River Fish Show Metal Stress and Higher Human Health Risks

Fish caught from the River Jhelum carry higher concentrations of toxic metals, greater physiological stress and more severe tissue damage than farm-reared counterparts, according to a new assessment of the widely consumed freshwater fish Cirrhinus mrigala. Researchers compared wild and farmed specimens and combined measurements of metal accumulation with hematological, biochemical and histopathological examinations. The results point to deterioration in the river environment and suggest that consuming fish from the river may create more significant health concerns than eating farmed fish.

The study is important because measuring a contaminant in fish tissue alone does not reveal its full biological effect. A metal can accumulate in an organ without producing an obvious external sign, while changes in blood chemistry and microscopic tissue injury can reveal physiological stress before populations or entire food webs are visibly affected. By examining all three levels at once, the researchers assessed not only how much material had entered the fish, but also whether the animals showed signs of injury, impaired function or a disturbed internal balance.

Wild and farm-reared C. mrigala were collected from the River Jhelum and local fish farms, respectively. The investigators analyzed the liver, gills and muscles for toxic metals and essential elements. The liver recorded the highest metal accumulation, followed by the gills and then the muscles. This pattern is consistent with the liver’s central role in metabolism and detoxification, while the gills provide a large interface between the fish and contaminated water. Muscle is the principal edible tissue in the assessment, making its concentration particularly relevant to questions about dietary exposure.

Calcium and magnesium were the most abundant essential elements in the analyzed tissues. Such elements are not contaminants in the same sense as toxic metals: they are normal constituents of the body and can perform essential biological functions when present in appropriate amounts. Their presence alongside potentially harmful elements illustrates why evaluating pollution requires more than identifying every chemical substance in tissue. The assessment also found that nickel, chromium and arsenic were the predominant toxic metals, pointing to a mixture of potentially harmful elements rather than contamination by a single substance.

The clearest difference between the two groups appeared in their physiological condition. Wild fish showed marked changes in hematological and biochemical indicators, which the researchers used to evaluate fish health alongside direct tissue analysis. Blood measurements can reflect changes in oxygen transport, metabolism and cellular regulation, while serum biochemical measurements can reveal disturbances in organ function and metabolism. Although the accessible summary does not report individual values for each marker, it identifies the combined pattern as evidence of a stronger stress response in river fish. The approach shows why a multi-biomarker strategy is more informative than relying on a single laboratory measurement.

Microscopic examination produced an equally concerning picture. The wild fish displayed severe histopathological damage in the gills, liver and muscles, whereas the farmed specimens showed lower overall contamination and less marked physiological disturbance. Gills are especially important in freshwater fish because their filaments and lamellae provide the principal surface for water exchange and oxygen uptake. Injury in this tissue can therefore impair respiration, while liver damage may interfere with metabolism and detoxification. Damage to muscle adds another dimension, affecting the structure and function of tissue commonly consumed by people.

The study’s human health risk assessment found a minimal risk from consuming farm-reared fish but warned that wild C. mrigala from the River Jhelum may pose significant health concerns. This contrast is not evidence that farmed fish are entirely free of contaminants, because metals can also enter controlled aquaculture systems through feed, water or other inputs. Rather, the results show substantially lower risk in the farmed specimens examined. For people who depend on the river as a source of food, the findings are more immediate: regularly eating wild fish from a contaminated environment may increase exposure to metals that accumulate in edible muscle and in organs that may also be consumed.

From an environmental perspective, the findings suggest that C. mrigala may serve as a useful indicator of metal pressure in freshwater systems. The species is widely consumed and can occupy waters affected by human activity, allowing researchers to connect water quality with body burdens and biological effects. The study does not identify a single source of the contamination, but the combination of arsenic, chromium and nickel is consistent with the need to examine multiple potential pathways rather than assume that every metal has the same origin. The River Jhelum results also reinforce the need for routine, geographically representative monitoring across seasons and sites.

The authors call for improved waste management, continuous environmental monitoring and regular limnological assessments to protect aquatic ecosystems and public health. Those recommendations are closely linked: pollution control reduces the input of metals, monitoring identifies whether interventions are working, and repeated biological assessments reveal effects that chemical measurements alone may miss. The comparison with farmed fish provides a practical signal that controlled production conditions can produce markedly different outcomes. The larger challenge is to determine whether the conditions allowing metal accumulation in the Jhelum can be reduced rapidly enough to protect wild fish, the food web and the communities that rely on the river.

Subject of Research: Assessment of metal accumulation, physiological stress and human health risks in wild and farmed Cirrhinus mrigala

Article Title: Physiological assessment of metal accumulation and multi-biomarker stress responses in wild and farmed Cirrhinus mrigala

Article References: Ijaz, S., Ullah, S., Impellitteri, F., & Faggio, C. (2026). Physiological assessment of metal accumulation and multi-biomarker stress responses in wild and farmed Cirrhinus mrigala. Environmental Monitoring and Assessment, 198(11), Article 1224. https://doi.org/10.1007/s10661-026-16076-5

Image Credits: AI Generated

DOI: 10.1007/s10661-026-16076-5

Keywords: River Jhelum, Cirrhinus mrigala, metal bioaccumulation, toxic metals, fish health, histopathology, hematology, aquatic pollution, human health risk, environmental monitoring, Physiological, assessment