Made available in DSpace on 2016-06-02T19:31:36Z (GMT). No. of bitstreams: 1 DissFEM.pdf: 2350745 bytes, checksum: c4041a3f7f82892ef0c37b2ea2b15d8d (MD5) Previous issue date: 2006-05-31 / Financiadora de Estudos e Projetos / The trophic ecology and bioenergetic aspects of most small fishes were not yet investigated, although they are important components in the ictiofauna, largely contributing to the richness of species and to the energy flow in aquatic ecosystems. The energy budgets and the food selectivity of two species of small fishes, Hyphessobrycon eques and Serrapinnus notomelas, were analysed. Natural populations were sampled from Monjolinho River, São Carlos, SP, in the period between September to December 2005, and January to April 2006. Food selectivity experiments and energy budgets experiments were performed in the laboratory using planktonic and benthic invertebrates as food items. Food selection was evaluated by Paloheimo index, by calculating the normalized forage ratio. Both species had preference and positive selection for the dipteran larvae Aedes aegypti, Chironomus xanthus and Chaoborus sp., as well as for the cladocerans Daphnia laevis and Ceriodaphnia silvestrii. They presented negative selection or absence of selection for Hyalella meinerti and Cypricercus mucronata. The positive selection of both species of fishes for the larvae of Aedes aegypti evidenced that they have potential to be used in the biological control on dengue disease epidemies. The results obtained from the energy balances revealed that S. notomelas has higher consumption and assimilation rates than H. eques, however its production efficiency is lower as a consequence of higher metabolic expenditures. On average the production efficiency was 53% for H. eques and 22% for S. notomelas. The values obtained for the instantaneous net production efficiency of both species were higher than those reported in the literature for carnivorous fishes (20%) and also higher than those reported for natural populations of small fishes in tropical regions. / A ecologia trófica e os aspectos bioenergéticos da maioria dos peixes de pequeno porte são desconhecidos, embora sejam componentes importantes da ictiofauna, contribuindo grandemente para a riqueza de espécies, e para o fluxo de energia dos ecossistemas aquáticos. Os balanços energéticos e a seletividade alimentar de duas espécies de peixes de pequeno porte, Hyphessobrycon eques e Serrapinnus notomelas, foram estudados. As populações naturais foram amostradas no rio Monjolinho, São Carlos, SP, entre setembro e dezembro de 2005, e janeiro a abril de 2006. Os experimentos de seletividade alimentar e de balanço energético foram realizados em laboratório, utilizando-se invertebrados planctônicos e bentônicos como itens alimentares. Ambas espécies apresentaram seleção positiva para: larvas de Aedes aegypti, Daphnia laevis, Ceriodaphnia silvestrii, Chironomus xanthus, Chaoborus sp, Oligochaeta e ausência de seleção ou seleção negativa para Hyalella meinerti e Cypricercus mucronata. A seleção alimentar positiva para as larvas de Aedes aegypti evidenciam estas espécies como promissoras para o controle biológico preventivo de epidemias de dengue. O balanço energético evidenciou que S. notomelas apresenta maior consumo e assimilação superior à de H. eques, contudo a sua eficiência de produção é menor, devido aos gastos mais elevados com a respiração. Ambas espécies tiveram eficiências instantâneas de produção líquida (K2i), mais elevadas do que aquelas reportadas na literatura como referência padrão para peixes com alimentação de origem animal, e também mais elevadas do que aquelas reportadas às populações naturais de peixes de pequeno porte em região tropical.

Many communities are currently seeking to balance urban water needs with preservation of sensitive fish habitat. As part of that effort, CE-QUAL-W2, a hydrodynamic and temperature model, was developed for Chester Morse Lake and the lower Cedar River, WA. Chester Morse Lake is approximately 10 km long with a maximum depth at full pool of 40 m. The Cedar River model started immediately downstream of the Chester Morse dam and ended 21 km downstream at Landsburg, where drinking water is diverted for the City of Seattle. This water quality model was coupled with a fish habitat and bioenergetics model for bull trout and was calibrated to temperature data between 2005 and 2008. Bull trout fish bioenergetics parameters were provided by the USGS. The CE-QUAL-W2 model was found to be highly accurate in modeling temperature variation in the lake - at most locations having an average absolute mean error of between 0.5 and 0.8 oC. The Cedar River model had an average absolute mean error of 0.7oC. This tool is designed to allow managers and operators to estimate the impact to fish habitat and growth potential from various management decisions including extent of drawdown, timing/volume of flows, and various pumping operations. Future studies could include incorporating further water quality parameters such as nutrients, algae, and zooplankton as they relate to fish productivity.