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Electrofishing and Hoopnet Data – Metadata

Program Element:
     South Delta Temporary Barriers Project.
     Fish community monitoring.

Contact: Michael P. Healey

    Element 2 of the Temporary Barriers Project was designed to measure 
changes in abundance and distribution of fish in southern Delta channel 
areas influenced by the barriers.It was also intended to monitor 
predator species abundance (such as striped bass, largemouth bass, 
squawfish, and channel catfish) near barriers.

Geographic range of field work:
     Southern Delta

Number of sites:
     15 permanent sites

Period of record:
     1992 - present

Sample frequency for Element 2:
     Sampling for temporary barriers is year-round and is conducted 
monthly for all sites. Sampling lasts two weeks.

     Sampling schedule will proceed as follows:  

         Day 1.  A hoop-net will be put out at each location during 
the afternoon and allowed to fish for two days.  Gill nets will be  
fished on the downstream side of barriers for 1 hour sets until dark 
(A minimum of four sets).

         Day 2.  Electrofishing will be conducted along 500 - 1,000 foot 
of shoreline at each designated site during evening hours.

         Day 3. Hoop nets from day 1 will be retrieved and relocated to 
another barrier site.  Gill nets will be fished accordingly.

         Day 4.  Electrofishing.

         Day 5.  Hoop nets will be retrieved.

Gear types used:
     Electrofishing and hoop-netting will be conducted at all sites 
and electrofishing and gill nets will be used to collect predators 
near barrier sites for stomach analyses.

Data collected:

     During collections all species caught or a subsample 
     thereof will be identified, measured and counted.
     Other measurements are:
 	Start and end time of sampling (Pacific standard time);
	Surface specific conductance (uS/cm);
	Surface water temperature (degrees Celsius);
	Secchi depth (cm);
	Dissolved oxygen (mg/l)

Description of field sampling procedures:

Stomach pumping.

     1.  Stomach contents will be taken from predators at barrier 
stations for the following size classes (up to 5 of each species):

                    Striped bass  	 ò180mm 
                    Largemouth bass      ò250mm
                    Channel catfish      ò250mm
                    Squawfish            ò250mm

         a.  stomachs will be pumped using a 1 1/3 gallon pump sprayer.

         b.  rinse out a 1 gallon plastic wash pail for collecting 
	     flushed stomach contents.

         c.  fill sprayer with water and pump approximately 20 - 25 
	     times to generate a moderate amount of pressure for 
	     flushing stomach.

         d.  select the appropriate size stomach pump tube to insert in 
	     the fish's pharynx. Attach to nozzle of sprayer.

         e.  insert the tube into the pharynx and hold the fish to 
	     the head is down and over the wash pail and a thumb is 
	     over the vent.

         f.  release water into stomach from pump, ensuring that 
	     water is not coming out of gills, but through the stomach 
	     pump tube.

         g.  remove stomach pump tube in a manner that allows the 
	     contents to empty into the wash pail.

         h.  repeat the above steps until assured that all stomach 
             contents have been removed.

         I.  return fish to water.

         j.  empty contents into a 1 quart jar.  Rinse pail with 
	     sprayer so that any remaining stomach contents are 
	     flushed into the collection jar,  Add enough formalin 
	     to form a 10 % solution.  Place a label with the 
	     appropriate information on fish type, length, method of 
	     capture, date, time, collector, and site of capture in jar.  
	     Ensure that the lid is tightly screwed on and no leakage 

         k.  repeat this procedure for each fish to be pumped.  

Each hoopnet will be left in the water for approximately 
forty-eight hours at each sampling station.

