Arthropod 'rain' into tropical streams: the importance of intact riparian forest and influences on fish diets

2008 ◽  
Vol 59 (8) ◽  
pp. 653 ◽  
Author(s):  
Eric K. W. Chan ◽  
Yixin Zhang ◽  
David Dudgeon
Keyword(s):  
Riparian Vegetation ◽  
Riparian Forest ◽  
Wet Season ◽  
Important Prey ◽  
Terrestrial Arthropods ◽  
Fish Diets ◽  
Terrestrial Insects ◽  
Forest Streams ◽  
The Tropics ◽  
Trophic Linkages

Terrestrial arthropods might represent an important energy source for stream predators, but these trophic linkages have seldom been studied in the tropics. Terrestrial arthropod inputs (essentially, arthropod ‘rain’) into four streams with different riparian vegetation (two draining shrublands and two draining forests) were measured over three consecutive seasons (dry, wet, dry) from 2005 to 2007 in monsoonal Hong Kong. Predatory minnows, Parazacco spilurus (Cyprinidae), were collected and their consumption of terrestrial arthropods was estimated. Inputs of arthropods were dominated by Diptera, Collembola, Formicidae and aerial Hymenoptera, accounting for ≥73% of the arthropod abundance. Seasonal variation was marked: numbers in the dry seasons were approximately half (47–57%) those in the wet season, and biomass fell to one-third (33–37%) of the wet-season value. Shrubland streams received 19–43% fewer individuals and 6–34% less biomass than shaded forest streams. An analysis of fish diets in three of the four streams showed that terrestrial insects and spiders were more important prey in the two forest streams, accounting for 35–43% of prey abundance (39–43% by volume) v. 28% (27%) in the shrubland stream. Because riparian vegetation is the source of terrestrial arthropod inputs to streams, degradation of streamside forests that reduce these inputs will have consequences for the diets of stream fishes.

scholarly journals Structure of the ichthyofauna of adventitious streams in the South Pantanal

2018 ◽  
Vol 108 (0) ◽  
Author(s):  
Virginia S. Uieda ◽  
César Y. Fujihara
Keyword(s):  
Riparian Vegetation ◽  
New Record ◽  
Riparian Forest ◽  
Habitat Characteristics ◽  
Fish Diversity ◽  
The South ◽  
Wet Season ◽  
Paraguay River ◽  
The One ◽  
Large Predators

ABSTRACT: The ichthyofauna of the Taquari River, one of the main tributaries of the South Pantanal, has been studied since the 1970s; however, there is a gap on the studies about the ichthyofauna present on the small adventitious streams of this highly dendritic system. These streams are small tributaries that flow directly into large rivers (mainstem), at least three orders greater in magnitude. The aim of this study was to analyze the structure of the ichthyofauna of five adventitious streams of the Upper Taquari River, South Pantanal, evaluating its temporal variation (dry and wet season) and the relation to the habitat characteristics and the conservation of the streams. Thirty-seven species were collected, from which 14 are exclusive to the Paraguay River basin, one species [Apteronotus albifrons (Linnaeus, 1766)] could represent a new record for this basin, and six species need taxonomic confirmation. The analysis indicated only the existence of spatial variation in the ichthyofauna structure of the streams sampled, with the similarity patterns related to the distance between the streams and to their conditions of conservation. The stream with greater size and preserved riparian forest was the one with the highest values of fish diversity and evenness. On the other hand, the stream with the smallest percentage of riparian forest and highest proximity to urban area presented the lowest diversity. The small size of these adventitious systems should serve as protection against large predators, which have their access to those areas hampered by their own size. Otherwise, the mainstem may also act as source of dispersal of small-bodied schooling fishes to the adventitious streams, where the greater heterogeneity of habitats and the presence of riparian vegetation should offer shelter and food supply for small species.

Crocodylus johnstoni in the McKinlay River Area, N.T. I. Variation in the Diet, and a New Method of Assessing the Relative Importance of Prey.

