Review On Some Heavy Metals Toxicity On Freshwater Fishes

Abstract

Heavy metals contamination is a serious problem in the aquatic environment. Some of them are very important, having biological roles for aquatic organisms, and called essential heavy metals. In contrast, other heavy metals are considered harmful even at low concentrations. The toxic levels of heavy metals may be of agricultural, industrial and mining activities. This will cause water pollution and changes in the physicochemical characteristics of the aquatic environment. This pollution has deleterious toxic effects on fish and raises concerns over its potential impact on human health. The most common heavy metals are arsenic, chromium, lead and mercury, which affect human health and are considered systemic toxicants. These metals induce organ damage even at low levels of exposure and according to the US Environmental protection agency and international agency for research on cancer, they classified as carcinogens. For all the above reasons, this review was written to contribute to heavy metals' role in the environment, toxic mechanism and toxic effects on fish.

Non-invasive sampling of bats reflects their potential as ecological indicators of heavy metal and trace metal contamination due to open cast diamond mining, northern Limpopo Province, South Africa

“…In rodents, bone concentration of Al >10 μg.g -1 has been considered to indicate a reduction in the ability of the animal to excrete Al or an indication of exposure to high concentrations of Al (Scheuhammer 1987). Aluminium is known to be toxic to invertebrates and freshwater shes (van Dam et al 2018, AL-Taee et al 2020, neurotoxic to humans as well as causing disturbances in cellular growth, communication and secretory functions, and reductions in bone tissue (Barabasz et al 2002). There is concern that important metabolic processes in birds and mammals could be negatively affected by Al uptake in environments containing high concentrations of Al (Rosseland et al 1990) since Al has been shown to negatively affect phosphorous (P) and Ca metabolism resulting in bone abnormalities, weakness of muscle and decreased growth rates (Scheuhammer 1987).…”

Acute and Chronic Toxicity of Endocrine Disruptive Heavy Metals and Pesticides Exposed to Freshwater Fish P. reticulata and P. sphenops

“…In the lowest sub-lethal concentrations of metals and pesticides, the fish survival was between 97.5% and 100%, hence these concentrations were found to be suitable for survival test. 50,51,52 Acute and Chronic Safe Concentrations Analogous to the acute safe level, the chronic safe values were also derived using the NOEC and LOEC values obtained through survival studies.…”

Climate-smart aquaculture in Tanzania: Assessment of transitional and heavy metals concentrationsin a commonly used local feed ingredientfor Tilapia farming

“…It can also accumulate in the thyroid and increase the risk of autoimmune disorders [30] In Tanzania, most of our local feed ingredients are multipurpose and used in the formulation of different animal feeds like pig feeds, poultry pellets, cattle feed and fish pellets. When taking up the feed, animals may also take some concentrations of heavy metals, transitional metals and end up metabolizing, excreting, storing or bio-accumulating them in the body [31]. Therefore, it is important for the feed ingredients to comply with the maximum limits of heavy and other toxic metals established by various regulatory authorities in the world and the present study aims to assess the concentration of transitional and toxic heavy metals in the commonly used feed ingredients for Nile tilapia (Oreochromis niloticus) diets obtained from northern part of Tanzania and ensure that fish feeds are not contaminated with toxic metals or do not exceed their maximum permissible limits.…”