Made available in DSpace on 2016-06-02T19:29:02Z (GMT). No. of bitstreams: 1 TeseNFOM.pdf: 709494 bytes, checksum: 789afd3e9ac18ee02e65bd17427b2035 (MD5) Previous issue date: 2006-06-06 / With aim to know the community structure of the Crustacea Brachyura and analyze the trophic dynamics of the species Callinectes dane, C. larvatus e C. ornatus in the seagrass bed of Halodule wrightii Aschers, studies were carried out during a dry period (February, 2001 and September to December, 2001) and the wet period (March to August, 2001) in the Forno da Cal beach, Itamaraca Island, Pernambuco, Brazil. The sampling method adopted was nocturnal trawling on the seagrass using a small (2m width) bottom net with internal mesh of 5mm and external of 2mm. Additional samplings were carried out on a period of 24 hours, in February, May, July, September and December, 2001. Samplings were also carried out on the adjacent sandy flat without vegetation, in March, June, August and December, having as objective to compare the biomass, abundance and diversity of this habitat with the seagrass in this same period. To determinate the gastric evacuation rate in the Callinectes sp., experiment was carried out. The results indicate that the Portunidae family contributed with 93% of the total captures. The species Callinectes ornatus, C. danae, C. larvatus and Portunus ordwayi were the most frequent. The highest density occurred in March, positively correlating with the air temperature, and the highest biomass was observed in July, with a positive correlation to density of cast algae. The seagrass presented the highest averages of densities, biomass, number of species, richness and diversity when compared to the adjacent sandy flat. Even if the number of species observed in the sand is higher, these presented well-distributed in the environment, with equitability value higher than in the seagrass. Animal organic matter, Gastropoda and Macrophyta were the food items that most contributed in the analysis of the stomach content of the species C. danae, C. larvatus and C. ornatus. It was observed that the smallest organisms have fed of small preys and with low mobility, as in the case of highest consume of Polychaeta, Copepoda and Amphipoda by specimens of smaller carapace width. Two feeding rhythms were observed for Callinectes: a diurnal one from 4:00 to 9:00 am and a nocturnal one between 21:00 and 22:00 pm. The evacuation rate (E) obtained by the regression analysis was E = 33.26% VE h-1. The daily ration in the sampled months in the 24-hour analyses was of 798.24% SV (the stomach fullness). After transforming the stomach fullness to somatic weight a day, the observed value was 20.748%.d-1. Then, C. ornatus with weigh of 1 g may consume 0.207 g food/ day. The seagrass bed represented as an important food source to Brachyura s population, due to the diversity of preys and refuge area, not only by the vegetation of seagrass but also by the abundance of cast algae, especially for the species Callinectes danae, C. larvatus and C. ornatus. / Com objetivo de conhecer a estrutura da comunidade de Crustacea Brachyura e analisar a dinâmica trófica das espécies Callinectes dane, C. larvatus e C. ornatus no ecossistema de prado de capim marinho Halodule wrightii Aschers foram realizados estudos durante o período seco (fevereiro/2001 e setembro a dezembro/2001) e chuvoso (março a agosto/2001) na praia de Forno da Cal, Ilha de Itamaracá, Pernambuco, Brasil. O método de amostragem foi através de arrastos noturnos sobre o prado marinho com uma draga leve retangular com rede interna de malha de 5mm e externa de 2mm de abertura. Coletas adicionais, no período de 24 horas, foram realizadas em fevereiro, maio, julho, setembro e dezembro de 2001. Em março, junho, agosto e dezembro foram efetuadas também coletas na planície de areia adjacente sem vegetação com o objetivo de comparar a biomassa, abundância e diversidade com o habitat de prado, nesse mesmo período. Para determinação da taxa de evacuação gástrica em Callinectes sp. foi realizado um experimento. Os resultados indicam que a família Portunidae contribuiu com 93% do total de capturas. As espécies Callinectes ornatus, C. danae, C. larvatus e Portunus ordwayi foram as mais freqüentes. A maior