it is not an necessarilly an ESA thing. the muckleshoots allow sport fishing on their hatchery chinook in the eliot bay bubble fishery which provided many days of excellent fishing this last summer(over 20 kings for me). it is probably just to protect the spawning stock once they are in the river system and to discourage people from targeting kings which will negatively impact the the wild kings in the system
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"time is but the stream I go a-fishing in"- Henry David Thoreau