Environmental gradients structure ichthyofaunal communities longitudinally along river networks via the selective filtering of species’ traits. In many instances, these environmental influences have created distinct zones of co-occurring fish species. Zonation studies have most often been conducted with taxonomic data (species x site matrices), but the increasing availability of functional trait data creates an opportunity to build more rigorous understanding of species’ co-occurrence patterns. Notably, zonation studies that use taxonomic data may not reveal the same patterns as studies based on trait data. In this study, we tested for distinct ichthyofaunal zonation in James River Basin, VA using a combination of historical (1950-1987) and contemporary fish occurrence records (1986-2016) that were aggregated within 12-digit hydrologic units (HU). Zonation tests were performed separately for taxonomic data and functional trait data, using a combination of non-metric multidimensional scaling and k-means cluster analysis. We detected three distinct taxonomic zones and three functional trait zones within the James River Basin. In addition, through identifying that taxonomic dissimilarity between HUs was strongly correlated with functional dissimilarity, these zonation patterns were determined to not be significantly different.

Thesis (M.Sc. ( Physiology )) --University of Limpopo, 2011 / Refer to document / the National Research Foundation

This study investigated the causes of high level of intra-and inter-population variation known to occur in the morphology of fish in the genus Hypseleotris Eleotride in southern Australia, particularly within the Murray-Darling river system. The three major objectives of the study were, identify the number and distribution of species,determine the genetic structure of the populations and analyse relationships between species and consider the process of speciation in this species complex. The investigation of morphological variation in Hypseleotris confirmed the presence of two well known species i.e. H. compressa and H. galli, in the coastal rivers and also of the inland species H. klunzingeri. Populations of Hypseleotris klunzigeri sensu lato in inland river were found to be very highly variable and analysis using discriminant functions and principle component analysis showed the widespread presence of three forms (A, B1 and B2). The analysis was confused by the presence of north/south clines and upstream/downstream variation in characteristic in each form. After these factors were removed, there was still a great deal of variation in each population. The presence of hybrids between each pair of inland species, identified by both morphological and genetic data, further confused the analysis and makes identification of all specimens to species in the field difficult. Examination of type material of H. Klunzingeri showed that this belonged to form B2. The other forms can be related to the undescribed species, Midgley's carp gudgeon and Lake's carp gudgeon. Keys to the species in the complex in southeastern Australia are given. The morphological and genetic data show that H. compressa and H. klunzingeri are sister species, primarily separated by the eastern uplands. Similarly, the coastal species, H. galli is related to form B1 and more distantly, to form A. Possible scenarios for the complex are given. / Doctor of Philosophy (PhD)

Freshwater systems offer important opportunities to investigate the consequences of intrinsic biological and extrinsic environmental factors on the distribution of genetic variation, and hence population genetic structure. Drainages serve to isolate populations and so preserve historical imprints of population processes. Nevertheless, dispersal between and within drainages is important if the biology of the species confers a good dispersal capability. Knowledge of the population genetic structure or phylogeographic patterns of Australia's freshwater fish fauna is generally depauperate, and the present study aimed to increase this knowledge by investigating patterns of genetic diversity in three Australian species of freshwater fish. I was interested in the relative importance of dispersal capability, the hierarchical nature of stream structure and the consequences of earth history events on patterns of genetic diversity among populations. I examined three species from three families of Australian freshwater fish, Pseudomugil signifer (Pseudomugilidae), Craterocephalus stercusmuscarum (Atherinidae) and Hypseleotris compressa (Gobiidae). These species are abundant, have wide overlapping distributions and qualitatively different dispersal capabilities. I was interested in attempting to unravel how the biological, environmental and historical factors had served to influence the patterns and extent of genetic diversity within each species, thereby inferring some of the important evolutionary processes which have affected Australia's freshwater fauna. I used allozyme and 500-650bp sequences from the ATPase6 mitochondrial DNA (mtDNA) gene to quantify the patterns of genetic variation at several hierarchical levels: within populations, among populations within drainages and among drainages. I collected fish at several spatial scales, from species wide to multiple samples within drainages; samples were collected from the Northern Territory, Queensland