Waste generation and disposal, particularly of plastics, have grown significantly over time due to the rapid expansion of urban development. Aquatic species are especially threatened by plastic pollution because the aquatic ecosystem serves as a sink for all contaminants. The capacity for regular development and reproduction is crucial for both human and wildlife health. The endocrine system, which comprises numerous glands that emit hormones to control blood sugar, growth, reproduction, metabolism, and the development of the brain, normally controls these functions. The majority of the synthetic organic chemicals used in plastics come from petroleum. It is well known that their effects cause the endocrine system's regular operation to be disrupted. Plastics are produced at a low cost, and their light weight and adaptability make them candidates for a wide range of uses in all facets of daily life. Plastic waste can enter the ecosystem through waste discharges from oil and gas platforms, aquaculture, and landfills, as well as through litter such as bags and plastic bits used as abrasives. Because they include indigestible particles that fill the stomach and lessen appetite, plastics have been implicated in harming the health of a variety of creatures. They were also discovered in the gastrointestinal tract of individual fish after one week, which disrupted the food's flow to the intestinal mucosa and had an impact on the fish's growth and physical condition. Additionally, fish exposed to plastics have been shown to exhibit changed behavior, decreased sperm motility, and increased thyroid hormone production. Therefore, exposure to varied amounts of polyethylene impairs an organism's normal physiological functioning and has the potential to impact negatively on both the health of the organism and its offspring. This review was aimed at highlighting the risks of plastic exposure to fish and people through the food chain.

The study was done to review some saltwater and freshwater fish species in the Niger Delta region of Nigeria. The Niger Delta is one of the most prominent regions in Nigeria, endowed with several water bodies that are distributed as freshwater like rivers, lakes, streams and creeks. These freshwater ecosystems in the region, are abundantly endowed with fish species such as Clarias gariepinus, Pila ovate, Labeo coubie, Synodontis budgetti and Synodontis eupterus. Apart from the freshwaters, the region also has vast marine ecosystem with abundance of fish species such as Elops lacerta, Mugil cephalus, Thais coronata, Periophthalmus papilio, Tympanotonus fuscatus, and Sardinella maderensis. Unfortunately, many of these fish species are endangered due to constant pollution in the Niger delta regional coastal environment. As a result, it is important to document some available freshwater and marine water fish species which will serve as a reference material for both academics and research institutions, should any of the fish species go into extinction.

The present study assessed the effects of human pressure on the surface water quality of the Ogbor Hill River, southern Nigeria. This river is among one of the important rivers in Southeast Nigeria for domestic, agricultural and industrial purposes. To assess the water quality, samples of water were collected monthly for eight months, and were preserved and transferred to the laboratory for further analysis. Electrical conductivity, pH, total dissolved solids, salinity, turbidity and temperature were determined in situ. Other parameters were determined in the laboratory using standard laboratory methods. The results revealed that the mean pH was acidic across the months with no significance difference (p > 0.05). Additionally, the mean total dissolved solids showed a significant difference (p < 0.05), with a higher value of 582.10 ± 83.41 in April and a lower value of 243.67 ± 40.62 in May. The highest mean conductivity of 1392.33 ± 156.18 was observed in April, and the lowest mean of 289.33 ± 97.37 in May. Dissolved oxygen indicated there was a significant difference among the study months (p < 0.05), with the highest mean concentration of 4.80 ± 0.37 in June and the least of 3.30 ± 0.20 in April. Biochemical oxygen demand, chloride and temperature all showed a significant difference (p < 0.05) across the sampling months. The mean concentration of Zn showed no significant difference among the study months. The mean concentration of Fe recorded showed the highest value of 2.68 ± 0.16 in April and the lowest mean of 1.96 ± 0.13 in July. Pb showed a higher concentration of 0.44 ± 0.33 in March and a lower mean of 0.033 ± 0.008 in July. A higher mean Cd of 0.052 ± 0.004 was observed in March and a lower mean of 0.023 ± 0.002 in December. Generally, the water parameters were elevated beyond the threshold for surface water, which was an indication that the river water was badly impacted due to human pressure and needed to be kept safe for human use. The present study revealed that most of the water quality parameters such as TDS, DO, BOD, pH, turbidity, and concentrations of the heavy metals Pb and Cd were higher in selected months, and further water management should be carried out while anthropogenic activities should be reduced around the river ecosystem.

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