densidade de braquiúro foi registrada em março, correlacionando-se positivamente com a temperatura do ar, e a maior biomassa em julho, com uma correlação positiva com a densidade de algas arribadas. O ambiente de prado apresentou as maiores médias de densidade, biomassa, número de espécies, riqueza e diversidade quando comparado a uma planície de areia adjacente. Embora o número de espécies encontradas na areia seja menor, estas se apresentaram bem distribuídas no ambiente, com valor de equitabilidade maior que nos prados. Na análise do conteúdo estomacal de C. danae, C. larvatus e C. ornatus os itens alimentares de maior contribuição foram Matéria Orgânica Animal, Gastropoda e Macrofita. Foi observado que os menores organismos se alimentaram de presas pequenas e de pouca mobilidade, como foi o caso do maior consumo de Polychaeta, Copepoda e Amphipoda por espécimes de menor largura da carapaça. Dois ritmos alimentares foram observados para Callinectes: um diurno das 4:00 ás 9:00 horas e outro noturno entre 21:00 e 22:00 horas. A taxa de evacuação (E) obtida através da análise de regressão linear foi E = 33,26% VE h-1. A ração diária para o total dos meses amostrados nas análises de 24 horas foi de 798,24% SV (volume estomacal máximo). Depois de transformado o volume estomacal máximo para peso somático por dia o valor encontrado foi de 20,748%.d-1 peso somático. Assim, C. ornatus com peso de 1 g consumiria 0,207 g por dia de alimento. Além de área de berçário, visto a captura de assentantes e juvenis, o prado de capim marinho é uma importante fonte de alimentação para a população de Brachyura, por causa da diversidade de presas, e área de refugio, não só pela própria vegetação, mas também pela abundância de algas arribadas, principalmente para as espécies de Callinectes danae, C. larvatus e C. ornatus.

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Blue Catfish Ictalurus furcatus are native to tributaries of the Mississippi River but are now invasive in several Atlantic slope drainages. This includes subestuaries of the Chesapeake Bay, where their feeding ecology and potential impact on native species was largely unknown. We collected stomach contents from 16,110 Blue Catfish at 698 sites in three large subestuaries of the Chesapeake Bay (James, York, Rappahannock rivers). Cumulative prey curves revealed that sample size was sufficient for diet description, though 1,000 – 1500 stomachs were needed per river. Blue Catfish are opportunistic generalists that feed on a broad array of plant and animal material. Logistic regression models reveal that Blue Catfish undergo significant ontogenetic diet shifts to piscivory at larger sizes (P<0.01) though the lengths at which these shifts occur varies by river system (500 – 900 mm total length; TL). Over 60% of Blue Catfish stomachs contained other invasive species, primarily Hydrilla verticillata and Asian clams Corbicula fluminea. Canonical Correspondence Analysis (CCA) revealed that salinity and season explained the most variation in Blue Catfish diet, while Generalized Additive Models (GAMs) demonstrated that there is considerable spatiotemporal and length-based variation in predation of species of concern. Species of concern include American Shad, American Eel, and river herring, which are imperiled, and blue crab, which support valuable fisheries in Chesapeake Bay. Predation of American Shad, American Eel, and river herring was rare (max predicted occurrence in Blue Catfish diets = 8%), while blue crab was much more common in the diet (max predicted occurrence =28%). Predation of American Shad and river herring peaks in freshwater areas in April, while predation of blue crab peaks in brackish areas in October. Predation of all species of concern is highest for large catfish (500 – 1000 mm TL). Field and laboratory-based estimates of consumption rate revealed that Blue Catfish feed at similar rates as Channel Catfish Ictalurus punctatus, and daily ration is estimated to be 2-5% bodyweight per day during warm temperatures, while peak feeding (maximum daily ration) can approach 10% bodyweight per day. While consumption of imperiled species is rare, Blue Catfish could still have negative impacts on these species due to dense catfish populations. / Ph. D.