The meniscus plays a central role in the transmission and distribution of load across the knee jo... more The meniscus plays a central role in the transmission and distribution of load across the knee joint. Meniscal lesions have recently been established as a cause of knee joint degeneration 1 . Meniscal calcifications are frequent and likely alter the normal biomechanics of the meniscus. Although MR imaging is the non-invasive technique of choice for the evaluation of knee, and more specifically meniscal pathology, it does not allow the facile visualization of meniscal calcifications 2 . This is due, in part, to a lack of contrast between the meniscal tissue and calcifications, both with relatively short intrinsic T2 relaxation times. In addition, the lack of spatial resolution with standard clinical sequences provides an additional challenge for the visualization of small, punctuate calcifications. We describe novel MR imaging techniques based on 2D-UTE inversion recovery and 3D-UTE data acquisition to address these factors. We assessed the ability of these sequences to allow the visualization, characterization and quantitative evaluation of meniscal calcifications. MATERIAL AND METHODS Ten human menisci with documented calcifications at visual inspection and with Faxitron imaging were analyzed. The specimens were placed in Perfluorooctyl Bromide solution. Imaging was performed on a 3T clinical magnet, using a high-resolution custom-built quadrature birdcage coil with an inside diameter of 2cm and a length of 10cm was used. MR sequences to characterize meniscal morphology were performed and included: T1 SE (TR 500/ TE 16.2/ FOV 7 / Slice thickness: 1.7mm/ matrix: 512x512 /NEX 2); 2D SPGR (TR 300/ TE 12/ Flip angle 30/ FOV 7 / Slice thickness: 1.7mm / matrix: 384 x 384 /NEX 2) ; PDFS (TR 2000 / TE 13 / FOV 7 / Slice thickness 1.7/ 512 x 384 /NEX 1); UTE FS (TR 500/ TE 8 microsecs / FOV 7 / Slice thickness 1.7 / 512 x 511/NEX 2) . A novel morphological and quantitative 3D UTE sequence was performed, using a short duration (40 μs) hard RF pulse for signal excitation followed by dual echo 3D radial ramp sampling. In order to quantify T2* values of the meniscal calcification, the dual 3D UTE acquisition was repeated three times with paired TEs of 8/5122 μs, 500/5622 μs, and 2000/7122 μs. Subtraction images were obtained for each pair of TEs. Other acquisition parameters included an isotropic FOV of 6 cm, TR of 35 ms, flip angle of 8 °, readout of 256, 40000 projections for a total scanning time of about 20-25 minutes. The projection data was re-gridded onto a 384×384×384 matrix and was followed by 3D Fourier transformation to produce the final 3D UTE images. Another quantitative technique using an IR pulse was also performed. An adiabatic inversion pulse (8.64ms in duration) was employed to invert the longitudinal magnetization of normal meniscal tissue and fat, while leaving the short T2 calcification largely unaffected. The images were viewed in the axial and sagittal planes. Menisci were divided into 3 thirds along their longitudinal axis, and the presence and absence of calcifications was noted. Whenever present, the calcifications were classified into punctuate or globular. The Faxitrons and MR sequences were analyzed independently by two musculoskeletal radiologists, in consensus. ROI placement on MR images was guided by comparison with Faxitron images of the menisci.
This study investigated for the first time the reproductive biology of Prochilodus lineatus in a ... more This study investigated for the first time the reproductive biology of Prochilodus lineatus in a system of rivers in southeastern Brasil, relating it to the role of tributary rivers in the reproductive success of this important commercial fish in the Upper Paraná River basin, where a cascade of hydroelectric dams were deployed. Specimens were caught bimonthly in three river sites: (S1) Grande River, downstream from the Porto Colômbia dam; (S2) Pardo River; and (S3) Mogi Guaçu River. Sex steroid plasma levels, fecundity, follicular atresia, oocyte diameter and gonadosomatic index (GSI) were compared among sites. In S1, fish exhibited changes in the reproductive parameters: lower GSI, oocyte diameter and fecundity and higher follicular atresia index, when compared to S2 and S3. Frequency of maturing fish was higher in S3 and spawning was only registered in S3. In sites S2 and S3, plasma concentrations of testosterone and 17b-estradiol in females and testosterone in males showed wide variations following gonadal maturation. Fish from S1 showed few significant variations in sex steroid concentrations throughout the gonadal cycle. These results indicate that P. lineatus does not reproduce in Grande River (S1), but probably uses the Pardo River (S2) as a migratory route towards the Mogi Guaçu River (S3) where they complete gonadal maturation and spawning. Our findings contribute for understanding the reproductive biology of P. lineatus and to highlight the importance of tributaries in impounded rivers as a favourable environment for migration and spawning of fish.
