This represents the fourth and last annual report of a five year study investigating the early life ecology of the bonytail and razorback sucker at Cibola High Levee Pond. The work in 2004 included: telemetry studies, collection of physical water quality measurements, zooplankton samples, netting fish, the collection of scale samples for aging, predator/prey tank tests and a preliminary analysis of the data base.

Juvenile bonytail and razorback suckers were collected this year, demonstrating that natural recruitment occurred for both species. Young from 2004, 2003, and 2002 were all represented in our sample. Unfortunately, we discovered that largemouth bass had also spawned. Approximately 100 young bass were observed during a snorkeling trip in late July. Bass ranged in size from an estimated 5 to 50 cm and were distributed throughout the pond.

Attempts to determine the cover preference of 30-cm bonytail met difficulties. Spawning occurred a month earlier than previous years due to an unseasonably warm spring. The combination of warmer temperatures and the vigors of spawning attributed to higher stress and associated mortality of study fish. We replicated our procedures under hatchery conditions on the chance that transmitter attachment was at fault but we experienced similar post-release mortality, including the control fish. This supports the long held contention that bonytail are extremely fragile during and after spawning.

In the predator-prey tests, young of every species tested ate razorback sucker larvae. The most aggressive predators tested in 2004 (n = 8 species) were young of the year green sunfish, channel catfish, and common carp. Bullfrog tadpoles and red swamp crayfish also ate razorback sucker larvae and eggs, showing predation is not limited to predatory fish. This work illustrates that early life stages are quite vulnerable to small predators that have easy access to shallow nursery habitats.

Remaining work will be finished this coming summer and a final report describing CHLP and the ecology of these fish will be completed by the end of 2005. We offer our assistance to the Fish and Wildlife Service in the pond’s renovation and support for the creation of additional refuge ponds. Funding for this work ends September 2005.