               (1)  Hoop-netting requires three people, but the 
		    job can be done with two experienced people 
		    if necessary.
                    (a)  Two of the three people will be involved 
			 in the setting and pulling of the nets, 
			 as well as the measuring of any caught
                    (b)  The third person will drive the boat and 
			 write down fish lengths as they are called 
		         out by the two samplers.
               (2) Transportation
                    (a)  One truck should be available to pull the 
			 boat out to the launch site.  
                    (b)  One boat, hopefully one with lots of 
			 floor space, should be available for 
Equipment Preparation
               (1)  Equipment List
                    (a)  Three to five hoopnets, depending on the area.
                    (b)  Three to five railroad ties.
                    (c)  Three to five 8lb. Danforth anchors with 
                    (d)  One bucket containing the grappling chain 
			 and sixty feet of rope.

Data Collection
                    (a)  Two measuring boards.
                    (b)  Clipboard with three to five HOOP-NETTING 
		         data sheets and pencils.
                    (c)  Secchi disk.
                    (d)  Fathometer.
                    (e)  Thermometer.
                    (f)  Tool box.
                    (g)  Round galvanized tub.
               Optional gear.
                    (a)  Rain gear.
                    (b)  Rubber calf boots.
                    (c)  Maps with appropriate sampling stations.
                    (d)  Fish identification keys.
Sampling Procedures

          I.   Readying the hoopnets for deployment into the water.
               (1)  Remove the duct-tape from the rope connected to 
		    the first hoopnet.  Unwind the ropes to get 
		    rid of knots.
               (2)  Attach a large anchor to rope at one end of 
		    the hoopnet using the caribeener.  At the 
		    other end of the hoopnet will be another loose 
		    rope with a loop on it.  Attach the railroad tie 
		    to this rope.
               (3)  Check the cod ends (small hoop)  of the net to 
		    be sure that they are tied shut.
Setting the hoopnet.

               (1)  Position yourself on the bow of the boat and be 
		    prepared for the boat to begin backing up.
                    (a)  The boat will back up parallel to the 
			 shoreline to fascillitate a straight setting 
			 of the net. 
                    (b)  The water should be at a depth from ten to 
			 fifteen feet to prevent the net from being 
			 exposed during low tide.
               (2)  When the driver asks you to, throw the anchor 
		    overboard and allow it to sink to the bottom.
               (3)  Hold firmly to the rope until the Danforth 
		    anchors itself to the riverbed.
               (4)  Grab the first set of hoopnets and toss them 
		    overboard. Watch your fingers.
               (5)  Hold on to the following rope until the first set 
		    of hoops stretch out tightly.
               (6)  Gradually allow the rope to feed out as the hoops
                    sink slowly into the water.
               (7)  Grab the next seven rings and toss them likewise 
	            into the water. Again, hold on to the rope following 
		    the rings until they stretch out.
               (8)  Tie the end of the rope to the end of the hoopnet 
		    rope to the railroad tie and feed the rope-end of 
		    the grappling chain through the loop of rebar on the 
		    railroad tie.
               (9)  Grab onto the free end of the rope in one hand, 
	            and with the other hand grab the part of the rope 
		    that leads to the grappling chain.
               (10) Allow the backing of the boat to pull the railroad 
		    tie into the water.  Keep hold of the free end of 
		    the rope.
               (11) Once the railroad tie hits the river substrate, 
		    brace yourself with both ends of the rope in hand.  
	            At this point the driver will begin to back more 
		    rapidly.  This will stretch the hoopnets out until 
		    they are fully extended.          
               (12) Let go of the free end of the rope and pull it back 
		    on board.
               (13) On the Hoop-netting data sheets, the designated data 
		    person (usually the driver) will write down 
		    information pertinent to finding the hoopnets after 
		    the forty-eight hours of sampling.
                    (a)  Landmarks on the riverbanks will be written 
		         down in order to locate both the anchor and 
			 the weight ends of the hoopnet.
                    (b)  After both ends of the net have been set in 
			 the water, write down the time (officially 
		 	 called the set time) and date (set date).  
		         This is also the appropriate time to gather 
			 any needed water quality data.

Retrieving the hoopnets.

