Iracema David Gomes

Environmental influences on the demersal fish assemblages in the Sepetiba Bay, Brazil

The structure of the demersal fish assemblage in Sepetiba Bay, southeast Brazil (22°54′–23°04′S, 43°34′–44°10′W) was described and related to environmental variables. A 3-yr long trawl survey (from July 1993 to June 1996) was conducted using a stratified random sampling strategy at 158 stations. One hundred and seven species of fishes in 80 genera and 44 families were identified. Gerreidae and Ariidae made up 30.5% and 28.6%, and 19.8% and 28.1% of the total number and weight, respectively. Sciaenidae, Engraulididae, Sparidae, and Carangidae were other prominent families. Three assemblages existed in the bay: one inhabited shallow, less saline and less transparent water in the inner zone (depth <5 m, transparency <2 m, salinity <30 psu, and slightly higher temperature); another in the outer zone with the opposite situation (depth >10 m, transparency >3 m, salinity >30 psu, and slightly lower temperature); and a third assemblage in the middle zone likely to prefer average values or show no clear preferences. Most species decreased in abundance over the 3-yr period of study. No seasonal change was detected in the assemblage structure, but many species were rare, indicating high spatial and temporal patchiness. Canonical correlation analyses were used to describe and compare the fish assemblages in the three different habitats. The outer zone had the greatest number of species recorded, lowest abundance, highest diversity and evenness, and was comprised mainly byCynossion leiarchus, Prionotus punctatus, Anchoa tricolor, Haemulon steindachneri, Diplectrum radiale, Etropus crossotus, andSphoeroides greeleyi; the inner zone had the lowest number of species recorded but the greatest number of species per sample, highest abundance, lowest diversity and evenness, being comprised mainly byDiapterus rhombeus, Genidens genidens, Cathrops spixii, Chloroschombrus chrysurus, Sciadeichthyes luniscutis, Cetengraulis edentulus, andArchorsargus rhomboidalis; while the third group had the lowest number of species per sample, being comprised by species widely distributed asGerres aprion, G. genidens, Gerres gula, andMicropogonias furnieri. Depth, followed by transparency and salinity, were the primary factors influencing assemblage distribution.

Fish Gills Alterations as Potential Biomarkers of Environmental Quality in a Eutrophized Tropical River in South-Eastern Brazil

Gill anomalies in three common fish species of different taxonomic order, habitat dwelling and feeding habits (one Characiformes, Oligosarcus hepsetus; one Siluriformes, Hypostomus auroguttatus; and one Perciformes, Geophagus brasiliensis) from a eutrophized tropical river in south‐eastern in Brazil were compared. The aim of this study was to search for sentinel species that could be used as potential biomarkers of environmental quality. Most fish had gills with histological changes, namely epithelial lifting, interstitial oedema, leucocyte infiltration, hyperplasia of the epithelial cells, lamellar fusion, vasodilatation and necrosis. On the other hand, lamellar blood congestion and lamellar aneurysm, which are more serious and often irreversible changes, were recorded for the water column carnivorous O. hepsetus and, to a lesser extent, for the bottom‐dwelling detritivorous H. auroguttatus. A histopathological alteration index (HAI) based on the occurrence and severity of gills anomalies indicated that O. hepsetus (mean score = 11.4) had significantly higher values (Kruskall–Wallis H2,41 = 15.95, P = 0.0003) compared with G. brasiliensis (mean score = 7.0). Overall, the omnivorous G. brasiliensis had comparatively lesser occurrence of most gill anomalies compared with other two species, being less suitable as biomarker of environmental quality. In contrast, the water column–dweller O. hepsetus (water column) and the bottom‐dweller H. auroguttatus had gills most susceptible to changes, making them more suitable for using as histological biomarkers of the environmental quality in entrophized tropical rivers.

Variações temporais e espaciais na composição e estrutura da comunidade de peixes jovens da Baía de Sepetiba, Rio de Janeiro

A year-long beach seine survey at the continental margin of Sepetiba Bay, Rio de Janeiro State, Brazil, catching mainly young-of-the-year and juvenile fishes was carried out from July 1983 to June 1984, in order to describe the community structure and their spatial and seasonal variations. Fifty-five monthly samplied carried out in five sites in the marginal surf zone waters yielded 11,463 fishes in 82 species, 59 genera and 31 families. Gerreidae, Engraulidi-dae, Atherinidae and Ariidae families amounted 87.01% of the total catch in number, and 81% in weight. Cerres aprion Cuvier, 1829, Anchoa januaria (Steindachner, 1879), Anchoviella lepidentostole (Fowler, 1911), Atherinella brasiliensis (Quoy & Gaimard, 1824) and Neluma barba (Lacepede, 1803) were the most numerous species, each one contributing more the 4% of total catch. Overall, both spatial and seasonal changes in fish were not evident although most individuais were more abundant in the outer Bay. The high number of fish species in this area, suggest the important role played by the Sepetiba Bay in the fish community to where many species probably migrate from the nearby sea and stay in the Bay during part of their life cycle. Decreasing diversity and high dominance of a few number of species seem to indicated a trend of environmental deterioration in the Sepetiba Bay over the last decade, as this date are compared whith similar sampling program carried out in 1993/94. It same to indicated that changes in fish populations which use this area as rearing grounds, occurred during their early life history.

