Estimating Largemouth Bass Age: Precision and Comparisons among Scales, Pectoral Fin Rays, and Dorsal Fin Spines as Nonlethal Methods

Reid L Morehouse Steven B Donabauer

doi:10.4172/2150-3508.1000074

Abstract

Scales are commonly used to age largemouth bass since the samples are easy to extract and process. Yet, scale annuli are often difficult to interpret among the largest (and presumably oldest) individuals. The goal of this study was to determine whether a more precise nonlethal structure could be used to age largemouth bass. We examined scales, pectoral fin rays, and dorsal fin spines from largemouth bass collected from six glacial lakes in northern Indiana. Collectively, 861 structures were aged by three analysts and post-concert reads concluded with 85%, 94%, and 99% agreement for scales, pectoral fin rays, and dorsal fin spines, respectively. Pre-concert exact (± 0 years) percent agreement among age analysts was highest for dorsal fin spines (27%) followed by pectoral fin rays (23%) and scales (2%). Mean coefficient of variation was lowest among dorsal fin spines (16%) followed by pectoral fin rays (22%) and scales (37%). Scales exhibited the most variability and bias, while dorsal fin spines were the least variable and most unbiased structure. We encourage researchers to use scales for younger fish and dorsal fin spines for larger fish when both: (1) nonlethal methods and (2) a higher standard of precision are sought to evaluate specific management objectives.

Highlights

Largemouth bass Micropterus salmoides are among the most sought after sport fish in the United States
Post-concert reads concluded with 85%, 94%, and 99% agreement for scales, pectoral fin rays, and http://astonjournals.com/faj dorsal fin spines, respectively
Exact percent agreement (±0 years) among analysts was lowest for scales (2%; Table 1) followed by pectoral fin rays (23%; Table 2) and dorsal fin spines (27%; Table 3)

Summary

Introduction

Largemouth bass Micropterus salmoides are among the most sought after sport fish in the United States. The United States Fish and Wildlife Service [1] conducted a nationwide survey that revealed 40% of all freshwater anglers target largemouth bass. In a 2005 angler survey, respondents ranked largemouth bass as the second most important species to manage in Indiana only behind bluegill Lepomis macrochirus [2]. Accurate and consistent age determination is a key aspect of managing sport fish populations [3]. Scales are the most commonly used calcified structure for determining the age of black bass [4, 5] since they are easy to extract and process. Researchers have demonstrated that otoliths are the most precise and unbiased structure to age largemouth bass [6,7,8].

Objectives

Methods

Results

Conclusion