Pre-Spawn Pacific Herring (Clupea pallasii pallasii) Distribution and Population Estimates in Yaquina Bay, Oregon

During 2014 and 2015, the Oregon Department of Fish and Wildlife (ODFW) Marine Resources Program initiated a pilot program to develop an acoustic survey to determine a pre-spawn population estimate for Pacific herring in Yaquina Bay on the central Oregon coast.  The goal of this survey was to develop a timely population estimate to set a quota for the commercial roe herring fishery, typically executed immediately prior to annual spawning events in February and March, and to describe herring distribution within the bay prior to and following those events.  Acoustic surveys were conducted opportunistically from late January through mid-March and a daily population estimate for Yaquina Bay was developed from each survey.  Acoustic population estimates suggest a buildup of herring biomass in the bay prior to spawning events and a dramatic drop-off immediately following an event.  Distribution of herring within the bay changed dramatically throughout the sampling period, potentially in response to spawning events and freshwater inputs.  Population estimates are compared to those developed from annual spawn surveys, conducted concurrent to the acoustic surveys, by the ODFW.