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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2. Study Specimens

L

A. Wild Larvae.

Wild razorback sucker larvae for study were captured from

throughout the Lake Mohave in 1992-93 and 1995, and from Ywna Cove in 1992.

Unless otherwise noted, subsamples were selected at random from totals captured on a

given date and place. Each subsample was again divided in half, with i 0 or more larvae

in each. Half the sample was preserved in 5.0% CaC03 -buffered formalin for histology

and morphology and the other half frozen in water for lipid and otolith analyses. Larvae

of unusually large size were preserved separately. Such larvae were rare and thus

selected to increase sample sizes of large individuals. None of these was included in

calculated mean total lengths (TL) of samples.

Samples were obtained exclusively at night by lights and dipnets or light traps,

exploiting a positive phototaxis of larvae (Minckley et al. 1991). Several methods were

employed. Capture in 1992 was by Q-beamR spotlight from a boat, with incoming larvae

secured by dipnet. Spotlights were used at first in 1993, then abandoned later in that

season for light traps (Mueller et al. 1993) powered by 12-volt automotive lights or 55-

watt halogen bulbs. Light traps proved valuable for determining presence of larvae in an

area, but their utility for capturing large nwnbers was plagued by their attraction of other

animals. Swarms of zooplankton made sorting and harvest of larvae difficult, predatory

sunfishes fed on incoming larvae in the ring of light, and odonate naiads packed so

densely into light traps in backwaters that larvae could not enter. Odonates.also preyed