The aim of this study was a comphensive assessment of the food of pikeperch fry in the monoculture rearing from the stage of summer fry to the stage of autumn fry in ponds with three different types of management and assessment of the influence of individual treatments for pikeperch production. The experiment was performed in small ponds in experimental facility of FFPW in Vodňany. The variants of pond treatment were: a) ponds with additional prey fish (fry of common carp (C. carpio) and grass carp (C. idella)), b) ponds with installed substrate from heather, c) control variant without any support of natural food of pikeperch. All treatments had four repetitions. Rearing of pikeperch fry lasted 97 days. In all treatments, the opportunistic food strategy of pikeperch fry was recorded during the whole period of rearing and the main recorded food was macrozoobenthos, especially insect larvae. Bigger species of zooplankton had also been often found in the stomachs of pikeperch. Considerable development of macrozoobenthos in all experimental ponds was probably caused by the presence of submerged macrophytes. Thus, this factor made harder to estimate influence of installed substrates from heather for production of pikeperch fry and composition of its food. In the treatment with prey fish, the total length (F (9. 450) = 91.1; p < 10-3) and weight (F (9. 450) = 61.9; p < 10-3) of pikeperch fry were for the whole period of rearing significantly higher in comparison to the other treatments. In addition, the survival of pikeperch in the treatment with prey fish reached to 56 - 92,4 % at the end of rearing. In the treatment with substrate from heather, the total length and weight of pikeperch was significantly higher in comparison to the control treatment only in the first term of sampling. In the rest of pikeperch fry rearing period were the values comparable or higher in control treatment. Thus, for the rearing of pikeperch from the stage of summer fry to the stage of autumn fry is appropriate to stock prey fish in ponds. In comparison to installation of artificial substrate, the diversity of water environment, which is subsequently able to provide sufficiently wide natural food for reared pikeperch, seems to be more decisive.

Um dos principais problemas relacionados aos estudos limnológicos realizados manualmente em laboratório consiste no grande esforço, tempo de análise e trabalho especializado necessário. Esses fatores limitam a quantidade de amostras possíveis de serem analisadas em um determinado estudo, já que recursos sejam eles reagentes, recursos financeiros ou tempo são limitados. No presente trabalho foi utilizado um sistema semi-automatizado de medidas de variáveis físicas e químicas da água. O sistema é composto por uma sonda multi-parâmetro (Horiba U-22) e um sistema de posicionamento global (GPS) acoplados a um micro-computador, que realizam medidas georeferenciadas em curtos intervalos de tempo, permitindo um rastreamento horizontal das características da água. Foi ainda desenvolvido um sistema semi-automático para coleta fracionada da comunidade planctônica por meio de bomba de sucção operada por bateria e filtro coletor com rede de plâncton de diferentes aberturas de malha. O material coletado foi fotografado por meio de sistema de aquisição digital de imagens (microscópio Zeiss equipado com câmera AxionCan). Neste trabalho foi produzido um software (Planktonscan) que a partir da análise das imagens capturadas permite produzir dados com estimativas das medidas e dimensões dos organismos, calcular biovolumes e, utilizando fatores de conversão, estimar os valores de biomassa. O software apresenta uma interface para identificação, calcula a densidade dos organismos e produz relatório gráfico com informações sobre os organismos individuais e sobre a comunidade. Os equipamentos e o software foram testados em análises limnológicas e amostragem de plâncton no reservatório do Monjolinho, São Carlos, SP, em dezembro de 2005. Os resultados obtidos foram comparados com os disponíveis na literatura e demonstraram a aplicabilidade do sistema. / A major problem associated with the study of planktonic communities lies on the difficulties of analyzing the collected material, a long time-consuming procedure. Biomass determination is also a step requiring great effort and is subjected to large errors. In the present work a semi-automated system for measuring physical and chemical variables in the water was developed. The system is made up by a flow-pump, a multi-parameter probe and a global positioning system coupled to a microcomputer that performs measurements at short time intervals, allowing a horizontal tracking of the water quality, in much shorter times than traditional methods. Another semi-automated device was developed for collecting separate plankton size fractions. It uses a battery operating suction-pump coupled to a filter with different mesh nets. The collected materials are then submitted to image computer acquisition (Axion Vision Zeiss System). Additionally, in this study a software was produced (Planktonscan), that taking the measures of individuals dimensions (length, width and height) calculates biovolume and using conversion factors calculate the biomass for each zooplankton organism identified in the sample. Both systems were tested, regarding the measurement of limnological variables and plankton sampling, in the Monjolinho Reservoir, SP. The performance was good, resulting in a larger number of points sampled (60) in a shorter sampling time (1 hour) than those usually required. The biomass results provided by Planktonscan software were compared to data from literature, obtained by the traditional gravimetric method for dry weight determination and also with data generated from the use of mathematical models (length dry-weight regressions) available. The results were expressed as species population densities, biomasses and size spectra, evidencing the applicability of the models here developed.