1982 ◽  
Vol 30 (6) ◽  
pp. 877 ◽  
Author(s):  
GJW Webb ◽  
SC Manolis ◽  
R Buckworth
Keyword(s):  
Stomach Contents ◽  
Target Size ◽  
Relative Importance ◽  
Wet Season ◽  
Crocodylus Johnstoni ◽  
Important Prey ◽  
Size Groups ◽  
Opportunistic Predator ◽  
Major Shift ◽  
Terrestrial Insects

The stomach contents of 153 C. johnstoni were examined by a modification of the method for stomach contents removal described by Taylor et al. (1978). Prey are analysed on the basis of taxonomy, although more emphasis is placed on prey equivalents, using a concept termed 'target size'. The relative importance of different taxa and prey equivalents is determined by a number of methods, and a ranking method is preferred. The most important prey are aquatic and terrestrial insects, fish and crustaceans. The most important sized organisms are target size 5, animals presenting a maximum area of 1.0-4.0 cm2. With regard to size of prey eaten, three size groups of C. johnstoni (16-25, 26-55 and 56-129 cm snout-vent length) were homogeneous within themselves but were significantly different from each other. With increased body size there was a significant increase in the proportion of aquatic prey eaten. Secondary ingestion did not appear a major bias. C. johnstoni ate appreciably more during the wet season than during the dry season, although seasonal comparisons were restricted due to the samples not coming from the same pools. Vegetation was found in 39.9% of crocodile stomachs, and its presence varied with season but not with crocodile size. Stomach parasites were present in 43.8% of animals, and the number of infected crocodiles varied with season and site. Stones were present in 88.2% of crocodiles; however, when compared with those of C. niloticus the stone loads were relatively small. Most data indicate that C. johnstoni is very much an opportunistic predator at the water's edge, which feeds primarily on small aquatic prey, although it may also take substantial numbers of terrestrial prey organisms. During the wet season there is a major shift in the importance of different prey taxa eaten, although the importance of prey equivalents remains largely unchanged.

Contribution of adult aquatic insects to riparian prey availability along tropical forest streams

2007 ◽  
Vol 58 (8) ◽  
pp. 725 ◽  
Author(s):  
Eric K. W. Chan ◽  
Yixin Zhang ◽  
David Dudgeon
Keyword(s):  
Hong Kong ◽  
Aquatic Insects ◽  
Prey Availability ◽  
Aquatic Insect ◽  
Total Biomass ◽  
Wet Season ◽  
Limited Dispersal ◽  
Terrestrial Insects ◽  
Forest Streams ◽  
Adult Aquatic Insects

The contribution of adult aquatic insects to riparian prey availability at four sites along three hillstreams in Hong Kong was estimated during 2004–2006 dry and wet seasons using light traps deployed at different distances from the banks. The number and biomass of aquatic and terrestrial insects collected were markedly higher during the wet season. Numerically, aquatic insects (especially Chironomidae and Philopotamidae) remained a major catch component along banks throughout the year comprising 77% (range: 61–85%) of total insects. Their contribution to total biomass was higher in the wet season (mean: 50%, range: 33–62%) than during the dry season (mean: 21%, range: 8–45%). Aquatic insect abundance decreased with increasing distance from streams during both seasons: numbers at 10–20 m distance were less than 45% of those at the banks, declining to less than 13% at 80 m distance. No such decline with distance was observed for terrestrial insects, but the limited dispersal of aquatic insects meant total insect catches were highest along stream banks. Changes in biomass with distance from streams were similar to those for abundance. Adult aquatic insects may represent an important water-to-land energy subsidy for riparian predators in Hong Kong, but the magnitude varied seasonally and fell sharply with increasing distance from streams.

scholarly journals Determinants of bird assemblage composition in riparian vegetation on sugarcane farms in the Queensland Wet Tropics

