EFEITO DA DENSIDADE DE ADIÇÃO DE Brachionus plicatilis NO CULTIVO DE PÓS-LARVAS DE Litopenaeus vannamei EM SISTEMA BIOFLOCOS

A produção de juvenis de camarões marinhos tem sido utilizada com estratégias de convivência com os patógenos, reduzindo as perdas produtivas na carcinicultura. A aplicação de microrganismos capazes de melhorar o teor nutricional dos flocos microbianos nas fases iniciais de cultivo, contribuindo para o maior crescimento dos camarões e melhora do sistema imune é uma ferramenta bastante promissora nessa fase. Neste sentido, o presente trabalho avaliou o efeito da densidade de adição do rotífero Brachionus plicatilis em diferentes densidades no cultivo de pós-larvas de Litopenaeus vannamei em sistema de bioflocos incentivado por fermentação de carbono ogânico e à base de mix de bactérias. Para tal, o desenho experimental foi composto por quatro tratamentos e três repetições cada, totalizando 12 unidades experimentais em delineamento inteiramente casualisado durante 42 dias. Os tratamentos foram: BFT (Bioflocos); BFT-10 (Bioflocos com adição de B. plicatilis na densidade de 10 organismos mL-1), BFT-20 (Bioflocos com adição de B. plicatilis na densidade de 20 organismos mL-1) e BFT-30 (Bioflocos com adição de B. plicatilis na densidade de 30 organismos mL-1). As pós-larvas de dez dias (PL10) com peso médio de 3,4 ± 0,02 mg foram estocadas na densidade de 3.000 indivíduos m-3em unidades experimentais de 40L de volume útil. A adição do rotífero B. plicatilis foi realizada no 1º, 10º, 20º e 30º dias. Os camarões foram alimentados com ração comercial com 45% de proteína bruta, quatro vezes ao dia com taxa de alimentação inicial de 35% da biomassa. Durante o experimento foi avaliado o desempenho zootécnico, qualidade da água, caracterização de bactérias do gênero Vibrio, comunidade planctônica, composição centesimal e contagem total de hemócitos. Sobre o desempenho zootécnico, podem-se destacar os maiores valores médios de peso final e produtividade nos tratamentos com adição de B. plicatilis, nos quais os camarões atingiram de 1,09 a 1,26g e 2,25 a 3,41 kg m-3, respectivamente. As variáveis de qualidade de água estiveram dentro do recomendado para camarões marinhos e não foram observadas diferenças significativas entre os tratamentos. O efeito das densidades de adição foi significativo para o consumo de água por quilograma de juvenil produzido, além da redução da porcentagem de colônias de sacarose negativas do gênero Vibrio presentes na água e no camarão. Os gêneros mais frequentes observados para fitoplâncton foram: Oscillatoria (6,97 a 9,27%), Aphanocapsa (6,48 a 7,85%), e para e zooplâncton foram: Brachionus sp. (21,49 a 33,73%), Daphnia sp. (15,44 a 31,25%) e Arcella sp. (12,75 a 20,62%). Os tratamentos com maiores níveis de inclusão do rotífero (BFT- 20 e BFT-30) obtiveram os melhores resultados em relação à quantidade de proteína e lipídios. Além disso, a adição de rotífero também proporcionou uma melhor resposta imunológica aos animais cultivados comprovada através da contagem total de hemócitos apresentando altas concentrações de hemócitos antes e após os animais serem submetidos ao teste de estresse salino. Portanto, a adição de rotífero em densidade de 20 a 30 organismos mL-1 demonstrou incrementar o desempenho zootécnico de juvenis de Litopenaeus vannamei na fase berçário em bioflocos.

