7952 ‎(2)‎

• UCREFRP Catalog Number: 7952
• Author: Miller, R. R. and B. Chernoff.
• Title: Status of Populations of the Endangered Chihuahua Chub,
• USFW Year: 1979.
• Copyright Material: YES

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V. Laguna Bustillos Basin
(A) Arroyo de Nopabechic (Fig. 1, ~~13), 106° 58' N long., 28° 30' W lat.,
ca. 2140 m, 27 May 1979. -Several Large isolated, stagnant pools, choked with
algae and garbage, were seen in the arroyo west of the bridge. Another pool
at the base of the bridge (ca. 7 m long, 1 m wide and up to 0.5 rn deep)
contained Gila nigrescens. The pool was supplied by a rheocrene with a very
slight flow to the east. Sand, coarse gravel, rocks and cobbles formed the
substrate, and filamentous green algae were present in the water. Five adult
chubs were seen, two adults (ca. 200 mm and 150 mm SL) in breeding color were
seined, photographed, and released. Thirty juveniles (less than 40 mm) were
captured and five were preserved for study. The total population size in this
pool was estimated to be 10 adults and 100 juveniles. The only other species
present was Cyrpinodon sp. The Chihuahua chub was last collected here in 1975
(UANL uncatalogued).
(B) Arroyo Ojo Caliente (Fig. 1, 4614), 106° 58' N long., 28° 34' W lat.,
ca. 1990 m, 27 May 1979. -Shallow, flowing water and some small standing pools
(ca. 10 cm deep)-were seen.. Within this 30-m wide arroyo, the water was often
restricted to 0.5 m or less. Upstream from the bridge the water was clear,
without filamentous algae; however, at the bridge a thick surface scum was
present. Only pupfish, Cyprinodon sp., and Bufo tadpoles were sighted within
200 m above the bridge; no collection was taken. The arroyo was dry below
(east of) the bridge.
(C) Arroyo Miguel Chiquito (Fig. 1, 4615), 106° 58' N long., 28° 32' W
__ lat., ca. 2000 m, 27 May 1979 -This arroyo was totally dry. Gila nigrescens
was previously collected here in 1975 (UANL 2493, 2 specimens).
(D) Arroyo San Antonio (Fig. 1, 4616), 106° 47' N long., 28° 30' W lat.,
ca. 1990 m, 27 May 1979. -This large arroyo (ca. 30 m wide) had sufficient
running water and pools to support fish. However, no fish or aquatic animals
were sighted or encountered. The water was murky green, often with suds and
scum floating on the surface. Bubbles were constantly rising from the bottom -~
probably the result of nutrient overload from the surrounding agricultural
fields. Thirty-eight specimens of Gila nigrescens were collected here in
1964 (UANL 552).
Discussion
The summary of collection data (Table 1) shows that Gila nigrescens
was present at only eight of the sixteen localities surveyed. Furthermore,
the chub could be considered abundant at only four of these stations. Two
places where the species- was abundant (Rio Piedras Verdes at Colonia Hernandez
and Arroyo del Aguila) should perhaps be considered as one locality due to their
proximity, thus reducing that number to three. 1'Iiese findings clearly support
the listing of Gila nigrescens in New Mexico and Chihuahua as endangered
(Hubbard et al., 1978:E-17; Deacon et al., 1979).
The latter authors cited (1) present or threatened destruction, modification,
or curtailment of habitat or range and (2) hybridization, effect of exotics and
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