Site Type

Site Name


TWX - Estuary Towed Array (Exp.)

The TWX site is located in the upper Columbia River estuary, between Eagle Cliff (rkm 84) and the west end of Puget Island (rkm 66). This site is sampled annually by NOAA Fisheries during the spring and summer outmigration of juvenile salmonids. There are currently three detection systems in use. The trawl, operated since 1995, is a surface pair-trawl with a matrix of six rectangular antennas fitted into the cod end of the net. The matrix is configured with three parallel antennas in front and three in the rear, forming a corridor that allows fish to pass through while being detected by the antennas. The flexible antenna system was developed in 2015 and is a modular array, consisting of up to twelve rectangular antennas, connected side-by-side in a vertical orientation. These are constructed of manufactured antenna cable and are also towed between two vessels. These two systems operate 3-7 days per week from mid March to mid June. The PIT tag detection barge is an autonomous floating platform supporting vertical antennas. The current system (designed and fabricated by West Fork Environmental, holder of 3 patents on vertical antenna arrays) has 12 FINS, each housing a coil that couples to its neighboring FIN. In this configuration the system is comprised of 6 nodes that are multiplexed through a controller for continuous interrogation of a 50-foot-wide by 8-foot-deep section of the river. The barge is anchored fore and aft in approximately 30 feet of water. West Fork is collaborating with NOAA Fisheries in an evaluation of the vertical floating array to detect passing PIT tagged salmonid smolts. The barge is being tested for the first time at this site during May and June 2018.

Operated by:


First year:


Last year:




Site Contacts


Erika Holcombe
(503) 861-1818


Paul Bentley
(503) 861-1818


Photo Gallery

Operational Dates

Year Start Date End Date Notes
2014 3/18/2014 8/1/2014 See event log for sampling schedule details.
2016 3/24/2016 7/5/2016
2015 3/19/2015 7/2/2015
2017 3/17/2017 6/16/2017
1996 4/24/1996 6/13/1996 The Start_date and End_date values reflect the first and last dates of detection, respectively. The actual interval of operational dates is not known.
1998 4/8/1998 6/21/1998 Dates and times based on first/last files submitted to PTAGIS.
1999 4/9/1999 6/8/1999 Dates and times based on first/last reported detections.
2000 4/18/2000 6/21/2000 Dates and times based on first/last reported detections.
2001 4/20/2001 6/22/2001 Dates and times based on first/last reported detections.
2002 4/13/2002 7/30/2002
2003 4/22/2003 6/30/2003 Dates per Dick Ledgerwood; times derived from first/last data files.
2004 4/14/2004 7/3/2004 While TWX files are available from April 8 onward, Dick Ledgerwood reports that TWX sampling operations did not begin until April 14, 2004.
2005 4/20/2005 8/5/2005 TWX sampling began 20 April 05. Sampling with 2 daily crews occurred between 27 April and 17 June. Sampling with a single daily crew working 4 or 5 days per week continued until 4 August.
2006 3/9/2006 10/30/2006 Refer to the TWX Event Log for sampling schedule and effort. There was no sampling between July 21 and September 5.
2007 3/7/2007 7/19/2007 Refer to the TWX event log for a detailed description of 2007 operations.
2008 3/7/2008 10/30/2008 Refer to the TWX event log for a detailed explanation of operations. Regular operations were suspended between August 20 and September 29.
2009 3/6/2009 8/12/2009 See event log for detailed operational comments.
2010 3/23/2010 8/4/2010 Refer to the TWX event log for details of TWX operations in 2010.
2011 3/22/2011 7/1/2011 Initial monitoring effort consists of sampling three days per week. Intensive sampling (two daily shifts) was conducted from May 2 to June 10.
2012 3/15/2012 7/30/2012 Sampling started on March 15 and ended on July 30.
2013 3/25/2013 7/25/2013 Sampled intermittently from March 25 - April 29. Two shift sampling (one daylight, one darkness) occurred from April 29 - June 6. Sampled intermittently from June 6 - July 25.

Current and Historic Site Configurations

Config Seq: 200

Start Date: 4/25/2018

End Date:

Config Seq: 190

Start Date: 4/25/2017

End Date: 4/25/2018

Config Seq: 180

Start Date: 4/19/2016

End Date: 4/25/2017

Config Seq: 170

Start Date: 3/1/2010

End Date: 4/19/2016

Config Seq: 160

Start Date: 3/1/2006

End Date: 3/1/2010

Config Seq: 150

Start Date: 3/13/2002

End Date: 3/1/2006

Config Seq: 140

Start Date: 4/1/2001

End Date: 3/13/2002

Config Seq: 130

Start Date: 3/30/2000

End Date: 4/1/2001

Config Seq: 120

Start Date: 4/9/1999

End Date: 3/30/2000

Config Seq: 110

Start Date: 3/1/1998

End Date: 4/9/1999

Config Seq: 100

Start Date: 4/13/1995

End Date: 3/1/1998

Event Logs