When conducting acoustic surveys of juvenile herring we have traditionally only made one observation per location. The ability to determine overwintering survival then depends on the snapshots providing accurate estimates of the juvenile herring population. There are several sources of error that may affect the population estimate from a single survey so we designed a project to test how consistent our population estimates from acoustics are.
Hydroacoustic surveys were conducted in Simpson and Windy bays each night for three nights. These surveys were repeated approximately every two weeks in the fall (October-December 2013) and late winter (February-March 2014) to provide a total of twenty-four surveys in each bay. Subsurface trawls were used to collect fish to determine the mix of fish present during each survey.
The primary purpose of this research was to determine how consistent acoustic estimates of herring populations are. The movement of fish in and out of a bay can lead to inconsistencies that need to be considered. We investigated if the phase of the moon or the tides affected the population estimate from the surveys.