C.C. Schwartz
R. O. Rye
K.A. Gunther
J.G. Crock
M.A. Haroldson
L. Waits
C.T. Robbins
L.A. Felicetti
2004
<p><span>Spawning cutthroat trout (</span><i>Oncorhynchus clarki</i><span> (Richardson, 1836)) are a potentially important food resource for grizzly bears (</span><i>Ursus arctos horribilis</i><span> Ord, 1815) in the Greater Yellowstone Ecosystem. We developed a method to estimate the amount of cutthroat trout ingested by grizzly bears living in the Yellowstone Lake area. The method utilized (</span><i>i</i><span>) the relatively high, naturally occurring concentration of mercury in Yellowstone Lake cutthroat trout (508 ± 93 ppb) and its virtual absence in all other bear foods (</span><span class="NLM_inline-graphic"><img src="http://www.nrcresearchpress.com/na101/home/literatum/publisher/nrc/journals/content/cjz/2004/cjz8203/z04-013/production/images/medium/ls.gif" alt="" /></span><span>6 ppb), (</span><i>ii</i><span>) hair snares to remotely collect hair from bears visiting spawning cutthroat trout streams between 1997 and 2000, (</span><i>iii</i><span>) DNA analyses to identify the individual and sex of grizzly bears leaving a hair sample, (</span><i>iv</i><span>) feeding trials with captive bears to develop relationships between fish and mercury intake and hair mercury concentrations, and (</span><i>v</i><span>) mercury analyses of hair collected from wild bears to estimate the amount of trout consumed by each bear. Male grizzly bears consumed an average of 5 times more trout/kg bear than did female grizzly bears. Estimated cutthroat trout intake per year by the grizzly bear population was only a small fraction of that estimated by previous investigators, and males consumed 92% of all trout ingested by grizzly bears.</span></p>
application/pdf
10.1139/z04-013
en
Canadian Science Publishing
Use of naturally occurring mercury to determine the importance of cutthroat trout to Yellowstone grizzly bears
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