ABSTRACT
The experiment had as objective to study the survival of Piaractus mesopotamicus and Oreochromis niloticus larvae subject to predation by Pantala flavescens larvae with different length classes. We used 120 larvae of P. mesopotamicus, 120 of O. niloticus, and also 24 larvae of Pantala flavescens, distributed in 24 aquariums with useful volume for 2 L, being placed one Odonate for aquarium. The treatments differed as regard to the prey species and the predator size, being kept a control treatment. An aquarium (2 L) containing one larvae of Odonate and 10 larvae of fish were considered an experimental unit. After the beginning, each three hours (18:00, 21:00, 0:00, 3:00, 6:00, 9:00, 12:00, 15:00 and 18:00h), the remnant larvae of fish (alive) in each experimental unit was quantified, and we replaced the consumed larvae, so that we always had 10 larvae of fish at each aquarium after each counting. For both fish species, there was a slight increase in consumption by the Odonate with intermediate size, but the values did not differ statistically (p > 0.05). Larvae of Odonate in the treatments with greater length presented a lower consumption (p 0.05) than in other treatments.
The experiment had as objective to study the survival of Piaractus mesopotamicus and Oreochromis niloticus larvae subject to predation by Pantala flavescens larvae with different length classes. We used 120 larvae of P. mesopotamicus, 120 of O. niloticus, and also 24 larvae of Pantala flavescens, distributed in 24 aquariums with useful volume for 2 L, being placed one Odonate for aquarium. The treatments differed as regard to the prey species and the predator size, being kept a control treatment. An aquarium (2 L) containing one larvae of Odonate and 10 larvae of fish were considered an experimental unit. After the beginning, each three hours (18:00, 21:00, 0:00, 3:00, 6:00, 9:00, 12:00, 15:00 and 18:00h), the remnant larvae of fish (alive) in each experimental unit was quantified, and we replaced the consumed larvae, so that we always had 10 larvae of fish at each aquarium after each counting. For both fish species, there was a slight increase in consumption by the Odonate with intermediate size, but the values did not differ statistically (p > 0.05). Larvae of Odonate in the treatments with greater length presented a lower consumption (p 0.05) than in other treatments.
ABSTRACT
The objective was to evaluate the feeding selection of food organisms for two species of fish larvae (pacu and curimba) at different ages (6, 12, 19 and 26 days after eclosion), in the presence or absence of Pistia stratiotes. Four treatments were used (T1 = pacu + P. stratiotes; T2 = pacu; T3 = curimba + P. stratiotes; T4 = curimba) and four replications. Every seven days, 24 fish larvae of each species were collected, and kept without food for 24 hours. After being distributed in the aquariums with plankton, the larvae stayed for three hours, and were collected and prepared for analysis, along with the water samples. The digestive tract of the fish larvae were removed and analyzed under an optic microscope. Statistic differences in selective feeding of plankton organisms were reported for larvae of the same species, of different age groups and also among larvae of different species of the same age. There were no observed differences as for the presence or absence of P. stratiotes. The fish larvae of pacu and curimba selected similar organisms at six days old, with changes until the 26th day. As they developed, the pacu larvae began to select cladocerans and ostracods, and the curimba selected protozoans and algae.
Objetivou-se avaliar a seleção alimentar de organismos-alimento por formas jovens de pacu (Piaractus mesopotamicus) e curimba (Prochilodus lineatus) com diferentes idades (6, 12, 19 e 26 dias), na presença e ausência de Pistia stratiotes. Foram utilizados quatro tratamentos (T1 = pacu + P. stratiotes; T2 = pacu; T3 = curimba + P. stratiotes; T4 = curimba) e quatro repetições. A cada sete dias, foram coletadas 24 larvas de cada espécie de peixe dos tanques, sendo estas mantidas em jejum por 24 horas. Depois de distribuídas nos aquários com plâncton, as larvas permaneceram por três horas, sendo coletadas e fixadas para análise, juntamente com as amostras de água. Os tratos digestórios das larvas foram retirados e analisados sob microscópio óptico. Observaram-se diferenças estatísticas na seletividade alimentar de organismos planctônicos por larvas de mesma espécie, em diferentes idades e também entre larvas de espécies diferentes, com mesma idade, não diferindo quanto à presença ou ausência de P. stratiotes. As formas jovens de pacu e curimba selecionaram organismos similares aos seis dias de idade, passando por alterações até o 26º dia. À medida que se desenvolveram, as larvas de pacu passaram a selecionar cladóceros e ostrácodos e as de curimba, protozoários e algas.
ABSTRACT
The present experiment was carried out to evaluate the effects of the replacement of corn Zea. Mays (0.00%; 33.00%; 66.67% e 100.00%) by millet P. americanum in grass carp Ctenopharyngodon idella fingerlings diets, during a 45 days period. One hundred and twelve carp grass fingerlings (0.75 g) were used, distributed in 16 net ponds (160 L), in randomized blocks with four treatments and four replicates. Each block corresponded to one fiber cement tank (1000 L) with four net ponds. Each net pond containing seven grass carp fingerlings was considered one experimental unit. The variables evaluated were: mean weight, mean weight gain, mean length, outward feed conversion, condition factor and survival rate. Differences on the performance parameters of the animals were not observed. The average values of temperature, pH, electric conductivity and dissolved oxygen was 24.5th C ± 1.39; 7.51 ± 0.32; 0.16 ± 0.01 µS/cm and 6.04 ± 1.28 mg/L, respectively. Results show that the millet can be included in Ctenopharyngodon idella fingerlings diets up to 33.70%, replacing the corn completely, without affecting the performance of the fish
O presente experimento com duração de 45 dias foi conduzido com o objetivo de avaliar o efeito da substituição do milho Zea mays (0,00%; 33,00%; 66,67% e 100,00%) pelo milheto Pennisetum americanum, em rações sobre o desempenho de alevinos de carpa-capim Ctenopharyngodon idella. Foram utilizados 112 alevinos de carpa-capim (0,75 g), distribuídos em 16 tanques-rede (160 L), em um delineamento em blocos casualizados, com 4 tratamentos e 4 repetições. Cada bloco correspondeu a uma caixa de fibrocimento (1.000 L) com 4 tanques-rede, onde cada um deles contendo 7 alevinos foi considerado uma unidade experimental. As variáveis avaliadas foram peso final médio, ganho de peso, comprimento final médio, conversão alimentar aparente, fator de condição e taxa de sobrevivência. Não foram observados efeitos da utilização do milheto sobre os parâmetros de desempenho produtivo analisados (p > 0,01). Os valores médios de temperatura, pH, condutividade elétrica e oxigênio dissolvido durante o período experimental foram de 24,5 ± 1,39ºC; 7,51 ± 0,32; 0,16 ± 0,01 µS/cm e 6,04 ± 1,28 mg/L, respectivamente. Conclui-se que o milheto pode ser incluído na ração para alevinos de C. idella em até 33,7%, substituindo totalmente o milho sem afetar o desempenho dos animais