DOI: 10.24431/rw1k1a
title: Validation of Acoustic Surveys for Pacific Herring, 2010-2016: EVOS Herring Program

description: These data are part of the Herring Program of the Exxon Valdez Oil Spill Trustee Council (EVOSTC) which is a multi-faceted program to determine why herring populations in Prince William Sound remain depressed since the early 1990s. As part of the Prince William Sound Herring Survey Program (EVOS project number 10100132), from March 2010 through March 2012 castnets and gillnets were deployed in bays of Prince William Sound to validate hydroacoustic surveys as well as to provide an index of juvenile herring during March. In the Cordova harbor castnets were also used to sample juvenile herring during various months of the year. 

Beginning in February 2012, a second study titled "PWS Herring Research and Monitoring: Validation of Acoustic Surveys for Pacific Herring Using Direct Capture" (hereafter referred to as the Direct Capture project") was funded by EVOS as part of an effort to validate herring population estimates and support other herring-related investigations from 2010-2016 (EVOS project numbers 12120111-A, 13120111-A. 14120111-A. 15120111-A, and 16120111-A). Slightly overlapping with the end of the previous PWS Herring Survey project 10100132, field work continued throughout Prince William Sound using castnets and gillnets to validate hydroacoustic surveys as well as to provide an index of juvenile herring during March.In the Cordova harbor, castnets continued to be used to sample juvenile herring during various months of the year. 
Importantly, for the Direct Capture project, a mid-water trawl was purchased for use in additional sampling in conjunction with herring hydroacoustic surveys. Problems with hydraulics prevented its use during the November 2012 herring cruise, however, the trawl was used for all subsequent juvenile herring hydroacoustic surveys. 

The Direct Capture project collected the data needed to estimate useful population level parameters for PWS Pacific herring obtained from acoustic surveys by coupling acoustic transects with direct-capture sampling efforts. Based on the acoustic surveys that occurred during spring and fall research cruises, targeted areas were identified and returned to for short-distance (0.1-1.6 km) trawls concomitant with acoustic surveys. At these targeted locations mid-water trawls were conducted. In addition, gillnet and cast nets were used when the boat was at anchor. 

The 2010-2016 dataset is comma-separated values (csv) files exported from a Microsoft Access database. The data contain measurements of collected fish; logs of gear deployment and catches; a master list of all survey cruises; and collection report summaries (available only for 2010-2012). Fish collected were sorted by species, the total of each species was weighed, and up to 200 fish of each species were individually weighed and measured. Measured herring were grouped into three age categories for purposes of analysis based on standard length: young-of-year (age-0; less than 105 mm), age-1 (106-150 mm), and age-2+ (greater than 150 mm). For 2013-2016, environmental data, including conductivity, temperature, and depth, were also collected during trawl transects using a sensor attached to the trawl gear. Fish collected were later sent to various projects associated with the PWS herring programs for additional analysis, including disease, energetics, and genetics investigations. A list of these projects and the associated EVOS project numbers is provided in Supplemental Information.