Hydrobiologia (2010) 651:279–289 DOI 10.1007/s10750-010-0307-7
PRIMARY RESEARCH PAPER
Structure and dynamics of stream fish communities in the flood zone of the lower Purus River, Amazonas State, Brazil Fa´bio R. Silva • Efrem J. G. Ferreira Cla´udia P. de Deus
•
Received: 16 April 2009 / Revised: 22 March 2010 / Accepted: 17 May 2010 / Published online: 4 June 2010 Ó Springer Science+Business Media B.V. 2010
Abstract The structure and dynamics of fish communities were characterized by richness, abundance, diversity and stability, during high-water and lowwater periods. These analyses were performed on data from the flood zone of four streams in the lower Purus River, in the Brazilian Amazon. A total of 188 species of fish were collected, distributed among 29 families and eight orders. The statistical test showed a difference in community diversity between periods. The high-water period showed higher evenness in comparison to the low-water season. The low-water period was marked by high species abundance. A great variation in community composition between the flood and low-water periods was encountered. The adjustments for species abundance models suggested that stochastic events structure the communities. Most of the species showed a temporal variation of abundance indicating low community
Electronic supplementary material The online version of this article (doi:10.1007/s10750-010-0307-7) contains supplementary material, which is available to authorized users. Handling editor: J. A. Cambray F. R. Silva (&) Museu Paraense Emı´lio Goeldi, Bele´m, Para´, Brazil e-mail:
[email protected] E. J. G. Ferreira C. P. de Deus Instituto Nacional de Pesquisas da Amazoˆnia (INPA), Manaus, Amazonas, Brazil
stability. Changes in the physico-chemical conditions of the water caused by the seasonal hydrological regime may be influencing the structuring of the fish communities. Keywords Amazon Fish Ecology Diversity Species abundance Temporal variation
Introduction The Amazon basin has high levels of annual rainfall, unevenly distributed within the region (Santos & Ferreira, 1999). In general, there is one season of low and one of high precipitation, ranging from 1,000 to 3,000 mm annually (Goulding et al., 2003). The rainfall is important in shaping the landscape of the Amazon sedimentary floodplain, determining the seasonal flood dynamics. In the floodplains, there are many lakes that, during the dry season, are fed by streams with springs in the surrounding forest. In the wet season, the riparian forest becomes flooded and the rivers supply these lakes with water. Many species of fish are adapted to this flood dynamic, migrating into the lakes during the flood period and migrating back during the falling-water period (Welcomme, 1979; Goulding, 1980). The flooding of the forest provides greater environmental heterogeneity and a higher input of resources; in this period, many species of fish migrate laterally, colonizing new areas within the
123
280
flooded forest (Goulding et al., 1988). The difference between the communities collected during the flood and dry period are well-documented and support the idea that changes occur in the composition and structure patterns of the fish communities (LoweMcConnell, 1963, 1975, 1999; Wootton, 1992; Agostinho & Zalewiski, 1996). Study in upland forested streams of the Brazilian Amazon, however, indicate that seasonal changes in habitat variables exert little effect on the structure of the communities so that deterministic processes can be more important in shaping the temporal stability of fish assemblages (Silva, 1995; Walker, 1995; Bu¨hrnheim & Cox-Fernandes, 2001). More recently, Rayner et al. (2008), studying fish-habitat dynamics in small rivers in Australia, observed that seasonal flow mediated change in habitat structure, and was the main factor affecting fish community composition. Temporal changes in fish assemblages can be related with the rainfall dynamics in streams. In the rainy season, the high rainfall results in complex pond networks connected to streams. The connectivity between stream channel and lateral temporary ponds can favor some species that migrate laterally towards these temporary ponds in search of more pristine sites for their ecological requirements (Espı´rito-Santo et al., 2009). The authors found significant variations in the richness and abundance between the rainy and dry seasons in this type of environment. When looking at environments under the direct influence of the flood pulse, like the Amazon floodplain, several studies indicate that there are stochastic processes structuring the fish community, which are basically caused by fluctuations in water level (Boneto et al., 1969, Lowe-McConnell, 1979, Arrington & Winemiller, 2006). According to Fittkau (1967), in general, the lower stretch of floodplain streams only show lotic characteristics during the low-water and falling-water period. In this period, the area reduction in the aquatic environment increases competition for autochthonous resources (Lowe-McConnell, 1975). Some species, such as detritivorous fish, take advantage of the large supply of nutrients available in the periphyton and detritus in the shallow waters and help in the cycling of nutrients, keeping them available in the water column (Cotner et al., 2006). In the high-water period, there is a rich fauna of invertebrates that lives associated to the marginal
123
Hydrobiologia (2010) 651:279–289
vegetation and together with seeds and fruits make up important food sources for the fish fauna. Walker (2001) demonstrated the great importance of the submerged litter for composition of the trophic web of streams subject to flooding. Fungi and bacteria, which develop in the submerged litter, are the basis of a food web. Several studies in the Amazon show that many fish species depend on these allochthonous resources (Sioli, 1967; Kno¨ppel, 1970; Fittkau et al., 1975; Saul, 1975; Goulding, 1980; Junk, 1983; Goulding et al., 1988; Lima & Goulding, 1998). According to Arrington & Winemiller (2006), in the rising-water and high-water periods there is the largest variation in the communities regarding habitat categories, which indicates the formation of temporary niches. As a response to environmental variations that occur between the low and high-water periods, the fauna exploiting the lower stretch of streams may also vary along the annual cycle. This study was conducted in streams draining into the Purus River, in the Piagac¸u-Purus Sustainable Development Reserve (SDR-PP), Amazonas State, Brazil. The lower parts (outfall) of the analyzed streams, located in the Amazon floodplain, are found in periodically flooded areas and are therefore influenced by the seasonal flooding of the main river. The communities found in the high- and low-water periods were compared and the hypothesis that the high and low-water events do not provoke a significant variation in the structure of fish communities was tested. The study of the dynamics of fish communities in a sustainable development reserve can provide basic information that may assist in establishing rules for the management of natural aquatic resources.
