**1. Introduction**

According to Ramelow et al. [1] and Schulz et al. [2], fishes are excellent tools to the aquatic environment biomonitoring because they are used for assessing a lot of environmental disturbing factors such as changes in the rate of growth and sexual maturation. Besides, changes in fish community structure, such as species abundance and diversity, may also reflect the effects of various stressors on the biotic integrity of a river [3].

**2. Methodology**

**2.2. Study area**

CP = Prata Waterfall.

**2.1. License and statement of ethics committee**

Ethics and Animal Experimentation Commission (CEEA).

Fish collection was done through the research authorization of the Chico Mendes Institute for Biodiversity Conservation—ICMBio (SISBIO, 55361/2017). The protocol of the ethics committee was approved by the State University of Maranhão (13/2017 CRMV-MA) through the

Genotoxic Biomarkers in Fishes of the Chapada Das Mesas National Park, Brazil

http://dx.doi.org/10.5772/intechopen.72558

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The Chapada das Mesas National Park (PNCM) (**Figure 1**) is a protected area, which is located in the South of Maranhão, between the following cities: Riachão, Estreito and Carolina [16].

The PNCM climate is tropical: humid and hot, characterized by having two defined seasons, one being dry and the other rainy. The rainy season is in the period from November to March, with rainfall concentrated in February [17]. This region contains an extensive and rich hydrographic network with approximately 400 springs and the main water courses that supply the city of Carolina. In addition, the PNCM protects numerous watercourses and springs from several rivers, such as the Farinha River (with numerous waterfalls), Itapecuru, Urupuchete, Corrente

**Figure 1.** Map of the Chapada das Mesas National Park, Brazil showing the sampling sites. CRS = São Romão Waterfall;

In this way, erythrocytes of fish have been shown to be a safe tool for the micronucleus test [4, 5]. The micronucleus test is considered an advantageous technique whose analysis is relatively simple. In addition, the simplicity and speed of obtaining peripheral fish blood make the technique even more suitable for the evaluation of environmental contamination [6].

In this context, the selection of species that can reflect the environmental situation of PNCM becomes of great relevance to monitor the interferences that this Conservation Unit has been suffering over the years. Fishes are excellent bioindicators because they are at the top of the trophic chain and reflect the impacts in a given ecosystem through their normal and/or organic composition in the medium or long term [7].

The development and standardization of methodologies capable of predicting the effects of contamination on aquatic organisms are extremely relevant for biomonitoring studies in a Conservation Unit. Among these methodologies, the use of biomarkers of aquatic contamination in fish is particularly important because it shows initial biological responses and may be useful to subsidize monitoring and environmental management actions [8]. Biomarkers are biological responses to stress caused by pollutants and/or physical stressors and can be used to identify early signs of damage to aquatic organisms [9].

Research indicates that when aquatic ecosystems are polluted with organic and inorganic contaminants, fish will inevitably be contaminated [10, 11]. The possible effects of such contaminants on fish can be assessed by using several types of biomarkers, which are defined as the biological responses, as well as the effects caused by the pollutants and which identify signs of initial damage in organisms [12]. Livingstone [13] considers as biomarkers the bodily fluids, cells or tissues, as well as the responses of the exposed organisms, in physiological as well as behavioral or energetic levels, being, therefore, molecular biomarkers, cellular or organisms, being some of them are specific pollutants.

The genetic material of eukaryotic cells of fish species can also be altered by exposure to dissolved chemicals in the water, resulting in the formation of micronuclei, which can be used as biomarkers to assess the degree of contamination in the environment [14]. The micronuclei are derived from chromosomal fragments resulting from breaks that are not incorporated into the main nucleus of the daughter cells after mitosis due to damage introduced into the parental cells [15]. Micronuclei tests have not yet been performed in PNCM and in the water ecosystems of southern Maranhão. Thus, these data may serve to obtain more complete clues of contaminants that may be inducing.

In this way, recognizing the need to provide the sustainable use of natural resources and the environmental quality of the PNCM and to the local communities, as well as the need to know the effect of the possible impacts on the fish of the region, the aim was to contribute with the scientific knowledge related to biomarkers genotoxic in two species of sweet fish (*Hypostomus pusarum* and *Mylossoma duriventre*) in order to subsidize biomonitoring and management programs in the protected areas.
