9489

• UCREFRP Catalog Number: 9489
• Author: Mueller, G.
• Title: The Role of Stocking in the Reestablishment and Augmentation of Native Fish in the Lower Colorado river Mainstream ‎(1998-2002)‎.
• USFW Year: 1998-2
• USFW - Doc Type: 03-288,
• Copyright Material: NO

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Table 1.6. Summary of the movements offlannelmouth suckers determined by recaptures from 1999 to 2002.

Sex Recaptured > 12 months R1 R2 R3 Ian max Ian
Females 121 82 58 10 2 3.5 56.4
Males 24 12 11 0 0 1.4 3.2
Immature 15 12 11 0 0 0.6 12.1
R1 :::::: returned to the same location the following year.
R2:::::: returned to the same location two years.
R3 :::::: returned to the same location three years.

Females range more than immature fish or males. The average distance detected for recaptured females was
3.5 Ian, compared to 1.4 and 0.6 Ian for immature fish and males. The maximum movement observed was a
female who traveled 56 Ian in one week. That movement was downstream and could have been triggered by
netting and handling stress.
Spawning. Two large schools of s ckers were commonly observed, one near the entrance of Laughlin
Lagoon and another near the ruins of Fort Mohave (Figure 1.7). Smaller schools (<25) were seen from
Harrah's Casino, downstream to just be ow the Bullhead City Water Craft Launching Facility. Typically, these
schools' number ranged from 10 to 10 , but during the spawning season they could swell to more than 200
fish. During spawning (March-April) fish (presumed males) were observed dispersed and resting on the
bottom. Occasionally a larger fish (pre umed females) would enter the area where she would attract males.
Actual spawning was observed several imes and was similar to previous reports (Weiss and others, 1998).
Suckers also appeared to move into aughlin Lagoon during the evening. We did not witness, but suspect
that suckers were also spawning in the 1 goon's entrance. The lagoon was deepened by dredge in 1999, which
provided fish a clean substrate. Hydro lectric power cycles causes a constant current through the lagoon's
entrance as it fluctuated through a d ily cycle of filling and draining. Culverts located upstream also
contributed to flow inside the backwat . The vast majority of the flannelmouth suckers were captured near the
lagoon's entrance.
The depth at which we observed sp ing was much deeper than previous reports (Chart and Bergersen,
1992; Thieme, 1997; Weiss and others, 1998). Depth varied due to hydropower cycles but spawning depth
normally ranged between 2 and 3 m. S bstrate was composed oflarge gravels and. cobble aggregate that was
covered with algae and periphyton. Sp wning fish would disturb the substrate, causing circular patterns of
cleaned material that were noticeable fr m the surface. Velocities were not measured but appeared to be in the
0.5 to 1 m/sec range.
Flannelmouth suckers were sexuall active during the entire months of March and April. Females were
found expressing gametes during this 8 eek period, while ripe males were found as early as October through
June. The prolonged spawning season lowed us to captured more than 250 sexually active fish, the majority
freely expressing gametes. We collecte 46 ripe females and 163 ripe males and 56 males that were not ripe
but were tuburculate. Ripe females av aged 57 cm and ranged in size between 46 and 62 cm. Ripe males
were slightly smaller, averaging 52 cm 33-61 cm) and similar in size to tuberculate males (36-58 cm). The
majority of ripe females (43%) were t en during the first half of April while we captured the most males
(28%, n :::::: 46) during the last half of A "I (Figure 1.8).

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