Ecology of the River Dolphin (Platanista gangetica) in the Upper Brahmaputra

There are nearly 200 species of aquatic vertebrates, almost exclusively fishes, in the Brahmaputra River System. This faunal composition includes not only a wide variety of food-fishes, but also about 50 varieties of aquarium fishes. The most spectacular animal in the Brahmaputra is undoubtedly the river dolphin, Platanista gangetica. The population of many species, particularly of the dolphin, is in steady decline. River dolphins, mostly juveniles, often entangle themselves in gill and drift nets, while feeding on trapped fishes. Proper implementation of Indian Fisheries Act, especially a total ban on destructive nets and on killing of brooders and juveniles by explosives and poisoning should be strictly implemented. Poor communication facilities in remote riverbank areas and lack of funds are two important reasons for the slow progress of the conservation of river dolphin and this endangered species is now on the verge of extinction. The anthropogenic activities and their impact on the habitat of river dolphin are discussed.     

Diel changes in the movement patterns of Ganges River dolphins monitored using stationed stereo acoustic data loggers

We monitored the underwater movements of Ganges River dolphins using stationed stereo acoustic data loggers. We estimated these movements using changes in the relative angle of the sound source direction (trajectory). Of the total acoustic recordings (66 h), 26.2% contained trajectories of dolphins, and 78.6% of these trajectories involved single animals, suggesting that dolphins tended to swim alone and were localized near the monitoring station. The observed trajectories were categorized as follows: staying type characterized by small changes in the sound source direction, moving type A (moving in the same direction), and moving type B (moving up and down the stream during recording). The average interpulse intervals of sounds in moving types A and B were significantly shorter than that of the staying type, suggesting that dolphins produce the former types of trajectories to echolocate across shorter distances during movement. The frequency of occurrence of moving type A increased during the night, whereas that of type B increased in the late afternoon and that of the staying type increased during the daytime. These results indicate that dolphins moving at night tended to use short‐range echolocation, whereas during the day, they remained in relatively small areas and used long‐range sonar.     

Population status and habitat occupancy of endangered river dolphins in the Karnali River system of Nepal during low water season

Ganges river dolphin abundance has undergone a predominant decline across its range since monitoring began. In Nepal, disappearance from some of the rivers it once used has already occurred. Today this species can only be found in three river systems in Nepal, the Karnali, Sapta Koshi, and Narayani, but numbers are low in these locations. To determine the abundance of dolphins remaining in the Karnali system (which includes the Karnali, Geruwa, and Mohana), and factors affecting dolphin habitat use, we conducted surveys where we recorded dolphin presence. Dolphins within this river system were sighted only in the Karnali and an abundance estimate of 5.04 ± 0.753 SE was calculated. This pattern of ranging differed from that previously reported (from previous sightings only in the Geruwa to current sightings only in the Karnali). River depth likely contributed to the presence or absence of dolphins. Shifts in available habitat between the Geruwa and Karnali have resulted from changes in the course of the main stream Karnali following construction of the Chisapani irrigation intake. Because of the low numbers of dolphins reported, there is great concern that loss of this species in Nepal is likely in the near future.     

漩涡模型及其在白暨豚种群管理中的应用

漩涡模型作为一种用于野生动物种群生存力分析的计算机模拟工具,已在濒危物种的保护和管理方面得到了广泛的应用。本文介绍了漩涡模型的产生和特征,同时使用这一模型完成了长江中白暨豚（Ｌｉｐｏｔｅｓｖｅｘｉｌｌｉｆｅｒ）种群生存力分析。模拟的结果表明,在未来１００年内,白暨豚在高、中死亡率的条件下,种群灭绝概率分别为１．０和０．５左右。但是,在死亡率低和极低的条件下,白暨豚的灭绝过程可能持续１００年以上,或永远也不会灭绝。开始种群大小对白暨豚的平均灭绝时间有一定的影响,但对种群生长率（ｒ）却没有影响。在高、中、和低死亡率条件下,白暨豚种群生长率分别为－０．０７、－０．０４和－０．０２。     

Population structure of bottlenose dolphins (Tursiops aduncus) impacted by bycatch along the east coast of South Africa

