The Chenab River is an important wetland of Punjab, Pakistan (Altaf et al., 2015). The water of river is getting polluted due to various anthropogenic activities such as industrial waste, urbanization, and intensification of agriculture (Kausar et al., 2020). Contamination of freshwater bodies, and consequently freshwater fish, with toxic heavy metals is a significant environmental concern (Singh et al., 2017). The trophic transfer of potentially toxic heavy metals into the human food chain, especially in fish, has also concerns for human health. (Ali and Khan, 2018). The main objectives of the study were to determine the heavy metals bioaccumulation in two fish species Mali (W. Attu) and Singhi (S. Seenghala) in the Chenab River.
The different metals such as Sodium (Na), Potassium (K), Calcium (Ca), Iron (Fe), Copper (Cu), Zinc (Zn), Chromium (Cr), Mercury (Hg), and Cadmium (Cd) were observed in two fish species Mali (W. Attu) and Singhi (S. Seenghala) collected from two different sites of the Chenab River in the forgoing study. It was noticed by the presence of different metals in fish samples that Chenab River is highly polluted and various other studies are also in line (Alamdar et al., 2017; Hanif et al., 2016; Qadir and Malik, 2011). The higher concentrations of metals like K, Na, Ca, and Fe in water might be due to various factors, such as geological characteristics of the region (Kaushik et al., 2009), industrial activities, and agricultural runoff (Xiao et al., 2013). Additionally, the composition of the soil and rocks through which the water passes can contribute to higher metal content (Zahra et al., 2014).
The observed variations in metal concentrations, particularly Potassium (K), Calcium (Ca), Iron (Fe), and Sodium (Na), between sites 1 and 2 indicate potential influences of environmental factors on metal accumulation in Mullee and Singhi fish. The distinct organ-specific trends for each metal suggest species-specific physiological processes governing metal distribution (Adams et al., 2011). The higher concentration of K in skin tissues, Ca in skin and gills, and Fe in skin and gills at site 2 may reflect the impact of localized environmental conditions on metal deposition. Das et al. (2017) also agreed that the site-specific differences highlight the importance of considering environmental factors in assessing heavy metal accumulation in fish organs. Further investigations into the specific environmental variables influencing these trends are warranted for a comprehensive understanding of metal dynamics in aquatic ecosystems (Filipović Marijić, and Raspor, 2012).
It is well known that the metals such as K, Na, Fe, and Ca plays crucial roles in maintaining physiological functions and growth in fish. These essential elements are involved in osmoregulation, enzymatic activities, and skeletal development (Mohanty et al., 2012; Terech-Majewska, 2016; Lall and Kaushik, 2021; Lall, 2022). However, an excess of these metals can lead to detrimental effects, disrupting the delicate balance within fish organisms. High metal concentrations may result in metabolic imbalances, impaired growth, and compromised health for fish (Kortei et al., 2020; de Almeida Rodrigues et al., 2022).
The metal concentration analysis reveals significant variations in the accumulation of Copper (Cu), Zinc (Zn), Chromium (Cr), Mercury (Hg), and Cadmium (Cd) in different organs of Mullee and Singhi fish at both sites. Copper concentrations, with higher levels in the skin and liver, exhibit organ-specific patterns, suggesting potential physiological roles and selective accumulation (Chen et al., 2020). Zinc concentrations, notably high in the heart, indicate organ-specific variations, with potential implications for the physiological functions of these organs in metal homeostasis. Chromium concentrations, concentrated in the skin and muscles, reflect distinct organ-specific trends, possibly influenced by local environmental factors. The amount of chromium in the diet is of great importance as Cr is involved in insulin function and lipid metabolism (Bratakos et al., 2002). Qadir and Malik (2011) observed highest accumulation of Cr in W. attu in this order (gills > liver > kidney > muscles) as compared to our findings.
Mercury concentrations, peaking in the skin, gills, and heart, signify potential bioaccumulation patterns in response to environmental exposure. Saeed et al., (2020) observed that Mean loads (µg/g) of mercury in gills and muscle of sampled fish was 0.03 ± 0.01 and 0.01 ± 0.02 respectively that was lower compared to present finding.
Cadmium concentrations, prominently present in the skin and liver, demonstrate organ-specific variations, with implications for the health of these organs. The observed variations in metal concentrations underscore the importance of considering organ-specific dynamics and environmental factors in understanding heavy metal accumulation in fish. Cadmium is known to be toxic to almost every system in the body (Lee et al., 2006). Shahsavani et al. (2017) reported high concentration of Cd (2.50 ± 0.007) which was greater than our study. Further investigations into the ecological and physiological factors influencing these patterns are crucial for comprehensive assessments of aquatic ecosystem health and the potential impacts on human consumption. Hanif et al. (2016) also agreed there was higher concentrations of Cd in water of Chenab River.
It is well known that Cu, Zn, Cr, Hg, and Cd are essential trace elements that play vital roles in various physiological processes in fish, including enzyme function, immune response, and antioxidant defense. However, an excess of these metals can lead to severe toxicity and adverse effects on fish health. Accumulation of heavy metals in fish tissues may result in impaired reproduction, organ damage, and disturbances in the overall aquatic ecosystem (Ali 2014). Moreover, as fish are part of the human food chain, the bioaccumulation of these metals poses a potential threat to human health through the consumption of contaminated fish (Moiseenko, 2015; Kortei et al., 2020). Monitoring and controlling the levels of these heavy metals in aquatic environments are crucial for safeguarding both fish populations and human consumers.