Photo: Stuart Allen's Lake Berryessa Line

The Putah-Cache Bioregion Project:

Ecological Research 1998-1999

Who | What | Where | Publications

The Putah-Cache Bioregion Project has supported in whole or in part a number of studies to improve our understanding of the ecology of lower Putah Creek, its riparian strip, and the organisms that live there. The studies all involved numerous undergraduates, usually supervised by graduate students, who acquired experience and enhanced understanding of ecological and restoration principles. The projects also involved participation of landowners along Putah and Cache Creeks and of local citizens interested in restoration. The following projects are summarized here:

  1. Riparian Inventory and Biomonitoring Program
  2. Distribution and Ecology of Putah Creek Fishes
  3. Wood Duck Study
  4. California Quail Restoration Study
  5. Feral House Cat Ecology Study

I. Riparian Inventory and Biomonitoring Program

During 1998-99, the Riparian Inventory and Biomonitoring Program of the Putah Cache Bioregion Project conducted Releve surveys of riparian and upland vegetation, avian point count surveys, mammal track surveys, and small mammal live trapping surveys at twelve sites along lower Putah and Cache Creeks. The study sites along Putah Creek were located at:
  1. the Davis South Fork Preserve,
  2. the UCD Riparian Preserve Old Davis Road,
  3. the UCD Riparian Preserve Alpha Phi Omega Picnic Area,
  4. the UCD LTRAS/Russell Ranch site,
  5. the Winters City Park,
  6. Dr. Michael Barbour's property in Winters,
  7. John Pickerel's property downstream of the Solano Diversion Dam,
  8. and the Putah Creek Fishing Access upstream of Lake Solano.
The study sites along Cache Creek were located at:
  1. County Supervisor Lynelle Pollack's property in Yolo,
  2. the Cache Creek Conservancy Correll site,
  3. the Cache Creek Preserve, and
  4. the Peterson property near Capay.

In addition to augmenting an ecological database on the biological communities of our local ecoregion, preliminary results from these surveys suggested that the biological communities of the different study sites differed markedly in species composition and abundance. These differences may be due to historic and present-day land uses at and adjacent to the sites, as well as to a gradient-effect operating along the linear riparian corridor. For example, changes in community composition, evidenced by species replacements and changes in proportion of exotic species, were observed as one moved downstream from largely unconverted sites to sites more highly influenced by agriculture and other human-generated disturbances. Data are currently being analyzed to to better understand the mechanisms underlying these dynamics. These data will be used to provide future management and restoration recommendations.

This year, the project supported one graduate research assistant, Melanie Allen Truan, and five undergraduate assistants, Brena Seck, Jamie Jackson, Louise Conrad, Emily Bjerre, and Michael Atamian. The graduate RA, with help from university and community experts, was responsible for designing, organizing and supervising the research and data-collection effort. In addition, she will be using the data for her own PhD dissertation research. undergraduate assistants were trained in the various taxa-related surveys, exposing them to a broad range of field and laboratory techniques in wildlife management. Some of the students also assisted with data entry and analysis.

One of the study sites was developed into a community and university-based restoration project, Restoria, where data will continue to be collected as restoration efforts proceed. Restoration activities, such as planting and watering of trees, were accomplished with the help of volunteers from the community, including high school students and members of a local church. A study of the success of the restoration project and how the community responds to it is part of the Ph.D dissertation of Daniel Leroy. This site and the Russell Ranch site were also used as field teaching sites for WFC 100 Field Methods in Wildlife Biology, offered Spring of 1999.

II. Distribution and Ecology of Putah Creek Fishes

During the past year, the following projects were conducted as part of the Putah-Cache Bioregion Project.

  1. Continuation of monitoring of adult and juvenile fish populations of Lower Putah Creek.
  2. Continuation of a larval fish sampling program for Putah Creek
  3. Monitoring of use of Putah Creek by anadromous fishes: chinook salmon, steelhead, and Pacific lamprey.

A. Fish Monitoring - Putah Creek

This study began in the spring of 1994. The goals of the initial investigation were simply to determine distribution and relative abundance of fishes within the lower 23 miles of Putah Creek. Eight sites were chosen to reflect changes in downstream habitat. The sites were:
  1. directly below Putah Diversion Dam (PDD),
  2. the reach where Dry Creek enters Putah,
  3. below the Highway 505 bridge,
  4. UC Davis' Russell Ranch property,
  5. downstream of the Stevenson Road bridge,
  6. the UC Davis picnic grounds,
  7. the Old Davis Road bridge, and
  8. downstream of Mace Boulevard bridge.

Each of these sites was sampled once a month for the first year, using hand seines, electroshocking (where appropriate), and gill nets. For 1995-1997, each of these sites has been sampled once a month during the late spring (May) through late summer (Oct.). Subsequently the sampling has been reduced to four times/year. The first two years of data were used extensively during the Putah Creek trial (Feb-March 1996).

At each sampling date, fish are collected using the methods above and the following data is recorded for all fish caught: species, standard length, weight, and relative number of external parasites. In addition the aquatic habitat is evaluated (substrate, aquatic cover, habitat types) and the following environmental data is recorded: pH, turbidity (NTU), conductivity (umhos), temperature (centigrade) and flow (cfs). All of this data is entered into a large computer database for analysis.

The study is designed to investigate the following questions:
  1. Is native fish abundance linked to stream flow?
  2. How does this link vary between years?
  3. How are fish communities structured in a regulated stream?
  4. What factors (biotic and abiotic) influence native fish distribution and abundance?
  5. What factors (biotic and abiotic) influence non-native fish distribution and abundance?
The data was analyzed as part of the Ph.D. dissertation of Michael Marchetti which was completed in June 1999. Two papers from the dissertation have already been accepted for publication.