2015 ◽  
Vol 21 (1) ◽  
pp. 60 ◽  
Author(s):  
Anita F. Keir ◽  
Richard G. Pearson ◽  
Robert A. Congdon
Keyword(s):  
Riparian Vegetation ◽  
Wildlife Conservation ◽  
Agricultural Landscape ◽  
Riparian Zone ◽  
Riparian Forest ◽  
Agricultural Landscapes ◽  
Generalist Species ◽  
Assemblage Composition ◽  
Bird Assemblages ◽  
Wet Tropics

Remnant habitat patches in agricultural landscapes can contribute substantially to wildlife conservation. Understanding the main habitat variables that influence wildlife is important if these remnants are to be appropriately managed. We investigated relationships between the bird assemblages and characteristics of remnant riparian forest at 27 sites among sugarcane fields in the Queensland Wet Tropics bioregion. Sites within the remnant riparian zone had distinctly different bird assemblages from those of the forest, but provided habitat for many forest and generalist species. Width of the riparian vegetation and distance from source forest were the most important factors in explaining the bird assemblages in these remnant ribbons of vegetation. Gradual changes in assemblage composition occurred with increasing distance from source forest, with species of rainforest and dense vegetation being replaced by species of more open habitats, although increasing distance was confounded by decreasing riparian width. Species richness increased with width of the riparian zone, with high richness at the wide sites due to a mixture of open-habitat species typical of narrower sites and rainforest species typical of sites within intact forest, as a result of the greater similarity in vegetation characteristics between wide sites and the forest proper. The results demonstrate the habitat value for birds of remnant riparian vegetation in an agricultural landscape, supporting edge and open vegetation species with even narrow widths, but requiring substantial width (>90 m) to support specialists of the closed forest, the dominant original vegetation of the area.

General Characteristics and Variability of Climate in the Amazon Basin and its Links to the Global Climate System

2001 ◽  
Author(s):  
Jose A. Marengo ◽  
Carlos A. Nobre
Keyword(s):  
Surface Temperature ◽  
Land Surface ◽  
Large Scale ◽  
Amazon Basin ◽  
Global Climate ◽  
River System ◽  
Climate System ◽  
Wet Season ◽  
Tropospheric Circulation ◽  
The Tropics

The Amazon region is of particular interest because it represents a large source of heat in the tropics and has been shown to have a significant impact on extratropical circulation, and it is Earth’s largest and most intense land-based convective center. During the Southern Hemisphere summer when convection is best developed, the Amazon basin is one of the wettest regions on Earth. Amazonia is of course not isolated from the rest of the world, and a global perspective is needed to understand the nature and causes of climatological anomalies in Amazonia and how they feed back to influence the global climate system. The Amazon River system is the single, largest source of freshwater on Earth. The flow regime of this river system is relatively unimpacted by humans (Vörösmarty et al. 1997 a, b) and is subject to interannual variability in tropical precipitation that ultimately is translated into large variations in downstream hydrographs (Marengo et al. 1998a, Vörösmarty et al. 1996, Richey et al. 1989a, b). The recycling of local evaporation and precipitation by the forest accounts for a sizable portion of the regional water budget (Nobre et al. 1991, Eltahir 1996), and as large areas of the basin are subject to active deforestation there is grave concern about how such land surface disruptions may affect the water cycle in the tropics (see reviews in Lean et al. 1996). Previous studies have emphasized either how large-scale atmospheric circulation or land surface conditions can directly control the seasonal changes in rainfall producing mechanisms. Studies invoking controls of convection and rainfall by large-scale circulation emphasize the relationship between the establishment of upper-tropospheric circulation over Bolivia and moisture transport from the Atlantic ocean for initiation of the wet season and its intensity (see reviews in Marengo et al. 1999). On the other hand, Eltahir and Pal (1996) have shown that Amazon convection is closely related to land surface humidity and temperature, while Fu et al. (1999) indicate that the wet season in the Amazon basin is controlled by both changes in land surface temperature and the sea surface temperature (SST) in the adjacent oceans, depending if the region is north-equatorial or southern Amazonia.