Um dos principais problemas relacionados aos estudos limnológicos realizados manualmente em laboratório consiste no grande esforço, tempo de análise e trabalho especializado necessário. Esses fatores limitam a quantidade de amostras possíveis de serem analisadas em um determinado estudo, já que recursos sejam eles reagentes, recursos financeiros ou tempo são limitados. No presente trabalho foi utilizado um sistema semi-automatizado de medidas de variáveis físicas e químicas da água. O sistema é composto por uma sonda multi-parâmetro (Horiba U-22) e um sistema de posicionamento global (GPS) acoplados a um micro-computador, que realizam medidas georeferenciadas em curtos intervalos de tempo, permitindo um rastreamento horizontal das características da água. Foi ainda desenvolvido um sistema semi-automático para coleta fracionada da comunidade planctônica por meio de bomba de sucção operada por bateria e filtro coletor com rede de plâncton de diferentes aberturas de malha. O material coletado foi fotografado por meio de sistema de aquisição digital de imagens (microscópio Zeiss equipado com câmera AxionCan). Neste trabalho foi produzido um software (Planktonscan) que a partir da análise das imagens capturadas permite produzir dados com estimativas das medidas e dimensões dos organismos, calcular biovolumes e, utilizando fatores de conversão, estimar os valores de biomassa. O software apresenta uma interface para identificação, calcula a densidade dos organismos e produz relatório gráfico com informações sobre os organismos individuais e sobre a comunidade. Os equipamentos e o software foram testados em análises limnológicas e amostragem de plâncton no reservatório do Monjolinho, São Carlos, SP, em dezembro de 2005. Os resultados obtidos foram comparados com os disponíveis na literatura e demonstraram a aplicabilidade do sistema. / A major problem associated with the study of planktonic communities lies on the difficulties of analyzing the collected material, a long time-consuming procedure. Biomass determination is also a step requiring great effort and is subjected to large errors. In the present work a semi-automated system for measuring physical and chemical variables in the water was developed. The system is made up by a flow-pump, a multi-parameter probe and a global positioning system coupled to a microcomputer that performs measurements at short time intervals, allowing a horizontal tracking of the water quality, in much shorter times than traditional methods. Another semi-automated device was developed for collecting separate plankton size fractions. It uses a battery operating suction-pump coupled to a filter with different mesh nets. The collected materials are then submitted to image computer acquisition (Axion Vision Zeiss System). Additionally, in this study a software was produced (Planktonscan), that taking the measures of individuals dimensions (length, width and height) calculates biovolume and using conversion factors calculate the biomass for each zooplankton organism identified in the sample. Both systems were tested, regarding the measurement of limnological variables and plankton sampling, in the Monjolinho Reservoir, SP. The performance was good, resulting in a larger number of points sampled (60) in a shorter sampling time (1 hour) than those usually required. The biomass results provided by Planktonscan software were compared to data from literature, obtained by the traditional gravimetric method for dry weight determination and also with data generated from the use of mathematical models (length dry-weight regressions) available. The results were expressed as species population densities, biomasses and size spectra, evidencing the applicability of the models here developed.