PROJECT

Background

Available evidence suggests the population of pollock in Prince William Sound (PWS) increased in the early and mid-1990s when the PWS herring population began to decline. Researchers have hypothesized pollock in PWS are limiting the recovery of herring due to their high abundance and the potential for mortality of herring from direct interactions. This project will conduct research and monitoring activities to assess the pollock population in PWS and investigate interactions between pollock and herring. Winter research surveys will quantify the PWS pollock spawning population and summer monitoring surveys will reestablish a 26-year index of abundance for pollock. We will provide information to assess herring mortality from interactions with pollock including the transmission of pathogens and predation.  

Methods

Acoustic-Trawl surveys along with bottom trawl surveys will be used to assess pollock abundance in PWS. Mid-water trawls for the sampling of acoustic backscatter will be conducted in tandem with trawl hauls to identify the species composition of acoustically observed fish aggregations. A sample of ~ 200 pollock per trawl will be collected, measured, and cataloged. Additionally, a bottom trawl survey will be conducted on the ADF&G R/V Solstice. The ability of pollock eggs to transmit parasites to herring will be determined by feeding wild pollock eggs to laboratory colonies of pathogen-free herring under controlled conditions. Analysis of stomach contents from pollock and other dominant groundfish collected on the surveys will evaluate the presence of herring and quantify consumption rates. These samples will then be analyzed with genetic techniques in a lab. 

What we are learning

The interactions between pollock and herring in PWS have been shown to be complex and significant. Our proposed research will fill a void in the current suite of studies taking place to examine major ecological drivers for herring. Our project will also build capacity for other research through sample collections of pollock, other groundfish, and forage fish, and provide a platform during winter and summer on which additional research and observation can occur. Furthermore, the assessment of pollock in PWS will inform the management of the PWS and Gulf of Alaska pollock fisheries.