André Luiz Machado Pessanha

Spatial, temporal and diel variations of fish assemblages at two sandy beaches in the Sepetiba Bay, Rio de Janeiro, Brazil

Fish assemblages from two beaches, one in the inner and the other in the outer Sepetiba Bay (latitude: 22 � 549–23 � 049S; longitude: 43 � 349–44 � 109W), Southeast Brazil, were sampled by beach seine net, simultaneously, on both seasonal and diel scales, between August 1998 and June 1999. Sites were selected to encompass different environmental conditions which reflect the two bay zones, thus providing a comprehensive assessment of the factors influencing surf zone fish assemblages, and their spatial, seasonal and diel variations. A total of 55 fish species was recorded, mostly young-of-the-year. Anchoa tricolor, Micropogonias furnieri, Gerres aprion, Diapterus rhombeus, Harengula clupeola, Atherinella brasiliensis and Mugil liza were numerically dominant and contributed to 95.2% of the total fish catches. Strong differences in fish assemblages were observed between the two areas, with higher number of species in the outer bay. Increases in fish numbers occurred in winter, while the highest biomass occurred in winter and summer. Transparency, followed by salinity, was responsible for most of the spatial variability and played an important role in structuring fish assemblages. Overall, diel patterns did not reveal any significant trends; however, if we consider each season separately, an increase in fish numbers during the day with peak at sunset was observed in winter, and a higher biomass occurred at night in winter and summer. Species preferences for various combinations of environmental variables are responsible for shifts in the structure and overall abundance of assemblages and dictated some patterns. The sciaenid M. furnieri, the second most abundant species, occurred only in the inner zone, being more abundant in winter. The species of Engraulidae were more abundant in the outer zone in winter/ spring during the day. The gerreids G. aprion and D. rhombeus occurred mainly in summer. Overall, temporal fluctuations act more at a specific level than at a structural one, and may be linked to some particular stages of the fish life cycle, but do not significantly influence the spatial organization. 2003 Elsevier Ltd. All rights reserved.

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.

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.

Recrutamento do peixe-rei, Atherinella brasiliensis (Quoy & Gaimard) (Atheriniformes, Atherinopsidae), na margem continental da Baía de Sepetiba, Rio de Janeiro, Brasil

The silverside, Atherinella brasiliensis (Quoy & Gaimard, 1824), a resident species of the shallows of bays, estuaries and coastal lagoons, was studied during two annual cycles, using beach seines (July 1996 to June 1998), in the continental margin of the Sepetiba Bay, aiming to assess recruitment and distribution patterns. A wide recruitment period, with young-of-the-year appearing from early spring to early autumn, was shown, with peaks of juveniles (Total Length-LT = 10-30 mm) being recorded in two periods of the year; one in November and another in March. The highest abundances, of both juvenile and adults, were recorded in Coroa Grande and Itacuruca, sites located in the outer Bay, during the whole summer, with significant differences were found. In spite of not having been found any statistically significant relationship between the environmental factors and the occurrence of this species, a trend of higher abundance in colder and more saline waters was detected. High values of growth coefficient (K = 0.93) and low asymptotic lenght (L∞ = 11.6 cm) indicated that this species shows a high growth rate and short life cycle, with life span of 3.09 years, in this system.

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.

Dieta de juvenis de Trachinotus carolinus (Actinopterygii, Carangidae) em praias arenosas na costa do Rio de Janeiro

Estudamos a dieta dos juvenis de Trachinotus carolinus (Linnaeus, 1766) em praias da Baia de Sepetiba (Rio de Janeiro, Brasil) entre janeiro de 2000 e abril de 2001. Procuramos avaliar a plasticidade trofica de peixes desta especie ao longo de um gradiente espacial com diferentes niveis de exposicao as ondas, sazonalidade, alem de avaliar mudancas ontogeneticas na dieta. Os itens alimentares foram analisados atraves do indice de importância relativa (IIR), determinado pelos valores das frequencias de ocorrencia, de numero e de peso. Os itens de maior importância foram do subfilo Crustacea, ordens Mysidacea, e o representante da ordem Decapoda Emerita brasiliensis (Schmitt, 1935), alem de Cefalochordata, representado por Branchiostoma platae (Fitzinger, 1862). Na zona de maior exposicao as ondas (praia de Barra de Guaratiba) e com substrato predominantemente arenoso, a dieta foi constituida principalmente por Emerita brasiliensis e Cirripedia, este ultimo presente nos costoes rochosos que limitam a praia; na zona de exposicao intermediaria (praia de Muriqui), houve um predominio de Mysidacea e Branchiostoma platae; na zona mais protegida (praia de Itacuruca), os itens de maior abundância foram Polychaeta, Mysidacea e Branchiostoma platae. Sazonalmente nao ocorreu variacao no uso de Mysidacea, enquanto Branchiostoma platae foi mais consumido durante o inverno, Polychaeta na primavera e Cirripedia e Emerita brasiliensis, no verao. Mysidacea foi o alimento predominante em todas as classes de tamanho, enquanto Polychaeta foi utilizado predominantemente por peixes menores que 20 mm de comprimento padrao e Emerita brasiliensis e Cirripedia foram consumidos principalmente por individuos maiores que 40 mm, somente na praia de maior exposicao. O sucesso no uso de praias desprotegidas e zonas de arrebentacao por esta especie de peixe pode ser em parte devido a estrategia trofica oportunista, que utiliza uma ampla variedade de recursos disponiveis no ambiente.