               (1)  Put yourself on the bow of the boat with grappling 
		    chain in hand.
               (2)  The driver will position you to where the weight 
		    end ( the most downstream side) of the hoopnet 
		    should lay in the water using the information on 
		    the data sheet.
               (3)  At the driver's signal, toss the grappling chain 
		    out into the water.  Give it enough slack so that 
		    it will drag on the riverbed.  As the boat backs 
		    away from the shoreline.
               (4)  When the grappling chain hooks itself onto the 
		    hoopnet rope, the grappling chain will drag 
		    considerably heavier than it normally does.  
	       (5)  Tell the driver that you've caught the net, and 
		    begin pulling in the rope and grappling chain.  
		    When you get to the net-rope, disentangle the 
		    grappling chain from the net-rope and place it
                    carefully back in the bucket.
               (6)  Commence pulling in the weight (railroad tie) first.
               (7)  Pull in the first (downstream hoops) hoopnet.  
                    (a)  Tie off the rope between the upstream 
			 and downstream sections of hoops to prevent 
		         the river flow from dragging the downstream 
			  hoops back in the water.
                    (b)  Holding the cod end (small ring side) at about 
		         chest level, shake the fish out of the net, 
			 ring by ring, into the boat. 
		    (c)  Measure every fork-length.  The driver will
                         be writing down the measurements, so be sure 
			 to speak clearly.  If you can't identify a 
			 fish, ask your crew members.  If no one on 
			 the boat is confident that they can identify the 
			 fish in question, bag it, or put it in a jar with
                         formalin. and bring it back to the office.  
			 Be sure to place a tag  with the size of the 
			 fish, and where and how the fish was collected.
                         (I)  If the hoopnet is full of a certain 
			      species, take a subsample of the 
			      species so as to get approximately 
		              50 measurements.
               (8)  Untie the hoopnet rope that you just tied to 
		    the boat railing,  and again pull in the rope 
	       	    connected to the final hoopnet.
               (9)  Once you get the hoopnet in hand, be sure that 
		    you don't dump out any fish back into the water.
		    Gather up the rings before you pull it out of 
		    the water to avoid losing any fish.
               (10) Again, holding onto the cod end of the rings, 
		    dump the fish out on the bow of the boat and 
		    measure them.
               (11) Once all of the fish are measured, pull in 
		    the rest of the rope and the anchor.
               (12) The data-person will write down the end time 
		    when the second hoopnet is pulled from the water.


