7406

• UCREFRP Catalog Number: 7406
• Author: Bestgen, K. R.
• Title: Status Review of the Razorback Sucker,
• USFW Year: 1990.
• Copyright Material: NO

eventually disappear because of lack of recruitment to older age
classes (Minckley 1983).
Razorback sucker larvae are annually abundant in Lake Mohave
and samples of more than 100 specimens are easily obtained during
and just after the reproductive season (Bozek et al. 1984, Marsh
and Langhorst 1988). Thirty-seven razorback sucker larvae were
collected from Lake Havasu in 1985 and 1986 (Marsh and Papoulias
1989). These larvae were apparently offspring of resident adult
razorback suckers and were not transported into Lake Havasu from
upstream (Marsh and Papoulias 1989).
Large numbers of razorback sucker larvae are produced
annually in Lake Mohave but disappear soon after emergence;
juveniles have been extremely rare in collections since the early
1950's (Minckley et al. in press). Three hypotheses were
forwarded to explain the absence of razorback sucker larvae
larger than 12 mm TL in Lake Mohave (Minckley et al. in press).
Larvae may move downstream through the reservoir and into the
Colorado River, but available evidence does not support this
hypothesis. A food deficiency hypothesis was indirectly tested
by comparing growth and survival of razorback sucker larvae in
hatchery ponds with differing invertebrate food densities
(Papoulias 1988) to the density of food items found in Lake
Mohave. It was concluded that starvation of Lake Mohave
razorback sucker larvae could occur but only rarely (Minckley et
al. in press). Predation on larvae was determined to be the
factor most likely limiting successful recruitment of razorback
11