Ecomorphology and resource use by dominant species of tropical estuarine juvenile fishes

Eleven ecomorphological attributes and diet of seventeen juvenile fish species were examined to test the hypothesis that morphological patterns determine resource uses in estuarine habitats. Species were separated according to the apparatus to food capture and habitat use (benthic or pelagic) in three different groups: (1) a group with depressed fish body, strong caudal peduncle and enlarged pectoral fins; (2) a second group laterally flattened with a wide protruding mouth, and (3) a third group strongly flattened with small pectorals fins. The following six trophic groups were organized based on prey categories: Zooplanktivores, Benthivores, Omnivores, Detritivores, Macrocarnivores and Insectivores. Significant results (PERMANOVA) between ecomorphological indices and habitat and between ecomorphological indices and trophic groups were found. These data indicate that similarity of ecomorphological forms, which minimize the influence of environment and partitioning of food, would help facilitate the co-existence of these fish when they are abundant in this tropical estuary.

Trophic relationships among fish assemblages on a mudflat within a Brazilian Marine protected area

O presente estudo visa verificar as variacoes temporais na dieta e nas guildas troficas nas especies de peixes dominantes em uma planicie de mare, durante as estacoes seca e chuvosa. A composicao da dieta e a organizacao trofica de 17 especies foi estudada no estuario do rio Mamanguape, Nordeste do Brasil. Foram identificados os itens dominantes e verificado os efeitos da sazonalidade sobre a organizacao das guildas. A dieta variou pouco entre as especies e as estacoes; durante a estacao chuvosa, a dieta das especies apresentou-se mais heterogenea. De acordo com a importância de presas nas dietas, foram identificadas cinco guildas alimentares principais: (1) Detritivora, (2) Zooplanctivora, (3) Zoobentivora-epifauna, (4) Zoobentivora-infauna, e (5) Piscivora. A maioria dos peixes predou uma variada gama de itens alimentares, mas fortemente baseados em presas do zooplâncton. Alguns peixes apresentaram tendencia para uma dieta especializada, com quase todas as especies mostrando algum grau de alimentacao oportunista. Um alto grau de sobreposicao de dieta foi encontrado entre as especies; no entanto, a ocorrencia de competicao por exploracao nao foi observada.

Spatial and size feeding niche partitioning of the rhomboid mojarra Diapterus rhombeus (Cuvier, 1829) in a tropical Brazilian Bay

Abstract We examined the stomach contents of 287 individuals of rhomboid mojarra Diapterus rhombeus collected between June 1999 and May 2000 in three zones (inner, middle and outer) of a Brazilian tropical bay. Fish were grouped in five size-class (Total Length1 ≤ 80 mm; TL2=81–110; TL3=111–140; TL4=141–170; and TL5 ≥ 171). The aim was to assess whether intraspecific spatial and size-feeding niche partitioning occurs and to describe the strategy used to explore the available resources. Crustacea and Polychaeta were the most important trophic categories and Harpacticoida (Index of Relative Importance, IRI = 66.9%) was the most preferred prey throughout all zones and size classes. The smallest individuals (TL≤140 mm) occurred exclusively in the inner zone and fed mainly on Harpacticoida, Calanoida, sedentary Polychaeta and Nematoda, while the largest individuals (TL>140 mm) fed mainly on Harpaticoida and Ostracoda. In the outer zone, the largest individuals feed mainly on Harpacticoida and Caprella. A high within-phenotype contribution to the niche width and a generalist zoobenthivore feeding strategy were detected. Partitioning the food items along space and growth seems to be the mechanism used by this species to decrease intraspecific competition.

Condicionantes ambientais na distribuição e no periodo reprodutivo do Orthopristis ruber (Cuvier) (Teleostei, Haemulidae) na Baía de Sepetiba, Rio de Janeiro, Brasil

Orthopristis ruber (Cuvier, 1830) is a very common species in the Brazilian coast, being found in large abundance in bays where they rank among the most numerical abundant species in bottom trawls. This work aims to assess environmental influences on spatial, temporal distribution and reproductive period of O. ruber in the Sepetiba Bay, a coastal semi-closed area in the Rio de Janeiro State. Monthly samplings were carried out using otter trawl from October 1998 to September 1999, in three Bay zones, defined according to the proximity of the sea (inner, middle and outer). Samples were taken as triplicate at each site as well as environmental measurements of water temperature, salinity, transparency and depth. Relative abundance was assessed by CPUE (capture per unit effort) in both number and weight. The reproductive period was determined by the gonadossomatic index. A total of 866 individuals was caught, with size ranging from 31 to 293 mm Total Length and sex ratio 1:1. Higher fish numbers and biomass were recorded in January/February and May, although no significant difference was found among seasons. Spatially, the highest number and biomass were recorded in the outer zone. Positive significant correlation between relative abundance and depth, salinity and transparency and negative with temperature were found. The reproductive period, indicated by the highest gonadosomatic index (IGS) occurred probably between June and September, coinciding with the lowest temperatures. This species seems to have distribution limited to outer bay zones, near to the sea influence, with the highest influxes in Summer, as a probable effect of the South Atlantic Central Waters (SACW) that compress Coastal Waters (CW) toward the bay.