and New South Wales. The species with the highest potential for dispersal, H. compressa, exhibited the lowest levels of genetic differentiation as measured at several allozyme loci (H. compressa: FST=0.014; P. signifer FST=0.58; C. stercusmuscarum FST=0.74). Populations of H. compressa also had low levels of mtDNA differentiation, with many recently derived haplotypes which were widespread along the coast of Queensland. This suggested either considerable gene flow occurs or recent demographic change in the populations sampled. As there was no relationship between geographic distance and genetic differentiation, the populations appeared to be out of genetic drift - gene flow equilibrium, assuming the two-dimensional stepping stone model of gene flow. Estimating contemporary gene flow was thus difficult. It was apparent that there has been a recent population expansion and / or contraction of H. compressa populations. It was concluded that there has been considerably more connectivity among populations of H. compressa in the recent past than either of the other study species. Populations of P. signifer showed considerable genetic subdivision at different hierarchical levels throughout the sampled range, indicating gene flow was restricted, especially between separate drainages. Two widely divergent regional groups which had high ATPase6 sequence divergence and approximately concordant patterns at allozyme loci were identified. Interestingly, the groups mirrored previous taxonomic designations. There was also significant subdivision among drainages within regional groups. For example, the adjacent Mulgrave-Russell and Johnstone drainages had individuals with haplotypes that were reciprocally monophyletic and had large allozyme frequency differences. This allowed me to examine the patterns of genetic differentiation among populations within drainages of two essentially independent, but geographically close systems. There was as much allozyme differentiation among populations within subcatchments as there was between subcatchments within drainages, and significant isolation by distance among all populations sampled within a drainage. This suggested that the estuarine confluence between subcatchments was not a barrier to P. signifer, but that distance was an important component in the determination of the distribution of genetic diversity within drainages in P. signifer. There were three main areas of investigation for C. stercusmuscarum: comparing upland and lowland streams of the drainages in north Queensland, investigating the consequences of eustasy on coastal margin populations and examining the intriguing distribution of the two putative sub species, C. s. stercusmuscarum and C. s. fulvus in south east Queensland. First, as populations in upland areas of east coast flowing rivers are above large discontinuities in the river profile, their occurrence is presumably the result of gene flow to and / or from lowland areas, or the result of invasions via the diversion of western flowing rivers. Concordant patterns at both genetic markers revealed that the latter possibility was the most likely, with fixed allozyme differences between upland and lowland populations, and large mtDNA sequence divergence. Indeed, it appeared that there may have been two independent invasions into the upland areas of rivers in North Queensland. Second, lowland east coast populations also had large, although not as pronounced, levels of population subdivision. Lack of isolation by distance, but with a concomitant high level of genetic differentiation among many comparisons, was consistent with a scenario of many small, isolated subpopulations over the range. Interestingly, widespread populations in central Queensland coastal populations (drainages which receive the lowest rainfall) were relatively genetically similar. This was consistent with the widest part of the continental shelf which at periods of lower sea level apparently formed a large interconnected drainage, illustrating the effect of eustatic changes on populations inhabiting a continental margin. Third, putative C. s. fulvus in lowland coastal Queensland drainages were genetically more similar to a population of C. s. fulvus collected from a tributary of the Murray-Darling (western flowing) than they were to adjacent putative C. s. stercusmuscarum. This implied that populations in south east Queensland, north to approximately the Burnett River, appeared to be derived from western flowing streams, and not via dispersal from other lowland east coast populations. Determining the relative importance of intrinsic and extrinsic factors to the development of population genetic structure is a difficult task. The present study demonstrated that the species with the highest dispersal potential had the lowest levels of genetic differentiation, waterfalls can limit gene flow, eustasy acts to join and separate populations leading to complex genetic patterns and that drainage rearrangements are important in determining the distribution of genetic diversity of populations now inhabiting isolated drainages. A difficulty with generalising about population genetic structure in obligate freshwater animals is the unique history of not only each drainage, but also the streams within that drainage and the idiosyncratic biological dynamics of the populations inhabiting those drainages.