scholarly journals Associations between fish assemblage and riparian vegetation in the Corumbataí River Basin (SP)

2007 ◽  
Vol 67 (2) ◽  
pp. 191-195 ◽  
Author(s):  
M. Cetra ◽  
M. Petrere JR.
Keyword(s):  
Species Richness ◽  
River Basin ◽  
Fish Species ◽  
Sugar Cane ◽  
Fish Assemblage ◽  
Vegetation Cover ◽  
Riparian Vegetation ◽  
Riparian Forest ◽  
The State ◽  
Multivariate Techniques

This work intends to examine if there are associations between fish species and the state of conservation of the riparian forest in the Corumbataí River Basin. Four main rivers were chosen for this study with three sites on each. Collections were carried out from March to June and from September to December 2001. Multivariate techniques were applied to determine the correlation between species richness and the order of the rivers, preservation level of the riparian forest, shade level, presence or absence of Eucalyptus, sugar cane and pastures, and surrounding declivity stability of the sites. Species richness was highest at locations with greater vegetation cover and preserved riparian forest.

scholarly journals Longitudinal dimensions of land-use impacts in riverine ecosystems

2019 ◽  
Vol 31 ◽  
Author(s):  
Rafael Feijó-Lima ◽  
Eugenia Zandonà ◽  
Bruna Suelen da Silva ◽  
Flavia Tromboni ◽  
Timothy Peter Moulton ◽  
...  
Keyword(s):  
Riparian Vegetation ◽  
Riparian Forest ◽  
Atlantic Rainforest ◽  
Fragmented Landscape ◽  
Macroinvertebrate Communities ◽  
Buffer Strips ◽  
Land Use Impacts ◽  
Stream Flows ◽  
Riverine Ecosystems ◽  
Forest Remnants

Abstract: Aim Rivers are linked longitudinally via the flow of water and the spatial dimensions of the changes in local riparian vegetation are still poorly understood. Recent modifications to the Native Vegetation Protection Law allow reduction of lateral buffer strips and amnesty for riparian vegetation removal, which might increase the fragmentation of native riparian vegetation, especially for Atlantic Rainforest streams. Methods We present two case studies conducted in a stream draining a fragmented landscape in the Atlantic Rainforest. The stream flows through two abrupt transitions (forest-pasture-forest) and we investigated how far the upstream effects of a given riparian condition could be detected in the downstream reach for a suite of variables. Results We show that the effects of land cover propagate downstream for both algal and macroinvertebrate communities. For some variables of interest, these effects might extend up to a km downstream from the transition. Conclusions There is a need to understand how the distribution of riparian forest remnants contribute to maintaining watershed-scale resilience to impacts.

scholarly journals Glacier Fluctuations and Climate in the Cordillera Blanca, Peru

1990 ◽  
Vol 14 ◽  
pp. 136-140 ◽  
Author(s):  
Georg Kaser ◽  
Alcides Ames ◽  
Marino Zamora
Keyword(s):  
Seasonal Temperature ◽  
Wet Season ◽  
Equilibrium Line Altitude ◽  
Cordillera Blanca ◽  
Covered Area ◽  
Recession Rates ◽  
Tropical Areas ◽  
Precipitation Records ◽  
The Tropics

