SJA_42_1_24-34

Introduction

Heavy elements still continue to attract much attention because they are able to be accumulated in fish tissues and can harm human health if consumed through food (Moiseenko and Gashkina, 2020). Because of their constant emissions from both natural and industrial sources, heavy metals are among the most harmful pollutants in the environment, leading to an increase in their concentrations in the atmosphere (Shah et al., 2020). Most heavy metal ions are toxic or carcinogenic and threaten human health and the environment (Burch, 2023). There are also many biochemical processes and environmental factors that control the transfer and readiness of heavy elements in the aquatic environment, such as adsorption, the formation of complexes on sediment organic compounds, and biological absorption through the effect of temperature and pH (Kraemer and Hering, 2004; Mohamed et al., 2012). The amount of these elements absorbed depends directly on their concentration in water and exposure time, as absorption increases with each increase (Shah et al., 2020). Currently, exposure to heavy metal pollution is regarded as one of the most dangerous things because heavy elements find their way into the environment through a variety of consumer products used by humans, eventually accumulating in high concentrations above their natural levels in water and living organisms, particularly fish (Al-Najare et al., 2017). Finally, transferred to higher trophic food levels through the food chain such as, to humans (Van den et al., 2002).

In general, humans can be exposed to the effects of heavy elements through industrial activity sources such as, fossil fuels, mining operations, agricultural fields, pharmaceuticals and technology applications (Seiyaboh and Izah., 2017; Al-yassein, 2022) as well as, the nature sources like the biosphere, rocks erosion, and earthquakes (Latif et al., 2022). Therefore, the amount and rate of heavy elements in the environment vary, whether they are within or above the required levels, depending on the sources that enter the environment, whether natural or industrial (Seiyaboh and Izah., 2017). Furthermore, it can affect and accumulate in various parts of fish organs, such as gills, muscles, liver, and reproductive organs, and lead to morphological changes in them (Al-Najare et al., 2022; Abed et al., 2025). Exposure to the high level of heavy metals impacts fish tissue histology (Hashim and Al-yassein, 2020). In addition, heavy metal pollutants are important and induce oxidative stress in many aquatic animals (Sevcikova et al., 2011). Thus, by monitoring fish bioaccumulation, risks that could endanger both human health and the aquatic population can be reduced; this makes it possible for researchers to take the necessary safety measures to lessen pollution of the marine environment (Naeem et al., 2010; Tsurkan et al., 2020; Aldoghachi et al., 2025).

Fish consuming is an essential part of healthy diet worldwide, as it is a highly valued source of digestible protein (Naeem et al., 2005) and omega-3 fatty acids (Isangedighi and David, 2019). An estimated 179 million tons of fish were produced worldwide in 2018, of which 156 million tons were consumed by humans, making the seas and oceans a significant source of animal protein (FAO, 2020). They are also one of the most important markers for determining the degree of heavy metal contamination in aquatic environments (FAO, 2020; Karim et al., 2022; Zaghloul et al., 2024). Tylosurus crocodilus is considered a fish that lives in the open sea and far from the coast, where it comes in the form of individuals or small groups that feeds on fish. They have a broad distributed across the Red Sea and East Africa, as well as in the tropical and warm temperate parts of the Indian and western Pacific oceans (Deidun et al., 2021; Yaseen et al., 2024). Therefore, the object of the current project was estimating the bioaccumulation of different heavy metals in different tissues of Needlefish T. crocodilus caught from Iraqi marine waters and demonstrate the possibility of using them for human consumption.

Material and Methods

Description of the study area

Samples of needlefish T. crocodilus were collected from the area marked by dots (5422767°5’41.7161”E 3476416°31’40.7591”N) Figure 1. The station is characterized by the proliferation of medium-sized and small fishing boats using trawl and drift gill nets (Al-Shamary, 2020).

Fish sample preparation and analysis marine flame

The goal of the study was to quantify the amount of heavy metals that were accumulated of Tylosurus crocodilus. Drifting gill nets with a length of 200-500 m and a height of 2.5 m, with holes of different sizes (15-35 mm), were used to catch fish in February, 2023. T. crocodilus on a fishing boat is 16 meters long and 3.5 meters wide, has 150 horsepower, and its fishing speed is 2 knots (Carpenter et al., 1997; Eschmeyer, 2017). About 50 seasonal samples of T. crocodilus were used. The average size was 1096.3 g, and the average length was 781 mm. The tissues (muscle, liver, gills, and ovaries) are represented in a specimen (0.5 g) from each sample of frozen fish in a freeze dryer, ground, and digested in 3 ml of a mixture of concentrated perchloric acid HCLO4 and nitric acid HNO3 in a ratio of 1:1 in tubes. The tubes were placed in a water bath at 70°C for 30 minutes, and after that transferred to a heating plate to complete the digestion process. The contents were condensed to 25 ml with double-distilled water, then filtered and transferred to a sterile plastic container with a screw top to allow it to cool. The container was labeled and kept at 4°C until analysis was required by using a Flame Atomic Absorption Spectrophotometer (FAAS, Shimadzu model AA 7000) equipped with a hollow cathode lamp for each element (Jakhrani et al., 2019).

