A Nonlethal Aging Technique for Threatened, Endangered, and Sensitive Fishes

Typical morphological structures used for aging fish include scales, otoliths, spines, opercular bones, vertebrae, branchiostegal bones, and fin rays.  Many of these structures are either unreliable for aging many native sucker species, or their use requires the fish to be sacrificed.  Pectoral fin rays offer a nonlethal and reliable alternative to aging native, sensitive, or listed fish species.  Since 1999, BIO-WEST, Inc., has developed, refined, utilized, and benefited from employing a nonlethal aging technique to understand the recruitment patterns of a wild, self-sustaining population of razorback sucker (Xyrauchen texanus) in Lake Mead, Arizona and Nevada.  To date, we have successfully aged 360 wild, naturally produced razorback suckers from Lake Mead.  BIO-WEST, Inc., has expanded the use of this technique to successfully age nearly 320 razorback suckers and 145 flannelmouth suckers (Catostomus latipinnis) captured from the Lower Colorado River. More recently, we have successfully aged 28 native suckers from Lake Powell, Utah.  This aging technique has demonstrated that reliable, nonlethal aging of rare and long-lived fishes is feasible. Furthermore, this technique has applicability to provide valuable ecological and management insight into a variety of fishes, even those considered to be threatened, endangered, or otherwise imperiled.