The overall objective of this thesis was to determine selenium (Se) levels in the major compartments of aquatic ecosystems and correlate these data with potential Se effects on early life stages of two native fish species. This work was conducted at two uranium (U) mines located in northern Saskatchewan, Key Lake mine and McClean Lake mine. In addition, a site fidelity study was conducted at Key Lake mine to evaluate movement patterns of northern pike inhabiting lakes receiving effluent discharges.<p> At Key Lake mine, Se was accumulated and biomagnified several orders of magnitude higher than its concentration in water (0.7-2.7 µg/L) in lakes receiving discharges, with Se in prey organisms reaching levels above the proposed 3-11 µg/g dry weight (DW) dietary toxicity threshold for fish. Increased concentrations of Se in aquatic biota led to an increase in the Se concentrations in eggs and tissues of northern pike that rely on these organisms as food sources. Furthermore, increases in the incidence of Se-induced deformities above 30% were recorded in fry originating from adults exposed to high levels of dietary Se (> 3µg/g, DW). The increased frequency of deformities found in northern pike fry was associated with a significant increase in the level of Se in northern pike eggs from exposure sites (31.28 - 48.23 µg/g DW) compared to reference (3.19 ± 0.29 µg/g DW).<p> At McClean Lake mine, Se was accumulated and biomagnified through the aquatic food chain with concentrations in some biota groups (e.g., forage fish) exceeding the lower limit (> 3µg/g DW) of the 3-11µg/g (DW) threshold for dietary Se toxicity in fish. Although both northern pike and white sucker females collected from the exposure site showed greater levels of Se in egg and tissues compared to fish collected from a reference site (likely caused by exposure to elevated levels of Se in prey organisms), no increases in Se-induced deformities were found in the developing fish larvae. The lack of a toxic response in fish larvae is in agreement with Se thresholds for early life stage deformities, with egg Se concentrations in northern pike and white sucker collected at the exposure site below the proposed 10 µg/g (DW) threshold associated with the presence of developmental abnormalities. The applicability of the proposed 7.91 µg/g (whole body, DW) Se toxicity threshold to cold water fish is controversial given that most of the research has focused on warm water fish. Therefore, there is an urgent need to conduct studies that allow us to better understand the environmental fate and effects of Se in north temperate (cold water) aquatic systems. The results of my research will contribute valuable information for the establishment of a realistic and environmentally relevant Se threshold for the protection of fish populations in Canadian waters. During the site fidelity study, fish locations were seasonally and daily recorded using a Lotek SRX_400 receiver with handheld Yagi antenna. The results suggest that tagged pike did not migrate out of the study area throughout the study period, with the mean distance traveled ranging from 50 to 400 m. Differences in movement (distance traveled) and home range were found between reference and exposure sites. Overall data suggest that radio-telemetry is a useful tool in environmental studies. This information on northern pike behavior will be valuable towards developing non-lethal sampling methods that could be applied for assessing the effects of industrial discharges in north temperate aquatic ecosystems.

Podeu escriure el text directament o arrossegar-lo des d'un altre documentL'objectiu d'aquesta tesi és contribuir a l'ús dels peixos continentals com a indicadors de l'estat ecològic a la conca Mediterrània. En el primer treball es va detectar que encara que tots els índex biològics estaven correlacionats significativament, els peixos integren i expressen els estressos de manera i a una escala diferents, aportant una informació complementària als altres índexs. Al segon article es van estudiar els cabals de sis conques catalanes. S'ha mostrat que els règims hídrics estan alterats amb una tendència a la disminució del cabal i del nivell dels aqüífers. S'ha detectat quatre mètriques de peixos que es troben significativament afectades en zones més castigades per manca d'aigua degut a l'activitat humana. Es discuteix la necessitat de conèixer en profunditat el règim hídric de cada conca abans d'utilitzar els índex biològics. Al tercer article es va detectar que la composició d'espècies capturades va variar significativament al llarg del buidat amb un augment de l'alburn (A. alburnus) a les aigües pelàgiques durant els dies de pitjor qualitat de l'aigua, confirmant que l'alburn és més tolerant a la mala qualitat de l'aigua que la madrilleta vera (R. rutilus) i suggereix el seu potencial com a bioindicador. La condició d'aquestes dues espècies va canviar significativament al llarg del buidat de manera molt estreta amb la qualitat de l'aigua. Al quart capítol es va estudiar la biologia dels peixos d'un embassament altament contaminat (Flix). El percentatge de DELT anomalies i la presència de paràsits externs era major en la zona impactada que als punts de control i els valors més alts de pes eviscerat i pes del fetge estaven als punts de control. Les