Aquatic innovation: Genome editing routes to designer fish

Ornamental fish constitute a significant sector of the global aquaculture industry, contributing substantial economic value through the aquarium trade, eco-tourism, and export markets. Beyond their aesthetic appeal, they serve as important model organisms in biomedical and developmental research, while also supporting livelihoods in many developing countries. The demand for novel varieties with enhanced colouration, unique morphological traits, and improved resilience to environmental stress has increased markedly in recent years. Conventional selective breeding, although effective, is time-consuming and limited in its precision. Genome editing technologies, particularly the CRISPR-Cas9 system, have emerged as transformative tools for accelerating trait development in ornamental fishes. CRISPR-Cas9 offers high precision, efficiency, and cost-effectiveness compared to earlier platforms such as transcription activator-like effector nucleases (TALENs) and zinc-finger nucleases (ZFNs). Its application enables targeted modifications of genes influencing pigmentation (e.g., mitfa, slc24a5, kit), fin morphology, growth patterns, and stress tolerance. In addition to generating novel phenotypes of commercial interest, genome editing can improve disease resistance, enhance adaptation to captive environments, and produce sterile strains to mitigate risks of genetic pollution from accidental releases. This review comprises recent advancements in the application of genome editing in ornamental fish.