Escapement is a term used in salmon management to mean, quite simply, how many salmon are able to “escape” premature death and complete their full life cycle. These escapees have run the gauntlet of natural mortality, recreational fishing, commercial fishing, and other life-threatening episodes for the opportunity to spawn in freshwater. Escapement is estimated by a number of different methods including fish counts (e.g., at a weir or dam viewing window) and carcass surveys (i.e., counting the dead salmon on spawning grounds). For salmon managers, the amount of escapement for each salmon run informs population estimates and appropriate fishing quotas and other management strategies for future fishing seasons.
Phenology is the study of seasonal or periodic cycles in ecosystems. It is, essentially, “nature’s calendar.” For fish, phenology is often linked to timing of important life events such as spawning, migrations, and hatching. These events are triggered by non-biological factors like day length, temperature, and precipitation. If the timing of the main “cue” shifts, the alteration can have significant implications for the fish populations that have evolved to optimize the timing of their life events with that factor.
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Kovach, R.P., Ellison, S.C., Pyare, S., Tallmon, D.A., 2015. Temporal patterns in adult salmon migration timing across southeast Alaska. Glob. Chang. Biol. 21, 1821–1833. doi:10.1111/gcb.12829