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<br />120 The Southwestern Naturalist vol. 28, no. 1 ~w
<br />(H. Tyus and R. Valdez, pers. comnt.l. Therefore this occurrence is undoubredl} very rare and
<br />probably had ]role influence on the decline of the Colorado squawEish.
<br />I thank R. Wydoski and C. Roger who participated in the collection. The Utah Cooperative
<br />Fishery Research Unit is jointly supported by the U.S. Fish and Wildlife Service, Utah Division o[
<br />Wildlife Resources, and Utah State University.-CeAxt.es t1'. Mcauw, Utah Coop. Fuh. Hes. Urit,
<br />C'b1C-52, Utah Stale Univ., Logan, L'T 89322. (Present address: U.S. Fish and 11'ildlife Service,
<br />551 2i.5 Rd., Suite B173, Grand Junction, CD 81501).
<br />SOUTHWESTERN CACTI GR0~1'ING AS EPIPH]'TES.-Humphrey (The Boojum and Its
<br />Home, Univ. of Arizona Press, Tucson, 1974) found Opuntia sp. and Ferocactus sp. growing on
<br />Idria columnaris in Baja California Norte, Mexico. He suggests 'They grow from bird deposited
<br />seed at places on the boojum where soil and debris accumulate. W'e wish to report here two
<br />instances o[ cacti growing on alligator juniper (Juniperus deppeana) in moist canyons of the
<br />northern Chihuahuan Desert. Opuntia phaeacantha was seen in august 1981 growing on the end
<br />of a horizontally Fractured branch (ca. 50 cm diameter) of a tree in ~fCK1CCrICk Canyon, Guadalupe
<br />Mountain National Park, Culberson Co., TX at an elevation of 1500 m. The cactus is well estab-
<br />lished with 14 joints, and is 2.5 m above the ground in a thicket of canyon bottom vegetation. A
<br />cluster of Five 3-6 cm tall F.chinocereus triglochidiahrs was seen in October 1978 and January 1982
<br />on a 151 cm dbh tree in Three Rivers Canyon, Otero Co., NM at 2100 m elevation. Much of this
<br />large, old tree is dead, and only 26% of the stem circumference has bark. The cacti ae 3 m above
<br />[he ground, and appear to have grown little between observations. They are bedded in decaying
<br />wood in a place that catches moisture and some leaf litter Erom nearby oaks. Both were left undis-
<br />turbed, and consequently our species indentifications are tentative.
<br />Growth of cacti as epiphytes seems the result of an infrequent combination of circumstances.
<br />There are Eew large, old trees in the region, and only a fraction of them have platforms to catch
<br />bird or rodem transported seeds, moisture, litter and some sunlight. The first author would appre-
<br />ciate copies of any published or unpublished observations of cacti growing on trees or other
<br />unusual places in the desens of southwestern North America.-Wtt.t.tAM RErn Auo RALPH KkAPPA,
<br />Laboratory Jor Environmental Biology, Univ. of Texas at El Paso, El Paso, TX 79968.
<br />MATURITY AND FECUNDITY OF THE BLUEHEAD SUCKER, CATOSTOiNI,/S DISCO-
<br />BOLUS (CATOSTOMIDAE), IN THE UPFER COLORADO RIVER BASIN, 1975-76.-The blu-
<br />ehead sucker, Calostomus discobolus, is native to the upper Snake River drainage, Idaho and
<br />Wyoming, Weber and Bear River drainages, Utah and Idaho, artd the Colorado River system
<br />ahn._ the ..... _rh pF the Gr,.nd r^ . 'SmitF.; lJn,. ~"t.^;. n"_'_. ZrOr_, _____ i ~~~ lc_.r__ .
<br />1966; Minckley, Fishes of Arizona, Arizona Game and Fish Dept. 293 pp , 1973). Although largely
<br />limited to areas of relatively swift water with cobble or gravel bottom, it is distributed throughout
<br />these rivers and is considered common to abundant in areas o[ suitable habitat. Information con-
<br />cerning bluehead sucker is generally limited to distribution (Vanicek et al., Southwestern Na[.
<br />9b:193.20b, 1970; Holden and Stalnaker, Trans. Amer. Fish. Soc. 104:217-231, 1975; Sigler and
<br />Miller, Fishes of Utah, Utah Dept. Fish and Game, Salt Lake City. 204 pp., 19fi3; Minckley 1973)
<br />or classification (Smith 1966), although Andreasen and Barnes (Copeia, 19"15:645-648, 1975) dis-
<br />cussed reproduction o[ the species in the Weber River, Utah. We studied maturity and feamdity of
<br />bluehead sucker in the Upper Colorado River Basin.
<br />Rluehead suckers were collected using electrofishing gear and !rammel nets from the Colorado
<br />River near Grand Junction, Colorado, in .4pri1, May, and June 1975; from the Green and Yampa
<br />rivers, near their confluence (Echo Park), in May and June 1975-76; and from the lower Gunnison
<br />River in blay 1976. Total lengths were meastued ro the nearest ntm; weight was determined to the
<br />nearest 20 g for fish weighing >200 g and to the neareast a [or Eish weighing <200 g. Mature
<br />males were identified by presence of [uherdes on the anal and caudal Fins. Female and immanrre
<br />fish were dissected to determine sex and maturity. Uvaries were removed from mature females,
<br />identified with a numbered tag, wrapped in cheesecloth, and preserved in 10 ~ [ormalin.
<br />In the laboratory, ovaries were soaked in water to remove formalin and 'blotted to remove excess
<br />moisture; eggs were then separated from ovarian tissue W'e estimated fecundity grvimetrically,
<br />using atriple-beam balance. Samples from anterior, middle, and posterior sections of the ovary,
<br />totaling about 10% of the entire ovary weight, were weighed to the nearest 0.1 g and counted. The
<br />rest o[ the ovary was weighed and fecundity estimated by direct proportion. Accurac, of the
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