Abstract Pesticide atrazine represents one of the most heavily used agricultural pesticides globally. The pesticide’s primary use in farms is to control the growth of weeds in corn and sorghum plantations. Arguably pesticides are potentially toxic to humans and aquatic life (Freeman et al., 2005). Pesticides like atrazine can stay in the soil and water for years. The use and application of pesticides in farms have continued to play a significant role in food production, protecting, and increasing yields. Tyrone Hayes and others highlighted that even trace levels of atrazine can adversely affect aquatic life. They observed that exposing frogs to trace levels of atrazine could cause severe health impacts that included a kind of chemical castration. The desire to provide complete data regarding the potential impacts of atrazine in development and reproduction in aquatic organisms begun in the 1990s and the primary focus has been on the amphibians and reptiles (Hayes et al., 2002). However, the effects of atrazine on development and reproduction in fish have not been fully addressed in the literature available at this time. This forms the basis of this research activity which seeks to determine the potential impacts of atrazine herbicide on the reproduction activities of fish. Introduction Atrazine has been widely used in agricultural production for years. Considering both its physical and chemical properties, atrazine is found though in small quantities in some surface water and aquatic habitats (Freeman et al., 2005). Evidence drawn from previous research works has indicated the effects of atrazine on aquatic life specifically amphibians. However, inconsistencies have continued to exist. This current paper is thus set against this background to provide an analysis based quantitative weight of evidence on the effects of atrazine on fish, amphibians, and reptiles. It is noted that exposure to atrazine does not kill aquatic life immediately. Fish and amphibians have been considered the most vulnerable species of aquatic life impacted by exposure to atrazine. Toxicology essentially evaluates and establishes the limits of concentration or quantity of chemical substances in a particular part of the environment (US EPA, 2002). This research paper would in entirety attempt to evaluate the chemical, behavior, and physical transformations on aquatic life due to exposure to high atrazine levels. Concentrations of atrazine commonly found in agricultural streams and rivers have caused a reduction in the reproduction and spawning of fish. Similarly, laboratory pieces of evidence have shown tissue abnormalities in fish. The methodology used in this study involved exposing fathead minnows to atrazine and consequently observing the effects of the pesticide on egg production, tissue abnormalities, and hormone levels. The organisms under study were exposed to atrazine concentrations that ranged between 0 and 60 mg per liter of atrazine for the 30 days. All tested levels of exposure are less than the USEPA Office of Pesticides Aquatic Life Benchmark of 65 micrograms per liter for chronic exposure of fish. Thus, substantial reproductive effects were observed in this study at concentrations below the USEPA water-quality guideline. Materials and methods Freshwater air-breathing fish acquired from local sources were subjected to prophylactic treatment to avoid any kind of dermal infections. This was done by bathing the fish in potassium permanganate solution for approximately two-three minutes. Under laboratory conditions, these organisms were left to acclimatize for another two weeks in semi-static systems. The specimens were fed on minced meat, boiled eggs, and other materials are drawn from poultry waste. To specifically reduce the water’s ammonia content, the fecal matter was removed daily. As per the USEPA guidelines, acute toxicity bioassays were conducted to particularly determine the value of atrazine in the semi-static laboratory system. Atrazine was then dissolved and added to the semi-static laboratory water system using a method outlined by Pluta (1989). To counterbalance the decreasing herbicide levels daily, the water was changed after 20 hours by adding fresh solutions for atrazine. The fish were exposed to 60 mg of atrazine with control specimens exposed at 0 mg. Following the probit analysis as described by Finley (1971), the value of atrazine for the fish specimen was determined. It is important to note that no specimen died during this study. The fish in this experiment were exposed to concentrated atrazine solutions alongside control experiments which continued for two weeks after which five fish specimens were randomly sampled for testing. Results Fish and other aquatic life can arguably serve as bio-indicators of environmental pollution. Due to this fact, they can play very significant roles in the assessment of potential risks that are associated with the contamination of the aquatic environment. Atrazine commonly used in agriculture usually finds its way to water resources through surface-runoff. Herbicides and pesticides are considered environmental contaminants that are known to modulate fish antioxidant defensive systems subsequently resulting in oxidative damage in these organisms. Due to oxidative stress, fish and other aquatic organisms can experience DNA damage and even worse death of cells. The information acquired through this current research study would be useful in the management and monitoring of atrazine contamination in aquatic environments. The Physico-chemical properties of the test waters The temperature of the test water specifically varied between 24 and 25 degrees Celsius, and the pH varied from 7.4 to 7.9. The dissolved oxygen concentration levels ranged from 6.5 to 7.5 mg L conductivity values ranging from 250 to 300 um during the experimental period. Characteristics Unit Mean Range Air Temperature 0C 26.20 25.6–26.6 Water Temperature 0C 24.40 24.2–25.4 pH 7.6 7.4–7.9 Dissolved Oxygen mg·L−1 6.8 6.7–7.8 Conductivity μMcm−1 282 260–300 Total hardness mg·L− 220 200–230 Fig 1.0. showing the physicochemical properties of the test waters. It is observed that sensitive