Aging Pacific cod (Gadus macrocephalus) from otoliths using Fourier‐transformed near‐infrared spectroscopy

Abstract

For decades, age‐structured stock assessments have been a key component to managing fishery resources worldwide. Fisheries management systems have been under increasing demand to generate a greater volume and quality of age estimates. Traditional aging techniques, which require physical preparation followed by microscopic examination of fish otoliths, are labor‐intensive, expensive, and inherently subjective among individual analysts, making repeatability and precision a challenge. Here we investigated an innovative approach to aging fish from their otoliths using Fourier‐transformed near‐infrared spectroscopy and partial least squares regression models. Models were fit to and validated on spectra and used to microscopically estimate ages of Pacific cod from three years of fishery‐independent otolith data out of the Bering sea. Calibrated and validated models for each year, as well as on an ensemble of the three years, yielded high precision for the multiyear model (R2 = 0.869, RMSE = 0.614, PA = 63%, CV = 7.412), and independent year models (R2 = 0.844–0.891, RMSE = 0.555–0.615, PA = 65%, CV = 6.313–6.775). These metrics of model performance were highly comparable to precision from the traditional microscopic aging approach (R2 = 0.763–0.869, RMSE = 0.639–0.737, PA = 63%–70%, CV = 5.671–6.698). In all cases, a two‐sided Kolmogorov–Smirnov test showed no significant difference between reference and model estimated age distributions. Our results illustrate how Fourier‐transformed near‐infrared spectroscopy can be utilized on otoliths to predict age estimates with substantially greater efficiency, good precision, high repeatability, and no loss in data integrity compared to the traditional microscopic method for aging Pacific cod.

Methodology Advances in Vertebrate Age Estimation

“…An innovative method for determining fish ages through otoliths using Fourier-transform near-infrared spectroscopy and partial least squares regression models has been developed. Compared to the traditional method of counting annuli in the otolith, this approach offers substantially greater efficiency, better precision, and higher repeatability [68].…”

Immunohistochemical and ultrastructural characterization of the inner ear epithelial cells of splitnose rockfish (Sebastes diploproa)

“…Emerging technology such as using Fourier Transformed Near-Infrared Spectroscopy (FT-NIRS) to fish age by estimating its protein absorbance (94)(95)(96)(97) is also at risk. Although FT-NIRS has the potential to greatly increase cost-efficiency and reduce human error, climate change could still introduce unanticipated errors to the FT-NIRS by altering the ratio of otolithic proteins (e.g.…”

Fourier transform near infrared spectroscopy as a tool to predict spawning status in Alaskan fishes with variable reproductive strategies

“…FT-NIR spectroscopy is being increasingly utilized in ecological research due to the ability to distinguish unique molecular structures based on the interaction of nearinfrared light with the chemistry of biological materials. 5,6 Recent applications include otoliths and other hard structures from fishes for age determination 5,[7][8][9][10][11][12] and tissues for quantifying fish condition. 13 A variety of vibrational spectroscopy techniques, including FT-NIR spectroscopy, have already been applied to ovarian tissue to correlate plasma spectra with developing oocyte features to determine the quality of farmed caviar; 14 monitor the growth of fertilized eggs; 15 characterize oocyte development stages; 16 and for the classification or characterization of follicular atresia.…”