Marine mammal interactions with fisheries are a growing major world-wide issue with both substantial ecological and economic consequences. Most longline fisheries operating around the world are seriously affected by these interactions i.e. marine mammals eating fish directly from fishing gear.

To begin addressing these issues globally, the first international workshop dedicated to odontocete depredation on demersal longlines operating in high latitudes was organised by the Coalition of Legal Toothfish Operators (COLTO) in Punta Arenas, March 2016. This workshop emphasised the urgent need to find global solutions to this issue.

The workshop concluded that routine data collection framework across fisheries confronted with interactions with odontocetes is important for a better understanding of depredation and for solutions to be developed, both locally and globally.

Using the COLTO workshop as an excellent example of international science, industry, government and NGO collaboration, this resulting document aims to provide basic guidelines for observer programmes that are relatively new to dealing with marine mammal interactions or are interested in expanding their observation efforts. It is based on ten years of experience around the islands of Kerguelen and Crozet (Southern Indian Ocean).