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<br /> <br />62 <br /> <br />QuESTIONS FOR DR. DEACON <br /> <br />GREAT BASIN NATURALIST MEMOIRS <br /> <br />197 <br /> <br />Q. Once a species is on its way to recovery, how does <br />one determine what the population level or popu- <br />lation density would be for the species to be consid- <br />ered no longer in danger? <br />A. That is an extremely knotty problem. In the case of <br />the Devils Hole pupfish we were primarily con- <br />cerned with maintaining a large enough population <br />to prevent population instabilities that might tend <br />to accelerate the process of extinction. It is generally <br />understood that populations have a minimum size <br />below which they are unlikely to maintain viability. <br />Bob Miller at the University of Michigan did some <br />experimental rearing of other species of pupfish in <br />the 19405 and also performed a number of trans- <br />plants into springs devoid of fish. His work indicated <br />that experimental populations started with small <br />numbers of individuals tended to decline in abun- <br />dance after a few generations, sometimes to extinc- <br />tion. His numerous transplants of pupfish into other <br />natural waters were never successful if fewer than <br />200 individuals were transplanted, and in only two <br />instances were they successful when more than 200 <br /> <br />~, <br /> <br /> <br />No.3 <br /> <br />individuals were transplanted. During the middle <br />1960s a graduate student of mine, Carol James (now <br />Ivy), did some work on the Devils Hole pupfish <br />which, in retrospect, indicated that its population <br />had probably never fallen below 200 indiViduals. Fi- <br />nally a transplant of 24 Devils Hole pupfish into an <br />artificial pond below Hoover Dam resulted in a pop- <br />ulation maximum of about 200 individuals, followed <br />by a decline to about 50 indiViduals. This pattern <br />suggested loss of viability may be occurring in the <br />transplanted population of Devils Hole pupfish. This <br />line of argument was successful in establishing the <br />fact that it would be unacceptably dangerous to per- <br />mit the population of Devils Hole pupfish to fall be- <br />low 200 individuals. Once that point was established <br />it was not difficult to show, with four or five years of <br />monthly data on estimated population size, that a <br />water level of 2.7 was necessary to sustain a popu- <br />lation of no fewer than 200 individuals. These eco- <br />logical relationships are being reported in the sym- <br />posium volume on research in the national parks to <br />be published in 1979. <br />Q. At what level do you consider the population to not <br />be threatened? <br /> <br />A. <br /> <br />Q. <br /> <br />A. <br /> <br />TABLE 6. Undescribed taxa of threatened freshwater fishes of western North America: 1979. <br /> <br />Q. <br /> <br />Killifishes, family Cyprinodontidae <br />Preston White River Creniehthys baileyi ssp. <br />springfish <br />Southern White River <br />springfish <br />Warm Springs White <br />River springfish <br />Devils River Conch os <br />pupfish <br />LeConte desert pupfish <br />Quitobaquito desert <br />pupfish <br /> <br />"J", <br /> <br />Common name <br /> <br />Trouts, family Salmonidae <br />Alvord cutthroat trout <br />Humboldt cutthroat trout <br />Redband trout <br /> <br />~,; ,- <br /> <br />;.; <br /> <br />"1 <br />j <br />1 <br />i <br /> <br />Minnows, family Cyprinidae <br />Catlow Tui chub <br />Sheldon Tui chub <br />Cow head Lake Tui chub <br />Hutton Spring Tui chub <br />Borax Lake chub <br />Foskett Spring speckled <br />dace <br /> <br />:.. <br />, <br /> <br />~. <br /> <br />Sculpins, family Cottidae <br />Malheur mottled sculpin <br /> <br />Scientific name <br /> <br />Salmo clarki ssp. <br />Salmo clarki ssp. <br />Salmo sp. <br /> <br />Gila bieolor ssp. <br />Gila bieolor ssp. <br />Gila bieolor ssp. <br />Gila bieolor ssp. <br />Gila sp. <br />Rhiniehthys oseulus ssp, <br /> <br />Creniehthys baileyi ssp. <br /> <br />Creniehthys baileyi ssp. <br /> <br />Cyprinodon eximius ssp. <br /> <br />Cyprinodon maeularius ssp. <br />Cyprinodon macularius ssp. <br /> <br />Cottus bairdi ssp. <br /> <br /> Present. Historical <br />Sta tus threat distribution <br />SC 1 OR <br />SC 1 NV . <br />SC 1,4 CA,OR,ID,NV A. <br /> <br />SC 1 <br />SC 5 <br />SC 1 <br />T 1 <br />T 1,5 <br />T 1,5 <br />T 4,5 <br />T 1,3,4 <br />SC 1,4,5 <br />T <br />E 1,4 <br />SC 1,5 <br />SC <br /> <br />OR <br />NV <br />CA <br />OR <br />OR <br />OR <br /> <br />NV <br /> <br />a <br />1 <br />( <br />] <br />e <br />I, <br />v <br />t <br />1 <br />Y <br /> t <br /> Y <br /> f, <br /> ti <br /> r, <br /> v <br /> s< <br />Q. ( <br /> <br />NV <br /> <br />NV <br /> <br />TX <br /> <br />CA <br />AZ <br /> <br />-I-Present or threatened destruction of habitat <br />2-Overutilization <br />3-Disease <br />4-Hybridization. competition, exotic or translocated <br />5-Restricted natural range <br /> <br />OR <br />