Most fishes with commercial importance from the São Francisco basin are migratory and do not comp... more Most fishes with commercial importance from the São Francisco basin are migratory and do not complete the reproductive cycle in lentic environments, such as hydroelectric plant reservoirs, hence natural stocks are declining and there is an urgent need to reduce the pressure of fishing on those wild populations. Therefore, studies on reproductive biology and its relationship with endocrine and environmental factors are key to improving the cultivation techniques of Brazilian fish species. This study examined the influence of water temperature on sex steroid concentrations (testosterone, 17b-estradiol and 17a-hydroxyprogesterone), spawning efficiency, fecundity, fertilisation rate, larval abnormality rates and involvement of the cytoskeleton during the final oocyte maturation of Prochilodus argenteus under experimental conditions. The results of our study showed that in captivity, sex steroid plasma concentrations and spawning performance of P. argenteus were clearly different for fish kept in water with different temperature regimes. In lower water temperature (23°C), it was observed that: 33% of females did not ovulate, fecundity was lower and vitellogenic oocytes after the spawning induction procedure exhibited a smaller diameter. Moreover, concentrations of 17b-estradiol and 17a-hydroxyprogesterone were lower and there was a delay in the final oocyte maturation and, consequently, ovulation and spawning. Our experiments showed direct influence of water temperature in the process of induced spawning of P. argenteus. Changes in water temperature also suggest the tubulin involvement in the nuclear dislocation process and the possible action of actin filaments in the release of polar bodies during final oocyte maturation of P. argenteus.
The curimatã-pacu Prochilodus argenteus is an important characiform from the São Francisco River ... more The curimatã-pacu Prochilodus argenteus is an important characiform from the São Francisco River basin that performs longdistance migrations for spawning upstream during the rainy season, when the temperature and photoperiod are elevated. Despite the interruption of the migratory routes by the Três Marias Dam and accentuated decline in fishing, the curimatã-pacu still sustains the fisheries at the Três Marias region in recent decades. The objective of this study was to evaluate the reproductive activity of P. argenteus in two sections of the São Francisco River, downstream from the Três Marias Dam, during the rainy season. In the first 34 km of the river, immediately below the dam, most of the females were in gonadal resting. At 34-54 km downstream from the dam, following the confluence with a medium-sized tributary, the Abaeté River, there was a high frequency of males and females in reproductive activity. Follicular atresia was more frequent in the upper section of the river while postovulatory follicles occurred predominantly in the lower section. Fulton's condition factor and gonadosomatic index indicated that the females were in a better physiological and reproductive condition below the confluence with the Abaeté River. In contrast to the females, the males were less affected by damming, and testicular maturation was largely achieved in two river sections. Thus, although the section of the São Francisco River immediately below the Três Marias Dam was found to be unfavourable for the reproduction of the migratory fishes due principally to the hypolimnetic water from the reservoir, reproductive success of P. argenteus was achieved below the Abaeté River. In this section, the species encountered appropriate conditions for maturation and spawning, i.e. warm temperatures above 24 C, high water flow and dissolved oxygen, and low water transparency. These results indicate the importance of a non-regulated tributary to minimize the ecological impact of a dam on the downstream native fish communities.
RESUMO O desenvolvimento ovocitário dos teleósteos Hemigrammus marginatus, Moenkhausia costae e R... more RESUMO O desenvolvimento ovocitário dos teleósteos Hemigrammus marginatus, Moenkhausia costae e Roeboides xenodon foi dividido em quatro estádios, de acordo com caracterís-ticas citológicas do ovócito e suas camadas envoltoras. Técnicas histoquímicas de-monstraram presença de glicoproteínas neutras nos glóbulos de vitelo, nas células foliculares e na zona pelúcida das três espécies. O conteúdo dos alvéolos corticais variou entre as espécies: glicoproteínas neutras e glicoconjugados ácidos carboxilados ou sulfatados. A camada externa da zona pelúcida de M. costae e H. marginatus contém também glicoconjugados ácidos carboxilados e glicoproteínas ricas em ácido siálico, respectivamente. As variações morfológicas dessas estruturas foliculares podem estar relacionadas com funções específicas durante a ovogênese e fertilização. Unitermos: Ovogênese, peixes forrageiros, represa de Três Marias. ABSTRACT The oocyte development of teleost species Hemigrammus marginatus, Moenkhausia costae and...