Statistical analysis

SPSS version 20 was conducted to analyze the results statistically. The significance of the differences between the means was tested using the least significant difference (L.S.D) test at a significant level (0.05) (Al-Rawi et al., 2000).

Results

All the current study results indicated an important difference (P< 0.05) in metal concentration in fish tissues and seasons at different sampling sites.

Cadmium (Cd)

The quantity of cadmium in fish tissues varies seasonally. The highest amount was in the winter in the muscles, liver, gills, and ovaries (26.5515, 33.831, 29.0035, and 27.8835 µg/g dry weight, respectively). The lowest ratio was in the ovaries and gills (0.8055, 9.666) µg/g dry weight, respectively in spring (Figure 2).

Copper (Cu)

The seasonal averages of copper concentration in the fish tissues studied are shown in (Figure 3). However, there were no significant differences (P>0.05) between muscles and ovaries in spring. The results show that the highest values were muscles, liver, gills, and ovaries were (9.927, 6.118, 13.236, and 9.927) µg/g dry weight, respectively, in the spring. In the winter the liver and gills had the lowest values (1.6545, 2.6545 µg/g dry weight, respectively), followed by the muscles and ovaries (0.041, 1.3345) in the summer.

Iron (Fe)

The results show that the lowest concentration values in the muscles, liver, gills, and ovaries were (90.5362, 26.4984, 46.3722, 68.4542) µg/g dry weight was recorded in the spring season, while the highest concentrations of iron in the muscles and liver were (439.4318, 119.2428) µg/g dry weight respectively in summer, and (264.984) µg/g dry weight for gills in winter, and in autumn, the highest concentration of Iron was recorded in the ovaries 845.7406 µg/g dry weight (Figure 4).

Manganese (Mn)

In the spring season, the muscles and gills had the highest concentrations (20.5942 and 28.083 µg/g dry weight, respectively), while the liver and ovaries had the lowest concentrations (2.0088 and 2.8833). During the autumn season, the liver and ovaries had the highest concentrations (46.805 and 65.527 µg/g dry weight, respectively), while during the winter and spring seasons the ovaries had the lowest concentration (3.7444) (2.8833) µg/g dry weight (Figure 5).

Nickel (Ni)

During the autumn season, fish tissues had the highest concentrations of nickel (7.4445, 23.6174, 31.4898, and 20.9932 µg/g dry weight) for muscles, livers, gills, and ovaries respectively, while the muscles and ovaries had the lowest concentrations (2.6241 and 0.048 µg/g dry weight, respectively during the winter). At springtime liver and gills had the lowest concentrations (2.2415 and 0.043 µg/g dry weight, respectively) (Figure 6).

Lead (Pb)

There were no significant differences (P>0.05) between the gills and the ovaries in the winter, otherwise, in the spring, between the liver and the ovaries and the liver and the gills. There are no significant differences (P>0.05) in the summer season between the gills and the ovaries, alternatively, between the liver and the gills. The highest and lowest lead concentration levels of muscles were in the winter and spring, which were (0.011and0.001) µg/g dry weigh respectively. Throughout the spring and winter, the liver reported concentrations of (0.006 and 0.001) µg/g dry weigh as the highest and lowest, respectively. The gills had the lowest and greatest concentrations in the summer and autumn measuring at (0.003, 0.011) µg/g dry weigh. The highest and lowest concentrations (0.004, 0.001) µg/g dry weight were found in the ovaries during the spring and autumn seasons respectively (Figure 7).

Discussion

Heavy metals primarily originate from industrial and human activities in the environment, along with wastewater from oil installations (Pourang et al., 2019). Consequently, pollutants discharge into water bodies represent a significant global issue. Heavy metal pollution has harmful effects on marine organisms only after organisms have taken up these metals and accumulated them in their biomass (Jezierska and Witeska, 2006). Various factors, including fish habitat, size, sex, and physiological metabolism status, influence the accumulation of contaminates in fish tissue (Naeem et al., 2010; Ismat et al., 2013; Luczyńska et al., 2020). According to the accumulated concentrations values, the heavy metal elements were Pb < Cu < Ni < Mn < Fe. It has been shown that metals accumulate in all organs and tissues of the organism concurrently, indicating that they are absorbed and dispersed throughout the body (Moiseenko and Gashkina, 2020). Lead is the most hazardous metal found in large quantities in the marine environment and the crust of the earth (Zaghloul et al., 2024). Latif et al. (2022) found that tissues values of Ctenopharyngodon Idella and Tor putitora exposed to lead in the following order: muscle > skin > gill > liver > gut.

