Department of Water Resources Home
IEP Banner

Splittail Studies – Metadata

Program Element
     Name of study:  Splittail Studies (Pogonichthys macrolepidotus, Ayers) 

     Program manager
          Name:	   Randall Baxter
          Agency:  California Department of Fish and Game
          Address: 4001 North Wilson Way
		   Stockton, CA  95205
          Phone:   (209) 948-7800

     Purpose/Objective:  
     The principle objectives of the study are: 1) determine if 
     juvenile (young-of-the-year and age-1 fish) and adult splittail 
     were resident in the Sacramento and/or San Joaquin rivers during 
     August, a non-spawning period; 2) document the August distribution 
     and relative abundance of juvenile and adult splittail in Suisun 
     Marsh, Suisun Bay, the Delta and the lower Sacramento and San 
     Joaquin rivers; 3) identify habitat and compare use of juvenile 
     and adult splittail, including proximity to vegetated channel 
     margins; 4) qualitatively compare catch between gill nets and trawls
     presently used to collect abundance trend data; and 5) describe the 
     age composition of the sampled population through scale analysis.


     Geographic range of field work:  The lower Sacramento and San
     Joaquin Rivers, the Delta, Suisun Bay and Suisun Marsh.

     Number of sites:  24

LOCATION/DESCRIPTION		                   LATITUDE  LONGITUDE  RIVER MILE

Subarea 1.  Lower Sacramento River.
11  Immediately upstream of Tisdale Weir  	   39 01.58  121 49.47	119
12  Verona					   38 47.05  121 37.07	 80
13  Mouth of Deep Water Shipping Channel	   38 33.42  121 31.11	 57
14  Walnut Grove at head of Georgiana Sl.	   38 14.23  121 30.57	 27

Subarea 2.  Mid-Sacramento River.
21  North of Colusa				   39 13.54  121 59.46	146
22  Butte City Boat Ramp			   39 27.43  121 59.34  165
23  North of Princeton				   39 25.33  122 00.33  169
24  Mouth of Pine Creek				   39 44.39  121 57.50	197

Subarea 3.  South Delta / San Joaquin River.
31  Old River at Indian Slough		  	   37 54.57  121 33.57	
32  Old River at Grantline Canal	 	   37 49.12  121 32.52
33  San Joaquin River at Turtle Beach		   37 46.34  121 18.07	 57
34  San Joaquin River at Gardner Cove		   37 38.19  121 13.07	 79

Subarea 4.  Honker Bay / Confluence/ Sacramento River.
41  Honker Bay at Mud Sl., E. of Dutton Is.	   38 04.29  121 57.30
42  Mallard Slough next to Pittsburg Power Plant   38 02.26  121 54.19
43  Northern end of Sherman Lake at Sacramento R.  38 03.10  121 47.54	  3
44  Horseshoe Bend				   38 05.12  121 42.38	  8

Subarea 5.  Suisun Marsh.
51  Suisun Sl. at Cordelia/Goodyear Sl.		   38 08.22  122 04.24
52  Nurse slough at Little Honker Bay		   38 10.36  121 55.10
53  Montezuma Sl. at Cutoff Sl.			   38 11.03  121 59.19
54  Suisun Sl. at Wells Sl.			   38 10.16  122 03.32

Subarea 6.  Central Delta / South Fork Mokelumne River.
61  Big Break and Dutch Sl. at the San Joaquin R.  38 01.32  121 43.26
62  San Joaquin R. just east of Santa Clara Shoals 37 06.02  121 36.58
63  Old River at the San Joaquin River		   38 04.11  121 34.37
64  South Fork Mokelumne R. west of Sycamore Is.   38 08.39  121 30.23


     Period of record (Start year):  August 1994

     Size for complete data base for program element in KB (MB):  267K

     Number of individual files:  1

     Sample frequency per time unit (second, week, month):  At each
     location, gill nets fished between the hours of 18:30 and 06:00
     on two nights a week apart.
 
     Duration:  1 hrs/set, rarely as long as 5 hrs/set.

     General category of data collected (e.g., media, flow, physical,
     common chemicals, metals, pesticides, nutrients, chlorophyll,
     fish, invertebrates, or phyto/zooplankton):  fish species, 
     fish length, gill net effort, water parameters: depth, tide,
     temperature, salinity (at some locations).

     Comments about element (e.g., idiosyncracies, changes over time,
     special events, etc.):  N/A

     Field Sampling
     Gear type or field instrument used:  variable-mesh, nylon gill nets.

     Brief description of sampling procedure, including sub-sampling,
     sorting, identification of organisms (this should include
     procedures for transport of sample from field to lab):

     Reconnaissance Phase.
     Field sampling was broken into two phases, 
     a reconnaissance phase and a study phase.  During the reconnaissance
     phase (27 June to 31 July 1994), six field crews surveyed their 
     respective project subareas during daylight hours and nonrandomly 
     selected four sampling locations within each, for a total of 24 
     locations. Within each location, three specific sites were selected
     where gill nets would be set during the study phase of this project.
     Finally, the reconnaissance phase also provided an opportunity for
     field crews to become familiar with their nets, equipment and sampling
     locations, and to use and refine sampling protocol.

