|
|
Napa County Resource Conservation District |
|
| back |  RCD home |
|
|
Napa County Resource Conservation District |
|
| back | RCD home |
The RCD biologist, along with other RCD staff and community volunteers, conducts a variety of surveys to monitor steelhead populations. The type of surveys used varies with the time of year and with the objectives of the various grants providing funding to the RCD. The following are descriptions of some of the surveys currently in use. All surveys are performed only with landowner consent.
Total Basin Fish Count
The Total Basin Fish Count protocol is an adapted version of a widely used protocol developed by the researchers Hankin and Reeves. Through this survey, a team of two walks a creek from the mouth to the headwaters and snorkels selected pool, riffle, and glide habitats to count steelhead. Typically every fifth pool, every eighth glide, and every eleventh riffle are counted. Measurements are taken at the selected habitat units of maximum depth, length and width and of available cover for fish. Water and air temperature are taken at the first and the last habitat unit of each day throughout the survey. Any other fish species observed during snorkel counts are noted, but not counted.
The objective of this survey is not (as the name implies) to count every fish within a watershed. The objective is to get a relative number of fish within the watershed surveyed that can be compared with counts from similar surveys in other watersheds. The RCD is performing this type of survey in order to gain increased knowledge of the distribution of steelhead in the various tributaries in the Napa River watershed and to get a total population estimate of steelhead in tributaries.
Electrofishing
The RCD occasionally performs electrofishing surveys at selected sites on Napa River tributaries under a California Department of Fish and Game permit. The RCD uses a 3-pass electrofishing method to collect information on steelhead populations. In this methodology, a 30-meter section of the stream is blocked off with seine nets on the upstream and downstream ends. An electrofishing unit is used within the netted area to temporarily stun fish. One person passes through the unit with the electrofisher while another person nets the fish. The team passes through the area 3 times to ensure that virtually all the fish within the 30 meter section are removed. The fish are measured and weighed, and then released into the stream unharmed.
The objective of this type of survey is to obtain accurate information on fish. It is performed in a section of the stream that is representative of typical habitat for the stream. The data collected can be used to gain an understanding of the structure of fisheries population in that stream. The length measurements provide information on the age classes of the fish present. The weight measurements provide information on fish biomass. This type of survey can be especially helpful in determining fish population trends when performed on a yearly basis.
Presence / Absence Surveys
It is sometimes useful to determine where in a stream steelhead (or other species of fish) are residing. The RCD uses presence/absence surveys to determine which Napa River tributaries have steelhead residing in them, and to determine where in the tributary steelhead are found. Staff members check tributaries for steelhead by observing fish from the stream bank and using a mask and snorkel.
|
|
 RCD home |
|
| back |