This initial Foundation topic consists of two parts; the Biology and Physiology of aquatic invertebrates (e.g. crustaceans and mollusks), followed by consideration of Diseases and Strategies to Maintain Health. Our overall objective is to present students with ideas about form, function, malfunction and aspects of husbandry and welfare which relate specifically to Aquaculture. The emphasis is placed on satisfying physiological and biological requirements in aquaculture, understanding energy flow and optimising culture conditions. The main viral, parasitic and fungal diseases of invertebrates and clinical examination and diagnosis, together with therapeutics, are reviewed. Practical sampling sessions and case studies provide the opportunity to gain some hands on experience. This topic will be a useful starting point for those wishing to gain broad knowledge of the main components of aquatic animal biology and health. Completion of topic will help students to understand legislation, regulations, and policies, as well as to address current issues of aquatic animal welfare.