respostes van ser diferents per cada espècie i la carpa va ser la que va mostrar més clarament els impactes. / Podeu escriure el text directament o arrossegar-lo des d'un altre documentThe aim of this thesis is to contribute to the use of freshwater fish as ecological indicators in the Mediterranean basin. In the first article we found that although most biological indices were correlated, fish reflected different ecological aspects due to their particular features. In the second article the stream flow regimes of six Mediterranean basins were studied. A decrease of streamflow and aquifer levels was detected, despite no observed decrease of rainfall precipitation. Of the thirty metrics tested to detect sites impacted by water abstraction, we detected four significant fish metrics. Furthermore, the role of biotic indices when the river is artificially dry is discussed. In the third article we found that species composition in the pelagic zone varied significantly during the drawdown with higher proportion of bleak (A. alburnus) during the days of worst water quality, confirming that bleak is more tolerant than roach (R. rutilus) to poor water quality. The weight-length relationship of roach and bleak also varied significantly during the drawdown with close relationship between water quality and fish condition. In the fourth article the condition and fecundity of freshwater fishes were assessed in a highly polluted reservoir (Flix reservoir). We have shown significant increases of DELT anomalies and ectoparasite prevalences and decreases in condition and fecundity of several freshwater fish at the impacted area. The responses to the pollutants were species-specific and common carp was the species that showed more markedly the effects.

The overall objective of this thesis was to determine selenium (Se) levels in the major compartments of aquatic ecosystems and correlate these data with potential Se effects on early life stages of two native fish species. This work was conducted at two uranium (U) mines located in northern Saskatchewan, Key Lake mine and McClean Lake mine. In addition, a site fidelity study was conducted at Key Lake mine to evaluate movement patterns of northern pike inhabiting lakes receiving effluent discharges.<p> At Key Lake mine, Se was accumulated and biomagnified several orders of magnitude higher than its concentration in water (0.7-2.7 µg/L) in lakes receiving discharges, with Se in prey organisms reaching levels above the proposed 3-11 µg/g dry weight (DW) dietary toxicity threshold for fish. Increased concentrations of Se in aquatic biota led to an increase in the Se concentrations in eggs and tissues of northern pike that rely on these organisms as food sources. Furthermore, increases in the incidence of Se-induced deformities above 30% were recorded in fry originating from adults exposed to high levels of dietary Se (> 3µg/g, DW). The increased frequency of deformities found in northern pike fry was associated with a significant increase in the level of Se in northern pike eggs from exposure sites (31.28 - 48.23 µg/g DW) compared to reference (3.19 ± 0.29 µg/g DW).<p> At McClean Lake mine, Se was accumulated and biomagnified through the aquatic food chain with concentrations in some biota groups (e.g., forage fish) exceeding the lower limit (> 3µg/g DW) of the 3-11µg/g (DW) threshold for dietary Se toxicity in fish. Although both northern pike and white sucker females collected from the exposure site showed greater levels of Se in egg and tissues compared to fish collected from a reference site (likely caused by exposure to elevated levels of Se in prey organisms), no increases in Se-induced deformities were found in the developing fish larvae. The lack of a toxic response in fish larvae is in agreement with Se thresholds for early life stage deformities, with egg Se concentrations in northern pike and white sucker collected at the exposure site below the proposed 10 µg/g (DW) threshold associated with the presence of developmental abnormalities. The applicability of the proposed 7.91 µg/g (whole body, DW) Se toxicity threshold to cold water fish is controversial given that most of the research has focused on warm water fish. Therefore, there is an urgent need to conduct studies that allow us to better understand the environmental fate and effects of Se in north temperate (cold water) aquatic systems. The results of my research will contribute valuable information for the establishment of a realistic and environmentally relevant Se threshold for the protection of fish populations in Canadian waters. During the site fidelity study, fish locations were seasonally and daily recorded using a Lotek SRX_400 receiver with handheld Yagi antenna. The results suggest that tagged pike did not migrate out of the study area throughout the study period, with the mean distance traveled ranging from 50 to 400 m. Differences in movement (distance traveled) and home range were found between reference and exposure sites. Overall data suggest that radio-telemetry is a useful tool in environmental studies. This information on northern pike behavior will be valuable towards developing non-lethal sampling methods that could be applied for assessing the effects of industrial discharges in north temperate aquatic ecosystems.