The present study illustrated that the fish’s liver had the highest quantity, while its muscle had the lowest. The liver is the largest part of a fish’s body, having a high capacity to absorb contaminants and also having a vital role in detoxification (Fernandes et al., 2008). Chronic exposure to heavy metal pollution will lead to tissue damage, which would negatively impact the detoxification process of the liver and muscles damaged by the accumulation of metal ions (Siraj et al., 2016). Therefore, cases of chronic or long-term heavy metal contamination are linked to elevated liver levels of some heavy metals (Allen-Gil and Martynov, 1995). All fish species showed that the liver had the highest amount of biochemical content (Zaghloul et al., 2024). In accordance with Mishra et al. (2024), the muscles of Baikari Clupisoma garua showed the lowest Pb ratio (0.07 µg/g), while the liver had the highest ratio (8.86 µg/g). Further, Dicentrachus labrax and Solae solea had the highest concentrations of Pb and Cu in their livers, whereas Angiula anguila had the highest values of Cd and Zn (Zaghloul et al., 2024). Baikari fish liver had the greatest observed Mn content (53.19 µg/g) (Mishra et al., 2024). On the other hand, the greatest concentrations of numerous compounds, including cadmium, iron, and nickel, were found in the liver of Black Sea (Bulgaria) at 0.25,69.30, and 505.75mg/kg w.w (Fazio et al., 2020). Due to the strong relationship between Cd metabolism and critical metals, particularly zinc, Cd can replace zinc in many crucial enzymatic reactions as well as disrupt and inhibit these (Annabi et al., 2013).

Heavy metal pollution can enter a fish’s body through a variety of routes, including the gills, body surface, and digestive tract, when the fish consumes food that has contains heavy metal (Garai et al., 2021). Several fish species had varying levels of heavy metal accumulated; for instance, gill tissue had the highest concentration of lead after 24 hours of exposure was 4.113 ± 0.831 mg/g, however, copper was (0.266 ± 0.029 mg/g), respectively (Shah et al., 2020). It was been observed a strong correlation (P ≤ 0.05) of T. crocodilus (Belonidae) between the standard length and Cu concentration in the muscle and gill tissues (Ebrahimi Yazdanabad et al., 2014). The highest concentration of Cr has been found at the gill of Labeo dyocheilus and Wallago attu, especially chromium which is a highly hazardous metal that can harm aquatic species’ embryos and cause cancer (Shah et al., 2020). On the other hand, the findings demonstrated that in three different fish species (Catla catla, Cirrhinus mirigala, and Labeo rohita) taken from ponds in the Pakistani province of Kashmore, bioaccumulation of trace elements was higher in the gills than in the liver and muscles (Jakhrani et al., 2019). The trend of zinc accumulation in Anabas testudineus had the greatest accumulation shown in the gills, which are thought to be the main entrance point for this metal (Nanda, 2014).

The concentration of metals in the marine animals muscles is particularly concerning, as these fish are abundant in protein that are widely eaten by humans (Shah et al., 2020). Generally, the bioaccumulation of metal levels increases with increasing duration of exposure (Latif et al., 2022). There was a variation in heavy metal level in fish muscles. For example, highest concentration of lead was found in the muscles of C. idella, followed by chromium and copper respectively (Shah et al., 2020). On the contrary, the lowest Pb concentration was found in A. testudineus muscle tissues (Nanda, 2014). The levels of Cu in the muscles of T. crocodilus were found to be lower than the WHO (Zaghloul et al., 2024). Fish has a lower metabolic rate than other tissues, there is less metal buildup in their muscles. Another important issue is that muscles have less broad blood circulation than other essential organs like the liver, kidney, and gills (Adhikari et al., 2009). The accumulation levels of (Cu, Zn) content in muscles was more than that of hazardous elements (Cd and Pb), with Zn > Cu > Pb > Cd. For every metal, the order is muscles < gills < liver, with the exception of Pb, which is in the reverse order (Zaghloul et al., 2024). Some fishes such as Gudusia chapra and Eutropiichthy vacha had Cu levels ranging from 10.26–20.53 and 10.11–14.82 mg/kg, respectively, with mean concentrations of 12.63 and 11.18 mg/kg. These findings can be considered a serious warning against anyone considering eating fish (Ajala et al., 2022). The organism’s natural adsorption of Cu may be the cause of the increased concentration of these elements in fish muscles (Kalipci et al., 2023). Zinc is necessary for healthy growth and regular metabolic activities in living organism (Kalipci et al., 2023). Additionally, it has been demonstrated to affect the physiology state of fish species, such as reproductive physiology and behavior (Garai et al., 2021). Among the elements examined, zinc content in G. chapra was the highest at 14.37 mg/kg. This could be because this species is omnivorous, which encourages the accumulation of Zn from a variety of food sources (Paul et al., 2020). Moreover, Zn elevation concentrations it could be because of anthropogenic activities in the research area, which include the dumping of domestic waste and raw sewage materials (Ajala et al., 2022). Several histopathological effects were observed in fish muscles as a consequence of Ni and Cd accumulation, so fish functioned as bio-indicators of pollution, which can be used to predict the direction of medical study in the search for detrimental impacts (Moiseenko et al 2018; Hahim and Al-yassein, 2020).

