Chapter 4: Choice of Structure for Estimating Fish Age and Growth
Quinton E. Phelps, Sara J. Tripp, Martin J. Hamel, Ryan P. Koenigs, and Zachary J. Jackson
A variety of techniques have been used to estimate age of fishes, including direct observation (i.e., monitoring of individual fish over time), statistical evaluation of length-frequency distributions, and analysis of calcified structures (DeVries and Frie 1996; Quist et al. 2012). Estimating ages for individual fish provides information on age structure of populations and can be used to estimate dynamic rate functions. Fishery managers use age-based population characteristics along with other information (e.g., catch per effort, length structure) to inform management decisions.
Use of calcified structures is the most widespread method for estimating age and growth of fishes because calcified structures are generally easy and inexpensive to collect and process. Although calcified structures can provide accurate and precise estimates of age (Alvord 1953; Hales and Belk 1992; Buckmeier et al. 2002; Jackson 2007; Seibert and Phelps 2013), accuracy and precision vary among structures, species, and readers (Isermann et al. 2003; Hurley et al. 2004; Edwards et al. 2005; Kowalewski et al. 2012). Accuracy and precision of age estimates represent two of many factors that must be considered when choosing a calcified structure for age estimation. The purpose of this chapter is to provide an overview of the considerations associated with choosing a structure and a general synthesis of the most common calcified structures used by scientists to estimate age of major fish taxa. Many of the considerations associated with choosing a structure are directly or indirectly discussed in Chapter 3; therefore, the emphasis of this chapter will be on reviewing previous research focused on validation and verification of calcified structures for estimating the age of freshwater fishes in North America.