Made available in DSpace on 2014-06-11T19:30:30Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-02-05Bitstream added on 2014-06-13T21:01:14Z : No. of bitstreams: 1 souza_ma_dr_jabo.pdf: 534415 bytes, checksum: b5ee5194dc95e8eab1f6290e4a93d680 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Universidade Estadual Paulista (UNESP) / O presente estudo objetivou a avaliação da eficiência do processo de ultrafiltração seguida da biodigestão anaeróbia no tratamento de efluentes de frigorífico de tilápia. Para tanto, realizada ultrafiltração dos diferentes resíduos gerados no processamento de tilápia (sangria - SG, filetagem - FL e processo contínuo - PC) com membrana de ultrafiltração modelo KOCH, HF1.0-45-XM50 visando avaliar a eficiência da mesma na redução de matéria orgânica, desempenho hidráulico e recuperação proteica. A partir do concentrado obtido na ultrafiltração foi possível avaliar a biodigestão anaeróbia dos diferentes resíduos utilizando estrume bovino como inóculo, estabelecendo quatro tratamentos sendo: sangria, processo contínuo, filetagem e controle, sendo este último composto somente de estrume bovino e água. No processo de ultrafiltração foi possível obter alta remoção de matéria orgânica em todos os efluentes gerados, principalmente em demanda química de oxigênio, nitrogênio total, sólidos suspensos totais e proteína bruta, tendo médias de redução de DQO de 95,21%, 96,21%, 76,26%, NT de 94,74%, 92,49%, 66,54%, SST 96,25%, 94,33%, 83,73% e PB 94,74%, 92,48%, 66,54% para sangria, processo contínuo e filetagem, respectivamente. O desempenho da membrana, medido pelo fluxo de permeado, e a retenção proteica não apresentam diferença significativa entre os tratamentos, sendo a recuperação proteica de 99,99% para todos os tratamentos. Já o concentrado do resíduo de sangria apresentou maior concentração protéica, com média de 70,43%, enquanto os demais tratamentos apresentaram médias de 60,42% e 41,44% para os tratamentos de processo contínuo e filetagem, respectivamente. Para a biodigestão anaeróbia ocorre diferença estatística (P<0,01) entre os tratamentos a partir do 37º dia, tendo o PC com maior produção acumulada, assim como para produção... / This study aimed to evaluate the efficiency of ultrafiltration followed by anaerobic digestion to effluent from tilapia’s frigorific. Therefore, ultrafiltration made of different wastes generated in the processing of tilapia (bleeding - BL, filleting - FL and continuous process - PC) by ultrafiltration membrane model KOCH, HF1.0-45-XM50 to evaluate the efficiency in organic matter redution, hydraulic performance and protein recovery. From the concentrate obtained in the ultrafiltration was possible to evaluate the anaerobic digestion using cattle manure as inoculum, establishing four treatments: bleeding, continuous process control and filleting, the latter being composed only manure and water. In the ultrafiltration process was possible to obtain high removal of organic matter in all effluents generated mainly in chemical oxygen demand, total nitrogen, total suspended solids and crude protein, with average reductions of COD 95.21%, 96.21 %, 76.26%, TN 94.74%, 92.49%, 66.54%, TSS 96.25%, 94.33%, 83.73% and CP 94.74%, 92.48% , 66.54% for bleeding, continuous process and filleting, respectively. The membrane performance, measured by the permeate flux and protein retention were not significantly different between the treatments, and the protein recovery was 99.99% for all treatments. The concentrated residue of bleeding had a higher protein concentration, with an average of 70.43%, while the other treatments had means of 60.42% and 41.44% for the continuous process and filleting, respectively. For the anaerobic digestion could be obtained statistical difference (P <0.01) between the treatments over the 37th day, and the PC with the highest cumulative production, as well as daily production (0,003 m3. biogas.day-1) and production by m3.kg-1 influent (0.0297). For gases composition does not occur difference among treatments, but FL has a higher methane average, with 78.05%, while... (Complete abstract click electronic access below)

