Oceanographic Institute

The common carp Cyprinus carpio is an omnivorous, highly fertile fractional spawner and a generalist species that can live in a wide range of biotic and abiotic conditions. The combination of these features contributes to their high invasiveness potential allowing its rapid spread and increased biomass. The species has already established in 91 out of 120 countries where it has been introduced, especially due to aquaculture and ornamental activities. This work, based on the presence of C. carpio inhabiting the Patos-Mirim system, Rio Grande do Sul, Brazil, provides the first evidence of advanced stages of gonadal development in both sexes, reinforcing the view that the species can adapt to regional environmental conditions and suggests high potential for establishment of self-sustaining populations in this system.

Nitrogenous compounds can be toxic to aquatic animals especially when they are reared at high stocking densities. Cobia (Rachycentron canadum) is a fast growing fish currently reared in cages, but with expanding production in intensive recirculating aquaculture systems (RAS). Therefore, the objective of this study was to evaluate the acute toxicity of ammonia and nitrite to juvenile cobia. Juveniles (1.74 ± 0.11 g for ammonia and 0.88 ± 0.06 g for nitrite toxicity evaluation) were acclimated to test conditions (temperature 26°C and salinity 22‰) and acutely exposed to ammonia (0.25-1.30 ppm NH 3 -N) and nitrite (30-210 ppm NO 2 -N) at 0.2 fish L − 1 . Tests were run in 50 L semi-static tanks, experimental water was fully renewed daily, and all test concentrations plus the controls were run in triplicate. Mortality, feeding and swimming behavior were observed during 96 h, toxic concentrations for 50% the population and the respective 95% confidence intervals for these three end points were estimated using the Trimmed Spearman Karber Method. Cobia ceased to eat at 0.62 (0.56-0.70) ppm NH 3 -N and 76.1 (73.2-79.0) ppm NO 2 -N. Swimming behavior was affected at higher concentrations: 0.80 (0.74-0.85) ppm NH 3 -N and 88.8 (82.6-95.5) ppm NO 2 -N. Even higher concentrations were necessary to kill juvenile cobia, LC50-96 h for ammonia was estimated at 1.13 (1.06-1.19) ppm NH 3 -N, and within the range of concentrations tested for nitrite it was not possible to estimate the LC50-96 h, as only 30% of the individuals died at the highest concentration after 96 h (210 ppm NO 2 -N). The results of the present experiments demonstrate that ammonia could be problematic at relatively low levels for the intensive rearing of juvenile cobia; however, it is unlikely that the high levels of nitrite needed to harm juvenile cobia would be reached in a well designed and properly operating RAS.

Cobia Rachycentron canadum is a fast growing fish with world-wide potential for aquaculture, and has been considered for rearing in recirculating aquaculture systems (RAS). Nitrate is considered the least toxic nitrogenous product in the ammonia nitrification process, but as it may accumulate in RAS, toxic levels can be reached. The objective of this study was to evaluate the acute toxicity and the histopathological effects of nitrate on juvenile cobia. Juveniles (6.87 ± 0.36 g; 11.8 ± 0.19 cm) were acutely exposed to six concentrations of nitrate (500-3000 ppm NO 3 − -N) plus a control during 96 h. At the end of this period of exposure, juvenile cobia were sampled for histopathological evaluation. The estimated LC 50 of nitrate to juvenile cobia was equal to 2407 and 1829 mg/L NO 3 − -N at 24 and 96 h, respectively. Cobia exposed to sub-lethal nitrate concentrations showed histopathologic alterations in the gills, esophagus and brain. The gills revealed epithelial hyperplasia with complete lamellar fusion, telangiectasia, and lamellar shorting induced by necrosis, and the esophagus presented hyperplasia of epithelium and mucus cells.

In the present study was evaluated the ontogenic of immunocompetent organs of cobia up to 53 days after hatching (dah) through histology and immunohistochemistry techniques. The kidney was the first lymphohematopoietic organ to appear, at 1 dah, followed by the spleen at 5 dah and the thymus at 7 dah. The first CD3 receptors on the lymphocytes were observed in 27% of the thymic tissue at 7 dah and in 99% at 53 dah. The phenotypic expression of CD3 receptors was registered in 10% of the kidney at 8 dah and in 32% at 53 dah. CD4 receptors were observed in 5% and 63% of the thymic area at 7 and 53 dah, respectively. In the kidney, T4 lymphocytes were first observed at 13 dah in 9% of the organ and in 28% at 53 dah, defining the functional development of the specific system associated with immunological memory capacity.