In our study there are no obvious differences between the ovaries and other tissues and seasons exposed to the Pb. Conversely, the highest levels of lead were found in the ovary. The Pb accumulation trend went as follows: ovary > liver > gill > muscle (Nanda, 2014). It was observed that exposure to metals like lead, mercury, and cadmium clearly affected the catfish Heteropneustes fossilis’s oocyte maturation and ovulation (Gautam and Chaube, 2018). Out of all the tissues examined, gills and liver, the ovary has the highest level of zinc accumulation with factor (4.08), as compared to the control in A. testudineus that might affect the reproduction mechanism of the fish (Nanda, 2014). Along with, a significant annual average value of heavy metal concentrations was found in Tilapia zillii ovary. As heavy metal concentrations rise, the proportion of mature oocytes falls and atresia rises, it was observed that certain fish ovaries at a station with the greatest quantities of heavy metals stopped maturing (Azab et al., 2019). Fish growth, development, reproduction, and survival, may be seriously threatened by the toxicity of heavy metals in water (Gautam and Chaube, 2018). Due to economic and nutritional significance of T. crocodilus’s and the increasing levels of toxins in Iraq’s marine waters, it is imperative to monitor environmental hazardous chemicals and their impact on the aquatic biota in order to assess the health of fish (Al-Najare et al., 2022).

The results of the current study showed that the concentrations of the heavy metals studied (copper, lead, nickel, and manganese) were at their lowest limits in the muscles, which is the edible part of the fish, and were within the permissible limits set by the Food and Agriculture Organization and the World Health Organization (FAO/WHO, 1984), and also according to Malaysian Food Regulations (MFD, 1985) Table 1.

Table 1: Permissible limits for heavy metals in fish (µg/g dry weight).

References	Ni	Mn	Fe	Cd	Pb
FAO/WHO 84 (Swami et al., 2001)	----	5.4	----	2	١.٥
(MFR, 1985) (Swami et al., 2001)	20	4.5	55	1	٢
FDA (2001) (Swami et al., 2001)	80	----	40	4	١.٧

The results of the current study showed a significant difference in the values of the heavy elements studied when compared with other studies conducted on species in Iraqi marine waters (Table 2). The reason may be that the accumulation of heavy metals is linked to feeding habits and behavior and also depends on the nature of the fish’s presence in the water, whether it is surface, benthic, or in the water column. In addition, the region is affected by tidal movements that can bring many pollutants from the coasts of neighboring countries, which are active with the movement of oil and commercial ships.

According to the results of the current study, a noticeable increase in iron, nickel, and cadmium was recorded in ovarian cells, as there is increasing concern about the increase in chemicals and heavy metals disrupting the reproductive cycle in aquatic organisms (Azab et al., 2019), and exposure to toxic agents. As a result, it may lead to metabolic disorders, genetic mutation, embryo damage, and decreased fertility (FAO, 2022). As Yokote (1982) pointed out, increased pollution may lead to damage to sperm cell tissue and enlargement of ovarian cells in most cases. This leads to an imbalance in the estrogen hormone and immaturity of the egg.

Conclusions and Recommendations

The results demonstrated that the heavy metal accumulation levels varied seasonally through all of the needlefish Tylosurus crocodilus’s organs. The highest impact was Ni, Mn, Fe, Cu, and Cd levels in µg/g dry weight. A significant variation in the lead results,

Table ٢: Comparison of heavy metal concentrations of some marine fish species with the current study.

References	Species	Pb	Ni	Mn	Fe	Cu	Cd
Al-Najare, et al, (2012a)	Acanthopagrus latus	--	ND	3.82	81.12	4.78	3.9
Al-Najare, (2012)	Liza subviridis	-	109	6.72	-	9.5	5.9
Al-Najare, et al, (2013)	Acanthopagrus latus	--	321.43	5.6	232.22	16.68	4.15
Al-Najare, (2014)	Chirocentrus dorab	5.3	12.6	--	984.5	29.4	--
Al-Najare, et al, (2015)	Tenulosa ilisha	0.19	1.7	0.1	-	63.9	4.6
Al-Najare, (2015)	Otolithes ruber	1.3	11.99	--	835	29.4	--
Al-Najare, et al, (2017)	Nemipterus japonicus	--	130	4-ND	80-5	8-ND	14-ND
Al-Imarah, et al, (2017)	Epinephelus coioides	0.12	0.28	0.99	--	4.01	1.36
Al-Imarah, et al, (2017)	Euryglossa orientalis	0.45	0.56	2.12	--	16.7	1.09
Al-Najare, et al, (2018)	Scomberoides commersonnianus	2.17	6.7	27.51	3422.9	327.7	20.8
Al-Najare, et al, (2022)	Saurida tumbil	2.85	4.56	--	8.44	1.45	--
Present study	Tylosurus crocodilus	0.001	2.624	0.21	90.54	0.041	11.28
		--	--	--	--	9.93	--
		0.011	7.44	20.59	439.43		26.55

among other tissues, and a significant reduction for the ovaries during the fall. The levels of copper, lead, nickel, and manganese in muscles were at their lowest but still within permissible limits.

Acknowledgements

We thank the Marine Science Center at the University of Basrah for their support in completing this research.

