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Program Element

       Name of study:  Fall Midwater Trawl Survey
 
       Program manager
              Name:    Donald E. Stevens
              Agency:  California Department of Fish and Game
              Address: 4001 N. Wilson Way
                       Stockton CA 95205
 
              Phone:   209-948-7800
 
       Purpose/Objective:
               To monitor the abundance and distribution of striped bass 
	       and other species which inhabit the estuary during the 
	       fall of the year.

       Geographic range of field work: Sampling was done in San Francisco 
       Bay during the early years until the Bay-Outflow program began in 
       1980.  Since then the survey starts in San Pablo Bay and samples 
       Suisun Bay and the Delta.

       Number of sites:
              The number of sites has varied over the years as study 
       objectives have been expanded and perceptions of sampling 
       efficiency have changed.  In all, 145 sites have been sampled, 
       exclusive of sampling in San Francisco Bay.  Only a subset of these 
       sites have been consistently sampled over all the years.
 
       Period of record (Start year): 1967 to present except for 1974 
       and 1979 when no sampling was done.
 
       Size for complete data base for program element in KB (MB):
       Number of individual files:  Catch files (several), Length files 
       (several).
 
       Sample frequency per time unit (second, week, month):  Sampled once 
       per month as early as July and as late as April.  The most 
       consistent sampling has been for the period September through 
       December.
 
       General category of data collected (e.g., media, flow, physical, 
       common chemicals, metals, pesticides, nutrients,  chlorophyll, fish,
       invertebrates, or phyto/zooplankton):
 
              Fish data: (all species are identified and enumerated; 
              striped bass are measured and assigned to an age group based 
              on size distributions and/or scale analysis to determine 
              their ages).  
	      Physical data collected are: secchi( measured since 1971; 
              also turbidity data was taken prior to secchi or in addition 
	      to it); water temperature; and specific conductance (measured
              at the surface).  Meter readings to measure water velocity 
              past the boat have been made in more recent years.  Prior to 
              that boat speed measurements were made with a Kenyon boat 
              speedometer.
 
 
       Comments about element (e.g., idiosyncracies, changes over time, 
       special events, etc.):
              The gear is efficient only for small fish.
Field Sampling
       Gear type or field instrument used:
              A 12 ft x 12 ft midwater trawl with variable meshes starting 
              with 8 inch mesh at the mouth of the net.  The cod end is 1/2
              inch  mesh.
 
       Brief description of sampling procedure, including sub-sampling, 
       sorting, identification of organisms  (this should include 
       procedures for transport of sample from field to lab):
              A ten minute diagonal tow is made with the midwater trawl.  
              The trawl does not reach the bottom in all cases where the 
              site depth is greater than the net depth, but the goal is to 
              fish close to the bottom. Fish are sorted by species and 
              counted.  All striped bass are measured and a random 
              subsample of other species are measured as time permits.  All
              shrimp caught are identified to Genus, i.e., as either  
              Crangon or Paleomon.
 
              Lengths of fish other than striped bass were not measured 
              until about 1972.  To estimate the number caught in large 
              catches of  abundant species like anchovies, volumetric 
              measurements are made of the total catch; subsamples are 
              counted and catch estimates expanded from the counts and 
              volumes.

       Reference to any written protocols and how to obtain a copy:
              Protocol copy is available upon request to the project 
              manager.
 
       Changes in gear or procedures which affected the data over time:
              The mode of data collection has been consistent.
 
Laboratory analysis - Chemical
       Name and address of laboratory(s) running analysis:
              N/A
              Current since (date):
              Historical lab (if known) or reference to other 
              documentation:
 
       Analytical methodology for each parameter or group of parameters:
 
       Reference to table which lists detection limits for each parameter:
 
              Current procedure since (date):
              Historical procedures (if known) or reference to other 
	      documentation:
 
       Quality assurance/control (QA/QC) protocols (if brief) or one-line 
	qualifier:
 
       Reference to any written QA/QC protocols and how to obtain a copy:
 
Laboratory analysis - Biological
       Name and address of laboratory(s) running analysis:
 
              Current since (date):
              Historical lab(if known) or reference to other documentation:
 
       Methodology for each analysis:
 
              Current procedure since (date):
              Historical procedures (if known) or reference to other 
	      documentation:
 
       Reference used for identification of organisms:
 
       Location of reference collection (if one exists):
 
       Reference to table listing scientific name, common name (if any), 
       and code used: