Validation and Comparison of Age Estimates for Smallmouth Buffalo in Oklahoma Based on Otoliths, Pectoral Fin Rays, and Opercula

Abstract

With an increased interest in nongame fishes such as buffalofishes (Catostomidae, Ictiobus), there is a need for better foundational data on their life history. Bigmouth Buffalo I. cyprinellus, for example, have been found to live for more than a century. Age estimates for other sucker species have similarly suggested long life spans, but validation studies as reference points are often lacking. We conducted a 3-year study on Smallmouth Buffalo I. bubalus in Oklahoma to validate annual increments on three hard part structures (otoliths [lapilli], pectoral fin rays, and opercula) typically used for age estimation. We marked wild fish with oxytetracycline (OTC) injection and stocked those fish into a hatchery pond to create a population of fish with known times since marking. Furthermore, reproduction in the pond allowed us to validate annulus formation in young fish. We analyzed 117 fish and found that otoliths were more reliable, precise, and accurate than the other two structures for detecting OTC marks and counting annuli. Age estimates, from 1 to 61 years, were greatest when otoliths were used, with 99% of estimates corresponding to known time since marking or known age. Otoliths appear to be the only reliable structure for accurately estimating the age of Smallmouth Buffalo within 1 year of actual age, and their use indicates that this species can live for more than six decades in Oklahoma.Buffalofishes (Catostomidae, Ictiobus) are becoming increasingly recognized for their intrinsic roles in the ecosystem (Rypel et al. 2021;Scarnecchia et al. 2021), such as altering water quality (Goetz et al. 2014) and serving as hosts for freshwater mussels (Freshwater Mussel Host Database 2017). Despite this, buffalofishes have historically been viewed as nuisance species that compete for resources with popular sport fish, and their numbers have

Centenarian lifespans of three freshwater fish species in Arizona reveal the exceptional longevity of the buffalofishes (Ictiobus)

“…Fishes provide an excellent opportunity to understand age demographics of wild populations because most species can be aged directly via the thin-sectioned otolith 47 , 56 . Indeed, this technique also allows for age validation of long-lived species 47 , which has been rigorously demonstrated for buffalofishes 16 , 19 , 33 .…”

“…Little is known about Arizona buffalofishes since the 1970s. New sport fisheries have emerged including catch-and-kill bowfishing, which has raised substantial conservation concern nationwide 16 – 21 , 31 – 33 , but conservation angling of buffalofishes (this study) has not previously been reported. Such activities, in practice, imply new game fish status to these species because they are recreationally pursued.…”

“…Otoliths are the most accurate structure for age analysis in fishes 47 , 55 , 56 . Furthermore, Long et al 33 recently age-validated otoliths of smallmouth buffalo, and the validated age-reading protocol that we developed for bigmouth buffalo 16 , 19 , 40 was readily applied to the other buffalofish species because of the otolith’s clear homologous structure (Fig. 2 ).…”

“…Following these results, an Oklahoma state record (for size: 101.5 cm total length and 30.10 kg) smallmouth buffalo I. bubalus was aged via the otolith and found to be 62 years old 45 , more than three times older than their maximum age reported prior to 2019 (18 years) 46 . Otoliths were subsequently age validated for smallmouth buffalo 33 . Despite these advances in knowledge, rising buffalofish sport fisheries, and the crucial importance of accurate age information for sustainable fisheries 47 , the age demographics of Arizona buffalofishes are unknown.…”