Quality biological sampling is a fundamental requirement for all kinds of work on diagnosing diseases and screening for pathogens. Fish sampling requires specific techniques and skills to collect good biological samples for accurate disease diagnosis. WorldFish and partners are developing a package of practices on fish sampling protocols for routine disease diagnostics and outbreak investigations in tilapia, carp and catfish production systems. These sampling protocols provide guidance and training to project team members, researchers, resident veterinarians, extension officers and farmers tasked with collecting quality biological samples for laboratory diagnosis whenever disease outbreaks occur on farms or hatcheries.