Fisheries managers use population models to determine the level of 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 aims 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) will conduct a lab study to determine if we can identify whether individual herring are immature (have never spawned), primiparous (have spawned only once), or repeat spawners. Researchers are testing to see if the age at first spawn can 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).
We will identify what percent of each age class is represented in the spawning stock. We will also determine whether scale analysis can be used in place of ovary histology to determine age at first spawn. Data on relative contributions of different age classes is required to improve herring population estimates.