Parasitic isopods in fish aquaculture: a review of current knowledge and future perspectives

Abstract

Aquaculture has become a dominant contributor to global seafood production, providing essential protein and supporting livelihoods while alleviating pressure on wild fish stocks. However, cultured fish face numerous health challenges, including infestations by parasitic isopods, notably cymothoid and gnathiid species, which cause significant economic losses through reduced growth, compromised health, and mortality. Infestations are usually influenced by host factors, environmental conditions, parasite traits, and aquaculture management practices, including cage design, stocking density, water quality, and interactions with wild fish populations. Pathological effects range from tissue damage and anaemia to impaired growth, secondary infections, and mortality, particularly in juvenile fish. Effective management relies on integrated strategies combining preventive husbandry, environmental manipulation, biological control, selective breeding, and targeted chemical interventions, with an emphasis on reducing reinfection and limiting resistance development. Emerging approaches, including immunotherapy, gene editing, natural compounds, nanotechnology, and biosensors, show promise for sustainable control but remain largely experimental and require further validation. Future research should focus on life-cycle dynamics, host-parasite interactions, and eco-friendly interventions to improve prevention and management in intensive aquaculture systems. This review synthesises current knowledge on parasitic isopods in aquaculture, highlighting the need for integrated, ecologically informed strategies to safeguard fish health, ensure production sustainability, and mitigate economic losses.