The production of juvenile marine shrimp has used strategies that involve coexistence with pathogens, reducing production losses in shrimp farming. One of these strategies is the application of microorganisms that can improve the nutritional content of microbial biofloc in the early stages of cultivation, contributing to greater growth of shrimp and stronger immune systems. This study evaluated the effect of addition of the rotifer Brachionus plicatilis at different densities to the cultivation of post-larvae Litopenaeus vannamei in a biofloc system supported by fermented base with a mix of bacteria. The experimental design consisted of four treatments with three replicates of each, generating a total of 12 experimental units in a completely randomized design for 42 days. The treatments iuncluded: BFT (Bioflocs); BFT - 10 (Bioflocs with the addition of B. plicatilis at a density of 10 organisms mL-1), BFT - 20 (Bioflocs with the addition of B. plicatilis at a density of 20 organisms mL-1) and BFT - 30 (Bioflocs with addition of B. plicatilis at a density of 30 mL-1 organisms). Ten-day-old postlarvae (PL10) with an average weight of 3.4 ± 0.02 mg were stocked at a density of 3,000 individuals m-3 in experimental units of 40L of useful volume. The rotifer B. plicatilis were added on the 1st, 10th, 20th and 30th days. The shrimps were fed with a commercial ration with 45% crude protein, four times a day with an initial feed rate of 35% of the biomass. During the experiment, we evaluated the water quality, zootechnical performance, and monitored the zooplankton community, centesimal composition, total hemocyte count, and quantified and characterized the Vibrio bacteria. The water quality variables were within the recommendations for marine shrimp and no significant differences were observed between treatments. At the end, regarding zootechnical performance, the highest average values of final weight and productivity were in treatments with the addition of B. plicatilis, in which the shrimp reached 1.09 to 1.26 g and 2.25 to 3.41 kg m-3. The most frequent phytoplankton genera observed were: Oscillatoria (6.97 to 9.27%), Aphanocapsa (6.48 to 7.85%), and for and zooplankton were: Brachionus sp. (21.49 to 33.73 %), Daphnia sp. (15.44 to 31.25%) and Arcella sp. (12.75 to 20.62%). The effect of the stocking densities was also significant for water consumption per kilogram of juveniles produced, and on the reduction in the percentage of negative sucrose colonies of the Vibrio genus in the water and the shrimp. The treatments with higher levels of rotifer (BFT-20 and BFT-30) had the best results for protein and lipids. The addition of rotifers also strengthened the immune system of the cultivated shrimp, as demonstrated by the total hemocyte count, with high concentrations of hemocytes before and after the animals were subjected to a salt stress test. Therefore, the addition of rotifer at densities of 20 to 30 mL-1 organisms coupled with an efficient fertilization strategy demonstrated excellent results in the production of L. vannamei juveniles.

Larvicultura de piava, Megaleporinus obtusidens: transição alimentar, densidade de estocagem e taxa de arraçoamento

O objetivo deste estudo foi avaliar o efeito da transição alimentar, densidade de estocagem e taxa de arraçoamento sobre a larvicultura da piava, Megaleporinus obtusidens; O momento adequado para realizar a transição alimentar para o alimento inerte foi determinado no experimento 1, que utilizou um delineamento inteiramente casualizado, com sete tratamentos, utilizados para avaliar o melhor período para início da transição alimentar, e dois controles, um exclusivamente com dieta inerte e outro com rotíferos; A densidade de estocagem e as taxas de arraçoamento foram avaliadas no experimento 2, conduzido em delineamento inteiramente casualizado em esquema fatorial 3 x 2, composto pelos fatores densidade de estocagem (10; 20 e 30 larvas L-1) e taxa de arraçoamento (100% e 150% do peso da biomassa inicial); Ambos experimentos tiveram duração de 30 dias; A sobrevivência das larvas do experimento 1 variou de 45,77 a 68,44 %, não tendo sido registrada mortalidade total em nenhum tratamento e nem diferença significativa entre eles; Verificou-se, portanto, que as larvas de piava aceitaram a ração desde o início da alimentação exógena, porém apresentaram um baixo desempenho zootécnico; No experimento 2 a sobrevivência foi mais elevada na densidade de 30 larvas L-1, independentemente da taxa de arraçoamento; O comprimento total e a taxa de arraçoamento das larvas não estiveram relacionados (p>0,05) à densidade; O peso final mostrou tendência de aumento na densidade de 20 larvas L-1 nas duas taxas de arraçoamento (p>0,05); Para a larvicultura de M; obtusidens recomenda-se a densidade de 30 larvas L-1 e a taxa de arraçoamento de 100% do peso da biomassa inicial.

The objective of the study was to evaluate the effect of the transition of this feed, stocking density, and feeding rate on the larvae of piava, Megaleporinus obtusidens. The appropriate time to perform the feeding for the inert food was determined in experiment 1, which used a completely randomized design, with seven treatments, applied to evaluate the best period to start the food transition, and two controls, one exclusively with an inert diet and another with rotifers. The stocking density and feed rates were evaluated in experiment 2, conducted in a completely randomized design in a 3 x 2 factorial scheme, composed of stocking density (10; 20 and 30 L-1 larvae) and feed rate (100% and 150% of the initial biomass weight) factors. Both experiments last 30 days. The survival of larvae in experiment 1 varied from 45.77 to 68.44%, with no total mortality recorded in any treatment, and no difference was registered between them. Therefore, the larvae of piava accepted the ration since the beginning of the exogenous feeding, but present low zootechnical performance. In experiment 2, the survival was higher in the density of 30 L-1 larvae, regardless of the feeding rate. The total length and feeding rate of the larvae were not related (p> 0.05) to density. The final weight showed a tendency to increase the density of 20 L-1 larvae at both feeding rates (p> 0.05). For the larviculture of M. obtusidens, it is recommended the density of 30 L-1 larvae and the feed rate of 100% of the initial biomass weight.