Biologia reprodutiva dos bagres marinhos Genidens genidens (Valenciennes) e Cathorops spixii (Agassiz) (Siluriformes, Ariidae), na Baía de Sepetiba, Rio de Janeiro, Brasil

The reproductive cycle of the marine catfishes Genidens genidens Valenciennes, 1833 and Cathorops spixii Agassiz, 1839 in the Sepetiba Bay, was assessed by an annual period of sampling from October 1993 to September 1994. The fishes were caught by standardized otter trawl and environmental parameters of temperature, salinity and transparency of water were recorded at each sampling. Five gonadal phases were described, based in macroscopic observations. Changes in the gonadosomatic index (GSI) and in the percentual of stages of gonadal development showed that G. genidens spawns in Summer/early Autumn, coinciding with low salinity and high temperature and transparency. Cathorops spixii spawns in late Spring/early Summer, coinciding with rising temperature and transparency and low salinity. Total spawning are shown for both species, as indicated by length-frequency of oocytes per stages of maturation with two groups synchronic development of oocytes. Fecundity is low (10-23 oocytes, for G. genidens and 24-30 for C. spixii), when compared with other teleosteans, and was not strongly correlated to the total length (G. genidens, r=0.65, C. spixii, r=0.76). Strategy-k is developed by both species as indicated by high brood and enbrions protection and high body length.

Can fish gill anomalies be used to assess water quality in freshwater Neotropical systems

Gill anomalies in two fish species (Geophagus brasiliensis and Astyanax bimaculatus) were compared among three freshwater systems with different water quality: one eutrophic river, one eutrophic reservoir, and one oligotrophic reservoir. The raised hypotheses are that reservoirs with low water quality (eutrophic) have fish with more gills anomalies compared with reservoirs with high water quality (oligotrophic), and that the more stable environmental conditions of eutrophic rivers have fish with better healthy conditions than eutrophic reservoirs that have lesser stable environmental conditions. Gills of 36 adult individuals of G. brasiliensis and 23 of A. bimaculatus collected during the winter 2008 and winter 2009 were examined, and the proportions of occurrence of nine histological alterations were compared for the two species among the three systems using a binomial t test for independent samples. Histological changes in fish gills that are reversible and unspecific, such as epithelial lifting, interstitial edema, leukocyte infiltration, hyperplasia of the epithelial cells, lamellar fusion, and vasodilatation were common in both fish species in the three systems. However, lamellar aneurism, which is a more serious and often irreversible anomaly, and lamellar blood congestion occurred only in fish from the two reservoirs. Alternatively, necrosis occurred more in fish from the river. Fish gill anomalies in both species did not differ between the two reservoirs, despite having different water quality. We rejected the hypothesis that reservoirs with lower water quality have fish with more gill injuries compared with high water quality reservoirs. Moreover, the eutrophic river seems to affect differently the healthy condition of fish species, compared with the eutrophic reservoir.

Influences of the reproductive cycle on condition of marine catfishes (Siluriformes, Ariidae) in a coastal area at southeastern Brazil

Marine catfishes use estuaries and bays as part of their life cycle for spawning and feeding purposes, respectively. We compared three species of the family Ariidae in two different environmental conditionsa relatively stable bay site and an estuarine site, which differ in their magnitudes of environmental fluctuation to investigate effects of spawning on condition. We found differences in the parameter b (slope) and in they-intercept (a) among species and sexes. The parameter a varied inversely with b, and thus is not a good indicator to express fish condition. Condition factor did not differ between the two sites for species and sexes when we consider the pooled data. Overall condition was associated with reproductive process, and was high before the reproductive season, decreasing during the spawning period in the estuary, then increasing when fish move to the bay (April–August). Temporal segregation in the reproductive period and small-scale movements between the estuary and the bay are the probable mechanisms to optimize the use of the area by the three species.

Histochemical and immunohistochemical study on endocrine cells (5HT, GAS, and SST) of the gastrointestinal tract of a teleost, the characin Astyanax bimaculatus

Endocrine cells secrete hormones through the mucosa of the gastrointestinal tract (GIT) and act on the overall regulation of digestive processes such as nutrient absorption, gut motility and intestinal blood flow. This study aimed to determine regional distribution and frequency of endocrine cells secretory of serotonin (5-HT), somatostatin (SST) and gastrin (GAS) in the GIT of a small-bodied widespread characin Astyanax bimaculatus using histological, histochemical and immunohistochemical techniques. Fragments of the stomach and gut fixed for 8h in Bouin liquid were subjected to histological processing and immunohistochemical routine. For the histological analyses, the technique of staining with hematoxylin and eosin (HE) was used, whereas for the histochemical analyses Gomoris trichrome, periodic acid+Schiff (PAS) and Alcian blue pH 2.5 (AB) were used to further immunohistochemical processing. The stomach has a mucosa lined with a simple columnar epithelium with mucus-secreting cells; the glandular region (proximal and distal portions) has folds and pits, whereas the non-glandular region has pits only. The intestinal epithelium is simple with plain cylindrical grooved and goblet cells. The anterior region has thin folds with few goblet cells, and the posterior region with thick folds and many goblet cells. The regional distribution and frequency of endocrine cells varied across regions of the GIT with the stomach showing the highest amount of immunoreactive (IR) cells. Only the 5-HT was found in the stomach (epithelia and glands) and gut regions, with comparatively higher frequency in the stomach. SST-IR cells were found in the stomach (epithelia and gastric glands) with higher frequency in the glandular region, whereas GAS-IR were found in the gastric glands only. The stomach was the only organ to have all the three types of endocrine cells, indicating that this organ is the main site of digestion of food in this species.

