Evaluating Long-Term Trends in Crayfish Populations from acid Sensitive Softwater Lakes in South-Central Ontario (1988-2004). <p> HR: <span class="hr"> 10:30h<br></span> AN: <span class="an"> NB52F-01 <a href="../absbook/sm05_NB52F.html">[Abstracts]</a><br></span> TI: <span class="ti"> Evaluating Long-Term Trends in Crayfish Populations from acid Sensitive Softwater Lakes in South-Central Ontario (1988-2004). <br></span> AU: <span class="au"> * Reid, R A<br></span> EM: <span class="em"> ron.reid@ene.gov.on.ca<br></span> AF: <span class="af"> Ontario Ministry of the Environment, Dorset Environmental Science Centre P.O. Box 39, Dorset, ON P0A 1E0 Canada <br></span> AU: <span class="au"> Bowman, M F<br></span> EM: <span class="em"> michelle.bowman@ene.gov.on.ca<br></span> AF: <span class="af"> Department of Zoology University of Toronto, 25 Harbord St., Toronto, ON M5S 3G5 Canada <br></span> AU: <span class="au"> Somers, K M<br></span> EM: <span class="em"> keith.somers@ene.gov.on.ca<br></span> AF: <span class="af"> Ontario Ministry of the Environment, Dorset Environmental Science Centre P.O. Box 39, Dorset, ON P0A 1E0 Canada <br></span> AU: <span class="au"> Somers, K M<br></span> EM: <span class="em"> keith.somers@ene.gov.on.ca<br></span> AF: <span class="af"> Department of Zoology University of Toronto, 25 Harbord St., Toronto, ON M5S 3G5 Canada <br></span> AB: <span class="ab"> We evaluated changes in crayfish abundance over time in 17 lakes on the Precambrian Shield with a modified Mann-Kendall trend test. Each year crayfish were sampled in midsummer using baited minnow traps. The lakes support as many as 3 crayfish species (e.g., Cambarus bartoni, Orconectes propinquus, and O. virilis). The trend test indicated significant linear declines in the relative abundances of C. bartoni in 7 of the 8 lakes where they were found. The decline of C. bartoni is unexpected, and somewhat surprising, since C. bartoni is more acid tolerant than the two orconectid species. Perhaps concomitant declines in lake-water calcium concentrations are affecting crayfish populations. The introduction of largemouth and smallmouth bass (Micropterus spp.) has affected crayfish catches in at least one lake. Long-term monitoring of crayfish and the evaluation of changes have allowed us to generate hypotheses regarding the cumulative effects of anthropogenic activities on the biota of lakes in south-central Ontario. <br></span> DE: <span class="de"> 9810 New fields (not classifiable under other headings)<br></span> SC: <span class="sc"> North American Benthological Society [NB]<br></span> MN: <span class="mn"> 2005 Joint Assembly<br></span></p></body></html>