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STOCKTON FWO: Biologists Lead Juvenile Salmon Survival Study Using Acoustic Methodology
California-Nevada Offices , December 18, 2009
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Fisheries Technicians Phil Voong and Amy Combs transfer acoustic tagged fish from the transport truck to Georgiana Slough.
Photo by USFWS
Fisheries Technicians Phil Voong and Amy Combs transfer acoustic tagged fish from the transport truck to Georgiana Slough. Photo by USFWS - Photo Credit: n/a
Amy uses a VR100 acoustic tag receiver to verify the tags are transmitting.
photo by USFWS
Amy uses a VR100 acoustic tag receiver to verify the tags are transmitting. photo by USFWS - Photo Credit: n/a
Fish biologist Mike Marshall transfers acoustic tagged fish to holding pens in Georgiana slough prior to release.
Photo by USFWS
Fish biologist Mike Marshall transfers acoustic tagged fish to holding pens in Georgiana slough prior to release. Photo by USFWS - Photo Credit: n/a

by Pat Brandes, Stockton FWO
During December of 2009, the Stockton Fish and Wildlife Office released juvenile salmon implanted with VEMCO hydroacoustic transmitter tags as part of a study to estimate the survival of juvenile salmon migrating through the Sacramento-San Joaquin Delta. One set of fish releases were made when the Delta Cross Channel (DCC) gates were open and a second set of fish releases were made when the DCC was closed.  This is the fourth year of the study using VEMCO acoustic tags and receivers. 

Previous mark and recapture studies have indicated that survival for juvenile salmon that enter the interior Delta is lower than survival for salmon that stay on the main stem Sacramento River (Newman, 2008).  Closing the DCC has been used in the past as a protective measure to increase the survival of listed winter-run salmon through the Delta by reducing the proportion of salmon that enter the interior Delta. Acoustic receivers deployed near the DCC and in the interior Delta will identify the proportion of the tagged juvenile salmon migrating downstream that enter the interior Delta through Georgiana Slough through each of these waterways under both gates open and gates closed conditions. The Stockton Fish and Wildlife Office partnered with UC Davis for the installation and maintenance of the receiver array and National Marine Fisheries Service for tagging the fish and maintaining the database. In addition, Coleman National Fish Hatchery provided the juvenile late-fall Chinook salmon used in the study.  A manuscript on the results of the first year’s study will soon be published in the North American Journal of Fisheries Management.

Tagged salmon were released on the Sacramento River upstream of Sacramento and into Georgiana Slough with the DCC gates open in early December and again with the DCC gates closed in mid-December.  To meet flow standards within the Delta, operators were required to close the DCC for one, 24 hour period during the early December DCC gates open release.  The acoustic technology allows us to identify when each individual tagged fish migrated past the DCC, so the effect of the short gate closure during the DCC gates open test period can be isolated during analyses.  This year’s study is unique in that the Corp of Engineers (COE) will be making additional releases at the same site upstream of Sacramento in January with both acoustic tagged Chinook salmon and acoustic tagged steelhead.   These COE releases will provide us with a way of estimating route and reach specific survival through the Delta for additional groups of juvenile late-fall Chinook salmon and steelhead and compare the estimates to those obtained from our releases made in December. 

Reference:  Newman K.B. 2008. "An evaluation of four Sacramento-San Joaquin River Delta juvenile salmon survival studies.” 3/31/08. 


Contact Info: Paul Cadrett, 209-946-6400 x 312, paul_cadrett@fws.gov



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