Materials and methods Four surveys were carried out in each stream, two in the high-water period and two in the low-water period. Low-water samples were collected in October 2004 and October 2005, whereas high-water samples were collected in June 2005 and June 2006 in the Caetano, Grande, Castanhal, and Itauba streams. The Caetano and Grande streams drain into Lake Uauac¸u, and Castanhal and Itauba drain into Lake Ayapua´ (Fig. 1). All sites are located in the SDR-PP, between the coordinates 4°050 S–61°730 W and 5°350 S–63°350 W, in the lower Purus River, Amazonas State, Brazil.
Hydrobiologia (2010) 651:279–289
281
Fig. 1 Map of the study area with the location of SDR Piagac¸u-Purus, Amazonas State, Brazil, and the drainage system of the Lakes Ayapua´ and Uauac¸u showing the streams where the samples were collected
The chosen streams have a similar structure, with lengths ranging from 3 to 6 km, and originate from springs located on ‘‘terra firme’’ (upland). Both lakes are white-water and are influenced by the Solimo˜esPurus system due to the flood pulse (Junk, 1983). The average distance from outfall streams to the collection points was approximately 300–500 m. The pattern of discharge in these streams is seasonal, reflecting the regional rainfall pattern. The rainy period occurs from November to June (rising and high-water period) and the dry season occurs from June to October (falling and low-water period). During the dry season, the lower course of these streams is narrow and receives a high incidence of light. The substrate consists mainly of fine detritus and decomposing material, such as leaves, large and small branches. In the rainy period, the riparian forest is flooded and a large area of the stream is hidden by the forest canopy. The bottom is composed mainly of leaves and there is wide availability of micro habitats, such as submerged roots, branches, and trunks. The collection method and sampling effort were standardized for all streams. Each stream was sampled along a 50 m stretch. Depth, width, speed of current, and type of substrate were measured for every location and the times of sampling were
recorded. Depth was measured at the bank and in the channel at 10 m intervals, the width also at these intervals. For the flow speed, three measurements were taken along 50 m stretches, and the type of substrate was recorded in a sequence of five measurements, in a transversal transect from one bank to the other. Fish were captured using gill nets of different meshes, dip nets (5 mm mesh), seine nets, and fyke nets. The ecological parameters of the community were measured according to Magurran (1988), by determining species richness, abundance, estimating the diversity indices (Berger-Parker, Simpson, Shannon, evenness), rarefaction curves and fit to species abundance models (geometric series, log series, lognormal and broken-stick distribution). The estimated diversity was represented in the three-dimensional space where species richness, species log abundance, and species evenness are, according to You et al. (2009), coordinates. The similarity was calculated using Chao–Jaccard (qualitative data) and Chao– Sorensen (quantitative data) as proposed by Chao & Shen (2003) using the free SPADE software. We applied UPGMA as grouping methods. The stability of the communities was measured by calculating the coefficient of variation (CV) of the species abundance
123
282
Hydrobiologia (2010) 651:279–289
Composition of the fish communities
according to Grossman et al. (1990). To compare assemblages by period (low-water and high-water), we used Shannon’s diversity t test (Poole, 1974) and ANOSIM non-parametric procedure (Clarke & Warwick, 1994), for testing the hypothesis of nonsimilarity between the two periods (McCune & Grace, 2002).