ABSTRACT Downstream impacts of dams on fish fauna are poorly studied, despite causing thermal and... more ABSTRACT Downstream impacts of dams on fish fauna are poorly studied, despite causing thermal and hydrological changes that affect the reproductive activity of the fish community. The present study aims to evaluate the reproduction of Leporinus reinhardti in 2 sections of the São Francisco River, Brazil, downstream from the Três Marias Dam. Section 1 (S1) is the first 34 km downstream from Três Marias Dam and section 2 (S2) is 34 to 54 km downstream from the dam, where the São Francisco River receives a mid-sized tributary called the Abaeté River. In S1, the values of temperature, dissolved oxygen and flow were lower than those obtained in S2. In S1,females and males did not complete reproduction, a fact proven by the absence of spawned females and males. In S2, reproductive success was proven due to the presence of spawned females and males. Furthermore, the values of total length, body weight, gonadosomatic index, fecundity and vitellogenic oocytes were statistically higher than those obtained in S1. The canonical correlation test indicated that the reproduction of females is more dependent on environmental factors than that of males. In S2, L. reinhadti found appropriate conditions for reproduction, probably influenced by the Abaeté River, confirming the need of preserving this tributary for the reproductive success of this species
In order to exploit native fish species for aquaculture, basic parameters of artificial reproduce... more In order to exploit native fish species for aquaculture, basic parameters of artificial reproducetion and estimates of reproductive potential for this fish must be determined to improve hatchery success. We analyze seven Brazilian commercial fish. Spawning was induced using the hypophysation method, with injection of crude carp pituitary extract (CCPE). Characiformes species signaled the spawning time with behavioral alterations (usually circular movements). The time of oocyte extrusion varied from 5.3 ± 0.3 h in Salminus franciscanus to 8.6 ± 0.1 h in Prochilodus argenteus after the second CCPE injection. The greatest diameter of a vitellogenic oocyte was registered for P. argenteus (873.9 ± 122.2 μm) and the smallest was for Pimelodus maculates (465.4 ± 36.3 μm). The diameter of vitellogenic oocytes was very similar among species belonging to the same family. The highest ROI values were registered for Prochilodus costatus(27.0 ± 3.5 μm) and P. argenteus (23.4 ± 3.7 μm), while the lowest values were found in Pseudoplatystoma corruscans (4.6 ± 0.9 μm) and P. maculatus (6.0 ± 1.3 μm). Absolute fecundity (number of oocytes released at spawning) was lowest in P. maculatus and highest in P. corrus-cans. Relative fecundity (RF) presented a high correlation (r = 0.98 to 0.99) with gonad weight, indicating high efficiency of spawning. The RF also presented a high correlation with body weight (r = 0.88 to 0.97) and total length (r = 0.86 to 0.92). The highest RF was registered for Leporinus obtusidens, and the lowest was for P. corruscans. Released fecundity had a negative correlation with the diameter of vitellogenic oocytes and with the height of the follicular cells, and a positive correlation with the thickness of the zona pelucida. These results indicate that the species studied herein are suitable candidates for aquaculture due to their reproductive and zootechnical characteristics.
The alterations to the hydrologic regime downstream from hydroelectric dams may cause an impact o... more The alterations to the hydrologic regime downstream from hydroelectric dams may cause an impact on the reproductive success of fishes. This study aimed to analyse the influence of the physical and chemical parameters of the water of the Grande and Pardo Rivers on gonadal maturation, oocyte diameter, follicular atresia and biological indices of Pimelodus maculatus collected from three river sections: Grande River, downstream from the Porto Colômbia dam (S1), Grande River, downstream from the confluence with the Pardo River (S2) and in the Pardo River channel (S3). Males and females captured in S1 presented significantly higher average values for total length and body weight than those captured in S2 and S3. The gonadosomatic index values were significantly higher in fish collected in S3 and the Fulton condition factor did not show significant differences in fish collected from the three sections. The oocyte diameter, the follicular cells height and the zona pellucida thickness did not show any statistical differences between the sections. Conductivity presented a significant difference between S1 and S3 and during the reproductive period, water transparency presented similar values in the two sampling sections of the Grande River, but a much lower value in the Pardo River. A low frequency of fish with reproductive activity was registered in S1, whereas in S2 and S3 higher frequencies were recorded, emphasising the need of preserving the tributaries for the reproductive success of P. maculatus of the Grande River in south-eastern Brazil.
