in this DPS do not face substantial entrainment loss. However there are significant concerns due to lack of information, flow and temperature issues, and habitat degradation. The Southern DPS is considered likely to become an endangered species in the foreseeable future. Green sturgeon in this DPS are concentrated into one spawning area outside of their natural habitat in the Sacramento River, making them vulnerable to catastrophic extinction. Green sturgeon spawning areas have been lost from the area above Shasta Dam on the Sacramento River and Oroville Dam on the Feather River. Entrainment of individuals into water diversion projects is an additional source of risk, and the large decline in numbers of green sturgeon entrained since 1986 causes additional concern. [ABSTRACT FROM AUTHOR] more...
- Published
- 2007
- Full Text
- View/download PDF
18. Assessment of the status of wild populations of land snail (escargot) Helix pomatia L. in Moldova: the effect of exploitation.
- Author
-
Andreev, Nadejda
- Subjects
EDIBLE snails ,ANIMAL populations ,HELIX pomatia ,ANIMAL population density ,ANIMAL species ,ENDANGERED species ,WILDLIFE conservation ,WILDLIFE management - Abstract
Helix pomatia L., the Roman snail, is a species faced with growing commercial interest in Moldova. Its life history characteristics (slow maturation and recruitment, high mortality among juveniles and low fecundity) along with its strong spatial aggregation, makes it especially vulnerable to exploitation. In this study, differences in density, shell size and age distribution were assessed in 7 unexploited and 10 exploited sites in the northern and central parts of Moldova. A significant impact of exploitation on snail population densities, shell size of adult snails and age distribution was revealed. Exploited sites had much lower densities than unexploited ones and in two places no live snails were found. This may suggest that exploitation is currently carried out at an unsustainable level, but additional information on the demography of populations and intensity of exploitation is required in order to make inferences regarding sustainability and long-term population management. There was a higher proportion of adult snails in exploited sites than in nonexploited, because of the collection strategies: not only adults, but also all other age groups are gathered. Bigger adult shell size in exploited sites may be related to lower population density, but further study is required to confirm this. Establishing of well-organized population monitoring systems and development of snail breeding enterprises are proposed in order to conserve the species in Moldova. [ABSTRACT FROM AUTHOR] more...
- Published
- 2006
- Full Text
- View/download PDF
19. Population, diet and conservation of Malayan flying Lemurs in altered and fragmented habitats in Singapore.
- Author
-
Agoramoorthy, G., Sha, C. M., and Hsu, M. J.
- Subjects
FLYING lemurs ,LEMURS ,CONSERVATION & restoration ,DIET ,DENSITY ,MAMMALS ,POPULATION ,TANNINS - Abstract
The Malayan flying lemur (Cynocephalus variegatus) is a nocturnal mammalian arboreal folivore that inhabits the forests of Southeast Asia. Surveys were conducted from August to November 2003 to estimate the population density of Malayan flying lemurs for the first time in the Singapore Zoological Gardens. The study area consisting of Singapore Zoo and Night Safari was located in the Central Catchment Nature Reserve, where most of Singapore's remaining natural forest is found. The Zoo consisted of 28 ha of landscaped habitat and the adjacent Night Safari consisted of 40 ha of secondary rainforest. The density estimates of flying lemurs in the Zoo and Night Safari were 15 and 24 individuals respectively. Seven plant species that were the preferred food items and an additional 10 plants that were common in the sites but not eaten by the flying lemurs were analysed to compare the mineral and phytochemical contents. Flying lemurs consumed leaves containing significantly less potassium and nitrogen but higher tannin (p < 0.05). The study shows that flying lemurs are able to survive in altered and fragmented landscapes. Conservation and management strategies are essential to protect the shrinking habitats in Singapore. [ABSTRACT FROM AUTHOR] more...
- Published
- 2006
- Full Text
- View/download PDF
20. Effect of certain socio-ecological factors on the population density of house dust mites in mattress-dust of asthmatic patients of Calcutta, India.
- Author
-
Modak, A. and Saha, G.K.
- Abstract
Allergy to house dust mites, particularly tothe genus Dermatophagoides is a fairlycommon problem in Calcutta and its adjoiningareas since last two decades. Both the commonspecies of the genus Dermatophagoidesi.e. D. farinae and D.pteronyssinus are found to be abundant in thedust samples collected from beds of patientssuffering from nasobronchial allergic disordes.The presence of these mites in quite a goodnumber in the patients' beds are clinicallycorrelated with the aetiopathology of variousallergic manifestations like bronchial asthma. Dermatophagoides mites may occupydifferent niches in the homes of asthmatics andare more common in beds than elsewhere in thehouse, however, the distribution and abundanceof these mites are influenced by somesocio-ecological factors. The aim and objectiveof the present study is to assess the impact ofsome common socio-ecological managementpractices like the age of house, age ofmattress, type of mattress, frequency ofcleaning of the mattress and even the economicstatus of the patients on the growth,multiplication and finally accumulation ofthese mites in the patients' surroundings.Proper identification of offending allergensand subsequent reduction of load of these miteallergens from the patient's environment may behelpful for the prophylactic management ofthese diseases in Calcutta metropolis. [ABSTRACT FROM AUTHOR] more...
- Published
- 2002
- Full Text
- View/download PDF
21. Seals in the human environment
- Author
-
Bonner, W. N.
- Subjects
- *
WILDLIFE exploitation , *HISTORY - Published
- 1986
22. Systematic status of two oyster populations of the genus Tiostrea from New Zealand and Chile
- Author
-
Buroker, N. E., Dinamani, P., Cranfield, H. J., and Chanley, P.
- Subjects
OYSTERS - Published
- 1983
- Full Text
- View/download PDF
23. The Ladoga seal (Phoca hispida ladogensis Nordq.)
- Author
-
Hyvarinen, H., Medvedev, N. V., and Sipila, T.
- Published
- 1996
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.