13,134 individuals of 188 species belonging to 29 families and eight orders were collected. Characiformes (54% of species), followed by Perciformes (24%) and Siluriformes (15%) were the dominant orders. Characidae (29%), Cichlidae (29%), and Hemiodontidae (6.5%) were the families with the greatest richness (Appendix 1—Electronic Supplementary material). Abundance and species richness varied among streams and seasonally within each site. The total number of species observed during the high- and low-water periods in each stream can be seen in Table 2. Only 67 species (35% of the total richness sampled) were captured in both the periods. In the high-water period, 1,708 specimens were collected. Among the 119 species identified in this period (from six orders and 26 families), 45 species (38%) occurred in a single stream (Caetano—12; Castanhal—7; Grande—11; Itauba—15 species) and 23 (19%) were found in the four sampled streams. Apistogramma sp. 1 (Cichlidae) represented 14% of the abundance, Hemigrammus gracilis (Characidae), and Copella nattereri (Lebiasinidae) were also encountered in high abundance, representing 9.5 and 9.3% of the sample, respectively. Plagioscion
Results Physical characteristics of the environment Table 1 shows the values of physical measurements for characterization of the environment during the study period. In the high-water period, the depth of the streams varied from 2 to 5.3 m and the width, 70 to 200 m. The area inundated becomes extended and, consequently, much of the water becomes relatively trapped, making the environment more lentic. An extensive area remains shared by the vegetation cover. In the low-water period, the waters retreat, leaving only a narrow, shallow channel of running water. Consequently, there is intense entry of light due to the lack of vegetation cover, and the substrate is covered by a fine layer of mud.
Table 1 Minimum and maximum values of environmental variables of the streams measured during the low and high-water periods Period
Depth (m)
High-water
2–5.3
Low-water
0.2–1.5
Width (m)
Flow velocity (m/s2)
Vegetation cover (%)
Substratum
70–200
0
71–80
Litter, branch and submersed trunk
0.011–0.064
0
Mud, branch and submersed trunk
3–12
Table 2 Ecological parameters estimated by the diversity and dominance indices for the fish communities in the four streams sampled during high-water and low-water periods Richness (both periods)
Uauacu
Ayapua
Caetano
Grande
Castanhal
Itauba
100
106
85
129
Low water
High water
Low water
High water
Low water
High water
Low water
High water
Richness (S)
70
63
66
67
50
59
94
69
Abundance (N)
2,811
398
2,015
218
1,552
476
5,048
316
Shannon (H0 )
2.85
3.15
2.86
3.3
2.58
3.18
3.01
3.28
Shannon (H0 ) biomass
2.52
2.88
1.54
2.79
1.72
2.74
2.6
3.2
Evenness (E)
0.67
0.76
0.68
0.78
0.66
0.78
0.66
0.77
Simpson (1D)
0.89
0.91
0.91
0.92
0.86
0.93
0.91
0.91
Berger–Parker (d)
0.26
0.19
0.17
0.23
0.25
0.15
0.13
0.24
123
Hydrobiologia (2010) 651:279–289
squamosissimus and Semaprochilodus taeniurus were the dominant species in biomass (18% of the total biomass). Metynnis hypsauchen (5%) was also among the most abundant species in this period. In the low-water period, a total of 11,426 specimens were collected from 136 species, eight orders and 33 families. In this period, 56 species (41%) were found in a single stream (Caetano—12 species; Castanhal—5; Grande—15; Itauba—24) and 20 (15%) were common to all four analyzed environments. The most abundant families were: Eleotridae, represented by Microphilypnus amazonicus (13%); Lebiasinidae, represented by Nannostomus eques (9%); and Characidae, represented by Hoplocharax goethei (8%). The highest values of biomass were found for Hoplias malabaricus (32%) and Potamorhina pristigaster (11%). Diversity
283
exclusive species for each period. The Berger–Parker index showed similar dominance values for both periods. Shannon’s diversity t test (t = 7.1922, P = 8.7 9 10-13, a = 0.05) showed a significant difference between the values calculated for the highwater and low-water periods. The diversity plotted in three dimensions (Fig. 2) demonstrated that no great richness variation occurred between periods, with the exception of the Itauba stream. The accentuated differences between periods occurred in the abundance and equitability values. In the low-water period, there occurred greater variation in the richness values between communities. Rarefaction curves plotted in the low-water period indicate that the number of species caught was close to the expected maximum. However, the pattern found in the high-water period showed a rising trend (Fig. 3).
