This Guidebook provides practical guidance to support the early detection, notification and response to priority diseases affecting tilapia and rainbow trout. It is based on a systematic review of scientific literature, as well as international and regional disease reporting systems and domestic notification frameworks across APEC economies. A structured, evidence-based approach was used to analyse diseases by species and subregion, identifying those of the highest impact and relevance for early detection.

The Guidebook focuses on the early detection of disease through Level 1 diagnosis. Level 1 diagnosis relies on observations of abnormal behaviour, water parameters changes, mortality, and clinical signs at farm level. This is complemented by a basic environmental assessment and veterinary anamnesis. The Guidebook is a practical application for early disease detection called 'Watch, Write and Warn', which aims to support small-scale farmers in the field.