Evaluation of spikedace Meda fulgida and loach minnow Tiaroga cobitis repatriations

Authors: Anthony T. Robinson, Clayton D. Crowder

Year: 2011 (xliii)

Abstract

Spikedace Meda fulgida and loach minnow Tiaroga cobitis, two federally-threatened species, have extant populations in few streams in Arizona and New Mexico and therefore repatriations are primary actions to recover these species. Since 2007, these two species have been repatriated to four streams in Arizona: Hot Springs Canyon, Redfield Canyon, Fossil Creek, and Bonita Creek. Success (population establishment) of these repatriations has been hard to judge because of the adherence to a strategy of annual stockings and difficulty in detecting individuals during monitoring. In Hot Springs Canyon, numbers of spikedace and loach minnow captured increased each year from 2008 thru 2010, and young-of-year were captured each year indicating that both species may have established populations in this stream. Numbers of spikedace or loach minnow captured or observed in the other three streams were much more variable during the same time period, and often only adults were captured, so it is far less certain if either species have established populations in these streams. Environmental features such as gradient or amount of suitable mesohabitat may influence the likelihood that either of these species establishes a population in repatriation streams. Gradient over a 5 km distance at historically occupied sites was less than about 2% for loach minnow and less than about 1.0% for spikedace. However, gradient over 5 km was greater than 1% through all of the repatriation streams: 1.1% in upper Bonita, 1.3% in lower Bonita, 1.5% in Hot Springs Canyon, 2.0% in Redfield Canyon, and 2.7% in Fossil Creek. Hot Springs Canyon has more cobble riffles and sandy runs than the other three streams, and so may have the best habitat for loach minnow and spikedace. Presence of green sunfish may have affected the likelihood of population establishment in Redfield Canyon and lower Bonita Creek; efforts to eradicate this nonnative species are ongoing. After cessation of repatriation efforts, continued annual monitoring for at least three years (the approximate life-span of these species) will be necessary to determine if these two species have established populations in the repatriation streams.