A transformative approach to ageing fish otoliths using Fourier transform near infrared spectroscopy: a case study of eastern Bering Sea walleye pollock (Gadus chalcogrammus)

Abstract

We investigated the use of Fourier transform near infrared spectroscopy (FT-NIRS), which is a method of measuring light absorbance signatures, to derive ages from eastern Bering Sea walleye pollock (Gadus chalcogrammus) otoliths. This approach is based on a predictive model between near infrared spectra in the otolith and fish age, which is calibrated and validated. The advantage of FT-NIRS over traditional methods is the speed and repeatability with which age estimates are generated. The application of FT-NIRS to walleye pollock otoliths yielded r2 values between 0.91 and 0.95 for the calibration models and good validation performance (between 0.82 and 0.93). This approach can be expected to predict fish age within ±1.0 year of age 67% of the time. When comparing approaches, the FT-NIRS had as good or slightly better precision (75% agreement) than the traditional ageing (66% agreement) and showed little or no bias at age before 12 years of age. Once the predictive FT-NIR model is calibrated and validated, age estimates using FT-NIRS can be done at 10 times the rate compared to traditional methods.

Age estimation of barramundi (

“…The potential use of FT-NIR to predict the age of otoliths has been demonstrated in several recent publications (Wedding et al 2014;Helser et al 2019;Passerotti et al 2020aPasserotti et al , 2020b, including for barramundi (Robins et al 2015). The results found in the present study, using barramundi otoliths from multiple seasons, are comparable to those of previous studies and to the traditional method of aging barramundi through reading sectioned otoliths.…”

“…Many otoliths are read several times, either by the same reader or independent readers, to verify the determined age. It is estimated that over 60 000 otoliths are collected and aged in Australia each year (Robins et al 2015), New Zealand ages between 30 000-40 000 annually (Moore et al 2019), whereas in the federally managed waters of Alaska, over 352 000 ages were estimated between 2009 and 2018 (Helser et al 2019).…”

“…Recently FT-NIR has shown promise in ageing otoliths of saddletail snapper (Lutjanus malabaricus; Wedding et al 2014), barramundi (Lates calcarifer) and snapper (Pagrus auratus; Robins et al 2015), eastern Bering Sea walleye pollock (Gadus chalcogrammus; Helser et al 2019) and red snapper (Lutjanus campechanus; Passerotti et al 2020a, b). FT-NIR has also been used to successfully age the vertebrae of hammerhead (Spyrna mokarran) and spot-tail sharks (Carcharhinus sorrah; Rigby et al 2016), and to age the dorsal fin spines, vertebrae and fin clips of deepwater sharks (Squalus magalops, Squalus montalbani; Rigby et al 2014).…”

Classification of fish species from different ecosystems using the near infrared diffuse reflectance spectra of otoliths

“…Recently, NIR spectroscopy has been applied in a few studies of biodiversity and ecological physiology studies. 31,32 Applications of NIR spectroscopy in fisheries science are currently limited, with five published studies having focused on biological structures such as otoliths of marine fishes [33][34][35] or shark vertebrae. 36,37 Traditional approaches to determine fish age from otoliths are often time-consuming and expensive, and can include observational subjectivity.…”

“…In contrast, NIR spectroscopy methods have shown the potential to increase the efficiency and improve the repeatability of ageing studies. 35 Near infrared spectroscopy has offered new possibility for classification of fish otoliths based on spectral properties. The ability of near infrared radiation to penetrate samples to a great depth 38 provides unique opportunity for capturing otoliths' capacity as biochronometers.…”