Metal content, Metallotionein and physiological condition (RNA/DNA ratio) were analyzed in Cachama, Colossoma macropomum from the Orinoco River. Juvenile samples were dissected and one gram of white muscle gills, kidney and liver was taken. Cu, Cd, Pb, Ni and Fe were analyzed by atomic absorption spectrophotometer using TORT and LUTSI as reference material. Metallothioneins were determined with Ellman´s reagent and RNA/DNA ratio was analyzed by fluorometric method. Results showed that Cd, Cu, Ni, Fe, and Pb levels were significantly higher in liver than muscle. There was no difference statistically between Mts concentrations in liver, kidney and gills; muscle showed the lowest Mts concentrations. Multivariate analysis ACP determined relationship between Mts-L and Cu and Mts-G and Cd. The Mts in muscle was related with Pb and Cd. There was no association between physiological condition and metals concentrations, however, the RNA/ DNA showed relationship with Mts-M and Mts-L

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During present study, the copper (Cu) mediated oxidative stress was measured that induced DNA damage by concentrating in the tissues of fish, Catla catla (14.45±1.24g; 84.68±1.45mm) (Hamilton,1822). Fish fingerlings were retained in 5 groups for 14, 28, 42, 56, 70 and 84 days of the exposure period. They were treated with 2/3, 1/3, 1/4 and 1/5 (T1-T4) of 96h lethal concentration of copper. Controls were run along with all the treatments for the same durations. A significant (p < 0.05) dose and time dependent concentration of Cu was observed in the gills, liver, kidney, muscles, and brain of C. catla. Among organs, the liver showed a significantly higher concentration of Cu followed by gills, kidney, brain, and muscles. Copper accumulation in these organs caused a significant variation in the activities of enzymes viz. superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD). The SOD activity varied significantly in response to the exposure time of Cu as 56 > 70 > 42 > 84 > 28 > 14 days while CAT activity exhibited an inverse relationship with the increase in Cu concentration. POD activity showed a significant rise with an increase in Cu exposure duration. Comet assay exhibited significant DNA damage in the peripheral erythrocytes of Cu exposed C. catla. Among four exposure concentrations, 2/3rd of LC50 (T1) caused significantly higher damage to the nuclei compared to control. Increased POD and SOD activity, as well as a decrease in CAT activity in response to Cu, demonstrates the involvement of a protective mechanism against reactive oxygen species (ROS), whereas increased ROS resulted in higher DNA damage. These above-mentioned molecular markers can be efficiently used for the biomonitoring of aquatic environments and conservation of edible fish fauna.

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This study examined the effects of six iso-caloric supplemental diets differing in amounts of protein (22, 24, 26, 28, 30, and 32%) on the fillet composition of rohu (Labeo rohita), catla (Catla catla), mrigal (Cirrhina mrigala), grass carp (Ctenopharyngodon idella) and silver carp (Hypophthalmichthys molitrix) raised in ponds containing natural feed. Control treatment with no supplemental feeding was also included. Mean muscle protein concentrations were significantly lower in fish from control ponds compared to ponds that received supplemental feeding, with 26% and 28% protein diets producing significantly highest muscle protein. Mean muscle lipids of 2.12% were significantly higher in muscles from fish receiving 32% protein diet compared to other treatments. Muscle ash was nearly double in fish from control ponds, where-as muscle carbohydrates were nearly double in fish from ponds receiving 22% protein diets. Among five fish species sampled, percent muscle protein was highest in rohu and lowest in silver carp, with all other species having intermediate values. Muscle lipid was greatest in grass carp and lowest in catla. Mrigal and silver carp had greatest muscle carbohydrate, while rohu had lowest. Supplemental feeding of diets with protein ranging from 26 to 28% is recommended during polyculture of cyprinids in ponds.