With threats to global biodiversity growing, it is increasingly necessary to examine the frameworks we employ to ensure conservation is successful and effective.Conservation of the ocean and its biodiversity can thus take many forms and area-based fisheries management has been used for centuries to improve the performance of fisheries and reduce their ecological impact. Such measures have also developed and in 2010 the Convention on Biological Diversity (CBD) recognized the importance of protected areas and Other Effective Area-based Conservation Measures (OECMs) in reversing biodiversity loss.Other Effective Area-based Conservation Measures (OECMs) are thus geographically defined sites outside of protected areas that can achieve the sustained long-term conservation of biodiversity and they can be managed by government organisations, indigenous peoples or local communities. The book is an updated version of a report prepared by members of the IUCN Fisheries Expert Group in 2021, following their close involvement in the elaboration and adoption of the concept of OECMs, and subsequent developments at international and national levels. This book focuses on OECMs as applied in marine capture fisheries, referred to as "fishery-OECMs".Included in the book are:A detailed description of this new instrument for managing fisheries and conservation.A complete account of the background and development of the OECM concept.Identification of how OECMs can be used to further economic and conservation goals.This book describes the OECM concept in the context of marine capture fisheries to inform those working, interested or involved in fisheries, conservation and the environment. It also reviews the opportunities and challenges presented when identifying, using and maintaining effective long-term fishery-OECMs, thus ensuring the effective management of fisheries and the conservation of marine biodiversity.