Resumo: O presente estudo objetivou a avaliação da eficiência do processo de ultrafiltração seguida da biodigestão anaeróbia no tratamento de efluentes de frigorífico de tilápia. Para tanto, realizada ultrafiltração dos diferentes resíduos gerados no processamento de tilápia (sangria - SG, filetagem - FL e processo contínuo - PC) com membrana de ultrafiltração modelo KOCH, HF1.0-45-XM50 visando avaliar a eficiência da mesma na redução de matéria orgânica, desempenho hidráulico e recuperação proteica. A partir do concentrado obtido na ultrafiltração foi possível avaliar a biodigestão anaeróbia dos diferentes resíduos utilizando estrume bovino como inóculo, estabelecendo quatro tratamentos sendo: sangria, processo contínuo, filetagem e controle, sendo este último composto somente de estrume bovino e água. No processo de ultrafiltração foi possível obter alta remoção de matéria orgânica em todos os efluentes gerados, principalmente em demanda química de oxigênio, nitrogênio total, sólidos suspensos totais e proteína bruta, tendo médias de redução de DQO de 95,21%, 96,21%, 76,26%, NT de 94,74%, 92,49%, 66,54%, SST 96,25%, 94,33%, 83,73% e PB 94,74%, 92,48%, 66,54% para sangria, processo contínuo e filetagem, respectivamente. O desempenho da membrana, medido pelo fluxo de permeado, e a retenção proteica não apresentam diferença significativa entre os tratamentos, sendo a recuperação proteica de 99,99% para todos os tratamentos. Já o concentrado do resíduo de sangria apresentou maior concentração protéica, com média de 70,43%, enquanto os demais tratamentos apresentaram médias de 60,42% e 41,44% para os tratamentos de processo contínuo e filetagem, respectivamente. Para a biodigestão anaeróbia ocorre diferença estatística (P<0,01) entre os tratamentos a partir do 37º dia, tendo o PC com maior produção acumulada, assim como para produção... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This study aimed to evaluate the efficiency of ultrafiltration followed by anaerobic digestion to effluent from tilapia's frigorific. Therefore, ultrafiltration made of different wastes generated in the processing of tilapia (bleeding - BL, filleting - FL and continuous process - PC) by ultrafiltration membrane model KOCH, HF1.0-45-XM50 to evaluate the efficiency in organic matter redution, hydraulic performance and protein recovery. From the concentrate obtained in the ultrafiltration was possible to evaluate the anaerobic digestion using cattle manure as inoculum, establishing four treatments: bleeding, continuous process control and filleting, the latter being composed only manure and water. In the ultrafiltration process was possible to obtain high removal of organic matter in all effluents generated mainly in chemical oxygen demand, total nitrogen, total suspended solids and crude protein, with average reductions of COD 95.21%, 96.21 %, 76.26%, TN 94.74%, 92.49%, 66.54%, TSS 96.25%, 94.33%, 83.73% and CP 94.74%, 92.48% , 66.54% for bleeding, continuous process and filleting, respectively. The membrane performance, measured by the permeate flux and protein retention were not significantly different between the treatments, and the protein recovery was 99.99% for all treatments. The concentrated residue of bleeding had a higher protein concentration, with an average of 70.43%, while the other treatments had means of 60.42% and 41.44% for the continuous process and filleting, respectively. For the anaerobic digestion could be obtained statistical difference (P <0.01) between the treatments over the 37th day, and the PC with the highest cumulative production, as well as daily production (0,003 m3. biogas.day-1) and production by m3.kg-1 influent (0.0297). For gases composition does not occur difference among treatments, but FL has a higher methane average, with 78.05%, while... (Complete abstract click electronic access below) / Orientador: Rose Meire Vidotti / Coorientador: Jorge de Lucas Júnior / Banca: Aldi Feiden / Banca: Claudinei da Cruz / Banca: Jairo Augusto Campos de Araújo / Banca: Lúcia Helena Sipaúba Tavares / Doutor

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No. of bitstreams: 1 Dissertação - Fabiola Artemis Souza do Valle.pdf: 1244841 bytes, checksum: 7cbbda8fc49088d694023b6c8fabfcfe (MD5) Previous issue date: 2013-03-25 / CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico / Variations in the type of submerged substrate and the depth of the channel are physical characteristic of the streams environments that play an important role in determining the trophic structure of the fish. However, that relation in tropical streams and Amazonian streams doesn’t know. In this sense, ecological aspectsrelated to trophic structure of fish communities in upland streamswere studied, especially those related to the influence that the heterogeneity of substrate and depth have on the composition of trophic categories of the fishes. The trophic structure of 59 streams of 1st and 2nd order in different areas of the Brazilian Amazon were studied, which resulted in the trophic classification of 172 species of fish. There