Research Article

Bioaccumulation of Metals in Fishes’ Scales – A Reliable Non-Lethal Assessor of Food Security

Hafiz Abdullah Shakir1*, Javed Iqbal Qazi2, Abdul Shakoor Chaudhry2, Muhammad Irfan3, Muhammad Khan1, Shaukat Ali4 and Saima Shahzad Mirza5

1Department of Zoology, University of the Punjab, Lahore-54590, Pakistan; 2School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne NE1 7RU, United Kingdom; 3Department of Biotechnology, University of Sargodha, Sargodha, Pakistan; 4Department of Zoology, Govt. College University, Lahore, Pakistan; 5Punjab Bioenergy Institute, University of Agriculture, Faisalabad, Pakistan.

Received | October 05, 2018; Accepted | December 08, 2019; Published | January 12, 2020

*Correspondence | Hafiz Abdullah Shakir, University of the Punjab, Pakistan; Email: hashakir.zool@pu.edu.pk

Citation | Shakir, H.A., J.I. Qazi, A.S. Chaudhry, M. Irfan, M. Khan, S. Ali and S. Mirza. 2020. Bioaccumulation of metals in fishes’ scales – A reliable non-lethal assessor of food security. Sarhad Journal of Agriculture, 36(1): 95-100.

DOI | http://dx.doi.org/10.17582/journal.sja/2020/36.1.95.100

Keywords | Urban sewage, Industrial effluents, River Ravi, Carps, Metal pollutants, Bioindicator.

Introduction

Water quality of major rivers is being spoiled speedily due to massive and untreated urban and industrial waste discharges. Such environmental exploitation has raised and the issue of food security significantly all over the world, especially in developing countries among the other issues (Khanna et al., 2007). Fishes exposure to water contaminated with metals does attain significant levels of different contaminants (Shakir et al., 2013a). Metals represent highly recalcitrant pollutants. It is well known that flesh as well as non-eatable organs do accumulate metals from water and sediments. The high metal contents in fishes not only cause detrimental effects on fish health but also disturb food chain. The fish specimens scarify first, in general, and then evaluate the metal profile in fishes. This metal profiling depicts contamination level in water body as well as in fishes. On the other hand, if the alternate procedure of metal contents determination is available without dissecting the fish specimens, it will facilitate the fish welfare.

Fish scales (calcified tissues) might be used as non lethal (alternate) means for assessing metals accumulation in fishes because scales of fishes are present most outside the body. The pollutants continuously incorporate in fishes scales during developmental stage because it constantly exposed with aquatic pollutants. Therefore, the scales can be used as potential specimen to express the metal profile in water body. Furthermore, fluctuation in temperature not cause any detrimental impact on preservation, storage and transportation of fish scales for evaluation of metals’ profile. This approach also facilitate during food security survey in remote areas. Therefore, the main objective of present study was to verify accumulation potential of selected metals in fish scales of the C. mrigala (bottom feeder), L. rohita (column feeder) and C. catla (surface feeder) sampled from four sampling locations during low and high flow seasons of river Ravi.

Materials and Methods

The selected study area of river Ravi from Lahore Siphon to Balloki Headworks receives discharge of untreated industrial effluents and urban sewage during its passage through Lahore (the second biggest city of Pakistan). The first upstream sampling location Lahore Siphon (A) had no point source and it was located at coordinates 31° 41′ N, 74° 25′ E. The downstream location B, Shahdera (31° 36′N, 74° 18′ E) was receiving untreated urban sewage from three major pumping stations while the downstream location C, Sunder (31° 21′N, 74° 3′E) was receiving municipal and industrial effluents from four major pumping stations and two drains called Hudiara and Deg. The last sampling location, Balloki Headworks (31° 13′ N, 73° 52′ E) was receiving diluted effluents due to a relatively clean water joining from the Qadirabad Link Canal (Figure 1).

Total 216 specimens comprising of nine fish specimens for each of the three species viz., C. Catla, L. rohita and C. mrigala of comparable size range representing each location and low (winter) and high (post monsoon) flow seasons were collected. After immediate transportation of sampled specimens to the laboratory, each fish specimen’s identification was verified (Mirza, 2003).

The scales of total 216 specimens of 3 fish species were removed from the second row of left side, just above the lateral line, directly under the anterior ray of dorsal fin with the help of tweezers. These scales were then gently rinsed, cleaned with distilled water and shifted in labelled polythene bags which were stored at -20 ºC till further use. Frozen fishes scale samples were thawed, rinsed in distilled water and blotted on blotting paper. Known weight of scales were shifted into respective labeled pre-weighed glass vials and kept in an oven at 105 °C till constant dried weight was achieved for a given sample. For fish scale digestion, 1g dried fish scale samples were incubated with 5 ml nitric acid (55%) and 1 ml perchloric acid (65%) for overnight at room temperature. Then, next day, 5 ml nitric acid and 4 ml perchloric acid were added to each flask following the addition of few glass beads in each flask to prevent pumping. The further acid digestion procedure was proceeded as reported by Shakir (2013).