The greatest number of species was found in streams Itauba and Caetano, with 94 and 70 species, respectively, both in the low-water period (Table 2). The values of the Shannon (H0 ) and Simpson (1D) indices indicated a larger diversity during the high-water period. The highest evenness was also found in this period. All of the streams presented a group of
Fig. 2 Representation in 3D of the diversity patterns (S richness, E eveness, and N log abundance) found in the four streams (cast Castanho, gra Grande, cae Caetano, ita Itauba) in the two periods analyzed (f flood, d dry)
Fig. 3 Rarefaction curves by stream for the communities found in low-water (A) and high-water (B) periods
123
284
Hydrobiologia (2010) 651:279–289
Species abundance models Table 3 presents the results of the adjustments to the species abundance distribution models considering the grouped data (high and low-water periods) and separate data. The data fitted the log-normal model for all the streams. In the high-water period, the Castanhal stream also showed a probability of fitting the log-series model (Table 3). The same analysis, conducted with biomass data, fitted the log-normal model for all communities in both periods of the
hydrological cycle. The graphic representation of the distribution of the species abundance for the communities showed a predominance of species with intermediate abundance (Fig. 4). Similarity analysis In order to analyze similarities between communities, grouping analyses were conducted utilizing Chao–Jaccard’s qualitative index (Fig. 5) and the Sorensen quantitative index (Fig. 6). The results
Table 3 Tests for goodness of fit of the fish communities to the species abundance models: geometric series, log series, log-normal distribution and broken-stick model Caetano
Grande
Both High periods water
Low water
Castanhal
Both High periods water
Low water
Itauba
Both High periods water
Low water
Both periods
High water
Low water
Geometric serie \0.001 \0.001 \0.001 \0.001 \0.001 \0.001 \0.001 \0.001 \0.001 \0.001 \0.001 \0.001 Log-serie Log-normal Broken stick
\0.001 \0.001 \0.001 \0.001 \0.001 \0.001 \0.001 0.32
0.57
0.19
0.2
0.53
0.17
0.31
\0.001 \0.001 \0.001 \0.001 0.45
0.58
0.1
0.84
\0.001 \0.001 \0.001 \0.001 \0.001 \0.001 \0.001 \0.001 \0.001 \0.001 \0.001 \0.001
95% significance level Fig. 4 General distribution of the species-abundance ratio of communities found in the four sampled streams
123
0.33
0.78
Hydrobiologia (2010) 651:279–289
285 Table 4 Average and standard deviation of the coefficient of variation (CV) of the species abundance present in the fish communities found in the four streams studied Stream
Average and standard deviation of CV
Caetano
1.21 ± 0.37
Grande
1.24 ± 0.38
Castanhal
1.21 ± 0.41
Itauba
1.26 ± 0.36
CV [ 0.75, highly fluctuating
Stability of the communities Fig. 5 Grouping analysis using presence and absence data of species from the fish communities. The Chao–Jaccard index was used as a similarity measure and UPGMA as a grouping method
Fig. 6 Grouping analysis using abundance data of species from the fish communities. Sorensen index was used as a similarity measure and UPGMA as grouping method
showed that the communities were grouped according to the low-water and high-water periods. The results obtained using the Sorensen quantitative index (Fig. 6), using abundance data, also showed a tendency to separate the streams between the periods, although the Caetano stream stands out from the others in the low-water period. Significant ANOSIM results were obtained for comparisons of seasons (high-water and low-water) using presence– absence (P = 0.0258, R = 0.9688) and abundance data (P = 0.0264, R = 1).
The stability analysis, measured by the coefficient of variation of abundance in the community, indicates that there is a predominance of highly fluctuating species (Table 4). Among the total richness sampled, 75% of the species are highly fluctuating, 11.7% are moderately stable species, 7% are moderately fluctuating species, and 6% of the species have high stability. The species that showed a lower coefficient of variation are small and can be considered residents of streams. Medium and large species, such as Osteoglossum bicirrhosum, Triportheus elongatus, Semaprochilodus taeniurus, and S. insignis have relatively stable behavior. They mainly inhabit the lakes, but use the stream environment for foraging and feeding.
