'Estimating Fecundity and Age: Auto-Diametric and FT-NIR Spectroscopy Methods'

This project investigated novel methodologies for estimating two key biological parameters, fecundity and age, for rockfish (Sebastes). Ongoing fecundity and length-at-age estimates for rockfish allow fisheries researchers to build reproductive and growth histories spanning across many years and estimate productivity at a given time in a fish’s life. Every year, ocean conditions and available energy resources fluctuate, resulting in varying egg production and mean size-at-age. This is crucial to monitor now, as ocean temperatures are on the rise. Fecundity and age estimates are important factors when creating sustainable fisheries management plans, however, the amount of time required to estimate fecundity by manually counting eggs, and to estimate age by the identification of growth increments on otoliths means that these types of biological data are not always available for all species. To improve fecundity data availability, we used an efficient, time-saving auto-diametric method to develop calibration curves for estimating fecundity from the unfertilized eggs of three rockfish species, Rosy rockfish (Sebastes rosaceus), Yellowtail (Sebastes flavidus), and Chilipepper (Sebastes goodei). Each curve used the relationship between mean egg diameter from a sample and egg density to estimate fecundity. Once a calibration curve is developed, fecundity can easily be estimated by semi-automated imaging and measurements of mean egg diameter instead of by the tedious traditional methods. Differences in calibration curve intercepts among the three species were statistically significant, indicating that each rockfish species requires its own curve. Determining growth is also time-consuming and expensive. To improve age collection data, we investigated a new methodology using near-infrared (NIR) spectroscopy as a proxy for age in Chilipepper rockfish.