With a total of 723 km2 of glaciers (1970) the Cordillera Blanca includes the largest glacier-covered area in the tropics. The climate is characterized by relatively large daily and small seasonal temperature variations as well as by a distinct succession between a dry (May–September) and a wet season (October–April). Since the early 1970s an ablation stake network has been installed on the tongues of the glaciers Uruashraju and Yanamarey. The determination of the equilibrium-line altitude at each end of a wet season was possible, showing a fair correlation with temperature, but not with the precipitation records of the nearby climatological station Querococha. Mean ablation rates at the lowest parts of the glacier tongues are markedly higher during the wet season than during the dry season. Reasons are presumably to be found in the seasonal variation of cloudiness and air moisture rates. Terminus variations of four glaciers in the Cordillera Blanca have been monitored since the early seventies, earlier positions are reconstructed back to 1948 by vertical air photographs. For the glaciers Uruashraju and Yanamarey the terminus positions of 1939 are known from an early map. The general retreat of glaciers in the Cordillera Blanca during the last five decades correlates with the global attitude of glaciers and especially with the attitude of glaciers in other tropical areas. Decreased recession rates with minor advances (1974–79 and 1985–86) are accompanied by lower annual temperatures and preceded and accompanied by years with relatively high annual precipitation sums.

Rainfall erosivity and its estimation for Australia's tropics

Soil Research ◽  
1998 ◽  
Vol 36 (1) ◽  
pp. 143 ◽  
Author(s):  
B. Yu
Keyword(s):  
Model Performance ◽  
Daily Rainfall ◽  
Annual Rainfall ◽  
Rainfall Erosivity ◽  
Wet Season ◽  
R Factor ◽  
Different Seasons ◽  
Monthly Distribution ◽  
The Tropics ◽  
Parameter Values

Pluviograph data at 6-min intervals for 41 sites in the tropics of Australia were used to compute the rainfall and runoff factor (R-factor) for the Revised Universal Soil Loss Equation (RUSLE), and a daily rainfall erosivity model was validated for these tropical sites. Mean annual rainfall varies from about 300 mm at Jervois (015602) to about 4000 at Tully (032042). The corresponding R-factor ranges from 1080 to 33500 MJ·mm/(ha ·h·year). For these tropical sites, both rainfall and rainfall erosivity are highly seasonal with a single peak in February mostly. Summer months (November–April) typically contribute about 80% of annual rainfall and about 90% of the R-factor. The daily erosivity model performed better for the tropical sites with a marked wet season in summer in comparison to model performance in temperate regions of Australia where peak rainfall and peak rainfall erosivity may occur in different seasons. A set of regional parameters depending on seasonal rainfall was developed so that the R-factor and its seasonal distribution can be estimated for sites without pluviograph data. The prediction error using the regional parameter values is about 20% for the R-factor and 1% for its monthly distribution for these tropical sites.

Scats can reveal the presence and habitat use of cryptic rock-dwelling macropods

2006 ◽  
Vol 54 (5) ◽  
pp. 325 ◽  
Author(s):  
Wendy R. Telfer ◽  
Anthony D. Griffiths ◽  
David M. J. S. Bowman
Keyword(s):  
Habitat Use ◽  
Radio Telemetry ◽  
Classification Tree ◽  
Habitat Preferences ◽  
Wet Season ◽  
Survey Tool ◽  
Faecal Pellets ◽  
Tropical Environments ◽  
The Tropics ◽  
Larger Sample

The rock-dwelling macropod species of the tropics of the Northern Territory, Australia, are behaviourally elusive and difficult to observe in their rugged habitats. Hence, little is understood about their ecology. We evaluated the potential of using scats (faecal pellets) as a survey tool for this faunal assemblage by: (1) developing a key to the scats of the species; (2) examining the rates of loss and decomposition of short-eared rock-wallaby (Petrogale brachyotis) scats in these tropical environments; and (3) comparing the distribution of scats of P. brachyotis with the species’ use of space and habitats as determined with radio-telemetry. Classification tree modelling discriminated the scats of the seven macropod species, primarily on the basis of width. The reliability of identification was greatly improved with larger sample sizes and inclusion of a habitat parameter. Rates of scat loss and decay were variable and the greatest losses occurred in the wet season, particularly on sandy soils. Scat censuses underestimated the total area used by P. brachyotis but the distribution of scats showed the same broad pattern of habitat use found by radio-telemetry. We conclude that scats can accurately indicate the presence and habitat preferences of rock-dwelling macropod species.

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