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The Problem
The California freshwater shrimp (Syncaris pacifica) is a federally listed endangered species whose distribution is seemingly restricted to low elevation perennial streams in Marin, Sonoma, and Napa counties north of San Francisco Bay, California. However, little is known about the habitat requirements of this shrimp. Previous studies have shown that shrimp are typically found within or on undercut stream banks, exposed roots, overhanging woody debris, and overhanging vegetation. The proposed study will add to our understanding of the habitat requirements of shrimp by quantitatively assessing the relation between shrimp abundance and selected habitat variables in reaches of Lagunitas and Olema creeks lying within or adjacent to National Park boundaries. Objectives The 5-year research goals of the Fisheries and Aquatic Resources Program are to understand relationships between and among aquatic species habitats and provide science for restoring and maintaining declining species and their required habitat. Specific objectives of this subtask are as follows: (i) to determine if shrimp are homogenously distributed throughout Lagunitas and Olema creeks or if their distribution is concentrated in certain localities; and (ii) to determine if shrimp distribution is associated with selected habitat characteristics (e.g., stream morphometry, water quality, types and amounts of underwater cover, cohabiting fish species). The subtask will allow the National Park Service to better assess whether past and current land use practices along these streams are adversely affecting shrimp abundance. Specifically, results from this subtask will be used to identify management actions that benefit the shrimp population in Olema Creek, but could also benefit shrimp in Lagunitas Creek and elsewhere. The ecological data will also contribute to
Methodology Sampling sites and times: The study area will consist of the 13-km reach of Lagunitas Creek located within or adjacent to the Golden Gate National Recreation Area and the 0.5-km reach of Olema Creek located within the Point Reyes National Seashore. A total of at least 10 pools, five riffles, and five glides will be randomly selected from the two combined creeks to serve as fixed sampling sites. Sampling trips will occur on at least four occasions spanning the wet and dry seasons.
Sample collections at fixed sampling sites will proceed from downstream to upstream. The evening before a fixed sampling site is intensively sampled, baited minnow traps will be installed and fished overnight. The next day, these minnow traps will be removed and the catch processed, then the site will be re-sampled by using dip nets and seines. In addition, the site will be measured for selected habitat variables. This sampling sequence will continue until all fixed sites within the two creeks have been visited. Intensive sample collections at fixed sampling sites will consist of collecting shrimp and fish, and measuring associated habitat variables. These collections and measurements will be made at multiple sampling points identified from a network of appropriately spaced grids (e.g., 5 m X 5 m) according to the "points sampling method" (Wright et al. 1981). Final determination of grid size will be determined after completing a preliminary sampling trip.
Shrimp and fish collections: Shrimp and fish will be collected by using a combination of baited minnow traps, minnow seines, and dip nets. To reduce the likelihood of over-saturating specific habitats with minnow traps, only one trap will be fished at each sampling point identified from the grid network. Fishing effort for minnow traps will be standardized at about 16 hrs to quantify the relative abundance (catch per unit effort) of shrimp. Bag seines and dip nets will be used to supplement minnow-trap catches of shrimp and fish. In general, a fixed sampling site will first be fished with the bag seine, then the site will be "rested" for at least 60 min before it is fished with dip nets. Fishing effort for seines will be standardized at about 5 m (the linear distance over which the seine is hauled), whereas fishing effort for dip nets will be standardized according to the linear distance of shoreline fished with this gear. Seines will be hauled indiscriminantly through open water (mid-channel) and along the shoreline in both vegetated and non-vegetated areas, whereas dipnetting will focus on vegetated shoreline areas.
Immediately upon capture, shrimp and fish will be placed into plastic buckets filled with site water. Shrimp will be sexed, measured for postorbital length and rostrum length, and the first 25 individuals will be weighed, then all shrimp will be released alive in the vicinity of capture. Fish captured by seining and dipnetting will be identified and counted, the first 10 individuals of each species (except salmonids and other protected fishes) from each fixed sampling site will be preserved in 10% formalin, then remaining fish will be released alive in the vicinity of capture. Preserved fish will be subsequently measured for standard and total lengths, weighed, and subjected to gut analysis to determine if shrimp are present in their diets. Habitat measurements: Fixed sampling sites will be characterized according to their morphometry, water quality, average current velocity, types and amounts of in-stream cover/shelter for shrimp, and bottom substrate composition. Data management and statistical analysis: Raw data will be stored as Excel files on a microcomputer and summarized with SAS, SAS Graph, Freelance graphics, or other appropriate statistical and graphical software. Unless specified otherwise, the level of significance for rejecting null hypotheses of statistical tests is P=0.05. Highlights and Key Findings Field work is scheduled to begin in FY-2003. Where Are We Headed In 2003 Field work will occur at quarterly (seasonal) intervals beginning on or about February 2003. We will collect data on abundance of shrimp and cohabiting fish species, and document physicochemical variables.
Project Contact Michael Saiki Email: michael_saiki@usgs.gov Publications |
