**1. Introduction**

Environmental change poses a devastating risk to human and environmental health. Environmental pollution is the most difficult challenge for all countries in the world, as it affects all living things and ecosystems under the concept of one health [1–3]. A rapid study of water conditions is necessary for monitoring, assessing, and addressing this global health hazard. Bio-indicators or biological monitors can monitor water quality changes in real-time. Zebrafish (*Danio rerio*) is an ideal bio-indicator for detecting environmental changes due to its biomedical equipment, widespread geographic distribution, and wellcharacterized specific properties against environmental pollutants [4,5]. *Danio rerio*, which is used to determine the toxicity (teratogenicity, cardiotoxicity, neurotoxicity, hepatotoxicity, and nephrotoxicity, etc.) effect of many chemicals, has also recently been used in the detection and research of diseases [6]. Considering the increasing use of zebrafish as an experimental animal against a wide variety of chemicals and pollutants in toxicity studies, it is also of grea<sup>t</sup> importance to improve laboratory conditions in terms of reproductive quality. Despite the zebrafish's numerous advantages, this model organism has several limitations. As a model for monitoring the toxicity of environmental pollutants, zebrafish have some disadvantages,suchaslowsensitivityandinconvenientstatisticalexperiments[3–6].

In general, a good animal model should have all or most of the following characteristics: (i) structural simplicity that also incorporates the basic cellular processes that more complex organisms have; (ii) easy accessibility for research; (iii) easy and economical to manufacture in the laboratory; (iv) prone to genetic changes; and (v) if possible, have a relatively small and stable genome [7]. The most popular fish species preferred

**Citation:** Çelebi, H.; Bahadır, T.; Sim¸ ¸ sek, ˙ I.; Tulun, ¸S. *Danio rerio*: A Sustainable Model for Monitoring Pollutants in Aquatic Environments. *Environ. Sci. Proc.* **2023**, *25*, 69. https://doi.org/10.3390/ ECWS-7-14310

Academic Editor: Athanasios Loukas

Published: 3 April 2023

**Copyright:** © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

in experimental processes are listed as *Danio rerio*, *Carassius auratus*, *Oryzias latipes*, *Poecia Reticulata*, *Gasterosteus aculeatus*, *Oncorhynchus mykiss*, *Takifugu rubripes*, and *Xiphophorus hellerii.* Research on zebrafish has become more popular in the last decade. *Danio rerio's* high fertility rate (ability to fertilize approximately 200–300 eggs every 5–7 days), economic maintenance, and ease of genetic modification make *Danio rerio* an alternative and valuable vertebrate model compared to other species [8]. The use of zebrafish as a model for toxicity studies is carried out according to standards. These standards are the Zebrafish Toxicity Test, listed as British standard BS/EN/ISO 7346-3-1998, German standard DIN/EN/ISO 7346-3-1998, and Chinese standard GB/T13267-91, OECD n 203-236-473-487-489-490 [9,10]. *Danio rerio* (*Cyprinidae* family: freshwater teleost) is considered a model organism in many research areas, especially in health and pollution detection. In this study, we describe the criteria for the use of this fish species as a model for research in environmental toxicology and argue that *Danio rerio* is an ideal bio-indicator for detecting the toxicity of pollutants.
