Post-stocking survival and movement of telemetered bonytail Gila elegans in Lake Havasu

Authors: Christine M. Adelsberger, Abraham P. Karam, Paul C. Marsh

Year: 2010 (xlii)

Abstract

Perseverance of bonytail Gila elegans in the Colorado River Basin relies entirely on stocking and Lake Havasu is one of few locations where they are occasionally contacted. Little information is available concerning the basic ecology of this critically endangered species and a limited number of telemetry studies have been conducted. Only one bonytail telemetry study has previously occurred in Lake Havasu and its results indicated a majority of telemetered fish dispersed near shore or in coves. Unfortunately, high mortality of tagged fish prevented conclusions from being drawn about seasonal dispersal or habitat preferences of bonytail in that system. This study examined post-stocking dispersal and mortality of bonytail stocked in Lake Havasu. In April 2010, 20 bonytail were implanted with 90-day acoustic transmitters and tracked actively by boat and passively with submersible ultrasonic receivers for three months. Fish dispersed between 2.6 km downstream and 27.1 km upstream of the stocking location, and were found between 1 and 503 meters from shore during active tracking events, averaging 129 meters from shore. By the end of the study, one mortality was confirmed using SCUBA. A tag retention study conducted at Dexter National Fish Hatchery and Technology Center from July-October 2010 confirmed our surgical techniques did not affect the health or growth of implanted fish and suggested that a larger, 6-month tag may be used for future bonytail telemetry studies.