Discussion The values for the richness observed in the streams studied are considered high for this type of environment. Similar results were found in other studies conducted in environments similar to that of this study. Galacatos et al. (2004) for example, examined the richness of species in streams connected to the lake, Jatuncocha in the Equatorial Amazon, and found, on average, 83 species in them. Streams that are not connected to lakes generally present a smaller number of species, as in the example of the works performed in the Amazon by Silva (1995), Sabino & Zuanon (1998), and Bu¨hrnheim & Cox-Fernandes (2003), who recorded totals of 44, 29, and 22 species, respectively. The connection of streams to lakes or
123
286
floodable areas can provide an increase in the number of species, principally in the lower stretches of streams, due to greater movement of species between the two environments that use them as feeding areas, hiding places, shelter or even for reproduction. The values for richness did not vary much between the high and low-water periods, but the composition of species was modified throughout the study period. Only 35.5% of the species identified were observed in both the periods. For example, species typical of the flooded areas, such as Plagioscion squamosissimus and Uaru amphiacanthoides (Saint-Paul et al., 2000), were only collected in the streams in the high-water period. These species generally move towards tributaries upstream, utilizing these environments as feeding grounds. In this study, the abundance and equitability also varied between the high-water and low-water periods. In the high-water period, the abundance of individuals was less due to their greater dispersion in the flooded forest area. In this period, there is an increase in available physical spaces, for example, amongst submerged branches and roots, and this can reduce the efficiency of the capture methods (Lowe-McConnell, 1963, 1999; Agostinho & Zalewiski, 1996). In this period, despite the lower abundance when compared to the low-water period, the recording of small size species was great; these fish being adapted to living among submerged aquatic plants and eating mainly larvae of small aquatic and semi-aquatic insects from riparian forest (Angermeier & Karr, 1984; Sabino & Zuanon, 1998). As representatives of this fauna, we found species of the genera, Apistogramma, Hemigrammus, Copella, Microphiyipnus, Carnegiella, Hyphessobrycon, Acarichthys, Acaronia, and Nannostomus. These small fish, in turn, serve as prey for larger species, consequently attracting them to the place. Plagioscion squamosissimus, for example, increased in abundance in this period. This observation is corroborated by Benneman et al. (2006). We also observed greater abundance of Serrasalminae, Metynnis hypsauchen, which feeds on fruits and seeds that are abundant in the flooded forest (Correa et al., 2007), as well as Triportheus elongatus, an omnivorous fish that feeds on insects of terrestrial origin (de Me´rona & Rankin-de-Me´rona, 2004). According to Lowe-McConnell (1999), the changes in the environment between the low and high-water periods
123
Hydrobiologia (2010) 651:279–289
affect mainly the availability of food, and the species constantly need to adjust to the new environmental conditions. In the low-water period, the most abundant ichthyofauna was represented by other species, more adapted to these new environmental conditions: murkier water carrying a greater load of sediment, and a smaller quantity of submerged organic material. The large predator species were represented by Acestrorhynchus falcirostris and Hoplias malabaricus. Species of the genus, Potamorhina, commonly found in lake environments, were caught in the lower stretches of the streams. Besides this, in this period, it was possible to observe shoals of the genus, Schizodon, Leporinus and Brycon, which were probably foraging while moving upstream. Some species that present high abundance during the low-water period also occur during the high-water period, albeit with lower density. They are small fish, representatives of various families, such as Eleotridae, Lebiasinidae, Characidae, Cichlidae, Engraulidae, Gasteropelecidae, Doradidae, and others. These families probably present species better adapted to life in low-water conditions rather than in those of high water. In general, the species collected in the low-water period better represent the structure of fish communities in stream environments (Fittkau, 1967). According to Lasso et al. (1999), aquatic environments in the low-water period acquire more defined characteristics in terms of width and depth. Thus, we could presume that the species present in the streams in the low-watery period are probably resident or exploit the environment with greater frequency. This fact, however, could be confirmed only if the analysis of stability were conducted over a longer period of observation and included various generations of the species that inhabit this area (Connell & Sousa, 1983). The greater diversity of fishes in the high-water period is a reflection of the greater equitability found between the numbers of individuals in each species. This fact may also be linked to greater availability of resources and greater physical heterogeneity in the system, which could be utilized by a greater number of species, or even by more individuals. Even though these factors were not measured for this work, they are events that support the opening of more ecological niches, as observed by Winemiller & Jepsen (1998) in tropical rivers of Africa and South America.
Hydrobiologia (2010) 651:279–289
The highest evenness value, also in this period, can be attributed to the same factors, particularly the recruitment of juveniles into the population, which could be detected in samples in this period. In fact, a significant difference in the diversity values between the sample periods (Shannon diversity, t test), and the results of the ANOSIM, indicate that the dynamic of the pulse of inundation leads to modifications in the environment, which affect the structure of the fish communities. In other words, the fish communities respond to these modifications in the environment, altering their composition and/or density of the organisms. The responses of the fish communities to the seasonal environmental changes have been documented by other authors (Arrigton & Winemiller, 2006; Rayner et al., 2008). Studies performed with communities in tropical environments have revealed a strong influence of seasonal environmental modifications on the structure of fish communities. Galacatos et al. (2004) compared fish communities collected in lakes, rivers and streams, and observed the occurrence of groups of species by type of environment and by seasonal period (dry and wet season). Silvano et al. (2000) also obtained the same pattern of results by comparing 23 samples collected in different environments along the Jurua´ River. Studies conducted in the SE (Bizerril, 1997) and NE of Brazil (Batista & Rego, 1996), showed the same pattern, but, in this case, it was related to the regime of rains in these regions. In the streams examined in this study, there was also a tendency to group the communities according to the rainfall in the region, represented by the highwater and low-water seasons. According to Grossman et al. (1982), stochastic processes influence the presence of unstable fish assemblages. According to Lowe-McConnell (1975, 1999), the hydrological dynamics of floodplain rivers favors the occurrence of stochastic communities, and, according to Goulding et al. (1988), other factors that restrict the fish fauna can contribute, such as hypoxia caused by the elevation of water and a marked decrease in the flow during the flood, which may be a factor in structuring communities. In our study, physico-chemical parameters, such as dissolved oxygen and conductivity were not measured, though alterations in these parameters certainly occur between high and lowwater periods, and fish communities may respond differently to all these factors.
