Status of the Westslope Cutthroat Trout (Oncorhynchus Clarkii Lewisii) in Alberta
Total Page:16
File Type:pdf, Size:1020Kb
Status of the Westslope Cutthroat Trout (Oncorhynchus clarkii lewisii) in Alberta Alberta Wildlife Status Report No. 61 Status of the Westslope Cutthroat Trout (Oncorhynchus clarkii lewisii) in Alberta Prepared for: Alberta Sustainable Resource Development (SRD) Alberta Conservation Association (ACA) Prepared by: Allan B. Costello This report has been reviewed, revised, and edited prior to publication. It is an SRD/ACA working document that will be revised and updated periodically. Alberta Wildlife Status Report No. 61 December 2006 Published By: Publcaton No. T/113 ISBN: 0-7785-4811-2 (Prnted Edton) ISBN: 0-7785-4812-0 (On-lne Edton) ISSN: 1206-4912 (Prnted Edton) ISSN: 1499-4682 (On-lne Edton) Seres Edtors: Sue Peters, Robn Gutsell, Nyree Sharp and Lsa Matthas Illustratons: Bran Huffman Maps: Ncole Hopkns For copes of ths report, vst our web ste at: http://www.srd.gov.ab.ca/fw/specesatrsk/ and clck on “Detaled Status” OR Contact: Informaton Centre - Publcatons Alberta Sustanable Resource Development Man Floor, Great West Lfe Buldng 9920 - 108 Street Edmonton, Alberta, Canada T5K 2M4 Telephone: (780) 422-2079 Ths publcaton may be cted as: Alberta Sustanable Resource Development and Alberta Conservaton Assocaton. 2006. Status of the westslope cutthroat trout (Oncorhynchus clarkii lewisii) n Alberta. Alberta Sustanable Resource Development, Wldlfe Status Report No. 61, Edmonton, AB. 34 pp. PREFACE Every five years, the Fish and Wildlife Division of Alberta Sustainable Resource Development revews the general status of wldlfe speces n Alberta. These overvews, whch have been conducted n 1991 (The Status of Alberta Wildlife), 1996 (The Status of Alberta Wildlife) and 2000 (The General Status of Alberta Wild Species 2000), assgn ndvdual speces “ranks” that reflect the perceived level of risk to populations that occur in the province. Such designations are determned from extensve consultatons wth professonal and amateur bologsts, and from a varety of readly avalable sources of populaton data. A key objectve of these revews s to dentfy speces that may be consdered for more detaled status determnatons. The Alberta Wldlfe Status Report Seres s an extenson of the general status exercse, and provdes comprehensve current summares of the bologcal status of selected wldlfe speces n Alberta. Prorty s gven to speces that are At Risk or May Be At Risk n the provnce, that are of uncertan status (Undetermined), or that are consdered to be at rsk at a natonal level by the Commttee on the Status of Endangered Wldlfe n Canada (COSEWIC). Reports n ths seres are publshed and dstrbuted by the Alberta Conservaton Assocaton and the Fsh and Wldlfe Dvson of Alberta Sustanable Resource Development. They are ntended to provde detaled and up-to-date nformaton that wll be useful to resource professonals for managng populatons of speces and ther habtats n the provnce. The reports are also desgned to provde current nformaton that wll assst Alberta’s Endangered Speces Conservaton Commttee n dentfyng speces that may be formally desgnated as Endangered or Threatened under Alberta’s Wildlife Act. To acheve these goals, the reports have been authored and/or revewed by ndvduals wth unque local expertse n the bology and management of each speces. EXECUTIVE SUMMARY Cutthroat trout (Oncorhynchus clarkii) s a polytypc (havng many forms) speces of trout endemc to western North Amerca. The speces s hghly varable n terms of phenotypc trats (physcal features) and lfe hstory characterstcs but has strct habtat requrements, requrng cold clean water and vared forms of cover to mantan populatons. Although the orgnal dstrbuton of cutthroat trout was lkely greater than any other form of North Amercan trout or salmon (wth the excepton of lake trout, Salvelinus namaycush), the varous cutthroat subspeces (of whch there are four man types and 10 further dervatves) have undergone dramatc declnes n ther numbers and dstrbuton snce European settlement; some have dsappeared from as much as 90% of the natve range. The only subspeces natve to Alberta, and the focus of ths revew, s the westslope cutthroat trout (O. clarkii lewisii), whose current global dstrbuton has become extremely fragmented nto solated, hgh elevaton headwater areas. Westslope cutthroat trout are natve to the Bow and Oldman dranages of the South Saskatchewan Rver and were orgnally found from the extreme headwaters of these systems throughout manstem stretches and down onto the grassland plans. Today, populatons are largely restrcted to the Rocky Mountan Natural Regon and the Parkland Natural Regon (Foothlls Subregon) n the uppermost reaches of manstem rvers and the extreme headwaters of a few major trbutares. Although ntroduced hatchery populatons of westslope cutthroat trout