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1.
Darren A. Whitehead Edgar E. Becerril-García David Petatán-Ramírez Abraham Vázquez-Haikin Rogelio González-Armas Felipe Galván-Magaña 《Journal of fish biology》2019,94(1):165-167
The present study analyses whale shark Rhincodon typus stranding in the Gulf of California, Mexico, reported by the public, scientists, authorities and artisanal fishermen. A total of 14 strandings were documented during the period 2001–2018. The total length of R. typus ranged from 350–1,102 cm, with a sex ratio of 3.5:1 (males: females). This study highlights potential stranding areas, the need for better stranding protocols to assist R. typus recovery and the importance of samples from dead animals for scientific research. 相似文献
2.
Whale sharks, Rhincodon typus, seasonally aggregate in coastal waters off Ningaloo Reef, Western Australia. We review the oceanographic setting of the region and present evidence that such aggregations form as a result of migratory behavior associated with climatic and oceanographic processes. We utilise records of whale shark abundance collected at Ningaloo Reef from dedicated searches by boat and aircraft and from log sheets recorded by the tourism industry. Measures of whale shark abundance derived from log sheet data sets were moderately correlated with the Southern Oscillation Index and weakly correlated with coastal sea level, an index of the strength of the Leeuwin Current, and sea surface temperature over the period 1993 to 1998. Abundances of whale sharks derived from boat searches from 1983 to 1992 were also correlated with fluctuations in the Southern Oscillation Index, except during a three year period from 1988 to 1990. We conclude that, at least in some years, there appears to be a link between the abundance of aggregating whale sharks and the physical and biological oceanography of the region, with greater whale shark numbers in La Niña years. The lack of correlation in other years may be due to a combination of uneven quality of data and/or aggregations occurring in response to a complex interaction between the physical and biological oceanography of the region. 相似文献
3.
Edgar E. Becerril-García Francesca Pancaldi Ariel A. Cruz-Villacorta Alma R. Rivera-Camacho Carlos A. Aguilar-Cruz Darren A. Whitehead Rogelio González-Armas Marcial Arellano-Martínez Felipe Galván-Magaña 《Journal of fish biology》2021,99(4):1524-1528
The aim of this study is to provide preliminary observations on the microanatomy of Rhincodon typus skin using histology and electron microscopy analyses. Skin biopsies were obtained from a deceased juvenile male shark (548 cm total length) stranded in La Paz, Mexico, during February 2018. The results of this study evidenced the basic structure of the dermal denticles in the epidermis of the trunk of the shark, as well as the composition of the connective tissue in the hypodermis. Histological images of the hypodermis showed a high concentration of collagen fibres, formed by a large number of fine and wavy fibres of compact shape and little intercellular substance. 相似文献
4.
Lynnath E. Beckley Geremy Cliff Malcolm J. Smale Leonard J.V. Compagno 《Environmental Biology of Fishes》1997,50(3):343-348
Available information on whale shark strandings around the coast of South Africa during the period 1984–1995 was collated.
Stranded animals ranged in size from 3–11 m TL, most were immature and the sex ratio was even. Aerial observations and sightings
by divers indicate that whale sharks are most abundant in South African waters during the austral summer and autumn months.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
5.
Ramírez-Macías D Shaw K Ward R Galván-Magaña F Vázquez-Juárez R 《Molecular ecology resources》2009,9(3):798-800
In preparation for a study on population structure of the whale shark (Rhincodon typus), nine species-specific polymorphic microsatellite DNA markers were developed. An initial screening of 50 individuals from Holbox Island, Mexico found all nine loci to be polymorphic, with two to 17 alleles observed per locus. Observed and expected heterozygosity per locus ranged from 0.200 to 0.826 and from 0.213 to 0.857, respectively. Neither statistically significant deviations from Hardy-Weinberg expectations nor statistically significant linkage disequilibrium between loci were observed. These microsatellite loci appear suitable for examining population structure, kinship assessment and other applications. 相似文献
6.