UTILIZAÇÃO DO FARELO DE ARROZ COM E SEM FERMENTAÇÃO NA PRODUÇÃO DO ROTÍFERO Brachionus plicatilis

O rotífero Brachionus plicatilis, é utilizado como primeiro alimento para uma grande variedade de espécies de peixes durante seus primeiros estágios de desenvolvimento. Os rotíferos são filtradores não seletivos o que facilita a sua alimentação podendo fornecer uma elevada diversidade de dietas, entre as quais, microalgas, leveduras, e os alimentos inertes. Os alimentos mais comuns utilizados para a alimentação dos rotíferos (microalgas e leveduras), apresentam problemas associados ao custo de produção (microalgas) e as leveduras que não possuem qualidade nutricional adequada. Por outro lado, o farelo de arroz e o farelo de arroz fermentado apresentam grande abundância, baixo custo, grande qualidade nutricional e componentes antioxidantes. Assim o objetivo do presente trabalho foi examinar a utilização do farelo de arroz integral e fermentado como fonte alimentar para a produção de rotíferos, Brachionus plicatilis. O estudo baseou-se em três experimentos, onde o primeiro experimento comparou o efeito de diferentes concentrações de farelo de arroz integral na taxa de crescimento do rotífero, sendo testados 4 tratamentos, com três repetições cada: 1) Controle (0,7 g levedura/1,0 x 106 rotíferos); 2) 0,5 g farelo integral/1,0 x 106 rotíferos); 3) 1 g farelo integral/ 1,0 x 106 rotíferos; 4) 1,5 g farelo integral/1,0 x 106 rotíferos. O segundo experimento, comparou o efeito de diferentes concentrações de farelo de arroz fermentado na taxa de crescimento do rotífero, onde testaram-se 4 tratamentos, com três repetições cada: 1) Controle (0,7 g levedura/1,0 x 106 rotíferos); 2) 0,5 g farelo fermentado/1,0 x 106 rotíferos); 3) 1 g farelo fermentado/ 1,0 x 106 rotíferos; 4) 1,5 g farelo fermentado/1,0 x 106 rotíferos. O terceiro experimento, comparou o efeito das melhores concentrações de farelo de arroz integral e fermentado, bem como a substituição de parte da levedura por estes farelos na taxa de crescimento populacional, qualidade de água e atividades antioxidantes dos rotíferos. Foram testados 5 tratamentos, com três repetições cada: 1) Controle (0,7 g levedura/ 1,0 x 106 rotíferos); 2) 1,5 g farelo integral/1,0 x 106 rotíferos); 3) 1,5 g farelo fermentado/ 1,0 x 106 rotíferos; 4) 0,35g levedura + 0,75g farelo integral /1,0 x 106 rotíferos; 5) 0,35g levedura + 0,75g farelo fermentado/1,0 x 106 rotíferos. Para cada tratamento foram inoculados em tanques de 2L a quantidade de 400.000 rotíferos ou 200 rotíferos/mL. Ao final do 3º dia de criação, os rotíferos foram lavados, determinado o crescimento populacional, e iniciado o cultivo novamente. Além dos parâmetros de crescimento, foram analisados os parâmetros de estresse oxidativo e qualidade da água. Os dados foram analisados por meio da ANOVA. Para tanto, foram previamente observados os pressupostos de normalidade e homogeneidade de variâncias por meio dos testes de Shapiro-Wilk e Levene, respetivamente. Quando a ANOVA resultou significativo, as médias foram contrastadas por meio de teste de Newman-Keuls. Todos os testes foram realizados no nível 5%. Os resultados dos experimentos mostraram que os rotíferos dos tratamentos com 0,7g levedura, 1,5g farelo fermentado, 0,35g levedura com 0,75g farelo integral e 0,35g levedura com 0,75g farelo fermentado obtiveram maior crescimento entre os tratamentos não diferindo entre si. O farelo de arroz integral e fermentado melhoraram a qualidade ambiental no cultivo, através da absorção da amônia da água. Não foi observada melhoria na resposta antioxidante dos rotíferos alimentados com farelo de arroz fermentado. O presente estudo demonstra que pode ser utilizado 1,5g farelo fermentado e substituição de 50% de levedura pelo farelo fermentado ou integral para alimentar rotíferos.