The water-soluble fraction (WSF) of petroleum contains a mixture of polycyclic aromatic hydrocarbons, volatile hydrocarbons, phenols, and heterocyclic compounds, considered deleterious to aquatic biota. Marine ''pejerrey'' Odontesthes argentinensis (Teleostei: Atherinopsidae) has a great commercial importance in local fisheries and a high potential for aquaculture. The aim of this study was to evaluate the histopathological effects in ''pejerrey'' larvae exposed to different concentrations of petroleum WSF. The chronic toxicity test was conducted with newly hatched larvae exposed for 21 days to sublethal concentrations of WSF (2.5, 5, 10, and 20 % of WSF), plus one control. Survival and growth were significantly lower in the highest concentration. Several histopathological changes were found in the gills (e.g., hyperplasia, aneurisms, edema, and necrosis), kidney (e.g., nuclear alterations, decrease in the hematopoietic cells), and liver (e.g., hypertrophy, karyorrhexis, and karyopyknosis). An index of branchial lesion was proposed to standardize gill lesions to different pollutants.

Initial information related to the reproduction, embryo development and larviculture of the barber goby has been described Abstract. The first feeding period is the most critical phase for the production of marine fish larvae. The utilization of n-3 HUFA enrichment on live feed has improved the results for several species during the larviculture. To evaluate the effect of n-3 HUFA enrichment on survival and growth of the barber goby Elacatinus figaro Sazima, Moura & Rosa, 1997, newly hatched larvae were divided in two experimental groups (200 larvae per group, with two replicates each). One group was fed on non-enriched rotifers Brachionus plicatilis and the other group was fed with n-3 HUFA enriched rotifers. After 14 days of experiment, survival of larvae fed n-3 HUFA enriched rotifers was three times higher (35.7 ± 3.1%) than those fed non-enriched rotifers (11.1 ± 5.2 %), however this difference was not significant. Growth was faster for larvae fed n-3 HUFA enriched rotifers after the first week of life, but at the end of 14 days, it was no longer significantly different between the two groups (6.09 ± 0.62 and 5.69 ± 0.66 mm). The results of this experiment suggest that barber goby should be fed n-3 HUFA enriched rotifer in order to maximize juvenile production.

The Brazilian flounder, Paralichthys orbignyanus, is a promising candidate for aquaculture, especially due to the euryhalinity demonstrated experimentally for large juveniles (3 g) and sub-adults. Flounder are observed in estuaries and were already reared in fresh and salt water, however little is known with respect of salinity tolerance during their early development. The objective of this work was to evaluate the effects of salinity from fertilization to juvenile settlement. Three experiments were conducted to evaluate the effects of salinity. In trial 1 adult flounder were captured in the wild, transferred to the laboratory and induced to spawn. The gametes were hand striped, split in four samples and fertilized with water at 10, 15, 25, and 35‰. Eggs were considered fertilized when the first cell divisions were observed under the microscope. For the trial 2 newly hatched larvae were reared in four salinities (5, 10, 20, and 30‰) and their growth and survival were observed until metamorphosis. In trial 3 larvae and juvenile of different ages (6, 16, 30, 45, and 60 dahdays after hatching) were evaluated for their tolerance to fresh water. Although the fertilization rate was directly proportional to salinity, hatching was successful only in full salt water. Larvae did not survive in low salinity water (5‰) longer than 6 days, whereas growth was improved when larvae were reared at 20 and 30‰. Young larvae cannot survive in salinities below 4‰, but at 30 dah juvenile presented 100% survival in fresh water. The present findings demonstrate the need for high salinity water (30-35‰) for the successful reproduction and incubation of P. orbignyanus eggs. Flounder can be reared successfully at intermediate salinities (20‰) during larviculture, but at lower salinities (5 and 10‰) their survival and growth are impaired. However, immediately after flounder metamorphose into juveniles they survive even in fresh water, demonstrating the strong euryhalinity of this species even at early stages of development.