Decline of Native Freshwater Fishes in a Mediterranean Watershed on the Iberian Peninsula: A Quantitative Assessment 总被引:2,自引:0,他引:2
Enric Aparicio Maria Josep Vargas Josep Maria Olmo Adolfo de Sostoa 《Environmental Biology of Fishes》2000,59(1):11-19
We examined changes in the distribution of 9 native and 18 introduced freshwater fishes in the south-eastern Pyrenees watershed, Iberian Peninsula, using data from 1996, 1984–1988 and historical information. This region suffers many modifications to its freshwater ecosystems that are linked to human activity in the Mediterranean regions. Fish communities, stream physical habitat and environmental degradation were assessed at 168 sites from 11 basins in 1996. Seven native species (78%) showed decline from previous data, one of which became extirpated in the first half of the 20th century. On the other hand, introduced species are expanding. As a consequence, intact native communities are increasingly rare, declining from presence in 22% of river courses in 1984–1988 to 15% in 1996. The most typical community type is a mixture of native and introduced species occupying 30% of river courses. Stream degradation seems to be the main cause of this process because fish communities differed between degraded streams and streams suffering less impact. A principal component analysis showed that water pollution and modifications to the habitat were the two anthropogenic factors that accounted for most changes in the fish community integrity. Habitat alteration, primarily through construction of dams and water diversions, has fragmented habitats and isolated native fish communities in headwater streams. Current protection measures do not offer effective conservation of threatened species and communities. A global conservation and restoration programme from an ecosystem-based approach is essential to reverse the trend affecting native freshwater fishes in this Mediterranean region. 相似文献
7.
Maeva DEWAS Jan HERR Laurent SCHLEY Christof ANGST Benoît MANET Philippe LANDRY Michel CATUSSE 《Mammal Review》2012,42(2):144-165
- 1 The Eurasian beaver Castor fiber suffered a drastic reduction in both geographical range and population size, due to human persecution, until the end of the 19th century. After the adoption of protection measures, natural expansion and reintroductions led to the recovery of this species over much of its European range.
- 2 We review historical events that led to the recovery of beavers in France, and summarize the status of beavers in various river systems. Beaver establishment in France is a story of overall success: several major river systems are presently occupied, so that the species is no longer at risk in France.
- 3 However, beaver recolonization took place in parallel with increasing human impacts on the environment. In addition to natural limiting factors, anthropogenic factors impeded beaver settlement in many areas. Today, beavers often occupy suboptimal habitats and, as a consequence, come into conflict with human activities. Effective solutions for preventing beaver damage include the restoration of riparian habitats to discourage crop damage and the provision of physical barriers to protect crops.
- 4 Beaver populations reintroduced into France all originate from the relict Rhône population. However, in recent years, beavers from populations in neighbouring countries have been expanding into north‐eastern France. Therefore, our review of beaver origin and distribution in these countries may contribute to the development of appropriate national management strategies and towards important decisions, e.g. the decision to try to keep Rhône beavers genetically isolated, or to allow populations to mix.
- 5 The recently discovered presence of North American beavers Castor canadensis in three countries surrounding France has raised an important issue. This species may out‐compete C. fiber in places where the species come into contact. A programme based on field‐trapping sessions and genetic analyses has recently been initiated in some western countries in order to eradicate this non‐native species.
8.
N. Sekulić S. Marić L. Galambos D. Radošević J. Krpo‐Ćetković 《Journal of fish biology》2013,83(3):659-666
Seventy‐six individuals of the European mudminnow Umbra krameri from two recent populations from Serbia (Bakreni Batar and Lugomir) and one from Bosnia and Herzegovina (Gromi?elj) were analysed for habitat preferences and population structure. The population from Lugomir is a newly recorded population in Serbia. Besides this new record, it is noteworthy that all three studied locations are outside the currently known species distribution range limits. 相似文献
9.
