International Journal of Aquaculture, 2025, Vol.15, No.4, 175-183 http://www.aquapublisher.com/index.php/ija 175 Review and Progress Open Access Habitat Degradation and Restoration in Aquatic Ecosystems: Implications for Fish Populations Wenzhong Huang1, Yeping Han2 1 Biomass Research Center, Hainan Institute of Tropical Agricultural Resouces, Sanya, 572025, Hainan, China 2 Institute of Life Science, Jiyang College of Zhejiang A&F University, Zhuji, 311800, Zhejiang, China Corresponding author: yeping.han@jicat.org International Journal of Aquaculture, 2025, Vol.15, No.4 doi: 10.5376/ija.2025.15.0017 Received: 20 May, 2025 Accepted: 29 Jun., 2025 Published: 24 Jul., 2025 Copyright © 2025 Huang and Han, This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Preferred citation for this article: Huang W.Z., and Han Y.P., 2025, Habitat degradation and restoration in aquatic ecosystems: implications for fish populations, International Journal of Aquaculture, 15(4): 175-183 (doi: 10.5376/ija.2025.15.0017) Abstract Aquatic ecosystems provide rich biodiversity and ecological service functions, but also face serious threats of degradation. This study reviews the main habitat types and characteristics of aquatic ecosystems, analyzes the main causes of habitat degradation, such as water conservancy engineering construction, pollution eutrophication, and overfishing, and discusses the impact of habitat degradation on fish population diversity, quantity and life cycle. At the same time, this study reviews a series of aquatic habitat restoration methods such as water conservancy engineering transformation, ecological restoration and ecological management, and discusses the positive role of these recovery measures on the restoration of fish population diversity, resource volume and ecological function. Based on the current research status and future trends, management suggestions such as strengthening comprehensive watershed management, promoting technological innovation and international cooperation were put forward, aiming to provide theoretical support and practical guidance for aquatic ecosystem restoration and fish protection. Keywords Aquatic ecosystems; Habitat degradation; Ecological restoration; Fish populations; Biodiversity 1 Introduction Aquatic ecosystems include various water ecological types such as oceans, lakes, rivers, wetlands, etc., and are an important carrier of global biodiversity. Although freshwater bodies account for only 0.8% of the earth's surface, they are home to about 15 000 freshwater fish species (nearly 50% of the global fish species) (Geist and Hawkins, 2016). A large number of studies have shown that the health of aquatic ecosystems is closely related to the survival of fish populations. In recent years, due to intensified human activities, aquatic habitats have suffered severe damage, and fish populations and diversity are facing a crisis of sharp decline. On the one hand, anthropogenic interference such as pollutant emissions, eutrophication, water conservancy engineering and overfishing has led to a decline in the quality of aquatic habitats, inhibiting the reproduction and growth of fish (Bennett, 2024); on the other hand, the protection and restoration of aquatic habitats are considered to be a key way to maintain and improve the health of fish populations (Theis et al., 2024). This study aims to systematically sort out the characteristics of different habitat types in aquatic ecosystems, causes of habitat degradation and their impact on fish populations, and review the current commonly used habitat restoration technologies and their positive effects on fish resource recovery. Finally, it proposes future research directions and management suggestions to provide reference for aquatic ecological protection and sustainable use of fish resources. 2 Aquatic Ecosystem Habitat Types and Characteristics 2.1 River ecosystem River ecosystems (moving water ecosystems) are one of the most active habitats on the earth, and their main features are continuous flow of water, sufficient oxygen, water temperature and water quality are significantly affected by upstream incoming water. The river presents obvious gradients of hydrological, chemical and
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