     Reconnaissance sampling was conducted with 10 by 100 ft variable 
     mesh (1, 1.5, 2, 3, 4 inch stretch mesh sections) monofiliment gill 
     nets.  Sampling locations were selected based upon geographic dispersal 
     through the subareas, proximity to known areas of splittail habitat 
     and the presence of emergent vegetation.  Set depth was held to less 
     than 20 ft to facilitate comparability across all locations and to 
     reduce problems associated with strong currents in deeper water.  
     Currents and leaf fall limited the locations that could be sampled 
     in the rivers to backwaters.  Net sites were separated as broadly as 
     logistically reasonable to reduce the potential for any net to affect 
     the catch of another.  Net sites in the Sacramento and San Joaquin 
     river locations were closer together than those elsewhere--generally 
     within the same backwater.  Based upon reconnaissance sampling, 
     criteria for net placement were established, but were somewhat 
     different for river and non-river subareas.  The principal net 
     placement criteria (subareas 3 - 6) were: net 1) inshore, perpendicular 
     to shore near vegetation, 5-12 ft deep, fine mesh toward shore; net 
     2) offshore, perpendicular to shore, 8-20 ft deep, fine mesh toward 
     shore; and, net 3) near shore, parallel to vegetated shallows or the 
     mouth of a small slough, 6-12 ft deep.  Secondary net placement 
     criteria, used primarily in subareas one and two where principal 
     criteria could not be used, were:  net 1) backwater, parallel to 
     shore just offshore of vegetation; net 2) backwater, perpendicular 
     to shore, small mesh inshore; and net 3) backwater entrance, 
     perpendicular to shore at mouth.  For most locations in subareas 3-6, 
     net 1 sampled fish from inshore vegetated habitats; net 2 sampled 
     fish using offshore, open water habitats; and net 3 sampled fish 
     moving between inshore and offshore habitats, but was primarily used 
     to increase catch at a location.

     Study Phase  
     During the study phase, which occurred from August 1 through 5 
     and 8 through 12 1994, three multifiliment (8x100 ft; 1, 1.5, 2, 2.5, 
     3 inch stretch mesh) gill nets were set overnight (between 18:30-06:00) 
     at each location once each week following established net placement 
     criteria.  Multifiliment gill nets were used to reduce fish injuries, 
     to enhance the catch of "small" fish, and to increase twine strength 
     relative to comparable monofiliment nets.  Net length was limited to 
     100 ft in an attempt to keep catches manageable and reduce potential 
     splittail mortality.  River water clarity necessitated night sampling 
     to reduce net avoidance and allow comparisons across river and Delta 
     locations.  Nets were checked at intervals that varied between 0.5 and 
     5.0 hours, depending upon catch and location.  Data were recorded for 
     each set of each net.

     Scale samples were taken from all splittail by scraping 
     their left side above the lateral line adjacent to the posterior 
     insertion of the dorsal fin.  Scales were stored in a labelled coin 
     envelopes.  All non-morbid fish greater than 199 mm FL were tagged 
     with numbered Floy anchor tags on the right side of the fish opposite 
     the area scales were taken.  All tagged and nontagged splittail were 
     held in 4 x 4 x 8 ft floating net pens anchored on location until 
     nightly sampling was complete, then live fish were released.  Dead 
     fish were retained for other work not reported in this document.

     
     Reference to any written protocols and how to obtain a copy:
     "Distribution and Relative Abundance of Splittail (Pogonichthys 
     macrolepidotus) in the Sacramento and San Joaquin Rivers and Delta 
     during August 1994."  To obtain a copy, contact the Program Manager.

     Changes in gear or procedures which affected the data over time:
     N/A

     Laboratory analysis - Chemical
     Name and address of laboratory(s) running analysis:  N/A

          Current since (date):  N/A
          Historical lab (if known) or reference to other documentation:
	  N/A

     Analytical methodology for each parameter or group of parameters:
     N/A

     Reference to table which lists detection limits for each parameter: N/A

          Current procedure since (date):  N/A

          Historical procedures (if known) or reference to other 
	  documentation:  N/A

     Quality assurance/control (QA/QC) protocols (if brief) or one-line
     qualifier:  N/A

     Reference to any written QA/QC protocols and how to obtain a 
     copy:  N/A

     Laboratory analysis - Biological
     Name and address of laboratory(s) running analysis: DFG Stockton, CA 

          Current since (date):  August 1994

          Historical lab (if known) or reference to other documentation: N/A 

     Methodology for each analysis:

     Aging    
     Splittail were separated into age classes based upon length 
     criteria and scale aging.  Historic CDF&G Bay Study splittail length 
     data were tabulated into five mm interval by month and examined for 
     "breaks" to establish length criteria for separating age classes. 
     The initial length interval (55-59 mm) included the smallest splittail 
     collected in August by the CDF&G Bay Study.  Minimum lengths for age-1 
     and age-2+(age -2 and older) fish in August were 140 and 220 mm FL, 
     respectively.  Gill net collected splittail were assigned to 
     young-of-the-year (YOY), age-1, and age-2+(age-2 and older) age groups 
     based upon length criteria.  YOY and age-1 splittail were considered 
     juveniles.