Biomarkers and bioindicators of the environmental condition using a fish species (Pimelodus maculatus Lacepède, 1803) in a tropical reservoir in Southeastern Brazil

The Funil Reservoir receives a large amount of xenobiotics from the Paraíba do Sul River (PSR) from large number of industries and municipalities in the watershed. This study aimed to assess environmental quality along the longitudinal profile of the Paraíba do Sul River-Funil Reservoir system, by using biomarkers and bioindicators in a selected fish species. The raised hypothesis is that Funil Reservoir acts as a filter for the xenobiotics of the PSR waters, improving river water quality downstream the dam. Two biomarkers, the ethoxyresorufin-O-deethylase activity (EROD), measured as fluorimetricly in S9 hepatic fraction, and the micronuclei frequency (MN), observed in erythrocytes of the cytoplasm, and three bioindicators, the hepatosomatic index (HSI), gonadosomatic index (GSI) and condition factor (CF) were used in Pimelodus maculatus, a fish species widely distributed in the system. Four zones were searched through a longitudinal gradient: 1, river upstream from the reservoir; 2, upper reservoir; 3, lower reservoir; 4, river downstream of the reservoir. EROD activity and HSI and GSI had significant differences among the zones (P<0.05). The upper reservoir had the lowest EROD activity and HSI, whereas the river downstream of the reservoir had the highest EROD and lowest GSI. The river upstream from the reservoir showed the highest HSI and GSI. It is suggested that the lowest environmental condition occur at the river downstream of the reservoir, where it seems to occur more influence of xenobiotics, which could be associated with hydroelectric plant operation. The hypothesis that Funil reservoir acts as a filter decanting pollution from the Paraíba do Sul River waters was rejected. These results are novel information on this subject for a native fish species and could be useful for future comparisons with other environments.

Opportunistic reproductive strategy of a non-native fish, the spotted metynnis Metynnis maculatus (Kner, 1858) (Characidae Serrasalminae) in a tropical reservoir in south-eastern Brazil

We investigated the reproductive strategy developed by the non-native fish Metynnis maculatus (Kner, 1858) to explain its success in establishing in a tropical reservoir in south-eastern Brazil. A total of 198 specimens were examined, 100 males (total length, TL = 110–172 mm) and 98 females (TL = 110–191 mm), collected using gill nets from September 2005 to August 2006. Sex ratio is balanced, although females significantly outnumber males in size larger than 160 mm TL. Six stages of oogenesis and five of spermatogenesis are described, based on staining aspect of the nucleus and cytoplasm structure with photonic microscopy. A protracted reproductive period from August to January was found with females producing several large clutches of small eggs. Oocyte mean diameter ranged from 19.6–48.3 μm in pre-vitellogenic ovarian stage to 83.4–149.4 μm in vitellogenic ovarian stage whereas in spawning stage ovary, oocyte diameter varied from 300 to 500 μm. In ripe stage, oocytes can reach diameter up to 2.00 mm. Batch fecundity ranged from 670 to 16,333 oocytes (mean fecundity = 7056 oocytes) for females having TL ranging from 145 to 191 mm and total weight ranging from 75 to 176 g. A tendency for opportunistic strategy was detected as indicated by a long spawning period, high fecundity, small oocytes and small body size that have proved to be effective in the Lajes reservoir.

Gonadal Development of the Piau Leporinus copelandii (Characiformes, Anostomidae) in a Tropical River in South-eastern Brazil

Histological analysis of the gonadal development of Leporinus copelandii Steindachner, 1875, a rheophilic Characiformes species in the Paraiba do Sul River, South‐eastern Brazil, was described. We expect that this species adapt gonadal development to succeed in this river basin that has its longitudinal profile blocked by several impoundments. Fishes were examined by routine macroscopic and histological techniques. Stages of oocyte and spermatocyte development were described, and gonadal maturation was proposed. Mean oocyte diameter obtained from histological observations increased from the pre‐spawning (4.2–175.5 μm) to spawning (148.5–262.0 μm) phases, followed by a sharp decrease in the post‐spawning (27.0–56.7 μm) phase. Based on occurrence of different oocytes phases and oocyte size distribution, this species has group‐synchronic development of oocytes. Further studies are necessary to clarify the spawning grounds for L. copelandii in the Paraíba do Sul River basin, especially considering that several impoundments obliterate the natural river course and this could limit spawning grounds.