was no correlation between the diversity of trophic categories of fish and diversity of substrates or channel depth on the areas sampling. However, the relative biomass of fish in the samples showed positive feedback with the diversity of substrates, but not with the depth. Analysis of stomach contents of fish revealed that items autochthonous origin have greater importance; most species studied were classified as autochthonous insectivorous. It is possible that the lack of relationship between the substrate heterogeneity and diversity of trophic categories result from the fact that the system of fish species occupy almost the entire small water column, show the generalized diet and foraging strategy opportunistic, consuming both autochthonous as allochthonous items explaining, therefore, the lack of relationship between the diversity of substrates and trophic categories.Thus, the different types of substrate are used for both shelter and foraging, explaining the lack of correlation. The depth of the environment didn’t influence the diversity of trophic categories, once headwater streams have smaller dimensions and well closed canopy, which impede the entry of light and, consequently, the presence of larger individuals.The lack of correlation of relative fish biomass with depth can be explained by the physical limitation to the use of space (represented by channel lower depth), that seems to be an important factor which impede the occupation of small streams by a greater diversity of species.On the other hand, the relationship observed between the relative fish biomass and diversity of substrates may be the result of energy resources derived from autotrophic processes, which seem to supply a large quantity of individuals and/or total weight of fish, which makes these organisms depend on food resources of autochthonous origin. / Variações nos tipos de substrato submerso e na profundidade do canal são características físicas de ambientes de riachos que desempenham papel importante na determinação da estrutura trófica das comunidades de peixes. Entretanto, essas relações em riachos tropicais e em igarapés amazônicos são insipientes. Neste sentido, foram estudados aspectos ecológicos relacionados à estrutura trófica de comunidades de peixes em igarapés de terra firme, especialmente aqueles relacionados à influência que a heterogeneidade de substratos e a profundidade exercem sobre composição das categorias tróficas dos peixes. Foi estudada a estrutura trófica de 59 igarapés de 1ª e 2a ordem em diferentes áreas da Amazônia Brasileira, que resultaram na classificação trófica de 172 espécies de peixes. Não houve correlação entre a diversidade de categorias tróficas dos peixes e a diversidade de substratos ou a profundidade do canal nas áreas de amostragem. Entretanto, a biomassa relativa dos peixes nas amostras apresentou relação positiva com a diversidade dos substratos, mas não com a profundidade. As análises de conteúdos estomacais dos peixes revelaram que os itens de origem autóctones tem maior importância; grande parte das espécies estudadas foi classificada como insetívoro autóctone. É possível que a ausência de relação entre heterogeneidade do substrato e diversidade de categorias tróficas decorra do fato do sistema das espécies de peixes ocuparem quase a totalidade da pequena coluna d’água, apresentarem a dieta generalizada e uma estratégia de forrageamento oportunista, consumindo tanto itens autóctones quanto alóctones explicando, portanto, a ausência de relação entre a diversidade de categorias tróficas e de substratos. Assim, os diferentes tipos de substrato são utilizados para abrigo e forrageamento, explicando a ausência de correlação. A profundidade do ambiente não influenciou na diversidade das categorias tróficas, uma vez que igarapés de cabeceiras possuem dimensões menores e dossel bem fechado, o que impede a entrada de luz e, consequentemente, a presença de indivíduos de maior porte. A ausência de correlação da biomassa relativa de peixes com a profundidade pode ser explicada pela limitação física para o uso do espaço (representada pela baixa profundidade do canal), que parece ser um fator importante e que impossibilita a ocupação dos pequenos igarapés por uma maior diversidade de espécies.Por outro lado, a relação observada entre a biomassa relativa de peixes e a diversidade de substratos deve ser resultado dos recursos energéticos oriundos de processos autotróficos, que parecem suprir uma grande quantidade de indivíduos e/ou peso total de peixes, o que faz com que esses organismos dependam de recursos alimentares de origem autóctone.