9488

• UCREFRP Catalog Number: 9488
• Author: Mueller, G. A., J. Carpenter, P. C. Marsh and C. O. Minckley.
• Title: Cibola High Levee Pond Annual Report 2003.
• USFW Year: 2003.
• USFW - Doc Type: Fort Collins.
• Copyright Material: NO

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REPORT SUMMARY

Bonytail and razorback sucker have once again spawned and produced swim-up larvae in
Cibola High Levee Pond (CHLP). CHLP continues to support annual recruitment of
bonytail while recent razorback sucker recruitment remains elusive. Thus far, razorbacks
have experienced intermittent years ofspawning success.

Both native species were observed spawning on, or near, the riprap on the river levee.
Razorbacks spawned from late January until mid-March over gravel and large cobble
along the levee toe (2-3 m depth) and bonytail spawned along the levee shoreline during
mid-April. Razorback suckers rapidly fin during the reproductive act, which flushes fines
from the substrate and leaves gravel relatively clean. Bonytail on the other hand, appear
to spawn over or on substrate that has been disturbed by beaver activity. Substrate scour
or disturbance appears to be an important factor in spawning site selection.

Spawning activity was recorded during approximately 120 hours of underwater
videography. These films revealed that expulsion of gametes typically triggered feeding
frenzies. Both species would aggressively feed on their own eggs and razorback suckers
were frequently found feeding among spavming bonytail. In contrast, bonytail were never
seen scavenging razorback sucker eggs although it appears they concentrated around the
periphery of spawning sites to feed on emerging larvae. Videos also recorded
concentrations (average 0.89 to 3.66 animals/m2) of bullfrog (Rana catesbeiana) tadpoles
and red swamp crayfish (Procambarus clarldi) on spawning sites. Preliminary tank tests
indicate both these nonnatives are effective egg and larvae predators.

Telemetry studies revealed that adult bonytail are nocturnal and occupied the interspaces
of large riprap during daylight hours. Study fish remained inside these cavities during
daylight hours and did not venture out into open water until after sunset. They showed a
high fidelity toward specific areas of the pond and often return. to the same cavities just
before sunrise. All life stages exhibited schooling behavior; however younger year
classes make up larger aggregations.

Gut contents suggest adult bonytail diets consist of algae, vegetative material, small fish,
and craytlsh. Small bonytail were observed feeding near or from the surface on large
zooplankton and invertebrates. At least 5 of27 adults (18%) were infested with intestinal
tapeworm (species unknown).

Some nonnative fish continue to occur in CHLP. Bluegill and largemouth bass were
removed in November 2002 and others have been observed with underwater cameras.

Predator/prey tank experiments revealed that most nonnatives were effective predators on
early life stages of razorback sucker. Bullfrog tadpoles consumed both eggs and larvae.
Literature suggests that at current densities, tadpoles have the potential to consume nearly
a million fish larvae per day in CHLP. Crayfish were also an effective predator of sucker
:fry. Small (< 6cm) sunfish, rainbow trout (5 and 18 cm), red shiner (<7 cm), largemouth

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