Shark nets placed along the coast of KwaZulu-Natal to protect bathers from shark attacks result in an incidental by-catch of bottlenose dolphins (Tursiops aduncus) at twice the level suggested by the IWC as the maximum sustainable capture rate for a cetacean population. Observational data reported the presence of at least two putative populations, one a seasonal migratory population moving into the KwaZulu-Natal area following the movement of sardines, and the other a coastal, apparently resident population. Some observations indicated possible further subdivision of the coastal population. We analysed nine microsatellite loci and 599 bps of the mitochondrial control region and found small but significant differentiation within the putative coastal population (F_ST = 0.022) separated north and south of Ifafa. There was weaker evidence for differentiation between the southern coastal and migratory populations (F_ST = 0.012). Genetic diversity was low for both types of markers in all populations, and the pattern of mtDNA variation was consistent with a founder event. Considering the high capture rate, the low level of genetic diversity, and the evidence of possible population differentiation along the coast, we suggest that particular care should be taken in managing the take from shark nets especially in the north coastal area of KZN where the population showed the higher degree of differentiation.     

Development and evaluation of methods to assess populations of black flies (Diptera: Simuliidae) at nests of the endangered whooping crane (Grus americana)

Hematophagous insects can negatively affect the reproductive success of their vertebrate hosts. To determine the influence of hematophagous insects on endangered vertebrates requires specially designed programs that minimize disturbance to the hosts and address problems associated with their small populations. We developed and evaluated a surveillance program for black flies potentially affecting a population of whooping cranes (Grus americana) introduced to central Wisconsin, U.S.A. In one of the few studies to survey host‐seeking female black flies and their immature stages concurrently, we processed nearly 346,000 specimens and documented 26 species, of which only two, Simulium annulus and Simulium johannseni, were attracted to nesting whooping cranes. Attempts to assess black fly populations with artificial nests and real crane eggs were unsuccessful. Carbon‐dioxide traps performed well in describing black fly taxa on the landscape. However, the number of black flies at whooping crane nests was consistently higher than the number captured in carbon‐dioxide traps. The carbon‐dioxide traps poorly described the presence/absence, population fluctuations, and periodicity of black flies at whooping crane nests. The weak performance of the carbon‐dioxide traps might have resulted from microhabitat differences between trap locations and nests or from Simulium annulus and Simulium johannseni using sensory cues in addition to carbon dioxide to find hosts. Choice of trapping techniques, therefore, depends on the information required for the particular study objectives.     

Living between rapids: genetic structure and hybridization in botos (Cetacea: Iniidae: Inia spp.) of the Madeira River,Brazil

Until the recent construction of hydroelectric dams, a series of 18 rapids divided the upper and lower Madeira River, and these rapids were thought to separate two species of Amazonian freshwater dolphins (boto): Inia boliviensis (above) and I. geoffrensis (below). Some reports and articles, however, mention the occurrence of botos within the rapids region and that they occasionally cross the rapids, but without mentioning the species concerned. Based on our previous studies, it is likely that I. boliviensis occurs in the region of the rapids. To test this supposition, we sampled 18 individuals from this region, and collected mitochondrial (control region, cytochrome b and cytochrome oxidase I) and nuclear (10 microsatellite loci) DNA data, in order to test if there is connectivity between the dolphins that were found within the rapids region and dolphins collected upstream and downstream of the rapids, and investigate population structuring between these localities. All animals in our study were molecularly identified using three mitochondrial markers as belonging to the species I. boliviensis. Animals upstream of the Teotônio waterfall, the main and highest waterfall of the region, had nuclear genome of I. boliviensis, while most dolphins downstream of the waterfall had nuclear genome of I. geoffrensis. Inia boliviensis collected in the rapids region above the Teotônio waterfall belong to a management unit (MU) distinct from the I. boliviensis MU occupying Bolivian rivers. Downstream of Teotônio waterfall most dolphins are I. boliviensis/geoffrensis hybrids, with remaining individuals being migrant I. boliviensis. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 114 , 764–777.     

珠江西部河口中华白海豚分布与环境因子的关系

2012年采用船基截线法在珠江口西部河口进行了中华白海豚(Sousa chinensis)调查,并同步对渔业资源和渔业环境要素进行了现场采样测定,以分析该水域中华白海豚空间分布与环境因子的关系。利用广义加性模型(GAM)分析了中华白海豚目击率与海况、水深、底层水温、盐度、pH值、溶解氧、游泳生物密度、捕食种密度和离岸距离等的关系。GAM模型对中华白海豚目击率分布的总偏差解释率为64.7%,游泳生物密度、水深、捕食种密度、离岸距离、底层水温等对中华白海豚的栖息地选择有较大的影响。模型分析结果显示:中华白海豚的活动与捕食种密度密切相关,但当捕食种密度达到一定程度时对海豚目击率的影响减弱,推测可能与食物较多时海豚逗留捕食时间减少有关;中华白海豚较为喜欢的水深在10m左右,这一模拟结果与以前的统计结果基本一致;中华白海豚对底层水温似乎有一定的选择性,当底层水温大于19.5℃时目击率明显下降,推测底层水温可能影响了捕食种鱼类的分布,进而影响海豚的活动;离岸距离3km范围内是中华白海豚较为喜欢的水域,因此对这一水域范围应给予重点保护管理。     

