Bycatch is any catch that is not the main objective of a fishing fleet. It is further defined as anything that is caught and discarded at sea, including targeted fish that are discarded due to undesired quality or size, or anything that is caught and taken back to port but that was not the target of the fishing trip, that is, “nontarget species.”


All fishing methods have some level of environmental impact, and that impact is often measured in terms of fishing mortality of nontarget species – including sharks, rays, finfish and sea turtles.


Each year, ISSF supports multiple initiatives to track, report on and minimize unwanted bycatch among purse seine fishing vessels, as well as conduct research across all fishing methods to define and promote best practices that positively impact this important issue.

Since its inception in 2009, ISSF has dedicated considerable effort to better understand the issues of concern in global tuna fisheries by using scientific information – primarily from scientific observer programs – to quantify relative impacts.

At the same time, ISSF conducts at-sea research to investigate potential mitigation measures, leads workshops with tuna vessel skippers to share mitigation techniques and to seek input about other potential mitigation measures, and advocates to global tuna RFMOs for the adoption of mandatory bycatch data-collection and mitigation measures.