Week of March 13, 2023

Last week of Intensive Field Season Updates

This week rep­re­sent­ed “Finals Week” for the UC Davis crew that has worked tire­less­ly through­out this crazy, but pro­duc­tive, field sea­son.  They have man­aged through not just one but two sep­a­rate bypass flood­ing events and they were still going strong as they man­aged through this final week com­prised of most­ly fish releas­es.

Updated Catch Numbers

The last date of fish cap­ture was March 11 as we lost con­trol of the field to the increas­ing Sut­ter Bypass flows that after­noon.  This left about half of the area of the field still flood­ed and with an unknown num­ber of uncount­ed nat­ur­al-ori­gin fish.  There was a tremen­dous num­ber of fish recov­ered in those last few days; so much so that work to com­plete the final catch data­base is still ongo­ing as of the date of this update.  How­ev­er, the list cur­rent­ly shows 933 fish hav­ing been cap­tured in seins or the fyke net.   Of these, 775 were iden­ti­fied as Chi­nook Salmon.  The UC Davis team record­ed 369 of these as part of the group of the lab-reared, PIT-tagged salmon leav­ing 406 as fish iden­ti­fied as nat­ur­al-ori­gin salmon.  Work is still being done to des­ig­nate all these fish as to their runs based upon the dai­ly size class chart. Over­all, 79 fall‑, 1 late-fal­l‑, 299 spring‑, and 24 win­ter run-sized fish were iden­ti­fied by length at date. All data are pre­lim­i­nary as they still need to under­go qual­i­ty assur­ance and qual­i­ty con­trol pro­ce­dures.

In the pre­vi­ous week’s report, we ref­er­enced that we began to see very few nat­ur­al-ori­gin salmon that were small enough to be des­ig­nat­ed as fall-run even though we sus­pect that most are fall-run based on the large per­cent of fall-run salmon end­ing up in the fyke dur­ing the bulk of the field sea­son.  This trend con­tin­ued all through­out the final catch days dur­ing field drainage.  There­fore, once the genet­ic test results come back lat­er this year, we expect it will show that we col­lect­ed a lot of very large fall-run from the field which would be a great indi­ca­tor of the qual­i­ty of food avail­abil­i­ty and rear­ing con­di­tions in the rice field.  More on this lat­er this year….

Field Activity Updates

This week was most­ly all about fish releas­es.  On March 15, the UC Davis Team per­formed a “prac­tice release” of our un-tagged salmon from the dry­side field.  You may recall that we held a dupli­cate num­ber of caged fish on a dry­side field as a con­tin­gency in the event bypass con­di­tions had neg­a­tive­ly affect­ed our caged fish on the wet­side which did not ulti­mate­ly hap­pen.

On March 17, both groups of our JSATS (Juve­nile Salmon Acoustic Teleme­try Sys­tem) teleme­try fish were suc­cess­ful­ly released into the water­shed.  This was a total of 462 fish; half lab-reared and half rice field-reared.  The release of both groups was even­ly split between a bypass release at the project field loca­tion (cur­rent­ly under sev­er­al feet of bypass flow) and the Sacra­men­to Riv­er.  The riv­er release loca­tion was picked so that it would be equidis­tant from the San Fran­cis­co Bay as the dis­tance for the release site in the bypass.

Tracking our JSATS-tagged Salmon

For those who may like to join in the fun (or maybe even “obses­sion” for some), our late-fall run year­lings can be tracked by going to this web­page and our juve­nile fall-run fish can be tracked at this web­page.

Monitoring of many JSATS-tagged Salmon

One last con­tin­u­ing field effort is what we are call­ing our JSATS mon­i­tor­ing array.  As a bonus fea­ture of our project, the UC Davis Team has placed two “cur­tains” of JSATS receivers into the Sut­ter Bypass.  One is near our project site and the oth­er is quite a dis­tance down­stream in the Sut­ter Bypass before it feeds into the Sacra­men­to Riv­er.  This area cov­ers a lot of rice ground and we are hope­ful to read both our JSATS-tagged fish, as well as those from oth­er projects, to col­lect even more valu­able infor­ma­tion about how salmon are using these rice habi­tat areas.   More on that down the road…

This is the final reg­u­lar update to be sent out as part of the 2022–23 inten­sive field­work activ­i­ties.  It’s been a plea­sure keep­ing you informed dur­ing this excit­ing field sea­son.  Hope you’ve enjoyed the show.