Comparison of Four Hard Structures Including Otoliths for Estimating Age in Blue Suckers

Abstract

The Blue Sucker Cycleptus elongatus is an imperiled North American catostomid in need of management and protection. No hard structures are validated for aging this species, but past studies focused on somatic structures such as fin rays and scales. Calculated parameters (mortality, recruitment, growth) that inform management decisions are directly influenced by the accuracy and precision of the hard structure used to estimate age. We identify the most precise and credible structure with which to age Blue Suckers while also completing the first in-depth investigation of their otoliths. We collected Blue Suckers (n = 168) from the lower Wabash River and compared ages estimated from scales, opercles, pectoral fin rays, and lapillus otoliths but were unsuccessful in estimating ages from cleithra. We identified structure bias between all structures and found scales (n = 67; maximum = 11 years, mean = 8.2 years) and opercles (n = 65; maximum = 15 years, mean = 8.3 years) to be substantially less precise than pectoral fin rays and lapillus otoliths. We found that otoliths (n = 128; maximum = 42 years, mean = 13.5 years) were more precise than fin rays (n = 167; maximum = 20 years, mean = 9.6 years) and yielded a much higher range of ages. We could not identify any range of ages or total lengths in which (nonlethal) fin ray age could be accurately corrected to (lethal) otolith age. Thin-sectioned otoliths are the gold standard for aging most fishes, including numerous age-validated catostomids, and the credibility of Blue Sucker otolith age estimates was additionally supported by a strong correlation between whole lapillus mass and estimated age (R 2 = 0.89). Overall, evidence indicates that Blue Sucker lapillus otoliths yield more precise and credible age estimates than other hard structures.

Development and Application of a Size Structure Index for Blue Sucker

“…However, accurate estimates of age and growth are imperative in understanding the reasons behind differences in PSD values. Comparable estimates of growth may not currently be available for Blue Suckers because fish have MANAGEMENT BRIEF 203 traditionally been aged using pectoral fin rays (Bednarski and Scarnecchia 2006;LaBay et al 2011;Acre et al 2017), but recent studies comparing the use of fin rays versus otoliths to age Blue Suckers have demonstrated that ages that are assigned using otoliths tend to be higher in larger individuals (Carlson et al 2021;Radford et al 2021). Although ages that are assigned by using otoliths and fin rays have not been validated for Blue Suckers, validations that have been performed for other species have demonstrated that otoliths provide more accurate age estimates (Buckmeier et al 2002;Buckmeier and Howells 2003;Lackmann et al 2019).…”

Otolith Weight as an Estimator of the Age of Seriola lalandi Valenciennes, 1833 (Carangidae), in the Southeastern Pacific

“…Age assignments are among the most important biological measures in fishery management [9]; spawner biomass, mortality, growth, recruitment and age at maturity in particular can be misconstrued if age estimators are inaccurate [3,4]. Consequently, biological reference points, which are used in inferring stock status in fisheries and are the targets or thresholds in fishery management, can be affected by an accurate estimate of age and, particularly, individual growth rates [39].…”

“…An accurate estimation of the age and growth of fish populations is a critical issue in stock assessment, population dynamics and successful fishery management [1,2]; specifically, spawner biomass, mortality, growth, recruitment and age at maturity in particular can be misconstrued if the age estimators are inaccurate [3,4].…”

“…Age structures in fish populations have traditionally been estimated by interpreting marks in bone structures such as scales and otoliths; the opercular bones of fish [4,5] have also been used, as has the analysis of annual rings in the otolith, one of the most common methodologies, which requires an initial preparation of the otolith (embedding, sectioning and polishing), and a microscopic examination and counts of the annuli [6]. This process is generally time consuming, and interpreting the annuli requires expertise; consequently, age determination from hard structures is very expensive [7] and is highly subject to the researcher's skills [8].…”

The Sport Fish Restoration Program as a Funding Source to Manage and Monitor Bowfishing and Monitor Inland Commercial Fisheries

“…These native species are being identified as having much longer lifespans and slower life history pace than formerly recognized (e.g., Bigmouth Buffalo: validated ages of up to 100+ years, the oldest age‐validated freshwater fish; Black Buffalo Ictiobus niger: a sole specimen from Michigan aged at 56 years [Lackmann et al 2019]; a Smallmouth Buffalo I. bubalus specimen from Oklahoma aged at 62 years [Snow et. al 2020]; Blue Suckers Cycleptus elongatus aged up to 42 years [Radford et al 2021]). These species mature at much older ages than formerly recognized, often show irregular recruitment, and exhibit sexual size dimorphism, with the largest fish removed being old females (Scarnecchia and Schooley 2020).…”