The meniscus plays a central role in the transmission and distribution of load across the knee jo... more The meniscus plays a central role in the transmission and distribution of load across the knee joint. Meniscal lesions have recently been established as a cause of knee joint degeneration 1 . Meniscal calcifications are frequent and likely alter the normal biomechanics of the meniscus. Although MR imaging is the non-invasive technique of choice for the evaluation of knee, and more specifically meniscal pathology, it does not allow the facile visualization of meniscal calcifications 2 . This is due, in part, to a lack of contrast between the meniscal tissue and calcifications, both with relatively short intrinsic T2 relaxation times. In addition, the lack of spatial resolution with standard clinical sequences provides an additional challenge for the visualization of small, punctuate calcifications. We describe novel MR imaging techniques based on 2D-UTE inversion recovery and 3D-UTE data acquisition to address these factors. We assessed the ability of these sequences to allow the visualization, characterization and quantitative evaluation of meniscal calcifications. MATERIAL AND METHODS Ten human menisci with documented calcifications at visual inspection and with Faxitron imaging were analyzed. The specimens were placed in Perfluorooctyl Bromide solution. Imaging was performed on a 3T clinical magnet, using a high-resolution custom-built quadrature birdcage coil with an inside diameter of 2cm and a length of 10cm was used. MR sequences to characterize meniscal morphology were performed and included: T1 SE (TR 500/ TE 16.2/ FOV 7 / Slice thickness: 1.7mm/ matrix: 512x512 /NEX 2); 2D SPGR (TR 300/ TE 12/ Flip angle 30/ FOV 7 / Slice thickness: 1.7mm / matrix: 384 x 384 /NEX 2) ; PDFS (TR 2000 / TE 13 / FOV 7 / Slice thickness 1.7/ 512 x 384 /NEX 1); UTE FS (TR 500/ TE 8 microsecs / FOV 7 / Slice thickness 1.7 / 512 x 511/NEX 2) . A novel morphological and quantitative 3D UTE sequence was performed, using a short duration (40 μs) hard RF pulse for signal excitation followed by dual echo 3D radial ramp sampling. In order to quantify T2* values of the meniscal calcification, the dual 3D UTE acquisition was repeated three times with paired TEs of 8/5122 μs, 500/5622 μs, and 2000/7122 μs. Subtraction images were obtained for each pair of TEs. Other acquisition parameters included an isotropic FOV of 6 cm, TR of 35 ms, flip angle of 8 °, readout of 256, 40000 projections for a total scanning time of about 20-25 minutes. The projection data was re-gridded onto a 384×384×384 matrix and was followed by 3D Fourier transformation to produce the final 3D UTE images. Another quantitative technique using an IR pulse was also performed. An adiabatic inversion pulse (8.64ms in duration) was employed to invert the longitudinal magnetization of normal meniscal tissue and fat, while leaving the short T2 calcification largely unaffected. The images were viewed in the axial and sagittal planes. Menisci were divided into 3 thirds along their longitudinal axis, and the presence and absence of calcifications was noted. Whenever present, the calcifications were classified into punctuate or globular. The Faxitrons and MR sequences were analyzed independently by two musculoskeletal radiologists, in consensus. ROI placement on MR images was guided by comparison with Faxitron images of the menisci.
This study investigated for the first time the reproductive biology of Prochilodus lineatus in a ... more This study investigated for the first time the reproductive biology of Prochilodus lineatus in a system of rivers in southeastern Brasil, relating it to the role of tributary rivers in the reproductive success of this important commercial fish in the Upper Paraná River basin, where a cascade of hydroelectric dams were deployed. Specimens were caught bimonthly in three river sites: (S1) Grande River, downstream from the Porto Colômbia dam; (S2) Pardo River; and (S3) Mogi Guaçu River. Sex steroid plasma levels, fecundity, follicular atresia, oocyte diameter and gonadosomatic index (GSI) were compared among sites. In S1, fish exhibited changes in the reproductive parameters: lower GSI, oocyte diameter and fecundity and higher follicular atresia index, when compared to S2 and S3. Frequency of maturing fish was higher in S3 and spawning was only registered in S3. In sites S2 and S3, plasma concentrations of testosterone and 17b-estradiol in females and testosterone in males showed wide variations following gonadal maturation. Fish from S1 showed few significant variations in sex steroid concentrations throughout the gonadal cycle. These results indicate that P. lineatus does not reproduce in Grande River (S1), but probably uses the Pardo River (S2) as a migratory route towards the Mogi Guaçu River (S3) where they complete gonadal maturation and spawning. Our findings contribute for understanding the reproductive biology of P. lineatus and to highlight the importance of tributaries in impounded rivers as a favourable environment for migration and spawning of fish.