The rotifer Brachionus plicatilis is used as the first food for a wide variety of fish species during their early stages of development. Rotifers are non-selective filters that facilitate their feeding and can provide a high diversity of diets, including microalgae, yeast, and inert foods. The most common foods used to feed rotifers (microalgae and yeast), present problems associated with the cost of production (microalgae) and yeasts that do not have adequate nutritional quality. On the other hand, fermented and non-fermented whole rice bran have high abundance, low cost, high nutritional quality and antioxidant components. Thus, the objective of the present study was to examine the use of fermented and non-fermented whole rice bran as a food source for rotifer production, Brachionus plicatilis. The study was based on three experiments, where the first experiment compared the effect of different concentrations of non-fermented whole rice bran on the rotifer growth rate, four treatments were tested with three replications each: 1) Control (0.7 g yeast / 1,0 x 106 rotifers); 2) 0.5 g non-fermented whole rice/ 1,0 x 106 rotifers); 3) 1 g non-fermented whole rice bran / 1,0 x 106 rotifers; 4) 1.5 g non-fermented whole rice bran / 1,0 x 106 rotifers. The second experiment compared the effect of different concentrations of fermented whole rice bran on the rotifer growth rate, where he tested 4 treatments with three replications each: 1) Control (0.7 g yeast / 1,0 x 106 rotifers); 2) 0.5 g fermented whole rice bran / 1,0 x 106 rotifers); 3) 1 g fermented whole rice bran / 1,0 x 106 rotifers; 4) 1.5 g fermented whole rice bran / 1,0 x 106 rotifers. The third experiment compared the effect of the best concentrations of fermented and non-fermented whole rice bran, as well as the replacement of part of yeast by these brans on the population growth, water quality and antioxidant activities of the rotifer. Five treatments were tested, with three repetitions each: 1) Control (0.7 g yeast / 1,0 x 106 rotifers); 2) 1.5 g non-fermented whole rice bran / 1,0 x 106 rotifers); 3) 1.5 g fermented whole rice bran / 1,0 x 106 rotifers; 4) 0.35g yeast + 0.75g non-fermented whole rice bran / 1,0 x 106 rotifers; 5) 0.35g yeast + 0.75g fermented whole rice bran / 1,0 x 106 rotifers. For each treatment was inoculated in 2L tanks the amount of 400,000 rotifers or 200 rotifers / mL. At the end of the 3º day of creation, the rotifers were washed, population growth determined, and cultivation started again. In addition to the growth parameters, the oxidative stress and water quality parameters were analyzed. Data were analyzed using X ANOVA. Therefore, the assumptions of normality and homogeneity of variance were previously observed using the Shapiro-Wilk and Levene tests, respectively. When ANOVA was significant, the means were contrasted by the Newman-Keuls test. All tests were performed at the 5% level. The results of the experiments showed that the rotifers from the treatments with 0.7g yeast, 1.5g fermented whole rice bran, 0.35g yeast with 0.75g non-fermented whole rice bran and 0.35g yeast with 0.75g fermented whole rice bran had higher growth between treatments not differing between you. Brown and fermented rice bran improved environmental quality in cultivation, through the absorption of ammonia from water. No improvement was observed in the antioxidant response of rotifers fed fermented rice bran. The present study demonstrates that 1.5g fermented whole rice bran and substitution of 50% of yeast for fermented or non-fermented whole rice bran can be used to feed rotifers.

AVALIAÇÃO DE DIFERENTES DIETAS E MEDIDAS PROFILÁTICAS SOBRE O DESENVOLVIMENTO LARVAL DO SIRI CANDEIA Achelous spinimanus (LATREILLE, 1819) EM LABORATÓRIO

