ASSESSMENT OF TOTAL MERCURY CONTENT IN COMMERCIALLY IMPORTANT FINFISH AND SHELLFISH OF THE GULF OF MANNAR COAST
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Date
2013-10-22
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Fisheries College and Research Institute, Thoothukudi, Tamil Nadu Fisheries University
Abstract
The present investigation deals with the assessment of total mercury content in commercially important finfish and shellfish of the Gulf of Mannar coast. Three fish landing centres namely, Thoothukudi (Station - 1), Keelakarai (Station - 2) and Veerapandianpattinam (Station - 3) were selected and the commercially important fish samples were collected for proximate composition, mercury, cadmium and lead analysis. Two fish species from each category viz. Pelagic (Sardinella longiceps and Selaroides leptolepis), demersal (Epinephelus quoyanus and Lethrinus lentjen) and bottom (Penaeus semisulcatus and Portunus sanguinolentus) were used for the present study. Totally six samples were collected periodically from October 2012 to March 2013 to assess the proximate composition, mercury, cadmium and lead content in the above selected fishes with respective stations. The proximate composition of collected fish samples were analysed by adopting the standard procedure. Among three landing centres, the highest value of moisture (81.73%) was observed in Portunus sanguinolentus followed by Epinephelus quoyanus (78.52%), Lethrinus lentjen (78.51%), Penaeus semisulcatus (78.08%), Selaroides leptolepis (77.73%) and Sardinella longiceps (74.73%). The maximum value of crude protein (19.77%) was recorded in Selaroides leptolepis followed by Penaeus semisulcatus (19.42%), Epinephelus quoyanus (18.91%), Lethrinus lentjen (18.79%), Sardinella longiceps (16.92) and Portunus sanguinolentus (16.90%). Similarly, the highest value of crude fat (6.87%) was recorded in Sardinella longiceps followed by Penaeus semisulcatus (0.62%), Lethrinus lentjen (0.49%), Selaroides leptolepis (0.47%), Epinephelus quoyanus (0.45%) and Portunus sanguinolentus (0.36%). In ash and carbohydrate contents in all the varieties of fishes there was not much variations observed. Mercury content was estimated using mercury analyser with the standard procedure. Among three landing centres, the highest mercury level (0.44 ppm) was reported in Portunus sanguinolentus followed by Epinephelus quoyanus (0.25 ppm), Penaeus semisulcatus (0.22 ppm) and Lethrinus lentjen (0.21 ppm). In pelagic type of fishes mercury content was absent in all the three landing centres. The cadmium and lead contents were also analysed using Atomic Absorption Spectrometer and the cadmium content was found in all the varieties of fishes. The maximum value of cadmium (0.15 ppm) was estimated in Portunus sanguinolentus followed by Penaeus semisulcatus and Lethrinus lentjen (0.14 ppm), Epinephelus quoyanus (0.13 ppm), Sardinella longiceps (0.12 ppm) and Selaroides leptolepis (0.11 ppm). According to present findings, the lead content was completely absent in all the varieties of fishes from three landing centres. The recorded results showed that the heavy metals concentrations studied in fishes could be arranged in the following descending order Hg → Cd → Pb.
The present study revealed that the levels of mercury content in analysed samples showed the narrow range of variations in all the three landing centres. The levels of mercury content in estimated fish samples were found to be below the legal limits (1 ppm) and all fishes from three landing centres were fit for human consumption. According to the present investigation, regular monitoring of heavy metals in the commercial fish varieties from the Gulf of Mannar coast is recommended in future.
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