Freshwater fish at risk or extinct in México

The Mexican freshwater fish that are at risk orextinct are listed by family, state,basin/region, and causes of risk. Of the 506known species, 168 are at some level of risk,and 25 are believed to be extinct. States withthe most reports are: Chihuahua (46); Coahuila(35); Nuevo León (20); Sonora (19); Durango(18); and Tamaulipas (15). With the exceptionof Sonora, these states are largely located inthe Río Bravo region, and are all arid orsemiarid. Most extinctions have occurred inNuevo León (8) and Coahuila (7). The maincauses of risk reported are: habitat reductionor alteration (86); water depletion (83);presence of exotics (76); small or decliningpopulation (73); and small habitat (57). Allof which result in very local endemism. Thesecauses of risk develop easily when thedistribution is small. The critical factor isaridity, which is associated withdesertization. Water conflicts were to beexpected, and the result is resource nonsustainability.     

赣江鱼类物种更新名录

赣江是长江的主要支流之一, 淡水鱼类多样性极其丰富, 但是目前对于该河流的鱼类多样性还未有充分的了解。本研究于2016年9月至2017年8月对赣江鱼类进行了实地调查, 结合历史文献资料并参考最新的分类学成果, 更新了赣江淡水鱼类名录。结果表明, 赣江共有淡水鱼类180种, 隶属于12目31科93属。其中, 土著鱼类174种, 外来鱼类6种。赣江鱼类以鲤形目为主; 鲤科种类最多, 其次是鲿科。更新的物种名录中, 包含23个新记录土著种, 其中有5个未被描述的新种; 有36个历史资料记载的种类被剔除出物种名录; 25个物种发生了分类地位的变更。此外, 本次调查有28种鱼类未采集到, 说明这些鱼类的种群数量正在急剧下降, 而这些鱼类分别属于洄游性、流水性和产漂流性卵等独特生态类型, 说明赣江鱼类多样性受到了严重的人为干扰。本研究所给出的赣江鱼类的更新物种名录, 可为今后的赣江鱼类多样性保护提供理论基础。     

Anthropogenically induced fish diversity reduction in Lake Valencia Basin, Venezuela

Lake Valencia in north central Venezuela, one of the largest natural inland bodies of water north of the equator, is undergoing a very rapid deterioration process as a consequence of anthropogenically induced changes. At the Ichthyology Laboratory of Instituto de Zoología Tropical, we have been studying the fishes of the northern tributaries of Lake Valencia since the early 1990's. As a result of collections made in seven northern tributaries of the basin from 1990 to 1993, we have identified 15 species of fish in 6 families. Comparison of our results with those of several authors who have collected in the area since the 1920's, indicate a 59.5%decrease in fish diversity in a 30 year span. The Lake Valencia region has undergone a rapid, considerable industrial and urban growth in recent years. This rapid increment in population size has produced a vast contamination of the lake and its tributaries by activities associated with a growing population. This study will contribute to the understanding of the biodiversity of the region by recording changes in the characteristics of the ichthyofauna in a highly modified environment.     

Dedication to Dr. Robert “Bob” Rush Miller

Reviews in Fish Biology and Fisheries -     

淡水鱼类功能多样性及其研究方法

目前,群落功能多样性备受生态学界关注,被认为是能解决生态问题的一种重要途径。我国对于群落功能多样性主要集中在植物群落和微生物群落,而在鱼类群落方面的研究几乎是空白。我国鱼类资源正面临着严重威胁,包括水坝建设导致的鱼类通道受阻、水库形成造成鱼类产卵场功能消失、过度捕捞、水质恶化和富营养化加重、外来种入侵等因素,导致渔业资源急剧衰退,水生生态系统功能下降。以淡水鱼类群落为例,对鱼类功能多样性的数据获取及处理分析与评价、测定指标及计算方法与研究难点等进行综述,以期为鱼类资源保护提供新的理论依据和切入点。     

Stress in Yucatan spider monkeys: effects of environmental conditions on fecal cortisol levels in wild and captive populations

