8155

• UCREFRP Catalog Number: 8155
• Author: Minckley, W. L.
• Title: Executive Summary
• USFW Year: 1985.
• USFW - Doc Type: Native Fishes and Natural Aquatic Habitats in U.S. Fish and Wildlife Service Region II West of the Continental Divide.
• Copyright Material: NO

\

spavJning of bon;dail in ~a.rthen pe,nds 3.t Dext~r, and their sur'Ji'.Ja.l and
growth wi th a mixed population of ~osquitofish and African cichl ids in
pc,nds at Bl:lthe, Californi.3. (SHti'Jn iI, p. 48) indic3.te that ~pec:es j.s
pe~haps mere hardy than expected. And, success at pond c~l ture of
razorback sucker indicahs a high sur'.)i'Hbilit/ of that sp~cies undH
cond: tions qui te different than those in the prime'H1 ri\!Hine habi tat.

Most segments of the lowermost mainstream must be assigned to C~te9Qry
III since al1 but a fel,<J reaches l,<Jould entail substantial ef-fort and e;{pen.3e
to maintain for big-river fishes, other than by stocking. There are,
hO~'Jever, three viable possibilities for re-establishment of native fishes
in the system (Hinckley 1986): 1) stocking of selected backwaters and
river reaches, including those of del iver;..' canals and perhaps drains, i..<Ji th
big-river fiShes, either as fry in segments from which non-native fishes
have been removed or suppressed, or reared to sizes where reasonable
chances of survival accrue; 2) creation of suitable habitat on the
extensive USR~S ~MR holdings or elsewhere along the Colorado River to be
managed for perpetuation of the indigenous fauna; or 3) a combination of
and 2 above, involving use of suitabl~ habitats on Refuge lands to rear
indigenous fish~s to sub-adult or adult size prior to r~lease in th~ open
r-iver.

Opportunistic stocking of naturally or artificially isolated
bacKwat~rs along margins of major r~servoirs, or even canals and drains
after repairs or winter drawdowns, may also be used to increase native fish
populations. Such plac~s should be used as "grow-out" habitats, especially
if drawn down annually, with nativ~ fishes removed and introduced elsewhere
in the winter of each annual c:..'cle. If fry or fingerlings cDuld be placed
in such semi-natural or artificial habitats prior to reinvasion by
non-native fishes, populations might be expected to establ ish and be
maintained for considerable lengths of time. Successful natural
reproduction and larval growth to more than 25 mm TL of razorbacK sucKer
occurr-~d in such a backwater of Lake Mohave cleared of non-native fishes in
1985; larvae produced in the adjacent reservoir disappeared at about 12 rnm
TL (Langhorst, ASU, pers. comm.). Broad, sand-bottomed areas in the reach
of Colorado River mainstream below Park~r, Arizona, are relatively dH'oid
of lar-ger predators (MincKley 1979a) and selected backwaters or shallow
areas behind sandbars could be readily treated for removal of undesired
species without widespread or long-term impacts on sport fisheries. It
seems advisable to anticipate problems of species interactions adverse to
the native forms and rear native fishes to be stocKed in the mainstr~am to
fingerling or larger sizes prior to reintroduction, and local er:idication
or suppr-ession of non-native fish ~.tock~~ti 11 1 ikely be necessar;t. It is
unl ikely that reestabl ishment of of native fish populations ~lIould ha'.)e
discernible effects on the sports fishery in this or other parts of the
IOlAler basi n.

Creation of hati tat or reclamation of existing habitat :n NWR hold.ings
and other federal lands along the Colorado River seems the most highly
'.}iable .an,: ~:<pe,:itic-!J.= '.'JaY to ree~t.;b1i-=h bi:;-r;'ler .:::":",;"::i12,,t's:,f the
i n d j 9 e n c: ~~. 7.~ una < 'v' a 1 C 2: do n d lr,J j C k : 9 S 1; r'~; n c ~< i e /" 1 986), e -=. pee : d. 1 1 / sin C 2
some of those spec!es are now knc~r to be capable of reproducing in lentic
habitats (Sec::on II, p. 48). Numerous c~t-~f+ ~~titats exist along The
lower Coloradc- River mainstream that could be rec:aimed by ichthyctcxin

~ ".~".,
1 :J '-