Restoring the endangered oyster mussel (Epioblasma capsaeformis) to the upper Clinch River,Virginia: an evaluation of population restoration techniques

From 2005 to 2011, the federally endangered freshwater mussel Epioblasma capsaeformis (oyster mussel) was reintroduced at three sites in the upper Clinch River, Virginia, using four release techniques. These release techniques were (1) translocation of adults (site 1, n = 1418), (2) release of laboratory‐propagated sub‐adults (site 1, n = 2851), (3) release of 8‐week‐old laboratory‐propagated juveniles (site 2, n = 9501), and (4) release of artificially infested host fishes (site 3, n = 1116 host fishes). These restoration efforts provided a unique research opportunity to compare the effectiveness of techniques used to reestablish populations of extirpated and declining species. We evaluated the relative success of these four population restoration approaches via monitoring at each release site (2011–2012) using systematic 0.25‐m² quadrat sampling to estimate abundance and post‐release survival. Abundances of translocated adult and laboratory‐propagated sub‐adult E. capsaeformis at site 1 ranged 577–645 and 1678–1700 individuals, respectively, signifying successful settlement and high post‐release survival. Two untagged individuals (29.1 and 27.3 mm) were observed, indicating that recruitment is occurring at site 1. No E. capsaeformis were found at sites where 8‐week‐old laboratory‐propagated juveniles (site 2) and artificially infested host fishes (site 3) were released. Our results indicate that translocations of adults and releases of laboratory‐propagated sub‐adults were the most effective population restoration techniques for E. capsaeformis. We recommend that restoration efforts focus on the release of larger (>20 mm) individuals to accelerate augmenting and reintroducing populations and increase the probability for recovery of imperiled mussels.     

Activity budget of inshore Indo‐Pacific bottlenose dolphins (Tursiops aduncus): A critical evaluation of methods and comparison among other populations

Activity budgets are widely used to compare behavior patterns but sampling methods vary, rendering comparisons difficult. The two main methods used are instantaneous and continuous sampling. Their comparability was examined by applying them to data obtained from bottlenose dolphins in the Port River estuary, South Australia. They gave comparable results for activity budgets, but instantaneous sampling did not detect most of the behavioral events. Individual differences in behavior and/or follow duration influenced results. Variability in activity definitions and categories among studies makes comparative analysis difficult. Comparison of the Port River dolphin's activity budget with other inshore populations indicated the former spent more time feeding and resting, and less time traveling. The greater feeding time seemed to be due to small prey size rather than reduced abundance or unpredictable distribution. The reduced traveling time, possibly the result of low predation pressure and/or evenly distributed prey, gave them more time to rest. They traveled mostly at 2.5 kn or less, consistent with studies from other shallow areas. Most feeding was individual, probably on demersal species. Surface feeding incorporated physical barriers rather than cooperative behavior. Activity durations ranged from 2 s to 2.9 h, with mean durations varying from 7.8 to 22.9 min.     

Diet of an endangered Neotropical catfish (Kalyptodoras bahiensis) from the Paraguaçu River,Bahia, Brazil

ABSTRACT

The present study investigates the diet composition and the feeding strategy of Kalyptodoras bahiensis by verifying variations during the hydrological cycle and between males and females. Samples were collected during the periods of rain and drought using various fishing gears adapted to each microhabitat. In laboratory, the fishes were weighed and measured. An abdominal incision was made to observe the gonads for sex determination and the stomach was removed for identification and quantification of food items. The importance of each item in the diet was calculated using the Feeding Index. Amundsen graphic analysis was used to define the feeding strategy. Kalyptodoras bahiensis was classified as an omnivorous species with an invertivorous tendency. The species presented a generalist feeding strategy and many individuals fed on Melanoides tuberculatus, an exotic mollusk that has spread to Brazilian rivers, causing damages to the native community. The high amount and frequency of M. tuberculatus in the diet of K. bahiensis suggest that the species may have a predatory impact on the local population of this mollusk. However, further studies are needed to better understand the interaction between K. bahiensis and M. tuberculatus.     