Ana Sequeira Camille Mellin David Rowat Mark G. Meekan Corey J. A. Bradshaw 《Diversity & distributions》2012,18(5):504-518
Aim Predicting distribution patterns of whale sharks (Rhincodon typus, Smith 1828) in the open ocean remains elusive owing to few pelagic records. We developed multivariate distribution models of seasonally variant whale shark distributions derived from tuna purse‐seine fishery data. We tested the hypotheses that whale sharks use a narrow temperature range, are more abundant in productive waters and select sites closer to continents than the open ocean. Location Indian Ocean. Methods We compared a 17‐year time series of observations of whale sharks associated with tuna purse‐seine sets with chlorophyll a concentration and sea surface temperature data extracted from satellite images. Different sets of pseudo‐absences based on random distributions, distance to shark locations and tuna catch were generated to account for spatiotemporal variation in sampling effort and probability of detection. We applied generalized linear, spatial mixed‐effects and Maximum Entropy models to predict seasonal variation in habitat suitability and produced maps of distribution. Results The saturated generalized linear models including bathymetric slope, depth, distance to shore, the quadratic of mean sea surface temperature, sea surface temperature variance and chlorophyll a had the highest relative statistical support, with the highest percent deviance explained when using random pseudo‐absences with fixed effect‐only models and the tuna pseudo‐absences with mixed‐effects models (e.g. 58% and 26% in autumn, respectively). Maximum Entropy results suggested that whale sharks responded mainly to variation in depth, chlorophyll a and temperature in all seasons. Bathymetric slope had only a minor influence on the presence. Main conclusions Whale shark habitat suitability in the Indian Ocean is mainly correlated with spatial variation in sea surface temperature. The relative influence of this predictor provides a basis for predicting habitat suitability in the open ocean, possibly giving insights into the migratory behaviour of the world’s largest fish. Our results also provide a baseline for temperature‐dependent predictions of distributional changes in the future. 相似文献
10.
B. M. Norman J. M. Whitty S. J. Beatty S. D. Reynolds D. L. Morgan 《Journal of fish biology》2017,91(6):1713-1720
Whale sharks Rhincodon typus were monitored via acoustic transmitters at the northern end of Western Australia's Ningaloo Marine Park to establish the extent to which the species inhabits the region beyond the whale‐shark ecotourism industry season, which usually extends from March to August in each year. Despite the vast majority (c. 98%) of photographic submissions of R. typus from Ningaloo Reef being between March and August, acoustic detections from the tagged R. typus at Ningaloo were recorded in all months of the year, but do not preclude the occurrence of extended absences. It is concluded that as a species, R. typus occurs year round at Ningaloo, where it generally remains in close proximity to the reef edge, but that some individuals move outside of the detection range of the array for extended periods. 相似文献
11.
12.
Gerald A. Cole 《Hydrobiologia》1981,76(1-2):27-32
A new species of the Amphipoda (Gammarus desperatus) is described from North Spring in Roswell, Chaves County, New Mexico. Apparently this is the same species reported erroneously as G. fasciatus Say from nearby Lander Springbrook by Noel (1954).Supported in part by NSF Grants GB-2461 and GB-6477X to W. L. MinckleySupported in part by NSF Grants GB-2461 and GB-6477X to W. L. Minckley 相似文献
13.
Juana López‐Martínez Marcos Porchas‐Quijada Francisco J. Álvarez‐Tello Marco A. Porchas‐Cornejo 《Journal of fish biology》2018,93(2):401-404
This study describes the first record of the whale shark Rhincodon typus association with the cannonball jellyfish Stomolophus meleagris in the Gulf of California, Mexico. Whale sharks were observed swimming and feeding among swarms of jellyfish, suggesting competition and predatory behaviour given the overlap in food preferences between both species. This finding is relevant because of the species‐wide distribution and the importance of these interactions, which should be considered in conservation strategies of R. typus and management of cannonball jellyfish fisheries. 相似文献
14.