Most fishes with commercial importance from the São Francisco basin are migratory and do not comp... more Most fishes with commercial importance from the São Francisco basin are migratory and do not complete the reproductive cycle in lentic environments, such as hydroelectric plant reservoirs, hence natural stocks are declining and there is an urgent need to reduce the pressure of fishing on those wild populations. Therefore, studies on reproductive biology and its relationship with endocrine and environmental factors are key to improving the cultivation techniques of Brazilian fish species. This study examined the influence of water temperature on sex steroid concentrations (testosterone, 17b-estradiol and 17a-hydroxyprogesterone), spawning efficiency, fecundity, fertilisation rate, larval abnormality rates and involvement of the cytoskeleton during the final oocyte maturation of Prochilodus argenteus under experimental conditions. The results of our study showed that in captivity, sex steroid plasma concentrations and spawning performance of P. argenteus were clearly different for fish kept in water with different temperature regimes. In lower water temperature (23°C), it was observed that: 33% of females did not ovulate, fecundity was lower and vitellogenic oocytes after the spawning induction procedure exhibited a smaller diameter. Moreover, concentrations of 17b-estradiol and 17a-hydroxyprogesterone were lower and there was a delay in the final oocyte maturation and, consequently, ovulation and spawning. Our experiments showed direct influence of water temperature in the process of induced spawning of P. argenteus. Changes in water temperature also suggest the tubulin involvement in the nuclear dislocation process and the possible action of actin filaments in the release of polar bodies during final oocyte maturation of P. argenteus.
The curimatã-pacu Prochilodus argenteus is an important characiform from the São Francisco River ... more The curimatã-pacu Prochilodus argenteus is an important characiform from the São Francisco River basin that performs longdistance migrations for spawning upstream during the rainy season, when the temperature and photoperiod are elevated. Despite the interruption of the migratory routes by the Três Marias Dam and accentuated decline in fishing, the curimatã-pacu still sustains the fisheries at the Três Marias region in recent decades. The objective of this study was to evaluate the reproductive activity of P. argenteus in two sections of the São Francisco River, downstream from the Três Marias Dam, during the rainy season. In the first 34 km of the river, immediately below the dam, most of the females were in gonadal resting. At 34-54 km downstream from the dam, following the confluence with a medium-sized tributary, the Abaeté River, there was a high frequency of males and females in reproductive activity. Follicular atresia was more frequent in the upper section of the river while postovulatory follicles occurred predominantly in the lower section. Fulton's condition factor and gonadosomatic index indicated that the females were in a better physiological and reproductive condition below the confluence with the Abaeté River. In contrast to the females, the males were less affected by damming, and testicular maturation was largely achieved in two river sections. Thus, although the section of the São Francisco River immediately below the Três Marias Dam was found to be unfavourable for the reproduction of the migratory fishes due principally to the hypolimnetic water from the reservoir, reproductive success of P. argenteus was achieved below the Abaeté River. In this section, the species encountered appropriate conditions for maturation and spawning, i.e. warm temperatures above 24 C, high water flow and dissolved oxygen, and low water transparency. These results indicate the importance of a non-regulated tributary to minimize the ecological impact of a dam on the downstream native fish communities.
RESUMO O desenvolvimento ovocitário dos teleósteos Hemigrammus marginatus, Moenkhausia costae e R... more RESUMO O desenvolvimento ovocitário dos teleósteos Hemigrammus marginatus, Moenkhausia costae e Roeboides xenodon foi dividido em quatro estádios, de acordo com caracterís-ticas citológicas do ovócito e suas camadas envoltoras. Técnicas histoquímicas de-monstraram presença de glicoproteínas neutras nos glóbulos de vitelo, nas células foliculares e na zona pelúcida das três espécies. O conteúdo dos alvéolos corticais variou entre as espécies: glicoproteínas neutras e glicoconjugados ácidos carboxilados ou sulfatados. A camada externa da zona pelúcida de M. costae e H. marginatus contém também glicoconjugados ácidos carboxilados e glicoproteínas ricas em ácido siálico, respectivamente. As variações morfológicas dessas estruturas foliculares podem estar relacionadas com funções específicas durante a ovogênese e fertilização. Unitermos: Ovogênese, peixes forrageiros, represa de Três Marias. ABSTRACT The oocyte development of teleost species Hemigrammus marginatus, Moenkhausia costae and...
