Book excerpt: This technical document has been developed in recognition of the increasingly diverse demands for water from irrigation systems and the need to introduce more holistic land uses into conventional irrigation management. Despite historical precedents and efforts in the twentieth and early twenty-first centuries, the potential for the integration of fish production (capture fisheries and aquaculture) and irrigation systems has yet to be fully realized. Capturing these underutilized opportunities for the integration of fisheries and aquaculture could significantly increase local economies, food security, household incomes and livelihood diversity within irrigated agriculture systems. To re-examine the potential of fisheries in irrigation systems, the concept of the extended command area (ECA) is used, expanding the conventional definition of an agriculture irrigation command area. The reason for this expanded definition is because all elements of an irrigation system, from upstream dam storage to downstream drainage areas, offer opportunities for increasing fish production. Many of these opportunities may be realized at no additional cost to the main irrigated crop. This document provides an introduction to the ways fisheries and aquaculture already co-exist with irrigation and explores the threats and opportunities that arise from this. A key concept for sustaining and enhancing inland capture fisheries is “connectivity”– a fundamental basis for ensuring adequate environmental conditions to allow fish to flourish within an aquatic ecosystem such as a river, lake, or wetland. Improving connectivity within an ECA can restore elements of ecological services that may have been compromised or degraded through irrigation, water management or through other rural infrastructure development such as road construction. Practical application of the integration of fisheries and irrigation systems is explored through the use of the Ecosystem Approach to Fisheries (EAF) in the context of irrigation systems. The proposed process links the development of an EAF management plan for fisheries to irrigation system operation and is given the acronym EAFm-i. A key part of this linkage is an assessment of water resources in the system and the management of water for delivery to fisheries. Additional tools to support the EAFm-i process are also described. Although the experience and approach are drawn largely from irrigation systems and inland capture fisheries in Southeast Asia, the application of the ECA concept and approach will be relevant to any irrigation or water management system where there is potential for the closer integration and harmonization of fisheries and irrigation systems and where water users are interested in realizing this potential. This short paper is intended to encourage fisheries and irrigation specialists to engage in greater dialogue and cooperation over the integration of fisheries into irrigation planning and to support piloting of an EAFm-i process, which can be the basis for further development.