8142

• UCREFRP Catalog Number: 8142
• Author: Horn, M. J.
• Title: Nutritional Limitation of Recruitment in the Razorback Sucker ‎(
• USFW Year: 1996.
• Copyright Material: NO

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heavily on sucker larvae (Horn et al. 1994). Therefore, in 1995, wild larvae were

dipnetted after attracting by commercial Crappie LightsR made of 55- watt, glass-sealed

halogen bulbs powered by batteri~s and suspended from the boat gunwales.

B. Larvae for Laboratory Study
Razorback sucker larvae for use in the laboratory were hatched from ova manually

stripped and fertilized from wild Lake Mohave fish (Hammon 1985). Adults were netted

after electronarcosis with a boat-mounted electrofishing unit (220-volt D.C. pulsed

current, at variable amps) at night and by trammel nets in daylight. The latter were used

as beach seines to encircle spawning, adults, seining and entangling them as the net was

slowly drawn ashore. "Running ripe" fish of both sexes were retained and spawned a few

minutes following capture, then released. Unripe fish were released immediately

following capture.

Abdomens of females were palpated and gently compressed to extrude ova into a

pan containing -0.5 L oflake water. Milt from 2 to 3 males treated in the same manner

was added to ova from each female, and gametes were mixed to enhance fertilization. A

slurry of bentonite in water sufficient to color the gamete/water mixture light gray was

added after - 30 seconds to prevent characteristic adhesion of ova after fertilization.

Bentonite-treated ova were quickly transferred to water harden in a 500 urn mesh net

suspended in the lake. Within a few hoW'S, ova were transferred to plastic bags and

transported to the laboratory in insulated containers. Ova were incubated and hatched at

the same facility where experiments were conducted, either at U.S. Bureau of