All the prepared scale samples were analyzed for the metals such as Cd, Cr, Cu, Pb and Ni by using Fast Sequential Atomic Absorption Spectrometer (Varian Spectra AA-240). While Mn and Fe concentrations were determined using Pye Unicam Atomic absorption spectrophotometer. Whereas the Hg and Zn were measured using variant atomic absorption spectrophotometer (variant AAS-1275) . Metal accumulation in scales samples were statistically analysed by using Minitab-16 software (General linear model).

Table 1: Mean (µg/g dry weight) of metal bioaccumulation in scales of fish specimens sampled from different sites during low and high flow seasons of the river Ravi.

The mean wet body weight and total length did not significantly different (P>0.05) for fish specimen captured from selected location during both flow seasons and were ranged from 636-665 g and 39.46-40.31 cm, 627-647 g and 37.44-38.09 cm and 621-643 g and 36.48-37.22 cm for C. mrigala, L. rohita and C. catla, respectively. The metals accumulation in scale samples significantly varied among different locations, flow seasons and fish species. Location-wise metal accumulation pattern was C > D > B > A. The lowest concentrations (µg/g) of the metals were recorded at site A in the order of Fe (42.99), Zn (31.73) > Cu (4.87) > Mn (3.36) > Cr (1.32) > Ni (0.52) > Pb (0.30) > Hg (0.17) and Cd (0.09) (Table 1). Jangu and Brraich (2014) reported that metals have high potential to be bioaccumulated in the scales of fishes. The metal contamination pattern in water, sediment and fish muscles for the same sampling sites and flow seasons were also revealed similar trend which were earlier reported by Shakir et al. (2013a, b). The variation of metal accumulation at different sites was reported by other researchers (Javed, 2003; Jabeen and Chaudhry, 2010a, b). All metal concentrations were significantly (P<0.001) higher during low flow than high flow season. Overall metal accumulation (µg/g dry weight) levels was; Fe (58.57 and 47.65) > Zn (54.77 and 48.88) > Mn (8.62 and 7.01) > Cu (6.85 and 6.20) > Cr (3.66 and 2.44) > Pb (2.98 and 2.18) > Hg (1.65 and 1.29) >Ni (1.53 and 1.28) > Cd (0.20 and 0.15) during low and high flow season, respectively when data were pooled to assess the impact of season on metal accumulation in fishes scales (Table 1). The variation in metal profile during different seasons might be associated with changing feeding behaviour of different fish species (Farkas et al., 2000). In present study, the bottom feeder (Cirrhius mrigala) showed highest Cr, Cu, Zn, Mn, Ni and Hg accumulation than column (Labeo rohita) and surface (Catla catla) feeder (Table 2) . While Catla catla showed highest accumulation of remaining studied metals. The trend of change in bioaccumulation of metals in scales of different fish species may be associated with differences in species’ trophic level in natural water bodies, uptake and absorption abilities of the fishes as reported by different researchers (Kotze, 1997; Kotze et al., 1999; Solhaug et al., 2010). The metal concentrations were found in the scales higher than the muscles of same sampled fish species (Shakir et al., 2013a). Similar results were reported by Rashed (2001) that Co, Cr, Ni and Sr concentrations in scales of Tilapia nilotica (tilapia) than muscles, intestine, stomach, vertebral column and liver. Teodorof et al. (2009) reported highest Cd, As, Pb and Zn bioaccumulation in scales than

different tissues of Cyrinus carpio, Hypophthalmichthys molitrix, Aristichthys nobilis and Ctenopharyngodon idella. Farrell et al. (2000) reported significant higher metals contents in scales in comparison with muscles of Arctic Graying. Higher concentration of metals in scales might be due to direct contact with contaminated water and river bed sediment. Several pollutants in water, river bed sediment and fish species were exceeded from threshold limit in the studied stretch proposed by National Environmental Quality Standards and World Health Organization as reported by Shakir et al. (2013a, b). These pollutants can cause fish death unless the fish has an alternate way of detoxification. Calcification is one of the important detoxification mechanism (Simkiss, 1977). The survival of fish species in the presence of high metals accumulation in select study area of river Ravi might be associated with detoxification of these metals by calcification. Different studies showed the feasibility of fish scale as a biosorbent (Mustafiz, 2003; Prabu et al., 2012). Several researchers described that normally a considerable portion of protein (collagen) containing sulfhydryl rich peptides (phytochelatines) was present in fish scale (Say et al., 2001; Mustafiz, 2003).

Conclusions and Recommendations

It is demonstrated from the present study that metal accumulation in fish scale is promising as a non lethal sensitive method for measuring aquatic pollution. Periodic monitoring of metals levels in fish scales without their scarification give better idea about water body and health of marketable fishes. This technique helps to ensure safety of consumers in the area. From the present study, it is also noteworthy revealed that the efficacy of these nonlethal techniques was highly variable across fishes of different trophic levels and likely depends on species-specific life-history characteristics. Further research is needed for determination of storage capacity of scales and lethal doses.

Novelty Statement

Fish scales might be used for assessing metals accumulation profile in fishes without sacrificing the animals.

Author’s Contribution

Hafiz Abdullah Shakir: Performed the experiments and drafted the manuscript.

Javed Iqbal Qazi: Designed and planned the study and revised the manuscript.

Abdul Shakoor Chaudhry, Muhammad Irfan, Muhammad Khan and Saima Shahzad Mirza: Revised the manuscript

Shaukat Ali: Analyzed the data.

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