The following observations were made:

1. The high flows that have occurred during the study period have created large areas of gravel suitable for spawning of salmon and other native fishes. Many of these areas are in the middle reaches of the lower creek (Russell Ranch - Pedrick Rd).

2. For the past three years, flows in the creek were high during the early spring and continued above the amount of water released from SDD through the entire summer. Much of the added flow (above releases from SDD) is believed to have originated through ground water inflow.

3. The creek maintained continuous flow out into the Yolo Bypass throughout the year.

4. Native fish spawning was extensive and large numbers of juvenile fish were observed and recorded (predominately Sacramento pikeminnow, Sacramento sucker and prickly sculpin). This large recruitment may have been due to the increased spawning gravels and increased flows. A particularly large increase in native fish was observed in the lower reaches of creek from Russell Ranch to Pedrick Road.

5. Non native fish abundance was reduced. The decreases occurred mainly for the introduced centrarchid (sunfish) species such as bluegill, green sunfish and largemouth bass. These decreases may have been due to the high flows during the winter months.

B. Larval Fish Sampling

The study of larval fish in the creek, initiated in 1997, has four goals:
  1. Describe the temporal occurrence of native and introduced fish larvae;
  2. Compare species distribution and abundance at two widely separated sites (Dry Creek, Pedrick Road);
  3. Compare two methods of capture (light traps and drift nets) in terms of selectivity and effectiveness;
  4. Determine the time of day in which most larval fish enter the drift.

Both sites were sampled once a week for the period March 1 through Aug. 1 1997, Feb. 15- Aug 15, 1998, and Feb. 15 - present, 1999. All four of the goals were met in terms of data collected. The study utilized a team of 5-10 undergraduate assistants each year.

From analysis of the results, the following observations can be made:

1. Native larval fish occur earlier in the year (March through May) than exotic fish (May through July). This corresponds to the known information regarding species specific spawning times. The native fish may be responding to environmental cues different from the non- native fish (high flows and low temperature vs. low flows and warm temperature respectively)

2. The Dry Creek site had more larval fish than the Pedrick Road site in the drift nets. The Dry Creek site also had more native larvae than introduced larvae using both sampling techniques. The Pedrick Road site had more introduced larvae than native larvae. This information suggests that the Dry Creek site provides better (or more) spawning and rearing habitat for native fish than the downstream Pedrick Road site.

A preliminary comparison of the two methods of capture suggests that a sampling approach utilizing both techniques is appropriate for a full characterization of low elevation California streams. The drift nets appear to be a more consistent method to capture larvae when the flows are high (early in the season) and larvae which exhibit a propensity to drift. The native fish both appear early in the season and are more inclined to drift than non-native centrarchids. The light traps are an excellent method to sample the slow moving and pool type habitats that are more abundant later in the season. Light traps, due to their passive sampling nature, are more sensitive to placement on a local microhabitat scale and are therefore good at sampling centrarchid species which tend to be locally abundant near their nest.

C. Anadromous Fish Monitoring

Chinook salmon juveniles were first observed in the creek during routine sampling in the spring of 1995 (at Dry Creek, Old Davis Road and Mace Boulevard) and again in the spring of 1997, 1998, and 1999. Adult salmon were observed spawning in the creek during the winter 1997-98 and 1998-99 and spawned out carcasses were found. Flows in the creek in November and December were low so that the connection of the creek to the Sacramento River (via the Yolo By-pass) was minimal. Nevertheless, a few adult salmon were observed spawning in the creek and juvenile salmon were abundant in the April and May. The large size and robust bodies of the juvenile salmon indicated rapid growth in the creek, suggesting Putah Creek has considerable potential as a nursery area.

Steelhead anglers who fish the creek every year were contacted and asked to provide evidence of their catches. Unfortunately, high water during the time the fish were likely to be in the creek prevented any from being caught by our contacts. Electrofishing the reach below SDD in the fall and spring, however, produced mainly juvenile trout, suggesting they were the progeny of steelhead.

In April and May, 1999, adult Pacific lamprey were observed spawning in some numbers in the creek. Although lamprey larvae have been captured annually in our samples, this is the first time that spawning has been observed.

III. Wood Duck Study

A crew of graduate and undergraduate students under the direction of Dr. John Eadie has been studying the ecology and reproduction of wood ducks along lower Putah Creek. They have found that the creek is an important habitat for these birds and that reproductive success in woodduck houses put up by cooperating landowners is high. A particularly critical finding is that many of the ducklings rear in one section of the creek (the reach between Old Davis Road and Mace Blvd just acquired by the University) and that disturbance by humans may negatively affect their survival. This reach should probably be declared off-limits for recreation during the spring and summer months when the ducklings are rearing.

IV. California Quail Restoration Study

In an effort to see if California quail populations can be increased along Putah Creek, undergraduates under the direction of graduate student Michelle Johnson have constructed some artificial quail shelters on University land near the creek. Evaluation of the use of these shelters by quail is underway.

V. Feral House Cat Ecology Study

Last year, a number of feral house cats living in the Putah Creek Riparian Reserve were tagged with radio collars and followed around by teams of undergraduates, under the direction of professors Douglas Kelt and Dirk Van Vuren. Cats are potentially major predators on migratory birds and other native organisms that use the narrow riparian corridor. This study has defined how they use the habitat and has wide applicability to other situations, especially where control of wild cats is deemed desirable. The results have been submitted for publication.

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