A long‐term study of bottlenose dolphins (Tursiops aduncus) in an Australian industrial estuary: Increased sightings associated with environmental improvements

Delphinids are long‐lived, have delayed maturity and low reproductive rates which necessitate long‐term monitoring programs to detect changes in abundance. Between 1990 and 2013, an observational study of bottlenose dolphins (Tursiops aduncus) was conducted in the Port River estuary (Adelaide, Australia). The estuary has received pollution from industry, sewage plants and storm water. In recent years, pollution entering the system has reduced and the establishment of the Adelaide Dolphin Sanctuary (ADS) increased dolphin protection from harassment and deliberate attacks. Nevertheless, the estuary remains a busy port. Over a 24 yr period, we conducted boat‐based surveys (n = 735) for dolphin groups (n = 3,634) along a predetermined route in the Inner and Outer Estuary of Adelaide's Port River estuary. It is our conjecture that major infrastructure changes and pollution abatement have yielded a more favorable marine environment for dolphins, resulting in an estimated 6% annual increase in sightings, from a near absence of sightings in the 1980s. Increased dolphin numbers were likely the result of improved water quality, augmented by surveillance and education arising from the proclamation of the ADS. This study highlights the importance of long‐term monitoring and has implications for dolphin conservation in heavily impacted urban areas and their protection via protected areas.     

First record of intraspecific cleaning behavior by the threatened Leuciscidae Squalius alburnoides (Steindachner, 1866) at the Guadiana River basin (Portugal)

Squalius alburnoides (Steindachner, 1866) is an endemic threatened species from the Iberian Peninsula. Here, we report the first observations of intraspecific cleaning behavior in isolated summer pools in the Guadiana River Basin (Portugal). We found that focal S. alburnoides solicited cleaning by adopting an immobile tail-stand position known as “posing,” which immediately signaled a response to a few conspecifics that approached and inspect them. Our study expands the list of cleanerfish species in freshwaters, giving emphasis to the importance of mutual positive behavior within an endangered species, particularly when facing seasonal disturbance.     

Potential distribution of the invasive freshwater dinoflagellate Ceratium furcoides (Levander) Langhans (Dinophyta) in South America

Dinoflagellates of the genus Ceratium are predominantly found in marine environments, with a few species in inland waters. Over the last decades, the freshwater species Ceratium hirundinella and Ceratium furcoides have colonized and invaded several South American basins. The purpose of this study was to create a distribution model for the invasive dinoflagellate C. furcoides in South America in order to further investigate the basins at potential risk, as well as the environmental conditions that influence its expansion. This species is known to develop blooms due to its mobility, resistance to sedimentation, and optimized use of resources. Although nontoxic, blooms of the species cause many problems to both the natural ecosystems and water users. Potential distribution was predicted by using a maximum entropy algorithm (MaxEnt). Model was run with 101 occurrences obtained from the scientific literature, and climatic, hydrological and topographic variables. The developed model had a very good performance for the study area. The most susceptible areas identified were mainly concentrated in the basins between southeastern Brazil and northeastern Argentina. Besides already affected regions, new potentially suitable areas were identified in temperate regions of South America. The information generated here will be useful for authorities responsible for water and watershed management to monitor the spread of this species and address problems related to its establishment in new environments.     

Squalius semae,a new species of chub from the Euphrates River,Eastern Anatolia (Teleostei: Cyprinidae)

In a study of the fishes of the Euphrates River (Persian Gulf basin) three species of Squalius belonging to the cephalus-group were found: The Tohma population was identified as S. seyhanensis and the Merzimen and Hilvan populations as S. berak. The comparison of 28 metric and 5 meristic parameters and morphological characters showed that the populations of the northern Euphrates River drainages are distinct and belong to a hitherto unnamed species. We describe it here as Squalius semae sp. n.

http://www.zoobank.org/urn:lsid:zoobank.org:pub:D195B69C-C6CB-4DEB-B85D-5B695F917CE5     

Habitat persistence for sedentary organisms in managed rivers: the case for the federally endangered dwarf wedgemussel (Alasmidonta heterodon) in the Delaware River