Novelty Statement

Fish bioaccumulation measurements are essential for evaluating environmental health and safeguarding human consumers. Because they live at different trophic levels in the food chain and are vulnerable to pollutants from water, fish make ideal bioindicators.

Author’s Contribution

Rajaa N. Al-yassein: Designed the experimentation. Kadhim H. Younis: Wrote the manuscript.

Ghassan A. Al-Najare: Wrote the first draft of the manuscript.

Khalid W. Farnar: Statistical analysis.

Zainab J. Obaid and Zahraa K. Shakir: Technical and operational support

Generative AI or AI assisted technology statement

This entire research endeavor was conducted without the aid of artificial intelligence technology.

Conflict of interest

The authors have no conflict of interest.

Reference

Abed, J.M., A.H. Ali, A.T. Yaseen, A. Al-Faisal, F. Mutlak, F.K. Jassim and L.A. Jawad. 2025. Barramundi (Lates calcarifer) from Iraq: a new record for the Arabian Gulf, with a highlight on it genetic origins and description of two skeletal deformities. New Zealand J. Zool., 52(1): 40-54.

Adhikari, S., L. Ghosh, B.S. Giri and S. Ayyappan. 2009. Distributions of metals in the food web of fishponds of Kolleru Lake, India. Ecotox. Environ. Saf., 72(4): 1242-1248. https://doi.org/10.1016/j.ecoenv.2008.10.011.

Ajala, O.A., M.R. Oke, T.F. Ajibade, F.O. Ajibade, B. Adelodun, J.O. Ighalo and L.F. Silva. 2022. Concentrations, bioaccumulation, and health risk assessments of heavy metals in fishes from Nigeria’s freshwater: a general overview. Environ .Sci. Pollu. Res., 29(55): 82660-82680.

Aldoghachi, M.A., A. Abdullah and D.A. Hussein. 2025. Bioaccumulation, Histological and Structural Changes in the Gills of the Nile Tilapia (Oreochromis niloticus) Exposed to Heavy Metals. J. Egypt. Aquat. Biol. Fish., 29(2): 2333-2345.

Al-Imarah, F.J.M., A.H. Amteghy, G.A. Al-Najar. 2017. Seasonal variation of some heavy metals in the tissues of two important Marine Fish Species Epinephelus coioides and Euryglossa orientalis from Iraqi marine. Mesop. Environ. J., Vol. 3 No. 3.

Allen-Gil, S.M. and V.G. Martynov. 1995. Heavy metal burdens in nine species of freshwater and anadromous fish from the Pechora River, northern Russia. Sci. Environ., 160: 653-659. https://doi.org/10.1016/0048-9697 (95)93634-T.

Al-Najare, G.A. 2014. The Bioaccumulation of some heavy metals in fish chirocentrus dorab collected from Iraqi Marine Waters. J. King Saud University., 26(2): 1-33.

Al-Najare, G.A. 2015. Seasonal variations of some heavy metals’ concentrations in some organs of Otrolithes ruber collected from Iraqi marine waters. Dhe. Qar. Sci. J., 4(1): 73-85.

Al-Najare, G.A., A.A. Hantoush, L.J.M. Al-Anber and H.T. Al Saad. 2012a. Bioaccumulation of heavy metals in Acanthopagrus latus collected from Al-Razazah Lake, middle of Iraq. Iraq. J. Aquac., 9(1): 5-22.

Al-Najare, G.A., A.T. Yesser, N.A. Al-Faiz, A.A. Jabir and K.H. Younis. 2022. Heavy metal accumulation in the tissue and food web of the Greater Lizardfish Saurida tumbil fish in Iraqi marine waters. Iran. J. Ichthyol., 9(3): 131-139. https://doi.org/10.22034/iji.v9i3.909.

Al-Najare, G.A.; N.A. Al-Faiz, J.M. Al-Noor. 2017. Bioaccumulation for some heavy metals in organs of Lethrinus nebulosus and concentrations in water and sediment Iraqi marine water. Iraq. J. Aquac., 14(1): 61-85. https://doi.org/10.58629/ijaq.v14i1.85.

Al-Najare, G.A., A.A. Hantoush, A.C. Al-Shammary and H.T. Al-Saad. 2013. Bioaccumulation of heavy metals in Acanthopagrus latus collected from Iraqi marine waters. Iraqi J. Aquac., 10(2): 107-122.

Al-Najare, G.A., A.A. Jaber, A.H. Talal and A.A. Hantoush. 2015. The Concentration of heavy metals (copper, nickel, lead, cadmium, iron, manganese) in Tenualosa ilisha (Hmilton, 1822) hunted from Iraqi marine water. Mesop. Environ. J., 1(3): 31-43.

Al-Najare, GA., M.F. Al-Bidhani and AA. Hantoush. 2018. Environmental assessment of the Shatt al-Arab water resource by measuring concentrations of some pollutants from heavy metals in Scomberoides commersonnianus fish tissues. Mesop. Environ. J., 4(3): 1-14.

Al-Najare, G.A. 2012. Concentration of metals in the fish Liza subviridis from the Iraqi marine Estimation. JKAU: Mar. Sc., 23(1): 129.