287
Our results suggest that the communities studied have structural instability, which is probably due to environmental fluctuations in the system. This instability can be perceived by the species composition variation, most species being collected in only one period of the year. We observed a high number of fluctuating species in the environment. Arrington & Winemiller (2006) found similar results when studying a river floodplain in Venezuela. It is noticed, however, that these fluctuations in the physical environmental conditions are cyclical alterations that, despite promoting structural instability in the fish communities, take place seasonally. In other words, they are alterations that can be considered predictable, though their intensity may vary from year to year. According to Hill & Hamer (1998), communities that are not influenced by disturbances tend to have a log-normal distribution. Among the ecological assumptions of this model are the ideas of niche partitioning and environmental variations independent of the species in the community (Engen & Lande, 1996). The model fits large communities with a large number of species with intermediate abundance and few dominant or rare species, such as the fish fauna of the streams examined in this study. An abundance distribution is caused by the number of interacting species, the type of ecological interactions and processes that determine the population dynamics, and the way in which the environmental variations affect the community. According to Halley & Inchausti (2002), communities that follow the log-normal distribution are more susceptible to fluctuations due to the changes in habitat, addition of new trophic levels and new taxa in the communities. This is similar to the situation found in the streams analyzed, where the high-water is accompanied by an expansion of the feeding sites, an opening of new niches and the entry of migratory species into the community. In our study, the connection between the stretch of the stream analyzed with large lakes possibly favors the movement of some species, which makes the stream community open to the flow of species from lake to stream. The differences in the physical environmental characteristics also observed in the lower stretches of these streams certainly influence the structure of the fish communities present. Arau´jo et al. (2009) analyzing the longitudinal distribution
123
288
pattern of the fish assemblage along 1,080 km of the Paraı´ba do Sul River, in Brazil, observed that the structure of communities differed more substantially along the river (longitudinal variation) than over time (temporal variation). In our study, the lower stretches of streams are important areas of transition between lakes and streams. In these areas, ecological interactions are established between the resident community in the streams and the community of fish in the lakes. These relationships are influenced by the seasonal dynamics of the flood process. The search for food, reproduction sites or partners, shelter and nursery areas make the colonization of this environment a crucial event for the maintenance of the integrity of the stream and lake communities.
Conclusion This study demonstrated that changes in composition and diversity of species observed in fish communities located in the lower courses of streams are events caused by environmental modifications. Modifications in the environment result in the movement of species that use different habitats of streams and lakes to accomplish their life cycles. The main factor affecting the communities seems to be the alterations caused by the rise and fall of the waters. The hydrography of these streams is shared by many other similar streams. It is important to maintain the integrity of these environments in order to conserve the biodiversity of the Amazon floodplains. Acknowledgments We thank Fundac¸a˜o o Botica´rio de Protec¸a˜o da Natureza for financing the project. Wildlife Conservation Society (WCS) for investing in the Reserva de Desenvolvimento Sustenta´vel Piagac¸u-Purus (SDR-PP) by supplying equipment to the support base where we worked. Instituto Nacional de Pesquisas da Amazoˆnia (INPA) for the laboratory infrastructure and the ichthyologists that helped to identify the species. Instituto Piagac¸u (IPi) for the logistic support and Fundac¸a˜o de Amparo a Pesquisa do Amazonas (FAPEAM) for granting a MSc scholarship to the first author for 2 years.
References Agostinho, A. A. & M. Zalewiski, 1996. A Planı´cie alaga´vel do alto rio Parana´: importaˆncia e preservac¸a˜o. Editora da Universidade Estadual de Maringa´, Maringa´.