Preliminary activities for gill-netting for Temporary Barriers Project
     a.   Scheduling
          I.   Gillnet sampling for TBP occurs on the same days on 
	       which hoop nets are set.
               (1)  Usually twice a week.  Mondays and Wednesdays.
                    (a)  Two gillnets are utilized.
                    (b)  Each gillnet is left in the water to sample for
                         approximately one hour.
                         (I)  One gillnet is placed on each side of the 
			      sampling location (i.e. a gill net on each 
			      side of the channel).
               (2)  Enough time should be scheduled to set hoop nets 
		    and to complete four gillnet sets.
                    (a)  Continue gill-netting until dark.
               (1)  Gill-netting usually requires three people, 
		    although it may be accomplished with two 
		    experienced people.
                    (a)  Two of the three people will be responsible 
			 for the setting and retrieval of the 
			 gillnets, in addition to measuring all fish 
                    (b)  The third person will be responsible for 
		         driving the boat and recording the data.
                         (I)  This entails writing down the 
		              lengths of the fish as they are called out.
Equipment preparation
               (1)  Equipment list
                    (a)  Two (2) large mesh gillnets.
                    (b)  A large canvas tarp.
                    (c)  Four (4) 5 lbs. Danforth anchors 
		         (two for each net) w/rope.
                    (d)  Eight (8) buoys (four for each net).
                    (e)  Galvanized tub and bucket.
                    (f)  Gillnet hook
                    (g)  Filet knife (or any sharp knife)
                         Stomach Pumping Equipment
                    (h)  One (1) 1/3 gallon pump sprayer
                    (I)  Two (2) cases of glass jars (24 jars)
                    (j)  One (1) box of assorted size stomach tubes.
                    (k)  Temporary Barriers Project (TBP) tags.
                    (l)  One (1) plastic bottle of formalin.
               (2)  Data collection
                    (a)  Measuring boards
                    (b)  Clipboard with three FIELD DATA sheets and 
                    (c)  Secchi disk.
                    (d)  Fathometer.
                    (e)  Thermometer.
                    (f)  Tool box.
             (g) Dissolved oxygen meter
               (3)  Optional gear
                    (a)  Rain gear (boots, raincoat, slickers, etc.)
                    (b)  Fish identification key.
                    (c)  Map(s) of the appropriate sampling area.
Field work for gill netting
         a.   Sampling procedures
          I.   Readying the gill nets
               (1)  Lay the canvas tarp down, across the bow of 
		    the boat so that as little of the boat bow 
		    is showing as possible.
		    (a)  This will prevent the gill net from snagging 
		         as it feeds into the water.
               (2)  With the aid of the second sampler, place the 
		    gill net tub on top of the tarp fairly close 
	  	    to the front of the bow.
               (3)  Attach one 5 lb. Danforth anchor to the white 
		    bridle on the front of the gill net.
               (4)  Attach an orange buoy to the beginning of 
		    the float line (where the bridle and float 
		    line come together).
          ii.  Setting the gill nets
               (1)  The boat driver will slowly approach the 
		   shore line.
               (2)  With the anchor in hand, position yourself 
	            on the bow of the boat.  Be prepared for the 
		    boat to begin backing up.
                    (a)  When the driver asks you to, throw the 
			 anchor overboard and onto the shore.
                         (I)  Hold firmly to the rope until the Danforth
			       anchor catches a firm hold on the shore.
               (3)  The driver will begin slowly backing the boat 
		    diagonally, away from the shore, and in the 
		    direction of the current.
               (4)  As the boat backs up in the direction of the current, 
		    feed the gill net off the bow of the boat into 
		    the water.
                    (a)  IMPORTANT!  As the net is feeding out, make 
			 sure that the thick green float line and 
			  the lead line do not cross over each other 
			  at any time.
               (5)  When half of the gill net is in the water, 
		    communicate to the driver that you would 
		    like him/her to stop backing up for a minute.
                    (a)  At this time, take an orange buoy and attach 
		         it to the float line of the gill net.
                    (b)  Express to the driver that they may begin 
		         backing up again.
                    (c)  Attach an orange buoy every 50 feet to the 
		         float line.
               (6)  As you come close to the end of the gill net and 
		    there is approximately 10-15 ft. of net left in 
		    the tub, instruct the driver to slow the boat.
                    (a)  Attach another orange buoy to the float line 
		         where the float line and white bridle come 
                    (b)  Depending on the current and/or area, the 
		         driver may decide that another 5 lb. 
			 Danforth anchor should be attached to the 
			 end of the bridle.
 	       (7)  After you have finished attaching the necessary 
		    items, the driver will resume backing the boat 
		    until the entire gill net is in the water.
               (8)  As the end bridle goes into the water, tell the 
		    driver that the set has begun so the time may be 
	 	    recorded on the data sheet.
               (9)  Repeat the above process with the second gill net.
          iii. Retrieving the gill nets
               (1)  Position yourself on the bow of the boat.
                    (a)  The canvas tarp should be across the bow of 
		         the boat and the gill net tub should be 
			 behind you, slightly to the side.
               (2)  The driver will approach the end buoy slowly.  
		    As you get closer to the buoy, reach down to water level 		    and grasp hold of the buoy with both hands.
                    (a)  Shout to the driver that you have a grasp of 
		         the buoy.
               (3)  Begin pulling the net in by grabbing both the float 
		    line and lead line simultaneously.
                    (a)  Try to gather the net, float line, and lead 
		         line together as you pull.
               (4)  Behind you, a second person will stack the net 
		    in the tub, in the form of figure eights, as you 
		    haul in the gill net.
                    (a)  If you are the net stacker, do not yank the net 
			 from the hands of the puller.  Let a small 
		         amount of slack develop between you and the 
			 puller as you  place the gill net into the tub.
               (5)  When the end of the gill net is reached and the bridle 
		    has been pulled out of the water, tell the driver "end 
		    set" so that the time may be recorded for the data 
               (6)  If you intend to reset the gill net, the buoys and 
		    anchors may be left on for the next set.
                    (a)  If you are not resetting the net, remove all 
			 buoys and anchors from the gill net as you are 
		         pulling it in.
                         (I)  This is usually done by the person stacking 
			      the net into the tub.
          iv.  Removing the fish from the gill net.
               (1)  Retrieval of the net is halted when a fish is caught 
		    in the net and brought on board the boat.
               (2)  Depending on how the fish is tangled and the species 
		    of fish, there are usually two ways that the fish 
		    can be removed.
                    General rule of thumb:
                    (a)  If the net is past the fishes gill plate and 
		         most of his head is through the netting, try 
		         pulling the fish through the netting (so that 
			 the netting slips over its body).
                    (b)  If the net is caught around the face and head of 
			 the fish, try backing the fish out of the net, 
			 pulling the net over the operculum and head.
                         (I)  Removing fish from the gill net efficiently 
			      takes practice.  Do not get discouraged.
               (3)  After the fish has been removed, measure the fork 
		    length and tell the driver so that it may be recorded 
		    on the data sheet.
                    (a)  If the species is a predator and of the correct 
			 size then its stomach must be pumped and the 
		         contents saved for lab analysis.
                         (I)  In this instance, the galvanized tub should 
			      be filled with water where the fish can 
			      remain until their stomach can be pumped.
                    (b)  If the species is not a predator then it may be 
			 thrown back into the water after the fork length 
			 has been recorded.
          v.     Stomach pumping
               (1)  Refer to the above-mentioned methods for stomach pumping