Al-Najare, G.A., A.A. Hantoush and H.T. Al-Saad. 2017. Seasonal Variations of Some Heavy Metal’s Concentrations in Nemipterus japonicus Collected from Iraqi Marine Waters. JKAU: Mar. Sci., 27(1): 43-52. DOI: https://doi.org/10.4197/Mar.27-1.5.

Al-Rawi, K.M., A. Khalaf Allah and M. Aziz. 2000. Design and analysis of agricultural experiments, Dar Al-Kutub for Printing and Publishing, Uni. Mosul., Iraq., 488: pages.

Al-Shamary, A.C.J. 2020. Environmental assessment of Shatt Al-Arab estuary and Iraqi marine waters using Estuarine Biological Integrity Index. Ph.D. Thesis. College of Science, University of Basrah. 203p.

Al-Yassein, R.N. 2022. Toxicity of fipronil and atrazine on Metapenaeus affinis (Milne-Edwards, 1837) and their effects on oxygen consumption. Int. J. Aquat. Biol., 10(3): 218-223. https://doi.org/10.22034/ijab.v10i3.1589.

Annabi, A., K. Said and I. Messaoudi. 2013. Cadmium: bioaccumulation, histopathology and detoxifying mechanisms in fish. Am. J. Res. Commun., 1(4): 60-79.

Azab, M.A., M.A. Aly-Eldeen, H.M.M. Khalaf-Allah and M.M.A. El-Battal. 2019. Effect of heavy metals on the ovary of Tilapia zillii in some canals of Nile Delta area, Egypt.Egypt. J. Aquat. Biol. Fish., 23(3): 329-345. DOI: https://doi.org/10.21608/ejabf.2019.45670.

Burch, E. 2023. Differential Levels of Nutrients and Heavy Metals in Tilapia Collected from Drains in Egypt (Master’s thesis, The American University in Cairo (Egypt). https://fount.aucegypt.edu/etds/2133.

Carpenter, K.E., F. Krupp, D.A. Dones and U. Zajonz. 1997. Living marine resources of Kuwait, eastern Saudi Arabia, Bahrain, Qatar and The United Arab Emirates. FAO. Rome., 293 p.

Deidun, A., B. Zava, M. Corsini-Foka, J. Galdies, A.D. Natale and B.B. Collette. 2021. First record of the flat needlefish Ablennes hians (Belonidae) in central Mediterranean waters (western Ionian Sea). Annal., 31(1): 9-16.DOI https://doi.org/10.19233/ASHN.2021.02.

Ebrahimi Yazdanabad, T., M. Emtyazjoo, P. Ghavam Mostafavi and Z. Sahebi. 2014. Evaluation of copper and vanadium concentration in the soft tissue of Tylosurus crocodilus in Bahregan region, Persian Gulf. Chem. Speciat. Bioavailab., 26(2): 92-98. https://doi.org/10.3184/095422914X13952273632308.

Eschmeyer, W.N. 2017. Catalog of fish. Org /research/http: research Calacademy. Org/research/ichthyology/catalog/ fishcatmint. Asp. Accessed 28 April 2017. http://researcharchive.calacademy.org/research/ichthyology/catalog/fishcatmain.asp.

FAO. 2020. The State of Food Security and Nutrition in the World 2020. Food and Agriculture Organization of the United Nations. https://www.fao.org/3/ca9692en/ca9692en.pdf.

FAO. 2022. General Fisheries Commission for the Mediterranean. https://openknowledge.fao.org/server/api/core/bitstreams/a3da2be2-7924-4556-87b312ba64b09ad9/content?utm_source=chatgpt.com.

FAO/WHO. 1984. List of maximum levels recommended for contaminants by the Joint FAO/ WHO Codex Alimentarius Commission. Second Series. CAC/FAL, Rome., Vol. 3: pp.1–8.

Fazio, F., C.D. Iglio, G. Capillo, C. Saoca, K. Peycheva, G. Piccione and L. Makedonski. 2020. Environmental investigations and tissue bioaccumulation of heavy metals in grey mullet from the Black Sea (Bulgaria) and the Ionian Sea (Italy). Anim., 10(10): 1739. https://doi.org/10.3390/ani10101739.

FDA. 2001. Fish and Fisheries Products Hazards and Controls Guidance, third ed.; Center for Food Safety and Applied Nutrition, US Food and Drug Administration.

Fernandes, D., M.J. Bebianno, and C. Porte. 2008. Hepatic levels of metal and metallothioneins in two commercial fish species of the Northern Iberian shelf. Sci. Tot. Environ., 391(1): 159-167. https://doi.org/10.1016/j.scitotenv.2007.10.057.

Garai, P., P. Banerjee, P. Mondal and N.C. Saha. 2021. Effect of heavy metals on fishes: Toxicity and bioaccumulation. J. Clin. Toxicol., 11 Iss. S18 (001):1-10.