The objective of this work was to evaluate the ideal feeding rate and frequency for juvenile pompano (Trachinotus marginatus). Two experiments were carried out in a completely randomized design, with three replicates each. In experiment I, 25 fish (4.8±0.6 g and 6.48±0.01 cm) were stocked in 15 tanks (50 L) during 21 days and fed 4, 8, 12, 16, and 20% body weight per day. In experiment II, 20 fish (4.1±0.1 g and 6.6±0.1 cm) were stocked in 15 tanks (40 L) during 28 days and fed 2, 6, 8, and 10 times a day. The tested feeding rates and frequencies did not influence survival. Final weight and length in experiment I were significantly lower in fish fed 4% body weight per day, whereas in experiment II only weight was significantly lower in fish fed 2 and 6 times a day. At the end of both experiments, apparent feed conversion showed significant difference, with the worst value observed for fish fed 20% body weight per day in experiment I and 2 times a day in experiment II. Juvenile pompa...

RESUMO O linguado Paralichthys orbignyanus é um forte candidato para a aquicultura na América do Sul e a produção de juvenis é uma das etapas cruciais para a sua produção em larga escala. Sabe-se que o enriquecimento da Artemia com ácidos graxos altamente insaturados (n-3 HUFA) pode otimizar a produção de muitos peixes marinhos. Portanto, o objetivo deste trabalho foi verificar os benefícios do enriquecimento da Artemia com n-3 HUFA para a produção de juvenis de P. orbignyanus. Juvenis recém-assentados de linguado foram transferidos para seis unidades experimentais, onde foram alimentados com náuplios de Artemia ou Artemia enriquecida. Os peixes foram alimentados ad libitum à temperatura e salinidade de 24°C e 32, respectivamente. Os linguados alimentados com Artemia enriquecida cresceram significativamente mais e tiveram maior sobrevivência (P<0,05) que os linguados alimentados com Artemia não enriquecida. Contudo, a taxa de pigmentação foi similar entre linguados alimentados com Artemia enriquecida e não enriquecida. Conclui-se que a produção de juvenis de P. orbignyanus pode ser otimizada através do enriquecimento da Artemia com emulsões comerciais ricas em n-3 HUFA.

Para determinar a viabilidade do cultivo de uma espécie, é importante o conhecimento dos fatores limitantes para sua produção. Conhecer a taxa de consumo de oxigênio pós-prandial pode auxiliar na determinação da freqüência alimentar ideal para as espécies cultivadas. O objetivo deste trabalho foi estudar a taxa de consumo de oxigênio pós-prandial para juvenis do pampo Trachinotus marginatus. A avaliação do consumo de oxigênio foi feita a 24°C e 33‰, com pampos (9,64±0,2g) alimentados com 12% da biomassa por dia com dieta NRD INVE (59% proteína). Foi observado um pico de consumo de oxigênio 30min após a alimentação (1,06mgO2 g-1 h-1) e seu retorno ao nível de jejum (0,79mgO2 g-1 h-1) depois de decorridos mais 120min. A alimentação de juvenis de pampo pode ser realizada com uma freqüência de aproximadamente oito vezes por dia, pois a cada 2,5h a taxa de consumo de oxigênio já não mostra a elevação característica da fase pós-prandial, sugerindo que os processos de digestão e assimilaçã...

Cobia (Rachycentron canadum) is a marine finfish with good potential for mariculture. This study analyzes the effects of probiotic Bacillus spp. on the performance of cobia larvae reared in a recirculating aquaculture system (RAS). Larvae were stocked into two independent RAS for 26 days after hatching. One of the systems (Probiotic treatment) received the addition of a commercial probiotic consisting of B. subtilis, B. licheniformis and B. pumilus directly into the water and by live feed. Survival, final weight and water quality were not affected by probiotics. Results showed larvae of the probiotic treatment demonstrated a greater resistance to salinity stress. Immunohistochemical analysis showed a higher expression of CD4 in probiotic treatment. These results suggest that Bacillus spp. probiotics used in RAS have a potential stimulating impact on immune system differentiation and increases salinity stress resistance of cobia larvae.