               1.   Electrofishing usually occurs twice a week during 
		    Temporary barriers project sampling. Sampling is 
		    done at night usually on Tuesdays and Thursdays.

          Dissolved oxygen meter (YSI)
          Insulated rubber gloves
          Life preservers
          One (1) 1/3 gallon pump sprayer
          Two (2) cases of glass jars (24 jars)
          One (1) box of assorted size stomach tubes.
          Temporary Barriers Project (TBP) tags.
          One (1) plastic bottle of formalin.
           (a) A crew of three persons is used 
                    I.  One person to operate the boat and two to collect 
		    and measure fish.
           (b)   Field activities for electrofishing.
                    1.   Electrofishing is done at every station during 
			 the Temporary Barriers Project (See hoop-netting 
		         Standard Operating Procedures for list of 
                    2.   Each station is approximately 1,500 feet long.
                    3.   Only the shoreline within the 1,500 feet is 
                    4.   Water quality is taken at the beginning of 
		         each site (Dissolved oxygen, secchi  depth, 
			 temperature and a water sample is taken back 
			 to the lab to process for turbidity and 

Electrofishing sampling procedures.
                         1.   After the boat has been set up and readied 
			      for shocking the boat driver approaches 
			      the shoreline so that the boat is  
			      perpendicular to the shore.
                         2.   When the boat is approximately 2 to 5 yards 
			      from the shore the  person netting steps 
			      on the electrofishing pedal which turns on   
			      the electricity through the water.
                         3.   The boat driver remains perpendicular to 
			      the shore for approximately 10 to 20 seconds.
                         4.   Fish that are stunned by the electrical 
			      current through the water  float to the 
			      surface and are easily scooped up by the 
			      person netting.
                         5.   The fish are then placed in a live-well.
                         6.   After the 10 to 20 seconds the driver 
			      backs up and proceeds downstream 15 feet 
			      to shock  more of the shoreline until the     
                              station is completed.
                         7.   At the end of the station the fish are 
			      identified, measured and released.
                         8.   The boat driver records the time and 
			      shocking seconds after each station.