ABSTRACT
An increasing demand for fish products has led to an intensive aquaculture production in Brazil, and cultivation of fish constituted 860 × 103 tons in 2022, contributing to the 87% of total fish consumption. Nile tilapia constitutes almost half of the aquaculture production, and most tilapia farms use floating net cages. One of the major constraints of intensive fish production is production of off-flavors. Release of nutrients by the fish leads to deterioration of the water quality and stimulates growth of microorganisms, also including off-flavor producing species. The objective of this study was to determine levels of taste and odor compounds (geosmin, 2-MIB and a selection of volatile compounds) and their impact on the flavor quality of Nile tilapia produced in net cages in reservoirs in São Paulo State, Brazil. GC-MS analysis of fish and water from six different farms showed concentrations of geosmin in the water from 1 to 8 ng/L, while geosmin in fish flesh ranged from 40 to 750 ng/kg. The level of 2-MIB in water was 2 to 25 ng/L, and 0 to 800 ng/kg fish. The GC-MS analysis also revealed presence of more than 100 volatile organic compounds in the fish flesh, consisting of aldehydes, alcohols, benzene derivatives, hydrocarbons, ketones and few other compounds. Geosmin and 2-MIB related flavor notes were detected in all fish by a sensory panel, and a high correlation between the chemical and sensory analyses was found. The potential impact of the volatile organic compounds on the fish flavor is discussed. Analysis of the water quality in the reservoirs indicated that levels of geosmin and 2-MIB levels were highly influenced by the nutrient levels in the water.
Subject(s)
Cichlids , Volatile Organic Compounds , Animals , Brazil , Naphthols/analysis , Naphthols/chemistryABSTRACT
The aim of this study was to observe how abiotic and biotic factors in a tropical region influence the rate of monogenean parasitism in Nile tilapia (Oreochromis niloticus) that are farmed in net cages. A total of 240 sexually reversed fish were analyzed, and 20 from each culture stage were collected during each sampling month. Overall, 60 fish were sampled in April (autumn), 60 in August (winter), 60 in November (spring), and 60 in February (summer). Fish were collected from a commercial fish farm located in Capivara Reservoir in the lower Paranapanema River region of Paraná, Brazil. In total, 3290 monogenean parasites were collected from fish gills of the following species: Cichlidogyrushalli, C. thurstonae, Scutogyruslongicornis, C. cirratus, C. sclerosus, and C. tilapiae. Higher parasitological indices were observed in colder seasons with lower precipitation. Autumn had the highest parasitic infection values compared to the other seasons. The occurrence of monogenean parasites showed a negative correlation with season, in contrast to the culture stage, in which there was a positive correlation. These results may provide a means for establishing adequate fish farm management to predict periods of high monogenean infestation.
ABSTRACT
This study investigated the enrichment influence due to fish farming in net cages on the phytoplankton composition, density and diversity in two arms of a subtropical reservoir (Salto Caxias, Paraná). There were no statistically significant differences in the phytoplankton composition and diversity, as well as for concentrations of nutrients among the handled treatment. The density values were higher during the summer. Richness and Shannon diversity values were low during the study period. The equitability values were high during the winter and low in the summer. Variations of phytoplankton community and nutrients were mainly influenced by seasonality. The absence of significant differences between the treatments was probably due to the small number of net cages and fish used, as well as to the hydrodynamics of the studied environments, which are influenced by upstream rivers inflows.
Este estudo investigou os efeitos do enriquecimento devido ao cultivo de peixes em tanques-rede sobre a composição, densidade e diversidade fitoplanctônica em dois braços de um reservatório subtropical (Salto Caxias, Paraná). Não foram registradas diferenças significativas para a composição e diversidade fitoplanctônica e para as concentrações de nutrientes entre os tratamentos utilizados. A densidade foi maior durante o verão. Os valores de riqueza de espécies e diversidade de Shannon foram baixos durante todo o período de estudo. A equitabilidade foi elevada no inverno e baixa no verão. As variações da comunidade fitoplanctônica e dos nutrientes parecem ter sido influenciadas principalmente pela sazonalidade. A ausência de diferenças significativas entre os tratamentos, provavelmente se devem ao pequeno número de tanques e peixes utilizados, e à hidrodinâmica dos ambientes estudados, os quais são influenciados pelos influxos dos rios à montante.
Subject(s)
Animals , Aquaculture , Biodiversity , Phytoplankton/classification , Brazil , Environmental Monitoring , Population Density , Population Dynamics , SeasonsABSTRACT
Avaliou-se a utilização da ractopamina como promotor de crescimento para carpa húngara em experimento com 56 dias de duração, realizado em 12 tanques-rede de pequeno volume, utilizando-se 360 peixes com peso inicial de 18,64±1,25g. Foram testadas três quantidades de ractopamina, 7, 14 e 21ppm/kg, mais a dieta controle. Avaliaram-se o peso médio, o comprimento total, a altura, a taxa de crescimento específico e o fator de condição. Foram também analisadas a composição corporal, a deposição tecidual e a glicose plasmática dos peixes. Não foi observado efeito significativo da adição de ractopamina sobre as características de desempenho. Observou-se maior concentração de glicose, 61,67mg/dL, nos peixes alimentados sem a adição de ractopamina na dieta. A adição de ractopamina na dieta proporcionou maior quantidade de gordura corporal nos peixes e não afetou a quantidade de proteína. Conclui-se que a adição de ractopamina na dieta não é eficiente para juvenis de carpa húngara.
The use of ractopamine as a growth promoter for hungarian carp was evaluated in an experiment with a duration of 56 days, accomplished in 12 net cages of lower volume using 360 fish with initial weight of 18.64±1.25g. Three amounts of ractopamine, 7, 14 and 21ppm/kg, plus control diet were tested. The mean weight, total length, height, specific growth rate and condition factor were evaluated. Body composition, tissue deposition and fish plasmatic glucose were also analyzed. No significant effect of ractopamine addition was observed on the characteristics evaluated. A higher glucose concentration of 61.67mg/dL was observed in fish fed without the addition of ractopamine to the diet. The ractopamine inclusion in diets promotes higher body fat levels in fish and does not affect the amount of protein. The conclusion is that the addition of ractopamine in the diet is not efficient for hungarian carp juveniles.
