Atlantic Herring (Culpea harengus) Spawning Dynamics in the Gulf of Maine as Inferred by Acoustic Methods

The Atlantic herring (Clupea harengus) is the center of the Gulf of Maine food web. It sustains a modest fishery of which a large portion is used as bait for the American lobster (Homarus americanus) fishery, the second most valuable fishery in the United States. In 2012, the Gulf of Maine experienced temperatures much warmer than normal which likely led to cascading impacts throughout the region. Herring typically spawn in the early fall, though the time of spawning events varies from year to year. I examined data from an acoustics survey performed by the Gulf of Maine Research Institute in September through early November of 2012, focusing on spawning Atlantic herring schools. This acoustics survey was unique in that it utilized ten individual fishing vessels as research platforms. This allowed for a wide spatial coverage including 38 transects spanning the entire coast of Maine (more than 200 miles of coastline). Due to the low cost of chartering the vessels, the survey was repeated weekly for nine weeks. In order to perform inter-vessel comparison of acoustic data, all acoustic equipment needed to be calibrated. The calibration process is described in Chapter 1. Chapter 2 describes the results of the first year of the survey, focusing on the location and timing of spawning herring schools. Although spawning is hypothesized to take place in the early fall (Aug 15 - Sept 15), potential spawning schools were found throughout the duration of the survey. This may be the result of warm temperatures in 2012, although it is difficult to draw conclusions with just one year of data. The data leads to questions regarding how much we really know about Atlantic herring spawning dynamics in coastal Maine and if current management practices, including seasonal closures are being appropriately applied.