Informações sobre o desenvolvimento larval do siri Achelous spinimanus são escassas e não há registro do seu desenvolvimento até a fase de juvenil em laboratório. O presente estudo visou estabelecer as condições ideais de alimentação e profilaxia para o desenvolvimento da espécie em laboratório. Fêmeas ovígeras foram coletadas em Ilhabela, São Paulo e transportadas para o Instituto de Pesca da Secretaria de Agricultura do Estado de São Paulo, Brasil. Larvas de zoea I foram mantidas em condições controladas de salinidade de 35, temperatura de 29º C, fotoperíodo de 12 h de luz com diferentes dietas e tratamentos com antibióticos. Para cada tratamento foram preparadas dez réplicas. Os controles consistiram de água do mar irradiada com lâmpada ultravioleta mantidos com (C1) e sem alimentação (C2) constituída de náuplios de artêmia. Os tratamentos com antibióticos das larvas alimentadas somente com artêmia consistiram de estreptomicina (T1 = 1,0 mg.L-1) e vancomicina (T2 = 1,0 mg.L-1). Os experimentos de alimentação receberam dietas combinadas que consistiram da microalga Nannochloropsis oculata e de náuplios de artêmia recém eclodidos (A1), do rotífero Brachionus plicatilis e náuplios de artêmia recém eclodidos (A2), e a combinação dos três (A3). No controle C2 sem alimentação houve 100% de mortalidade das larvas na fase de zoea I após 4 dias. No controle C1 com artêmia, foi observado desenvolvimento até a fase de megalopa com 30% de sobrevivência no 26º dia. Nas dietas A1 (microalga+artêmia) e A3 (microalga+rotífero+artêmia) foi observado desenvolvimento até a fase de megalopa com 20 e 50 % de sobrevivência no 25º e 21º dias, respectivamente. Na dieta A2 (rotífero+ artêmia) foi observado desenvolvimento até a fase de zoea IV com 50% de sobrevivência no 15º dia. No tratamento com estreptomicina (T1) foi observado desenvolvimento até a fase de juvenil VI com 20% de sobrevivência no 58º dia. Neste tratamento (T1) foram observadas seis fases de zoea, uma de megalopa e seis estágios de juvenil. No tratamento com vancomicina (T2) foi observado desenvolvimento até a fase de zoea IV com 40% de sobrevivência no 13º dia. O tratamento T1 apresentou o melhor desenvolvimento dos organismos. A alimentação apenas com náuplios de artêmia mostrou-se adequada para o desenvolvimento até o estágio de juvenil e o tratamento das larvas com uso contínuo do antibiótico estreptomicina foi o único que apresentou o desenvolvimento até a fase de juvenil VI, evitando possível contaminação bacteriana.

Information on the larval development of Achelous spinimanus crab is scarce and there is no record of its development until the juvenile stage in the laboratory. The present study aimed to establish the ideal feeding conditions and prophylaxis for the development of the species in the laboratory. Ovigerous females were collected in Ilhabela, São Paulo and transported to the Institute of Fisheries of the Department of Agriculture of the State of São Paulo, Brazil. Zoea I larvae were kept under controlled conditions of salinity of 35, temperature of 29º C, photoperiod of 12 h of light with different diets and treatments with antibiotics. Ten replicates were prepared for each treatment. The controls consisted of seawater irradiated with ultraviolet light maintained with (C1) and without feeding (C2) constituted of artemia nauplii. The antibiotic treatments of larvae fed only with artemia consisted of streptomycin (T1 = 1.0 mg.L-1) and vancomycin (T2 = 1.0 mg.L-1). Feeding experiments were fed diets consisting of the microalgae Nannochloropsis oculata and newly hatched artemia (A1), rotifer Brachionus plicatilis and newly hatched artemia (A2), and the combination of the three (A3). In control C2 without feeding there was 100% mortality of larvae in the zoea I phase after 4 days. In control C1 with artemia, development until the megalopa phase with 30% survival on the 26th day was observed. In the diets A1 (microalga + artemia) and A3 (microalga + rotifer + artemia), development was observed up to the megalopa phase with 20 and 50% survival in the 25th and 21st days, respectively. In the diet A2 (rotifer + artemia), development was observed until the zoea IV phase with 50% survival v on the 15th day. Treatment with streptomycin (T1) showed development until the juvenile VI stage with a 20% survival on the 58th day. In this treatment (T1) six stages of zoea, one of megalopa and six stages of juvenile were observed. In treatment with vancomycin (T2), development was observed until the zoea IV phase with 40% survival on the 13th day. T1 treatment showed the best development of organisms. Feeding only with Artemia nauplii was adequate for juvenile stage development and treatment of larvae with continuous use of the antibiotic streptomycin was the only one to present development until juvenile VI stage, avoiding possible bacterial contamination.

