Changes in fish populations and habitat in East Fork of the Black River from 1988 to 2009

Authors: Kelly J. Meyer, Michael Lopez, Mark Terrill

Year: 2010 (xlii)

Abstract

In 1988, Arizona Game and Fish Department did a survey on fish habitat and fish numbers In the East Fork of the Black River. Since 1988, there had been numerous changes in the stream including: removal of cattle from the upper drainage, construction of pools in the stocked section of stream, changing the stocking from rainbow (Oncoryhhnchus mykiss) to Apache trout (Oncoryhynchus gila apache), and increase of exotic crayfish in the stream. In 2009, we repeated the survey of habitat and fishes at the reference sites. The stream habitat has had statistically significant changes. The stream is now significantly narrower, has more stable banks, more canopy cover, less fine sediments, more rubble, and more pools; these changes are consistent with removal of cattle grazing. The stream also had less rooted vegetation in the stream channel which is consistent with establishment of crayfish. We also found significant and dramatic changes in the fish fauna. Brown trout (Salmo trutta) and speckled dace (Rhinichthys osculus) numbers increased by fourteen fold and three fold respectively. Sonora (Catastomus insignus) and desert suckers (Catostomus clarki)decreased in number by six fold and fifteen fold respectively. Loach minnow (Tiaroga cobitis) have not been found in this stream since 2005 and are likely extirpated. Stocked trout were of low density (0.4 fish/100 meters) in all studies over the past twenty years, with brown trout outnumbering stocked trout at 250 to 1 or more. In addition, stocked trout were not found upstream of areas stocked (where loach minnow have been found). Most fish captured had marks on them from crayfish predation. The biggest threat to loach minnow and native suckers in this drainage are crayfish and exotic wild brown trout.