In the Yucatán Peninsula, spider monkeys Ateles geoffroyi yucatanensis are generally found in two contrasting conditions: large tracts of conserved forest or small fragments surrounded by human populations. In the present study, we analyzed fecal cortisol levels of spider monkeys to investigate whether environmental conditions have an influence on stress; specifically, we compared fecal cortisol across individuals living in conserved forests, fragmented forests and captive conditions (zoos and pets). Radioimmunoanalysis of fecal samples from 121 individuals indicated significant differences in mean cortisol for A. g. yucatanensis based on habitat type, with the lowest levels found in the conserved forest condition. The higher cortisol levels in both fragmented forest populations and in captive individuals may be the result of metabolic and behavioral stress. The mean male fecal cortisol concentration was significantly higher than that of females, and the fecal cortisol concentration was higher in the dry season compared with the wet season in a conserved habitat. Therefore, we emphasize the importance of considering sex and seasonality when monitoring fecal cortisol concentrations of spider monkeys, and more generally of frugivores, as they face a seasonal variation in food availability. Finally, our results suggest that forest fragmentation may create long-term stressors for spider monkeys, affecting the viability of populations living under such conditions.     

Is Echeveria gibbiflora (Crassulaceae) fecundity limited by pollen availability? An experimental study

1. An experimental approach, manually pollinating all the flowers of individual plants, was used to measure the effect of pollen limitation on female fecundity of the hummingbird-pollinated perennial shrub Echeveria gibbiflora in the ecological preserve of Pedregal de San Angel around México City, México. Eleven randomly selected plants were manually over-pollinated in all their flowers and another 11 were left to be freely visited by natural pollinators.
2. Manually pollinated plants produced significantly more fruit and seeds than control plants (1·38 and 1·74 times, respectively). There was no change in average mass of fruits.
3. Considering individual fruit production per plant sampled three times in one season, decreases in fruit mass and average seeds per fruit were observed within the same reproductive season for both treatments. For the manually pollinated plants, from the start to the end of the reproductive season, seed set decreased 55·9%; while in control plants seed set decreased 33·4% in the same period. For both treatments, average fruit mass decreased 26%.
4. Vegetative growth was not significantly different between control and experimental plants but hand-pollinated plants showed a smaller reproduction probability for the following year.
5. It is concluded that female fecundity in E. gibbiflora is limited by pollen early in the reproductive season and by resources in the middle and the end of the season.     

Zoogeography and biodiversity of the freshwater fishes of Southeast Asia

The ichthyofauna of the freshwater system of Southeast Asia is extremely diverse. A recent estimate of about 1000 species is probably an understatement. More than 10 new species are being added to the list annually. The distribution pattern of the Southeast Asian freshwater fishes can be divided into five zoogeographic regions. The first one is the Salween basin in Burma, with fishes mainly of the Indian subcontinent origin such as Amblypharyngodon atkinsoni, Bangana almorae and Brachydanio jayarami. The second zoogeographic area is the Mekong, Chao Phraya and Mae Khlong drainages which harbour fishes typical of the mainland of Southeast Asia such as Acanthorhodeus deignani, Barbichthys nitidus and Cirrhinus siamensis. The Malay Peninsula is the third region whose species composition is heavily influenced by the Siamese (such as Homaloptera smithi, Tuberoschistura baenzigeri and Botia beauforti) and Indonesian (such as Botia hymenophysa, Luciocephalus pulcher and Parosphromenus deissneri) elements. The islands of Sumatra, Borneo and Java are the fourth zoogeographic area of fish distribution. These islands show a high degree of endemism, especially in fishes of the family Belontiidae. Finally, the freshwater system of the Philippines is the last zoogeographic region of Southeast Asia. The area is characterized by the presence of closely related species of the cyprinids especially in Lake Lanao. Currently, high diversity of these freshwater fishes is being threatened by land development, such as deforestation, road construction and land expansion for plantation. Recent studies in the Gombak River basin show the extermination of 41 per cent of native fish species from 1969 to 1990. This is probably due to the construction of highways, logging, as well as land clearing for agriculture.