Document Type

Technical Report

Publication Date

12-1989

Abstract

Studies done by the Nevada Department of Wildlife (NDOW) and the Arizona Fish and Game between 1978 and 1981 indicate that inadequate cover may be limiting the production and survival of largemouth bass at the Lake Mead National Recreation Area (LMNRA). As a result of these studies, NDOW initiated a contract in 1986 with the Lake Mead Research Center (LMRC) to investigate means of improving habitat for game fish by introducing natural and/or artificial cover.

During Phase I (1986-1987) of this contract, the shoreline of Lake Mead was surveyed for aquatic and terrestrial plant growth. Also during this time, submerged Christmas trees and Berkley Fish Habitat Modules were evaluated for their effectiveness in providing cover. Christmas trees appeared to provide cover for juvenile bluegill, a largemouth bass prey species. However, submerged trees lost their structure in about three years. Berkley Habitat Modules did not appear to be an effective form of cover. The National Park Service (NPS) asked that the introduction of artificial forms of cover not be continued until research was completed on the use of native plant material.

Methods for aquatic and terrestrial plant introductions were determined during Phase II (1987-1988) of this contract. Other agencies and individuals involved in revegetation of reservoir inundation zones were contacted, and the literature was reviewed for plant material collecting procedures, planting guidelines, and site maintenance. A "Plant Introduction Manual" was compiled based on this information and was approved by the National Park Service for use in the Lake Mead National Recreation Area. During the winter, dormant cuttings were taken of two woody species, Goodding's Willow and seepwillow baccharis (Salix gooddingii and Baccharis glutinosa) to be planted in the spring of 1988. In addition, collections were made of three emergent species (Typha angustifolia, Scirpus robustus, and Phragmites australis). Plant material was transported to the Nevada Division of Forestry (NDF) nursery where it was rooted and placed on pots for planting in May 1988. Sago pondweed (Potamogeton pectinatus) tubers were introduced into small study plots in the spring of 1987. More tubers became established and were healthier in fertilized plots than in unfertilized plots.

During Phase III (1988-1989) of this study, plant material was introduced into one cove in the lower basin and two coves in the upper basin of Lake Mead in April and May of 1988. Unpredicted low lake levels resulted in the loss of many plants. Survival rates of rooted material, however, were better than those of direct cuttings of woody plants. Site selection, particularly the soils of the site, appears to play a large part in survival. Seepwillow baccharis had the highest survival rates. In addition, greenhouse studies indicate that emergent plant tubers have some tolerance to dessication.

Twelve hundred sago pondweed tubers were planted in April 1988 in one cove in the upper basin, and 1,200 tubers were planted in a cove in the lower basin. Tubers had 100 percent germination success and provided 70 percent cover for fish by July 1988. Approximately 10,000 sago pondweed tubers were planted in April 1989 in Waterbarge Cove in the lower basin. Tubers were planted in water depths ranging from very shallow to 12-15 meters deep. Germination and establishment of tubers were very good in depths less than 7 meters; however, little or no germination of tubers was noted at depths greater than 7 meters.

A one-acre area of shoreline was hydroseeded in October 1988. Germination and establishment of seedlings was highest where soil moisture was between 20 and 30 percent. However, many seedlings were lost when water levels began to rise in January 1989.

Keywords

Aquatic plants; Environmental monitoring; Freshwater biology; Freshwater fishes; Lake Mead (Ariz. and Nev.); Vegetative covers

Disciplines

Aquaculture and Fisheries | Biology | Desert Ecology | Environmental Indicators and Impact Assessment | Environmental Monitoring | Environmental Sciences | Fresh Water Studies | Life Sciences | Natural Resources Management and Policy | Plant Biology

Language

English

Comments

From the Lake Mead Limnological Research Center, University of Nevada, Las Vegas.