Manejo alimentar de alevinos de tilápia do Nilo, <em>Oreochromis niloticus</em> (L.), associado às variáveis físicas, químicas e biológicas do ambiente

Abstract

Para estudar o manejo alimentar de alevinos de tilápia do Nilo (Perciformes, Cichlidae) foram estocados 1680 exemplares dessa espécie, com aproximadamente 24 mm de comprimento médio e 0,30 g de peso médio. Esses foram distribuídos em 24 caixas de água com capacidade de 250 L cada. Foram alimentados com ração comercial, sendo a mesma oferecida quatro vezes ao dia. O experimento foi constituído por quatro tratamentos, com diferentes níveis de vitamina C, com seis repetições cada. Foram analisadas as seguintes variáveis físicas, químicas e biológicas: temperatura do ambiente e da água, transparência, oxigênio dissolvido, níveis de amônia e níveis de nitrito presentes na água, pH, biovolume de fitoplâncton e de zooplâncton, período do dia, número da coleta e efeito do tratamento. Conclui-se que o grau de repleção do estômago (GR) é influenciado pela temperatura do ar, período do dia, temperatura da água, pH, biovolume do fitoplâncton e número da coleta. Os maiores valores para o GR foram obtidos nos horários mais quentes do dia, demonstrando que o consumo de alimento ocorre, preferencialmente, em temperaturas mais elevadas, o que coincide com o período de maior luminosidade, caracterizando a espécie como diurna. O tipo de alimento preferencial foi o artificial, seguido pelo fitoplâncton, que é consumido constantemente, confirmando a tendência fitoplânctófoga e filtradora da espécie. Palavras-chave: tilápia do Nilo, grau de repleção do estômago, fitoplâncton, zooplâncton, hábito alimentar. ABSTRACT. Feeding management of fingerlings of Nile tilapia Oreochromis niloticus (L.) associated with physical, biological and chemical variables of the environment. Feed management of 1680 Nile tilapia fingerlings (Perciformes, Cichlidae) with approximately 24 mm of mean length and 0.30g of mean weight is provided. The fingerlings were distributed in 24 tanks with 250 liters each. capacity each one. They were feed on a commercial diet four times a day. Four treatments with different levels of vitamin C and six repetitions constituted the experiment. Data of physical-chemical and biological variables, environment and water temperature, water transparency, dissolved oxygen, ammonium and nitrite levels in water, pH, phytoplankton and zooplankton biovolume, period of day, number collect and effect of treatment were analyzed. Stomach repletion degree is influenced by water and environment temperature, period of day, pH, phytoplankton and zooplankton biovolume and number of collect. Highest values of RD were obtained in the hottest hours of the day, which shows that the feed intake occurs in the highest temperature, coinciding with the time of the most intense light species characterized as diurnal. Artificial diet was preferred, followed by phytoplankton. This confirms the phytoplanktivorous habit of the specie, its diet and filtered, non-visual predation.

Contributions of the periphyton to the growth of Nile tilapia (Oreochromis niloticus) fingerlings on different fixation substrates: an ecological approach

“…These algae were the most consumed natural item by fish in the control treatment, possibly because of the absence of substrate that allows the growth of the periphytic community. Loures et al (2001) observed that for tilapia from fish farms fed mainly on feed, at certain times, the consumption of phytoplankton was almost equal to that of the feed provided by the researcher. The phytoplankton and periphytic communities require practically the same nutrients to grow, a higher consumption of phytoplanktonic algae (mainly from the Scenedesmus genus) in the control treatment supports the hypothesis that the absence of a substrate in this treatment favored the development of phytoplanktonic algae.…”

Performance of the nile tilapia with varying daily feeding amounts, using a commercial diet

“…The amount of food supplied or the frequency with which it is administered may influence its utilization, once the feed is placed directly in the water. The portion of unconsumed feed will either be diluted or leached, causing increased feed conversion rates and reduced water quality (LOURES et al, 2001). Yao, Umino and Nakagawa (1994), analyzing the effects of feeding frequency on Plecoglossus altivelis (ayu), reported that the fish fed four times a day, as occurred in the respective experiment, had a lower level of triglycerides than those fed only twice a day.…”

“…Santos et al (2015) evaluated the performance of Nile tilapia fingerlings (Oreochromis niloticus) submitted to different feeding levels (6, 9 and 12% of body weight per day) and feeding frequencies (4 and 6 times a day) for a period of 35 days fed with ration bran containing 48% crude protein and observed that the feeding frequency did not influence the productive performance of the fish and that the best performance of the fingerlings was observed with the feeding level of 9% of live weight per day, in four daily meals. Loures et al (2001) evaluated the food management of Nile tilapia fingerlings, O. niloticus, fed with commercial ration, offered four times a day, with different levels of vitamin C and observed that the degree of repletion of the stomach (GR) is influenced by air temperature, time of the day, water temperature, pH, phytoplankton biovolume and collection number. The highest values for GR were obtained during the hottest times of the day, demonstrating that food consumption occurs, preferably, at higher temperatures, which coincides with the period of greatest luminosity, characterizing the species as diurnal and that the type of preferential food was the artificial (commercial ration).…”

Interrelationships between morphometric variables and total weight in male fish Chondrostoma regium (Heckel, 1843) evaluated by path analysis in Ghamasiab river Kermansha, Iran

“…Sang et al (2009) also reported that body measurements were effective in the estimation of weight and body yield in catfish (Pangasianodon hypophthalmus). The interpretation of results was based on the following criteria: if an independent variable (x) does not present a significant correlation coefficient with the dependent variable (y), this indicates that it is not determining the variation in y, regardless of any presence or absence of any high direct effect on y; if an independent variable (x) has a significant correlation and high direct effect on the dependent variable (y), this indicates that it is determining the variation of y; and, if the independent variable (x) show a significant correlation but low direct effect on the dependent variable (y), this indicates that it should not be used alone as a determining factor for y (Loures et al, 2001).…”