7338

• UCREFRP Catalog Number: 7338
• Author: Valdez, R. A. and R. D. Williams
• Title: Endangered Fishes of Cataract Canyon
• USFW Year: 1986
• USFW - Doc Type: Desert Fishes Council
• Copyright Material: YES

! 'I' 'Iii'

216

Table 2. l-lun'bers of colorado ~-uawf ish and h.U1l"pback churl e;.-:rfltn-;r.cd 1. n t-t'..~
cataract Canyon rP.gion in ]980 by GgP r..""1tc.gm'i0s.

---- ----~,,_._._---- --~ ---.-.....--...- _.----------,- - - _....__.. -, ~- .--~-- ~. ~ ..~-

AGE CATEGORY

COLORADO SQUA~lFISH

HUrrPBAGK CHUH

,~
J
,~

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.'

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ADULT

45fi ')'
L._.
44 U
5 3
505 33

YOY

JTNENILE

pools wher:e their death seEme..r:i imminent becau...,e ot Irick of l-.u.'Y9fm or dH"~:dcl_;atjon.
The same ];henomenon was seen in yay; hOw:!Ver, Thesf: often ()(,;G\1'Pt'l~1 in s.-'naLlf1r,
lcw-lying pools that: eVt~ntua)ly became in1l11dated I:7f higher rtver flews in. late
sununer. The nun-ber of endangered fish That: Sl1C:c:lIDlb to deat11 by bt-~f;oming stranded
in isolated pools is unknewn.

Hrnnpba.ck Chub

The hatching date ot each yay squa\<Jtish capturai in 1985 TNaS est-imat:8d by
using a formula developed by Haynes et a] (1~B!)), and tl1eSe daTa were canp3red
wi th hatching dates for YeN r..apTm-ed in lmm (Valdez 8t aJ. E.lHtl). Week.ly
hatching dates indicate ti-.at Colorado squawtish capturai in the rc-gio."'1 of
C'..ataract c.-myon in HJ85 hatched ber.leen June 19 and Septf"~ntier 9, H.lS6 (Figure 2).
The majority of the fish san-pled (62%) hatched be-tween. July 30 and August 19. . In
1985, hatching was estimated to occur betw:!en ~1a.y 1 and August: 26, with tbe
majori ty (60%) occurring i::let:w::!en JUI1e 26 a."'1d ."July 2~~. These prpliminari data
show that hatching varied between the 2 years by a full month. v./atel"
ter(perat:llres and river fIGS for the same t:ime periOli indicate Theit hrtTchiTh.] in
1986 was delayed because suitable squawfisb spawning tEJIT'""~rat:ures of 2~! to 25 G
did not occur unit mid-Jul y. Kaeding et a1. ( 1986) i1aVQ indicated That: 1a1:.,-:
spawning by Colorado squawi ish disadvantagt=!s the young, wh tch have to enter the
winter season relatively ~1Eller a"'1d presumably weaker.

A total of 33 humptack chub \<.Ere captured during this 1986 study. This
included 21 YOY, 9 juvenileS, and 3 adults (Table 2). All of the YOY and most of
the juveniles \<Ere identified by the Larval 1;'is11. Laboratory (lu.""L). Many of these
specimens were classified -l7f The LFL as "possible ~ila ~" because the
diagnostic characteristics of some. did not positively distinf./uish than from the,
sYllpatric roundtail c.~ub (Q.:.. rohlsta). Many yay and juveniles, ho\<Ever exhibited
\ characters considered very t7tPical of the species. The 3 adults were also
considered typical humpback chub; these were weighed, measured, tagged,
};i1otographed, and released.