Gautam, G.J. and R. Chaube. 2018. Differential effects of heavy metals (cadmium, cobalt, lead and mercury) on oocyte maturation and ovulation of the catfish Heteropneustes fossilis: an in vitro study. Turk. J. Aquat. Sci., 18(10): 1205-1214. DOI: https://doi.org/10.4194/1303-2712-v18_10_07.

Hashim, E.S. and R.N. Al-Yassein. 2020. Effect of Sublethal Concentrations of Cadmium on the Histo-pathological Changes of Muscles of Planiliza abu Juveniles (Heckel, 1843). Basra. J. Agric. Sci., 33(2): 207-217. https://doi.org/10.37077/25200860.2020.33.2.18.

Isangedighi, I.A. and G.S. David. 2019. Heavy metals contamination in fish: effects on human health. J. Aquat. Sci., 2(4): 7-12. DOI: https://doi.org/10.22259/2638-5481.0204002.

Ismat, N., M. Ashraf, M. Naeem and M.H.U. Rehman. 2013. Effect of different feed ingredients on growth and level of intestinal enzyme secretions in juvenile Labeo rohita, Catla catla, Cirrhinus mrigala, and Hypophthalmichthys molitrix. Int. J. Aquac., 3(16): 85-91.

Jakhrani, S.A., J.A. Ujjan, M.A. Jakhrani, F.Z. Dayo and H. Mazari. 2019. Investigation of different biochemical parameters in three economical important fish species captured from ponds of district Kashmore, Sindh, Pakistan. Int. Nat. Sci., 14(4): 387-392. http://dx.doi.org/10.12692/ijb/14.4.387-392.

Jezierska, B. and M. Witeska. 2006. The metal uptake and accumulation in fish living in polluted waters. In Soil and water pollution monitoring, protection and remediation (pp. 107-114). Springer Netherland. DOI: https://doi.org/10.1007/978-1-4020-4728-2_6.

Kalipci, E., H. Cüce, F. Ustaoğlu, M.A. Dereli and M. Türkmen. 2023. Toxicological health risk analysis of hazardous trace elements accumulation in the edible fish species of the Black Sea in Türkiye using multivariate statistical and spatial assessment. Environ. Toxicol. Pharmacol., 97: 104028. https://doi.org/10.1016/j.etap.2022.104028.

Karim, R.M., K.K. Al-Khafaji, A.T. Yaseen and F.M. Mutlak. 2022. First occurrence of two crab species, Actaea calculosa (Milne Edwards, 1834) and Atergatis integerrimus (Lamarck, 1801), family Xanthidae in Iraqi coast waters. Egypt. J. Aquat. Biol. Fish., 26(2): 331-338.

Kraemer, S.M. and J.G. Hering. 2004. Biogeochemical controls on the mobility and bioavailability of metals in soil and ground water. Aquat. Sci., 66(2004): 1-2. DOI https://doi.org/10.1007/s00027-004-0004-6.

Latif, M., M. Zahoor, A. Muhammad, S. Naz, A.W. Kamran, R. Ullah and A. Sayed. 2022. Bioaccumulation of lead in different organs of Ctenopharyngodon Idella (grass fish) and Tor putitora (Mahseer) fish. Braz. J. Biol., 84: e260355. DOI: https://doi.org/10.21608/ejabf.2019.45670.

Łuczyńska, J., R. Pietrzak-Fiećko, A. Purkiewicz and M.J. Łuczyński. 2022. Assessment of fish quality based on the content of heavy metals. Int. J. Environ. Res. Public Health., 19(4): 2307. https://doi.org/10.3390/ijerph19042307.

M.F.D. Malaysian Food and Regulations. 1985. In Hamid Ibrahim, Nasser and Yap Thiam Huat. Malaysian law on food and drugs. Kuala Lumpur, Malaysia Law Publisher.

Mishra, B., G.J. Gautam, R.K. Chaturvedi, N.G. Ansari and V.N. Mishra. 2024. Ecological and Health Risk Assessment of Heavy Metals Bioaccumulation in Ganges Fish near Varanasi, India. Biol. Trace Elem. Res., 202(10): 4751-4766. DOI: https://doi.org/10.1007/s12011-023-04020-4.

Mohamed, A.R.M., N.A. Hussain, S.S. Al-Noor, F.M. Mutlak, I.M. Al-Sudani and A.M. Mojer, 2012. Ecological and biological aspects of fish assemblage in the Chybayish marsh, Southern Iraq. Ecohydrol. Hydrobiol., 12(1): 65-74.

Moiseenko T.I. and N.A. Gashkina. 2020. Distribution and bioaccumulation of heavy metals (Hg, Cd and Pb) in fish: influence of the aquatic environment and climate. Environ. Res. Lett., 15(11): 115013. DOI https://doi.org/10.1088/1748-9326/abbf7c.

Moiseenko, T.I., B.A. Morgunov, N.A. Gashkina, V.V. Megorskiy and A.A. Pesiakova. 2018. Ecosystem and human health assessment in relation to aquatic environment pollution by heavy metals: case study of the Murmansk region, northwest of the Kola Peninsula, Russia. Environ. Res. Lett., 13(6): 065005. DOI https://doi.org/10.1088/1748-9326/aab5d2.