Zooplankton of an urban coastal lagoon: composition and association with environmental factors and summer fish kill

Zooplankton may be regarded as a sensitive tool for monitoring environmental variations in coastal lagoons due to their ability to immediately react to changes in the water column trophic features and salinity levels. As a coastal lagoon with a broad history of anthropic influence, Rodrigo de Freitas Lagoon (Rio de Janeiro, Brazil) is widely used for water sports and artisanal fishing. The present study aimed to expand the knowledge base about zooplankton in the Rodrigo de Freitas Lagoon by assessing the composition and time-spatial distribution of the major zooplankton groups. Samples were collected fortnightly from at four distinct sampling points August 2001 to July 2002. At each point, salinity, temperature, dissolved oxygen and water transparency were measured. During the study period, the lagoon behaved as an spatially homogeneous environment in what regards the abiotic variables. However, all these variables showed significant differences along the time, mainly related to seasonality (air temperature and rainy and dry periods). The zooplankton community showed low taxonomic richness, with the predominance of species commonly found in coastal lagoons, especially with mesohaline conditions, as well as those found in estuaries. An interesting fact was the rise in zooplankton abundance at all sampling points right after a fish kill event. Such increase was caused mainly by the Brachionus plicatilis O.F. Müller 1786 species. Thus, the zooplankton community was affected by physical and chemical factors, mainly by the dissolved oxygen decline event and variations in the influx of seawater into the lagoon. In addition, phytoplankton availability and fish predation pressure were suggested as important regulating factors of the zooplankton community.

Zooplankton of an urban coastal lagoon: composition and association with environmental factors and summer fish kill

Zooplankton may be regarded as a sensitive tool for monitoring environmental variations in coastal lagoons due to their ability to immediately react to changes in the water column trophic features and salinity levels. As a coastal lagoon with a broad history of anthropic influence, Rodrigo de Freitas Lagoon (Rio de Janeiro, Brazil) is widely used for water sports and artisanal fishing. The present study aimed to expand the knowledge base about zooplankton in the Rodrigo de Freitas Lagoon by assessing the composition and time-spatial distribution of the major zooplankton groups. Samples were collected fortnightly from at four distinct sampling points August 2001 to July 2002. At each point, salinity, temperature, dissolved oxygen and water transparency were measured. During the study period, the lagoon behaved as an spatially homogeneous environment in what regards the abiotic variables. However, all these variables showed significant differences along the time, mainly related to seasonality (air temperature and rainy and dry periods). The zooplankton community showed low taxonomic richness, with the predominance of species commonly found in coastal lagoons, especially with mesohaline conditions, as well as those found in estuaries. An interesting fact was the rise in zooplankton abundance at all sampling points right after a fish kill event. Such increase was caused mainly by the Brachionus plicatilis O.F. Müller 1786 species. Thus, the zooplankton community was affected by physical and chemical factors, mainly by the dissolved oxygen decline event and variations in the influx of seawater into the lagoon. In addition, phytoplankton availability and fish predation pressure were suggested as important regulating factors of the zooplankton community.

Zooplankton of an urban coastal lagoon: composition and association with environmental factors and summer fish kill

Zooplankton may be regarded as a sensitive tool for monitoring environmental variations in coastal lagoons due to their ability to immediately react to changes in the water column trophic features and salinity levels. As a coastal lagoon with a broad history of anthropic influence, Rodrigo de Freitas Lagoon (Rio de Janeiro, Brazil) is widely used for water sports and artisanal fishing. The present study aimed to expand the knowledge base about zooplankton in the Rodrigo de Freitas Lagoon by assessing the composition and time-spatial distribution of the major zooplankton groups. Samples were collected fortnightly from at four distinct sampling points August 2001 to July 2002. At each point, salinity, temperature, dissolved oxygen and water transparency were measured. During the study period, the lagoon behaved as an spatially homogeneous environment in what regards the abiotic variables. However, all these variables showed significant differences along the time, mainly related to seasonality (air temperature and rainy and dry periods). The zooplankton community showed low taxonomic richness, with the predominance of species commonly found in coastal lagoons, especially with mesohaline conditions, as well as those found in estuaries. An interesting fact was the rise in zooplankton abundance at all sampling points right after a fish kill event. Such increase was caused mainly by the Brachionus plicatilis O.F. Müller 1786 species. Thus, the zooplankton community was affected by physical and chemical factors, mainly by the dissolved oxygen decline event and variations in the influx of seawater into the lagoon. In addition, phytoplankton availability and fish predation pressure were suggested as important regulating factors of the zooplankton community.