species of aquatic organisms may experience adverse and serious effects when exposed to lower levels of atrazine. However, the potential impacts of phytotoxic concentrations of atrazine for extended periods have not been documented. Atrazine has been found in significant levels in lakes and streams, and whose concentrations peak during spring when its agricultural usage is also advanced (Hamilton et al., 1987). The significant concentration of atrazine in the aquatic environment is significantly attributed to runoff waters directly adjacent to treated fields. Atrazine greatly affects aquatic organisms at concentrations of 10 ug/l or higher by reducing the food supply. Study results from this project indicated that normal reproductive cycles of the fish were disrupted by atrazine and the fish’s spawning activity reduced considerably. It was observed that the egg production for the fish that were exposed to higher atrazine levels was considerably lower than that of the control specimens. Findings from this study indicated that atrazine exposed fish spawned less and there were abnormalities in the reproductive tissues of both the males and the females. Dewey (1986) documented the adverse effects associated with atrazine herbicide on freshwater aquatic fauna. Their findings were arguably indirect, for instance, the decline in benthic insects and other aquatic insects was significant with the addition of atrazine. The effects presumably had indirect impacts on the survival of fish populations in the habitats affected by atrazine. Similarly, dietary habits and reproductive success of the organisms are negatively impacted after the 15-day exposure in water aquariums containing high levels of atrazine. As observed at the end of the experimental period, the reproduction channel of the fathead failed as measured by the number of the young in each pond. Evidence obtained from this research activity indicated a lower egg production in all atrazine exposed fish as compared to the control experiment within 15 days of exposure. Atrazine considerably affected the reproductive tissues in both the females and the male organisms. Atrazine is considered as one of the commonly used herbicides in the USA in the production of corn, sugarcane, and sorghum. It is normally used in the management of broadleaf and grassy weeds and is generally applied in the spring, a period where most fish in North America are reproducing (Tillitt et al., 2010). Endocrine compounds are associated with intersex and reproductive effects in fish. Through this research, it is argued that chemicals contained in atrazine herbicide can adversely affect fish endocrine systems consequently affecting the endocrine functions. Discussion Water from excessive rainfall and irrigation always finds itself in groundwater and freshwater sources. This is usually possible because it is not possible to hold the water within the soil structure. Pesticides and residues transported through surface runoff are responsible for the contamination of surface water sources over a large geographical area. Atrazine as an individual herbicide contains unique chemical properties that affect aquatic life. Atrazine is one of the two most heavily used pesticides in the US today with over 35 million kilograms’ active ingredients applied yearly. Fish specimens exposed to solutions of atrazine herbicide exhibited uncoordinated behavior. It was observed that at the initial stages of the experiment, the fish seemed alert, with reduced swimming activities, remained in static positions to particularly respond to the sudden changes occurring in the aquarium. Atrazine herbicide resulted in toxic stress and poisoning in the fish specimen which consequently resulted in reduced reproductive activities (Solomon et al., 2008). In the aquariums with higher concentrations of the test herbicide, the fish swam erratically subsequently becoming exhausted and lethargic. Fish have in most occasions been used in Ecotoxicological studies since they arguably play several roles in the trophic web, therefore the use of fish can permit early detection of aquatic environmental problems (Boden, M. J. & Kennaway, 2006). The results obtained in this study indicated that the toxicity of atrazine for aquatic organisms is dependent on time and herbicide concentration. Findings from this study concurred with those of previous researchers that highlighted the impacts of atrazine on the endocrine-related functions in bluegill and zebrafish. The findings pointed out that exposure to higher and toxic levels of atrazine lowered fish reproduction and caused abnormalities in fish reproductive organs. The flathead minnows used in this study showed reduced egg production. The cumulative egg production considerably reduced for the fish in the contaminated aquariums compared to the control experiments. Secondly, abnormalities were physically observed in both the exposed female and male fish. Female fish exposed to atrazine were found to have increased ovarian lipid accumulation and atretic follicles; three female fish were also found to have “multiple ovarian cysts that occupied a large portion of the ovary. For the male minnows, there were visible testicular abnormalities (Baxter et al., 2013). These changes present possible explanations for the significant reductions in reproduction levels. The impacts of atrazine on fish egg production and spawning suggest great reproductive risks to fish and other aquatic life in high agricultural areas where the impact of the herbicide may be underestimated. As observed by Hayes et al. (1987), the effect of atrazine herbicide on wild leopard frogs where male frogs exposed to the chemical exhibited abnormalities in the gonads, similar findings were registered in this study considering the significant reduction in fish eggs. Researchers in this study tracked egg production, tissue abnormalities, and hormone levels in the exposed fish in comparison to the unexposed specimen. Findings revealed substantial reproductive effects. It is however important to note that the atrazine concentrations were below the USEPA water quality guidelines. Despite the observable risks atrazine