1. To manage the environmental flow requirements of sedentary taxa, such as mussels and aquatic insects with fixed retreats, we need a measure of habitat availability over a variety of flows (i.e. a measure of persistent habitat). Habitat suitability measures in current environmental flow assessments are measured on a ‘flow by flow’ basis and thus are not appropriate for these taxa. Here, we present a novel measure of persistent habitat suitability for the dwarf wedgemussel (Alasmidonta heterodon), listed as federally endangered in the U.S.A., in three reaches of the Delaware River. 2. We used a two‐dimensional hydrodynamic model to quantify suitable habitat over a range of flows based on modelled depth, velocity, Froude number, shear velocity and shear stress at three scales (individual mussel, mussel bed and reach). Baseline potentially persistent habitat was quantified as the sum of pixels that met all thresholds identified for these variables for flows ≥40 m³ s^?1, and we calculated the loss of persistently suitable habitat by sequentially summing suitable habitat estimates at lower flows. We estimated the proportion of mussel beds exposed at each flow and the amount of change in the size of the mussel bed for one reach. 3. For two reaches, mussel beds occupied areas with lower velocity, shear velocity, shear stress and Froude number than the reach average at all flows. In the third reach, this was true only at higher flows. Together, these results indicate that beds were possible refuge areas from the effects of these hydrological parameters. Two reaches showed an increase in the amount of exposed mussel beds with decreasing flow. 4. Baseline potentially persistent habitat was less than half the areal extent of potentially suitable habitat, and it decreased with decreasing flow. Actually identified beds and modelled persistent habitat showed good spatial overlap, but identified beds occupied only a portion of the total modelled persistent habitat, indicating either that additional suitable habitat is available or the need to improve habitat criteria. At one site, persistent beds (beds where mussels were routinely collected) were located at sites with stable substratum, whereas marginal beds (beds where mussels were infrequently collected or that were lost following a large flood event) were located in scoured areas. 5. Taken together, these model results support a multifaceted approach, which incorporates the effects of low and high flow stressors, to quantify habitat suitability for mussels and other sedentary taxa. Models of persistent habitat can provide a more holistic environmental flow assessment of rivers.     

Comparative analysis of the phytoplankton of fifteen lowland fluvial systems of the River Plate Basin (Argentina)

The phytoplankton of fifteen lowland courses of the River Plate Basin is compared and characterized by means of multivariate analyses.The cluster analysis performed with the more abundant species of each fluvial system reveals three main groups. Rivers with a high discharge and a large floodplain are grouped on the basis of the dominance of several Aulacoseira species. An eutrophic flora typified by Cyclotella meneghiniana, Synedra ulna and several green algae occurs in the smaller rivers with high conductivity, low transparency and important discharge variations. A third group comprises the Uruguay River and its tributaries, characterized by the presence of several pennatae diatoms and flagellates: Amphipleura pellucida, Surirella tenera, Terpsinoe musica, Navicula cuspidata, Eudorina elegans, Pandorina morum and Peridinium gatunense.The Principal Component Analysis based on a data matrix of physical, chemical and hydrological parameters revealed similar results. The ordination according to the first two components reflects the geographic location of these systems in the River Plate Basin, responding to a decreasing gradient of conductivity, pH and solids and an increasing minimum temperature. The rivers were ordinated by means of a Correspondence Analysis based on the main algal groups.     

Distribution and microhabitats of native and non-native gammarids (Amphipoda, Crustacea) in Brittany, with particular reference to the endangered endemic sub-species Gammarus duebeni celticus

Aim  To assess temporal changes in gammarid distribution in Brittany and microhabitat-use overlap between the endangered endemic Gammarus duebeni celticus Stock & Pinkster, 1970 , the expanding natives G. pulex (Linnaeus, 1758) and Echinogammarus berilloni (Catta, 1878), and the introduced G. tigrinus Sexton, 1939.
Location  Brittany and adjacent regions in western France.
Methods  The spatial and temporal patterns in distribution of gammarids at the scale of Brittany were studied using 351 sites. Longitudinal distributions (from the source to the estuary of the river) and microhabitat-use (substratum type and water velocity) were also considered in selected rivers.
Results  At the regional scale, all species occurred together less often than expected statistically, with significant deviations from expected for G. pulex vs. both G. duebeni celticus and G. tigrinus , and for E. berilloni vs. both G. duebeni celticus and G. tigrinus . However, at the microhabitat scale, E. berilloni occurred significantly more often than expected with the endemic G. duebeni celticus , and this appears to be due to similar substratum and water velocity preferences, although at both the regional and microhabitat scales E. berilloni prefers wider streams than G. duebeni celticus . This study reveals a decline in the endangered G. duebeni celticus since 1970.
Main conclusions  The longitudinal and local distributions of G. duebeni celticus , and the higher-than-expected co-occurrence of the species with G. pulex , suggest that the decline of the endemic species may be due to changes in the environment and/or interference from native G. pulex , which is expanding its range in Brittany. The results are discussed as regards to the consequences for regional biodiversity.