External Parasites of Fish: A Comprehensive Overview

Abstract

Fishes are a diverse group of gill-bearing aquatic craniate animals characterized by their limbless bodies. These creatures are susceptible to various diseases, both infectious and non-infectious, which can significantly impact fish populations. One critical factor contributing to reduced fish productivity is parasitic infestation. This paper aims to provide a comprehensive overview of the external parasites that affect fish. In aquatic environments, host-parasite interactions are complex, with crustacean parasites often playing a prominent role in fish diseases and the management of captive and cultured fish stocks. Among the most common crustacean parasites of fish, we find copepods, brachiura, and isopods. Copepods, for example, encompass two major crab families: Ergasilidae and Lernaeidae. In contrast, Branchiura (Argulidae) and Isopoda members, both parasitic, generally exhibit larger body sizes than copepods. While these parasites may cause only mild harm to their hosts when present in small quantities, copepods are the most prevalent crustacean parasites in various aquatic habitats, including freshwater, brackish water, and saltwater. In the context of fish health and productivity, prevention often proves more effective than treatment. Implementing strategies such as strict controls when introducing new fish to a newly established tank, robust quarantine procedures, mechanical removal using forceps, freshwater or saltwater dips, and water treatments involving organophosphates can significantly reduce the incidence of external parasite infestations. Therefore, exercising caution when introducing new fish into a population is essential.