herbicide imposes on the aquatic life, the study was however to unable to reveal any effects on fetal viability or embryo development. The study however revealed in entirety that atrazine herbicide exposure presented no effects on the hatching of the already laid eggs but presented a significant impact on the overall reproduction procedure. Hatching is generally an apical endpoint in terms of survival. Concurring to a previous study by Dionne (1992) on the hatching success of P. Promelas which had been exposed to atrazine concentrations ranging between 150 and 200 ug/L for 30 weeks. This research project observed no effects on the hatching success of the eggs and was similar to the other full life cycle studies reported on the percentage of egg hatching. Similarly, studies conducted on the egg hatching success of the salamander showed a significant reduction in the hatching at concentrations of formulated atrazine ranging from 50 to 400 ug/L. Explanations advanced for this reduction was the considerable reduction in the algal formation due to over-concentration of atrazine chemical in the water. Salamander is argued to be biologically unique and is one of the few amphibians having symbiotic relationships with the algae (Baxter et al., 2013). Atrazine is generally a photosynthetic inhibitor and presents a plausible effect on algal development. Hamilton et al. (1987) argued that the presence of algae in the water contributed significantly to the hatching success and subsequent survival of the salamander eggs. Considering this symbiotic relationship between the salamander and the algae, it was possible to contend that they could be more sensitive to atrazine exposure than other aquatic organisms including the fathead minnows involved in this current study. Researchers in this study argued that the exclusion of algae in the determination of egg hatching success would present better-informed findings on the egg hatching success and the sensitivity to atrazine exposure. Reduced reproduction activities were observed in this study were particularly due to reduced mating activities by the fish due to reduced spawning activities. Overall, there was no strong evidence for the effects of atrazine on the hatching of eggs of fish. Besides, due to reduced spawning activities, several female minnows exhibited a swollen abdomen supporting the lack of successful mating with an increase in atretic ovarian follicles. Observations drawn from this current project were arguably similar to that of Tillitt et al. (2010) after exposing adult fathead minnows to varying atrazine concentration solutions for 15 to 30 days. There was a decrease in spawning events and cumulative egg production. The observations seemed to be more evident with increasing concentrations of atrazine herbicide. This study also had similar observations in fathead minnows exposed to higher atrazine concentrations in a semi-static laboratory environment. In conclusion, it was possible to conclude that atrazine exposure to fish alters reproductive behavior in various species of fish (Moore & Lower, 2001) Recommendations Herbicides are arguably one of the most commonly used pesticides globally. Herbicides are used in agriculture to control and manage weed development. Although herbicides are meant to be less toxic to animals than plants, they cause toxicity in organisms at large concentrations. Herbicides used in agriculture such as atrazine have continued to be leading pollutants of surface water sources. Surfactants are surface-active agents and can interfere with the fish physical formation, interfering with the gills consequently causing toxicity that can affect their reproductive activities (Konnecker et al., 2011). Against this understanding, the application of herbicides on agricultural farms needs to be regulated to particularly avoid over-application of the chemicals that subsequently trigger leaching into the soil and consequent contamination of the surface and groundwater sources. Since the 1980s, extensive measurements have been carried out to particularly assess the concentrations of herbicides within some jurisdictions such as the US, these findings have revealed significant risks posed by the extensive use of herbicides on the environment. Against this background, the recommendations formulated through this study require the regulatory agencies that permit the usage of all herbicides and pesticides to control the application of these chemicals to avoid spreading toxicity to non-target organisms. Acute toxicity data for fish needs to be made available. Characterizing toxicity of the herbicides would avail robust data with quality assurance and quality control to inform the decision of farmers applying herbicides on the correct amount that should be applied to avoid over-application and subsequent over-concentration of the chemical in the soil. It is argued that the early development, growth, and reproduction in fish are essential aspects for the long-term maintenance of fish population and health. It is possible that continued exposures to atrazine herbicides could adversely impact the stability of the fish populations in the natural ecosystems considering the significant reduction in the number of cumulative eggs laid. Conclusion The effects of atrazine herbicide on fathead minnows have been considered in this project. This research has in an entirety investigated the toxic effects of atrazine on the minnows. Atrazine greatly affects the reproduction process of the fish since it negatively impacts on the spawning events. For this reason, proper and efficient labeling of all products containing atrazine is needed to inform users of the acceptable uses and potential hazards to fish and wildlife. Similarly, users are advised to avoid the use of atrazine in well-drained soils, particularly in areas that border surface water sources that are highly susceptible to surface run-off contamination. Moreover, to maintain a healthy fish population, currently, permissible tolerances for atrazine must be followed by all users. This is because the over-concentration of the pesticide in the soil and water sources is harmful to aquatic organisms.