To investigate distribution, habitat characteristics, and current conservation status of the endangered endemic species, rapid small gudgeon Microphysogobio rapidus (Cyprinidae), we surveyed a total of 79 sites from the historic records (20 sites) plus additional sites (59 sites) with good habitat conditions, analyzed their sites, and compared them with historic recorded sites to reveal the factors of extinction threats and causes. We found only eight out of 79 sites in the Nam River areas. The habitats were greatly reduced and restricted compared with the historic sites, which mainly cause from habitat modification, such as various types of river renovations at the main stream and tributary streams of the Nakdong River. The present habitats are higher water temperature and more number of fish species than the absent ones, but conductivity, total nitrogen, and number of weir are lower. In addition, the present sites are lower low velocity at pool and higher mean substrate at pool. From this study, we suggest that maintaining good water quality and preventing anthropogenic impacts greatly aid conservation of the M. rapidus in South Korea. 相似文献
15.
C. W. Speed †‡ M. G. Meekan D. Rowat § S. J. Pierce A. D. Marshall C. J. A. Bradshaw †¶ 《Journal of fish biology》2008,72(6):1488-1503
This study recorded the scarring rate and severity for whale sharks Rhincodon typus from three Indian Ocean aggregations (Australia, Seychelles and Mozambique), and examined whether scarring (mostly attributed to boat strikes and predator attacks) influences apparent survival rates using photo‐identification libraries. Identifications were based on spot‐and‐stripe patterns that are unique to individual whale sharks. Scarring was most prevalent in the Seychelles aggregation (67% of individuals). Predator bites were the most frequent source of scarring (aside from minor nicks and abrasions) and 27% of individuals had scars consistent with predator attacks. A similar proportion of whale sharks had blunt trauma, laceration and amputation scars, the majority of which appeared to be caused by ship collisions. Predator bites were more common (44% of individuals) and scars from ship collisions were less common at Ningaloo Reef than at the other two locations (probability of among‐site differences occurring randomly = 0·0007 based on a randomized multinomial contingency analysis). In all aggregations, scars occurred most often on the caudal fin, which may result from the fin being the body part closest to the surface when boats pass over, or they may provide a large target for predator attack. No evidence was found for an effect of scarring on apparent survival (φ; mean ±s .e .) for the Ningaloo (not scarred φ= 0·858 ± 0·033; scarred φ= 0·929 ± 0·033) or Seychelles populations (not scarred φ= 0·502 ± 0·060; scarred φ= 0·538 ± 0·070). The lower apparent survival of the Seychelles population may be attributed to a high number of transient whale sharks in this aggregation that might bias estimates. This study indicates that while scarring from natural predators and smaller vessels appears to be unrelated to whale shark survival, the effect of deaths related to ship strike need to be quantified to assist in future management of this species. 相似文献
16.
Aristide K. Takoukam Dylan G. E. Gomes Mark V. Hoyer Lucy W. KeithDiagne Robert K. Bonde Ruth FrancisFloyd 《Ecology and evolution》2021,11(21):15212
The present study aims at investigating the past and current trophic status of Lake Ossa and evaluating its potential impact on African manatee health. Lake Ossa is known as a refuge for the threatened African manatees in Cameroon. Little information exists on the water quality and health of the ecosystem as reflected by its chemical and biological characteristics. Aquatic biotic and abiotic parameters including water clarity, nitrogen, phosphorous, and chlorophyll concentrations were measured monthly during four months at each of 18 water sampling stations evenly distributed across the lake. These parameters were then compared with historical values obtained from the literature to examine the dynamic trophic state of Lake Ossa. Results indicate that Lake Ossa''s trophic state parameters doubled in only three decades (from 1985 to 2016), moving from a mesotrophic to a eutrophic state. The decreasing nutrient gradient moving from the mouth of the lake (in the south) to the north indicates that the flow of the adjacent Sanaga River is the primary source of nutrient input. Further analysis suggests that the poor transparency of the lake is not associated with chlorophyll concentrations but rather with the suspended sediments brought‐in by the Sanaga River. Consequently, our model demonstrated that despite nutrient enrichment, less than 5% of the lake bottom surface sustained submerged aquatic vegetation. Thus, shoreline emergent vegetation is the primary food available for the local manatee population. During the dry season, water recedes drastically and disconnects from the dominant shoreline emergent vegetation, decreasing accessibility for manatees. The current study revealed major environmental concerns (eutrophication and sedimentation) that may negatively impact habitat quality for manatees. The information from the results will be key for the development of the management plan of the lake and its manatee population. Efficient land use and water management across the entire watershed may be necessary to mitigate such issues. 相似文献
17.
