Although the weirs typically function as a barrier to upstream migration, some salmon are often allowed to continue their upstream movement and spawn naturally, both before and after the weir is operated. At the weir, efforts are made to collect salmon for brood stock from a range of run timing components (i.e., early- and late-run). Salmon (especially chum salmon) that have escaped coastal fisheries are often stopped during their upstream migration by weirs placed in the river to catch the fish for use as hatchery brood stock. Escapement Monitoring and Estimation in Japan The first step is to document the methods used to monitor and estimate salmon escapement in the NPAFC member countries.įor convenience, references and links to additional information are found at the bottom of this web page. The Working Group on Stock Assessment is compiling information on the state of knowledge of their spawner escapement data. Escapement data are a basic element in salmon fisheries management, including forecasting adult returns to fisheries. ![]() In addition, knowledge of total run-size for a population (escapement plus catch) is required to compute the survival and productivity of the previous salmon generation and to monitor trends in abundance and/or productivity.Įscapement can be estimated using counting fences, mark recapture, visual surveys including area-under-the-curve, and electronic, video, and hydro-acoustic counters. Knowledge of escapement (i.e., the number of spawners) is necessary to develop spawner recruit relationships and forecast the production of the next generation, including the number of salmon potentially available to harvest. Why is it Important to Know Salmon Escapement? ![]() Salmon Escapement What is Salmon Escapement?Įscapement is the number of salmon that “escape” fisheries (i.e., are not harvested) and return to fresh water to spawn.
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