ABSTRACT Downstream impacts of dams on fish fauna are poorly studied, despite causing thermal and... more ABSTRACT Downstream impacts of dams on fish fauna are poorly studied, despite causing thermal and hydrological changes that affect the reproductive activity of the fish community. The present study aims to evaluate the reproduction of Leporinus reinhardti in 2 sections of the São Francisco River, Brazil, downstream from the Três Marias Dam. Section 1 (S1) is the first 34 km downstream from Três Marias Dam and section 2 (S2) is 34 to 54 km downstream from the dam, where the São Francisco River receives a mid-sized tributary called the Abaeté River. In S1, the values of temperature, dissolved oxygen and flow were lower than those obtained in S2. In S1,females and males did not complete reproduction, a fact proven by the absence of spawned females and males. In S2, reproductive success was proven due to the presence of spawned females and males. Furthermore, the values of total length, body weight, gonadosomatic index, fecundity and vitellogenic oocytes were statistically higher than those obtained in S1. The canonical correlation test indicated that the reproduction of females is more dependent on environmental factors than that of males. In S2, L. reinhadti found appropriate conditions for reproduction, probably influenced by the Abaeté River, confirming the need of preserving this tributary for the reproductive success of this species
In order to exploit native fish species for aquaculture, basic parameters of artificial reproduce... more In order to exploit native fish species for aquaculture, basic parameters of artificial reproducetion and estimates of reproductive potential for this fish must be determined to improve hatchery success. We analyze seven Brazilian commercial fish. Spawning was induced using the hypophysation method, with injection of crude carp pituitary extract (CCPE). Characiformes species signaled the spawning time with behavioral alterations (usually circular movements). The time of oocyte extrusion varied from 5.3 ± 0.3 h in Salminus franciscanus to 8.6 ± 0.1 h in Prochilodus argenteus after the second CCPE injection. The greatest diameter of a vitellogenic oocyte was registered for P. argenteus (873.9 ± 122.2 μm) and the smallest was for Pimelodus maculates (465.4 ± 36.3 μm). The diameter of vitellogenic oocytes was very similar among species belonging to the same family. The highest ROI values were registered for Prochilodus costatus(27.0 ± 3.5 μm) and P. argenteus (23.4 ± 3.7 μm), while the lowest values were found in Pseudoplatystoma corruscans (4.6 ± 0.9 μm) and P. maculatus (6.0 ± 1.3 μm). Absolute fecundity (number of oocytes released at spawning) was lowest in P. maculatus and highest in P. corrus-cans. Relative fecundity (RF) presented a high correlation (r = 0.98 to 0.99) with gonad weight, indicating high efficiency of spawning. The RF also presented a high correlation with body weight (r = 0.88 to 0.97) and total length (r = 0.86 to 0.92). The highest RF was registered for Leporinus obtusidens, and the lowest was for P. corruscans. Released fecundity had a negative correlation with the diameter of vitellogenic oocytes and with the height of the follicular cells, and a positive correlation with the thickness of the zona pelucida. These results indicate that the species studied herein are suitable candidates for aquaculture due to their reproductive and zootechnical characteristics.
The alterations to the hydrologic regime downstream from hydroelectric dams may cause an impact o... more The alterations to the hydrologic regime downstream from hydroelectric dams may cause an impact on the reproductive success of fishes. This study aimed to analyse the influence of the physical and chemical parameters of the water of the Grande and Pardo Rivers on gonadal maturation, oocyte diameter, follicular atresia and biological indices of Pimelodus maculatus collected from three river sections: Grande River, downstream from the Porto Colômbia dam (S1), Grande River, downstream from the confluence with the Pardo River (S2) and in the Pardo River channel (S3). Males and females captured in S1 presented significantly higher average values for total length and body weight than those captured in S2 and S3. The gonadosomatic index values were significantly higher in fish collected in S3 and the Fulton condition factor did not show significant differences in fish collected from the three sections. The oocyte diameter, the follicular cells height and the zona pellucida thickness did not show any statistical differences between the sections. Conductivity presented a significant difference between S1 and S3 and during the reproductive period, water transparency presented similar values in the two sampling sections of the Grande River, but a much lower value in the Pardo River. A low frequency of fish with reproductive activity was registered in S1, whereas in S2 and S3 higher frequencies were recorded, emphasising the need of preserving the tributaries for the reproductive success of P. maculatus of the Grande River in south-eastern Brazil.
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