Naeem, M., A. Salam and A. Jafar. 2005. Induced spawning of major carp Catla catla by a single intramuscular injection of Ovaprim-C and fecundity at Fish Hatchery Islamabad, Pakistan. J. Bio. Sci., 5(6): 776-780.

Naeem, M., A. Salam and A. Zuberi 2016. Body composition of freshwater rainbow trout, Oncorhynchus mykiss, in relation to body size and condition factor from Pakistan. Pak. J. Agric. Sci., 53(2): 468-472.

Naeem, M., A. Salam, S.S. Tahir and N.A.S.E.E.M. Rauf. 2010. Assessment of the essential element and toxic heavy metals in hatchery reared Oncorhynchus mykiss. Int. J. Agric. Biol., 12(6): 935-938.

Nanda, P. 2014. Bioaccumulation of heavy metals and physiological response in Anabas testudineus on exposure to paper mill effluent. J. Environ. Anal. Toxicol., 5(1): 1-8. DOI: https://doi.org/10.4172/2161-0525.1000244.

Paul, A.K., S. Iqbal, U. Atique and L. Alam. 2020. Muscular tissue bioaccumulation and health risk assessment of heavy metals in two edible fish species (Gudusia chapra and Eutropiichthys vacha) in Padma River, Bangladesh. Punjab Univ. J. Zool., 35(1): 81-89. https://dx.doi.org/10.17582/journal.pujz/2020.35.1.81.89

Pourang, N., A. Bahrami and H. Nasrolahzadeh Saravi. 2019. Shells of Bufonaria echinata as biomonitoring materials of heavy metals (Cd, Ni and Pb) pollution in the Persian Gulf: with emphasis on the annual growth sections. Iran. J. Fish. Sci., 18(2): 256-271. dio: https://doi.org/10.22092/ijfs.2018.115734.

Seiyaboh, E.I. and S.C. Izah. 2017. Review of impact of anthropogenic activities in surface water resources in the Niger Delta region of Nigeria: a case of Bayelsa state. Int. J. Ecotoxi. Ecobiol., 2(2): 61-73. doi: https://doi.org/10.11648/j.ijee.20170202.12.

Sevcikova, M., H. Modrá, A. Slaninova and Z. Svobodova. 2011. Metals as a cause of oxidative stress in fish: a review. Veter. Medic., 56(11): 537-546. DOI: https://doi.org/10.17221/4272.

Shah, N., A. Khan, R. Ali, K. Marimuthu, M.N. Uddin, M. Rizwan and M. Khisroon. 2020. Monitoring bioaccumulation (in gills and muscle tissues), hematology, and genotoxic alteration in Ctenopharyngodon idella exposed to selected heavy metals. Biom. Res. Int., 2020(1): 6185231. https://doi.org/10.1155/2020/6185231.

Siraj, M., M. Khisroon and A. Khan. 2016. Bioaccumulation of heavy metals in different organs of Wallago attu from River Kabul Khyber Pakhtunkhwa, Pakistan. Biol. Trace Elem. Res., 172: 242-250. http://dx.doi.org/10.1007/ s12011-015-0572-4. PMid: 26637495.

Swami, K., C.D. Judd, J. Orsini, K.X. Yang and L. Husain. 2001. Microwave assisted digestion of atmospheric aerosol samples followed by inductively coupled plasma-mass spectrometry determination of trace elements. Fresenius J. Anal. Chem., 369(1): 63-70 DOI: https://doi.org/10.1007/s002160000575.

Tsurkan, L.V., Y.M. Volichenko and I.M. Sherman. 2020. Ecological and hematological Components of wintering of carp carpets in the conditions of the South of Ukraine. Water Bioresour. Aquacult., 2: 59-69. https://doi.org/10.32851/wba.2020.2.6.

Van den Broek, J.L., K.S. Gledhill and D.G. Morgan. 2002. Heavy metal concentrations in the Mosquito fish, Gambusia holbrooki, in the manly Lagoon Catchment. UTS Fresh water Ecology, Department of Environmental Science, university of Technology, Sydney. doi: https://doi.org/10.1088/1755-1315/416/1/012010.

Yaseen, A.T., S.S. Hassan and A.K. Resen. 2024. Patterns of Abundance and Diversity of Fishes in Iraqi Estuarine and Marine Waters of the Northwestern Arabian Gulf. Egypt. J. Aquat. Biol. Fish., 28(1): 223-243.

Yokote, M. 1982. Digestive system. In: An atlas of fish histology normal and pathological features (T, Hibiya, ed.). pp. 74-93: Kodarisha Ltd., Tokyo. DOI:https://doi.org/10.1007/s00429-006-0103-3.

Zaghloul, G.Y., H.A. Eissa, A.Y. Zaghloul, M.S. Kelany, M.A. Hamed and K.M.E. Moselhy. 2024. Impact of some heavy metal accumulation in different organs on fish quality from Bardawil Lake and human health risks assessment. Geochem. Trans., 25(1): 1. https://doi.org/10.1186/s12932-023-00084-2.