123
Hydrobiologia (2010) 651:279–289 Angermeier, P. L. & J. R. Karr, 1984. Fish communities along environmental gradients in a system of tropical stream. In Zaret, T. M. (ed.), Evolutionary Ecology of Neotropical Freshwater Fishes. Dr. W. Junk Publishers, The Hague: 39–57. Arau´jo, F. J., B. C. T. Pinto & T. P. Teixeira, 2009. Longitudinal patterns of fish assemblages in a large tropical river in southeastern Brazil: evaluating environmental influences and some concepts in river ecology. Hydrobiologia 618: 89–107. Arrington, D. A. & K. O. Winemiller, 2006. Habitat affinity, the seasonal flood pulse, and community assembly in the littoral zone of a neotropical floodplain river. Journal of the North American Benthological Society 25: 126–141. Batista, V. S. & F. N. Rego, 1996. Ana´lise de associac¸o˜es de peixes em riachos do estua´rio do Rio Tibiri, Maranha˜o. Revista Brasileira de Biologia 56: 163–176. Benneman, S. T., L. G. Capra, W. Galves & O. A. Shibata, 2006. Dinaˆmica tro´fica de Plagioscion squamosissimus (Perciformes, Sciaenidae) em trechos de influeˆncia da represa Capivara (rios Paranapanema e Tibagi). Iheringia, Se´rie Zoologia 96: 115–119. Bizerril, C. R. S. F., 1997. Mudanc¸as temporais de comunidades ´ıcticas em uma bacia hidrogra´fica do leste brasileiro. Comunicac¸o˜es do Museu de Cieˆncia e Tecnologia da PUCRS, Se´rie Zoologia 10: 53–75. Boneto, A. A., W. Dioni & C. Pignalberi, 1969. Limnological investigations on biotic communities in the Middle Parana River valley. Verhandlungen der Internationalen Vereinigung fu¨r theoretische und angewandte Limnologie 17: 1035–1050. Bu¨hrnheim, C. M. & C. Cox-Fernandes, 2001. Low seasonal variation of fish assemblages in Amazonian rain Forest streams. Ichthyological Exploration of Freshwaters 12: 65–78. Bu¨hrnheim, C. M. & C. Cox-Fernandes, 2003. Structure of fish assemblages in Amazonian rain-forest streams: effects of habitats and locality. Copeia 2: 255–262. Chao, A. & T. J. Shen, 2003. Program SPADE (Species Prediction and Diversity Estimation). Program and User’s Guide [available on internet at http://chao.stat.nthu.edu.tw]. Clarke, K. R. & W. M. Warwick, 1994. Similarity-based testing for community pattern: the 2-way layout with no replication. Marine Biology 118: 167–176. Connell, J. H. & W. P. Sousa, 1983. On the evidence needed to judge ecological stability or persistence. The American Naturalist 121: 789–824. Correa, S. B., K. O. Winemiller, H. Lo´pez-Ferna´ndez & M. Galeti, 2007. Evolutionary Perspectives on Seed Consumption and Dispersal by Fishes. BioSciense 57: 748– 756. Cotner, J. B., J. V. Montoya, D. L. Roelke & K. O. Winemiller, 2006. Seasonally variable riverine production in the Venezuelan llanos. Journal of the North American Benthological Society 25: 171–184. de Me´rona, B. & J. Rankin-de-Me´rona, 2004. Food resource partitioning in a fish community of the central Amazon floodplain. Neotropical Ichthyology 2: 75–84. Engen, S. & R. Lande, 1996. Populations dynamic models generating the lognormal species abundance distribution. Mathematical Biosciences 132: 169–183.
Hydrobiologia (2010) 651:279–289 Espı´rito-Santo, H. M. V., W. E. Magnusson, J. Zuanon, F. P. Mendonc¸a & V. L. Landeiro, 2009. Seasonal variation in the composition of fish assemblages in small Amazonian forest streams: evidence for predictable changes. Freshwater Biology 54: 536–548. Fittkau, E. J., 1967. On the ecology of Amazonian rain-forest streams. Atlas do Simpo´sio sobre Biota Amazoˆnica, Rio de Janeiro 3: 97–108. Fittkau, E. J., U. Irmler, W. J. Junk, F. Reiss & G. W. Schimidt, 1975. Productivity, biomass and population dynamics in Amazonian water bodies. In Solley, F. B. & E. Medina (eds), Tropical Ecological Systems. Trends in terrestrial and aquatic research, New York: 281–311. Galacatos, K., R. Barriga-Salazar & D. J. Stewart, 2004. Seasonal and habitat influences on fish communities within the lower Yasuni River basin of the Ecuadorian Amazon. Environmental Biology of Fishes 71: 33–51. Goulding, M., 1980. The fishes and the forest: explorations in Amazonian natural history. University of California Press, Berkeley. Goulding, M., M. L. Carvalho & E. J. G. Ferreira, 1988. Rio Negro, rich life in the poor water. SPB Academic Publishing, The Haugue. Goulding, M., R. B. Barthem & E. J. G. Ferreira, 2003. The Smithsonian Atlas of the Amazon. Smithsonian Books, Washington. Grossman, G. D., P. B. Moyle & J. O. Whitaker Jr, 1982. Stochasticity in structural and functional characteristics of an Indiana stream fish assemblage: a test of community theory. The American Naturalist 120: 423–454. Grossman, G. D., J. F. Dowd & M. Crawford, 1990. Assemblage stability in stream fishes: a review. Journal of Environmental Management 14: 661–671. Halley, J. & P. Inchausti, 2002. Lognormality in ecological time series. Oikos 99: 518–530. Hill, J. K. & K. C. Hamer, 1998. Using species abundance models as indicators of habitat disturbance in tropical forest. Journal of Applied Ecology 35: 458–460. Junk, W. J., 1983. As a´guas da regia˜o amazoˆnica. In Salati, E., H. O. R. Schubert, W. J. Junk & A. E. Oliveira (eds), Amazoˆnia Desenvolvimento, Integrac¸a˜o, Ecologia. CNPq/ Editora Brasiliense, Brası´lia: 10–18. Kno¨ppel, H. A., 1970. Food of Central Amazonian fishes: contribution to the nutrient-ecology of Amazonian rain forest streams. Amazoniana 2: 257–352. Lasso, C. A., B. Anabel Rial & M. Lasso-Alcala, 1999. Composicio´n y variabilidad espacio-temporal de las comunidades de peces en ambientes inundables de los llanos de Venezuela. Acta Biologica Venezuelana 19: 1–28. Lima, C. A. & M. Goulding, 1998. Os frutos do tambaqui: ecologia, conservac¸a˜o e cultivo na Amazoˆnia. Sociedade Civil Mamiraua´, CNPq, Brası´lia. Lowe-McConnell, R. H., 1963. The fishes of the Rupununi savana district of Britsh Guiana, South Ame´rica. Part 1. Ecological grouping of fish species and effects of the seasonal cycle in fish. Journal of the Linnean Society 45: 103–143. Lowe-McConnell, R. H., 1975. Fish communities in tropical freshwater: their distribution, ecology and evolution. Longman, London.