populatons are wdespread n Alberta, only 60–70 streams are beleved to contan genetcally pure natve strans (the total Alberta populaton sze of wld, natve westslope cutthroat trout s lkely much smaller than 7000 mature ndvduals). Many of the natve rver mgratory populatons are beleved to be severely depressed, f not already extrpated; some dsappeared followng the constructon of dams early n the last century, whereas others have declned as a consequence of habtat degradaton and the stockng of non-natve speces. The greatest threats to westslope cutthroat trout n Alberta contnue to be the human-caused manpulaton and degradaton of the envronment n whch they lve. Introgressve hybrdzaton (permanent ncorporaton of foregn genetc materal) between natve westslope cutthroat trout and ntroduced speces (prmarly ranbow trout) s beleved to be wdespread, and the contnued presence of non-natve speces threatens the genetc ntegrty of remanng westslope cutthroat trout populatons. In November 2006, the Commttee on the Status of Endangered Wldlfe n Canada desgnated the remanng genetcally pure populatons nhabtng the natve range n Alberta as Threatened (.e., lkely to become endangered f lmtng factors are not reversed). A comprehensve assessment of the genetc ntegrty of the remanng populatons and thorough revew of the current stockng program n Alberta seem necessary f natve populatons of westslope cutthroat trout are to be mantaned n the provnce. v ACKNOWLEDGEMENTS I would like to thank the many biologists and fisheries professionals who assisted in the preparation of ths document; from Brtsh Columba: James Baxter (BC Hydro), Sue Pollard (B.C. Mnstry of Envronment), Bll Westover (B.C. Mnstry of Envronment), Don McPhal (Unversty of Brtsh Columba), Emly Rubdge (Unversty of Brtsh Columba) and Erc Taylor (Unversty of Brtsh Columba). From Alberta, specal thanks to Jm Stelfox (Alberta Sustanable Resource Development), Gord Court (Alberta Sustanable Resource Development), Robn Gutsell (Alberta Sustanable Resource Development), Lsa Matthas (Alberta Sustanable Resource Development), Nyree Sharp (Alberta Conservaton Assocaton), Sue Cotterll (Alberta Sustanable Resource Development), Charle Pacas (Parks Canada, Banff), Dave Mayhood (Freshwater Research Lmted), Sue Peters (Alberta Conservaton Assocaton), Ncole Hopkns (Ducks Unlmted Canada) and finally Bruce McCullough (Department of Fisheries and Oceans). Preparaton of ths report was funded by the Alberta Conservaton Assocaton and the Fsh and Wldlfe Dvson of Alberta Sustanable Resource Development. v v v TABLE OF CONTENTS PREFACE .......................................................................................................................... EXECUTIVE SUMMARY ................................................................................................ v ACKNOWLEDGEMENTS .................................................................................................v INTRODUCTION ...............................................................................................................1 SPECIES INFORMATION .................................................................................................1 HABITAT .............................................................................................................................2 1. Habtat Descrpton ................................................................................................2 2. Trends .....................................................................................................................3 CONSERVATION BIOLOGY .............................................................................................3 1. Lfe Hstory Dversty ............................................................................................3 2. Reproducton ..........................................................................................................4 3. Survval ..................................................................................................................4 4. Movements and Dspersal ......................................................................................4 5. Nutrton .................................................................................................................5 6. Interspecific Interactions and Hybridization ..........................................................5 DISTRIBUTION ..................................................................................................................6 1. Alberta ....................................................................................................................6 2. Other Areas ..........................................................................................................10 POPULATION SIZE AND TRENDS ...............................................................................10