Expanded Adult Biomass Surveys

PROJECT

Expanded Adult Biomass Survey

Background

Since 1993 the Prince William Sound Science Center has annually conducted surveys of the spawning biomass using hydroacoustic techniques.  This information can be used as a biomass index in the age-structure-analysis model for determining the population biomass.  In most years the focus has been on the main spawning stock and there hasn’t been an effort to quantify smaller stocks.  It is possible that fish spawning outside the primary spawning area may include a significant portion of the biomass, so an effort is underway to try and quantify the biomass of fish spawning outside of the primary spawning location.

Methods

Surveys are conducted using a towed hydroacoustic sensor in the same manner as is used with the primary spawning biomass.  The expanded survey effort is primarily focused on the spawning areas along Montague Island, where there have been consistent small spawning events for the past ten years.  Other areas will be surveyed if there is an indicator of herring present.  Most often this is detected through whale sightings.

What we will learn

By surveying the biomass outside the primary spawning location we can provide a more accurate biomass estimate in PWS.  The expanded surveys also provide an opportunity to observe if stocks elsewhere in the Sound are growing or shrinking.