289 Lowe-McConnell, R. H., 1979. Ecological aspects of seasonality in fishes of tropical waters. Symposia of the Zoological Society of London 44: 219–241. Lowe-McConnell, R. H., 1999. Estudos Ecolo´gicos de Comunidades de Peixes Tropicais. Edusp, Sa˜o Paulo. Magurran, A. E., 1988. Ecological Diversity and its Measurement. Cambridge University Press, Cambridge. McCune, B. & J. B. Grace, 2002. Analysis of Ecological Communities. MjM Software, Gleneden Beach. Poole, W. H., 1974. An Introduction to Quantitative Ecology. McGraw-Hill, New York. Rayner, T. S., B. J. Pusey & R. G. Pearson, 2008. Seasonal flooding, in stream habitat structure and fish assemblages in the Mulgrave River, north-east Queensland: towards a new conceptual framework for understanding fish-habitat dynamics in small tropical rivers. Marine and Freshwater Research 59: 97–116. Sabino, J. & J. Zuanon, 1998. A stream fish assemblage in Central Amazonia: distribution, activity patterns and feeding behavior. Ichthyological Exploration of Freshwaters 8: 201–210. Saint-Paul, U., J. Zuanon, M. A. Villacorta-Correa, M. Garcia, N. N. Fabre´, U. Berger & W. J. Junk, 2000. Fish communities in Central Amazoˆnia white and blackwaters floodplains. Environmental Biology of fish 57: 235–250. Santos, G. M. & E. J. G. Ferreira, 1999. Peixes da Bacia Amazoˆnica. In Lowe-McConnell, R. H. (ed.), Estudos Ecolo´gicos de Comunidades de Peixes Tropicais. Edusp, Sa˜o Paulo: 345–373. Saul, W. G., 1975. An ecological study of fishes at a site in upper Amazonian Ecuador. Proceedings of the Academy of Natural Sciences of Philadelphia 127: 93–134. Silva, C. P. D., 1995. Community structure of fish in urban and natural streams in the Central Amazon. Amazoniana 13: 221–236. Silvano, R. A. M., B. D. do Amaral & O. T. Oyakawa, 2000. Spatial and temporal patterns of diversity and distribution of the Upper Jurua´ River fish community (Brazilian Amazon). Environmental Biology of Fishes 57: 25–35. Sioli, H., 1967. Studies in Amazonian waters. Atas do Simpo´sio sobre biota aqua´tica 3: 9–50. Walker, I., 1995. Amazonian streams and small rivers. In Tundisi, J. G., C. E. M. Bicudo & T. M. Tundisi (eds), Limnology in Brazil. Brazilian Academy of Sciences, Rio de Janeiro: 167–193. Walker, I., 2001. Maintenance of biodiversity in the benthic fauna of an Amazonian forest stream. In Chao, N. L., P. Petry, L. Prang, L. Sonneschien & M. Tlusty (eds), Conservation and management of ornamental fish resources of the Rio Negro basin, Amazonia, Brazil— Project Piaba. Editora da Universidade do Amazonas, Manaus: 145–160. Welcomme, R., 1979. Fisheries Ecology of Floodplains Rivers. Longman, London. Winemiller, K. O. & D. B. Jepsen, 1998. Effects of seasonality and fish movement on tropical river food webs. Journal of Fish Biology 53: 267–296. Wootton, R. J., 1992. Fish Ecology. Chapman Hall, New York. You, M., L. Vasseur, J. Re´ginie`re & Y. Zheng, 2009. The three dimensions of species diversity. The Open Conservation Biology Journal 3: 82–88.
123