     Scales were read without reader knowledge of the length of the 
     fish.  The record number, from the length database, of each fish 
     scale sampled was written on the upper right corner of its scale 
     envelope and the length taped over prior to reading scales.  Scales 
     were viewed through binocular scopes at five power.  Each scale was 
     examined independently by two separate readers experienced in reading 
     striped bass scales.  Annuli were identified based upon "crossing 
     over" of circuli and other criteria listed in Bagenal and Tesch 
     (1978).  When annuli counts differed, scales were re-examined and 
     annuli counted a third time.  If this count coincided with a previous 
     count it was accepted as correct, otherwise readers discussed 
     observations and criteria until a decision could be made.  It was 
     assumed that annulus formation occurred in February or March 
     (Caywood 1974). 

     Data Analyses  
     Catch-per-unit-effort (CPUE) was calculated as the number of 
     splittail caught per hour of fishing time.  CPUE data were grouped 
     differently for different analyses: 1. CPUE for each net-night (n=6, 
     for each location)--for analysis of variance; and 2. CPUE for each 
     location (n=24)--within a location, the average of all net-night 
     values--used to represent effort corrected catch at each location; 
     3. CPUE for salinity intervals (0-11, by 1 ppt), tidal stage (high 
     slack, ebb, low slack, flood), and time interval (set start times: 
     1800-2000, 2030-2230, 0300-0430, 0500-0630) was calculated as the 
     quotient of total catch within a category or interval and the hours 
     fished within the same category or interval.  Data for Location 62, 
     night 3, net 1 were not included in any analyses because the net was 
     fished less than half the night and most of the splittail catch in 
     the remaining nets occurred when net 1 was not fishing.  Individual 
     net sets were not included in any analyses when catch and net 
     condition at retrieval indicated that the net was not fishing 
     correctly during most of the set.  In analyses of tide and time 
     affects on CPUE, only data from Suisun Marsh locations, 51-54, were 
     used.  At these locations sets were consistently short enough 
     (<90 min) to represent distinct tides and time intervals.

     Analysis of variance procedures (ANOVA) on SYSTAT were used to 
     determine the effects of location and habitat (proximity to shore/
     vegetation=NET) on splittail CPUE.  CPUE data were not normally 
     distributed and the variance increased with the mean; CPUE data 
     were transformed--Log10(CPUE+1)--before ANOVA procedures were run.  
     Null hypotheses were rejected at P 0.05.  Tukey multiple comparison 
     tests (e.g. Zar 1984, p. 230-231) were used to determine whether 
     splittail Log10(CPUE+1) at a particular location differed 
     significantly from those at all other locations.  Analyses of 
     variance procedures were repeated without NET 3 data or data from 
     locations where no splittail were caught to determine if these 
     factors obscured any significant habitat (i.e., inshore-offshore) 
     effects on Log10(CPUE+1).

     The potential relationship between splittail abundance and 
     emergent vegetation was examined by relating the average 
     Log10(CPUE+1) by location to a Geographic Information System (GIS) 
     summation of the total area (m2) of emergent vegetation within a one 
     mile radius of each location.  Emergent vegetation habitat types 
     summed for this analysis included:  1. PEMV: palustrine, emergents, 
     permanently tidally flooded; 2. PEMR: palustrine, emergents, 
     seasonally/tidally flooded; 3. PSSR/PEMR: palustrine, shrub/scrub 
     and emergent, seasonally/tidally flooded; 4. PEMT: palustrine, 
     emergents, semipermantly/tidally flooded; 5. PFO/EMR: palustrine, 
     forested and emergents; 6, PSS/EMR, PEMC, PEMR, E2EMN (U.S. Fish and 
     Wildlife Service wetlands and deepwater habitats classification 
     system, Cowardin et al. 1979).  Only locations where splittail were 
     collected were used for the correlation analysis.  It was assumed 
     that parameters other than emergent vegetation were responsible for 
     the lack of catch in upstream areas.

     Other Species  
     Data for other species were summarized as total catch by 
     species and location for all nets and both nights.  Note that effort 
     was less at Sacramento and San Joaquin River locations outside of 
     the central Delta than for locations in the central Delta and to the 
     west because of the closer proximity of the three nets in river 
     locations.  Maximum salinties at the point of capture also were 
     reported for the more common species and for Cyprinids.


     Current procedure since (date):  August 1994

     Historical procedures (if known) or reference to other 
     documentation: Bagenal and Tesch (1978) Lit Cited.

     Reference used for identification of organisms:
     Moyle, P.B. 1982. Keys to the inland fishes of California.
     Inland fisheries informational leaflet No.34. 14pp.

     Location of reference collection (if one exists):  N/A

     Reference to table listing scientific name, common name (if 
     any), and code uesd:
	GN code	  Common Name	    Scientific Name

	CHEMCT	  shimofuri goby    Tridentiger bifasciatus (Steindachner)
	GSF	  green sunfish     Lepomis cyanellus (Rafinesque)