Introduction
Release mortality rates are a key factor in determining the incidental and total mortality impacts of fisheries, particularly for non-retention or mark-selective fisheries that release both legal and sublegal sized fish. These overall release mortality rates depend on many factors. For example, fish size, lure type, and wound location and severity have typically been found to be statistically significant factors associated with mortality of incidentally caught Chinook in Chinook non-retention troll fisheries (Wertheimer, 1988).
Unfortunately, this dependence on specific fishing practices and conditions leads to release mortality rates that are highly variable between studies and fisheries, and makes it difficult to determine an appropriate rate for fisheries that have not been subject to expensive in situ studies, such as the Columbia River upriver spring Chinook recreational fishery. Due to vastly improved abundance of upriver spring Chinook over the last decade, increased fishery opportunity, and a move to mark-selective fishing methods, there is an urgent need to determine the best available estimate of release mortality rates for the spring Chinook recreational fishery.