World Aquaculture December 2019

50 DECEMBER 2019 • WORLD AQUACULTURE • WWW.WA S.ORG curve (Baussant et al . 2011). Many significant composite factors are involved in investigating ecological communities, such as the processes of metabolism, human disturbance and environmental structure transformation. Investigators must possess professional knowledge of botany, zoology and other fields. Above all, this progress produces a significant amount of investigation and analysis data and includes substantial labor and material resource costs (Garshelis and Johnson 2013). DNA damage has been used to evaluate the environmental quality of water after an oil spill. This indicator can reflect the cumulative effect of pollutants, confirm the causal relationship between pollutants and biological effects and reveal exposure characteristics of pollutants. Furthermore, good results have been achieved in practical applications (Apraiz et al . 2009). The degree of heat, heavy metal and estrogen pollution of a water body can be indicated by DNA damage in goldfish Carassius auratus (Yan et al . 2012). The traditional freshwater Chinese goldfish was selected as the experimental species in this study. DNA damage of goldfish juveniles was the assessment criteria to evaluate the long-term influence of the light fraction of oil spilled in an estuarine environment. This research focused on testing the feasibility of using goldfish juveniles as a biological indicator to assess the influence of an oil spill in an estuary and lay the theoretical foundation for application of biological monitoring indicators of estuarine oil pollution. Study Methods Goldfish reproduce fromApril to August and are distributed widely throughout the fresh waters of China and are prevalent in many rivers in Asia. Experimental fish were native to the Yalu River estuary, near Donggang City of Liaoning Province. The species used in the experiment was not the ornamental goldfish. The average body length of adult fish was 20 ± 5 cm and the average body weight was 325 ± 25 g. Experimental juveniles were acclimated in an aquarium for more than 5 d. Their body mass was 3.0 ± 0.3 g, body length was 5.9 ± 1.4 cm, with an age of about 30-35 days. The. The physical comparison of adult and juvenile goldfish are shown in Figure 1. Experimental fish behaved normally, had no disease and there was less than 5 percent mortality during acclimation. Juveniles were not fed the day before beginning the experiment. Healthy, responsive juveniles of nearly the same size were chosen and grouped randomly. O il spills in estuarine areas of China have increased in recent years (Liu et al. 2014). Estuaries serve as a filter for many pollutants between land and sea and are central channels of energy flow, material recycling and information transmission as they connect watershed with ocean. Monitoring environmental quality is needed after an oil spill occurs. Evaluating changes in environmental quality in the oil spill region objectively and accurately with appropriate monitoring methods has scientific and legal significance. Monitoring approaches include physicochemical monitoring and biological monitoring. The former analyzes the existing forms and concentrations of contaminants in different environmental media and the latter analyzes biological reactions to contaminants in the environment (Shan and Liu 2007). There are two representative, comprehensive evaluation models of estuarine and coastal ecological environment quality used widely in the world: the European Commission “Guidance on typology, reference conditions and classification systems for transitional and coastal waters” and the U.S. Environmental Protection Agency “National coastal condition report” (USEPA 2001). The investigation and analysis of biological residual toxins and ecological communities are the primary means of biological monitoring and include analysis of petroleum residues in fish, shrimp ( Pandalus ) and mussel tissue and the composition and abundance of aquatic plants. The mussel has been used as a key marine indicator species of oil pollution because high concentrations of hydrophobic compounds can accumulate biologically in its tissue. Thus, the mussel is particularly suitable for demonstrating the biological effects of oil pollutants in detail (Baussant et al . 2011), although the exposure time or contact with pollutants usually requires several months. Using mussels does not allow the rapid evaluation of the effect of oil contaminants. Furthermore, some studies have shown that the certain components of oil in the living body are excreted easily during routine metabolism of the organism (Geffard et al . 2003). Therefore, residual petroleum hydrocarbons in the living body does not completely reflect the exact situation of contaminated water, especially in a short time frame. In addition, when the petroleum hydrocarbon content of organisms is analyzed, more than 12 h is required to saponify samples and it is complex to do the standard DNA Damage in Juvenile Goldfish as a Biological Indicator of Estuarine Oil Pollution Y.N. Yang, H.J. Gong and Muhammad Aamir Bashir FIGURE 1. Adult and juvenile goldfish Carassius auratus .