The distribution of golden langurs (Trachypithecus geei) is limited to a small area of western Assam in northeast India and Bhutan between the rivers Manas in the east, Sankosh in the west, and Brahmaputra in the south. It is one of the most seriously endangered primate species of India. A comparative analysis based on satellite images taken in 1988 and 1998 showed a 50% loss of original golden langur habitat. Data on population dynamics collected using line transect and total count methods are presented here. An average group size of 8.2 (range 4.0-22.0) individuals was recorded. A total of 1,064 individuals were counted living in 130 groups. The sex ratio was 1.9-2.5 adult females for each adult male. A low percentage of juveniles and infants suggests that the population is unstable. Most of the groups had only one adult male. Small group sizes, isolated distribution, proportionately few infants and juveniles, and degrading habitat are all causes of concern. Demographic trends indicate a decline in the golden langur population. 相似文献
18.
ANDREW P. VOVIDES NISAO OGATA VICTORIA SOSA ESPERANZA PEÑA-GARCÍA 《Botanical journal of the Linnean Society. Linnean Society of London》1997,125(3):201-210
Observations indicate that natural regeneration in the field of the cycad Microcycas calocoma (Miq.) A.DC. is extremely low, and has been so since early this century. It appears that populations of its insect pollinator are practically extinct, but some pollinator activity appears to be present in the largest population of Microcycas. Recommendations for identification and captive breeding of die pollinator are suggested as a complementary conservation strategy to a Microcycas propagation programme already established at the Cuban National Botanical Garden. 相似文献
19.
The present paper reports a protocol for minimum growth conservation of Drosophyllum lusitanicum (L.) Link. in vitro. Double-node cuttings were maintained for 4, 8 and 12 months at 5 or 25 °C in the dark. The effects of sucrose either alone
at 5, 20, 30, 40 and 60 g dm−3 or at 20, 40 and 60 g dm−3 in combination with 20 g dm−3 mannitol, on survival and post-storage shoot multiplication efficiency were investigated. The cultures could effectively
be conserved under minimum growth at 5 °C for 8 months on Murashige and Skoog’s medium supplemented with 60 g dm−3 sucrose, 20 g dm−3 mannitol and 0.91 μM zeatin. Following extended conservation, the cultures could be successfully regenerated into new shoots,
and they were morphologically similar to those of non-stored controls. 相似文献
20.
该文对《国家重点保护野生植物名录》(2021年)及《浙江省重点保护野生植物名录》(2023年,待发布)中在浙江分布的珍稀濒危植物的物种组成特征、地理分布格局进行了分析,运用濒危系数、遗传价值系数和物种价值系数定量分析浙江全省珍稀濒危植物优先保护顺序.结果表明:(1)浙江分布的珍稀濒危植物共101科229属333种,其中种子植物共311种,占比高达93.39%,以兰科(Orchidaceae)植物种类最为丰富,有32属56种.(2)从区域水平分布看,浙江的珍稀濒危植物密度较高地区主要集中在浙西北天目山区(147种)、浙西南洞宫山区(164种),浙北平原分布的珍稀濒危植物种类少.(3)从垂直分布看,随着海拔的升高,珍稀濒危植物的种类先增加后减少,呈现倒\"U\"形的分布趋势,在海拔601~800 m范围种类最多(60科113属144种).(4)根据优先保护定量分析,属于优先保护I级82种(24.62%)、Ⅱ级144种(43.24%)、Ⅲ级85种(25.53%)、IV级22种(6.61%).浙江珍稀濒危植物种类丰富,通过分析直观地反映了省内各珍稀濒危植物保护的迫切程度,各物种现状与分析结果大致相符,需加强监测并及时对优先保护顺序进行动态调整. 相似文献