Age at First Spawn for Herring in Prince William Sound, 2012-2015, EVOS Herring Program

These data are part of the Herring Program of the Exxon Valdez Oil Spill Trustee Council (EVOSTC), project numbers 12120111-J and 13120111-J, which is a multi-faceted study to determine why herring populations in Prince William Sound (PWS) remain depressed since the early 1990s. Fisheries managers use population models to determine the level of commercial fishing to allow annually. These models are based on the number of fish observed during the spawning period. However, this method fails to count a portion of the younger fish, because they do not participate in the spawn. This project, conducted from 2012 to 2015, aimed to improve the estimate of the total herring population by examining the percent of fish of various ages that join the herring stock after the spawning period. Using a captive population of wild adult herring, researchers from the National Oceanic and Atmospheric Administration (NOAA) in Juneau, Alaska conducted a lab study to assess the feasibility of identifying whether individual herring were immature (have never spawned), primiparous (have spawned only once), or repeat spawners. Researchers tested whether the age at first spawn could be determined by analyzing the history of egg development in the ovaries (histology), or by using growth increments on herring scales (which is a less expensive method). This dataset is six comma-separated value (csv) files. Three files relate to the laboratory component of the study, including water temperature herring were reared in (EVOSTC_Project 13120111-I_Primiparous Herring_Final_2011_lab_water_temp.csv), photoperiod during the laboratory experiment (EVOSTC_Project 13120111-I_Primiparous Herring_Final_2011_lab_photoperiod.csv), and results of histological analysis of post-spawn herring, as well as biological characteristics of those fish (gender, fork length, mass, and gonadosomatic index; EVOSTC_Project 13120111-I_Primiparous Herring_Final_2011_lab_histology.csv). One file pertains to the 2012 field-caught fish, including results of histological analysis, scale growth measurements, fish age, and biological characteristics of the fish (EVOSTC_Project 13120111-I_Primiparous Herring_Final_2012_field_sample_histology.csv). The final file pertains to the 2013 collection of herring from Prince William Sound spawning aggregations, and includes fish age, biological characteristics, and scale growth measurements (EVOSTC_Project 13120111-I_Primiparous Herring_Final_2013_spawning_aggregations.csv). The EVOSTC_Project 13120111-I_Primiparous Herring_Final_attributes.csv file serves as a data dictionary, defining the columns of the data files described above.