18 February 3 , 2023 VOL . 42 • ISS . 2
Zero Delta Smelt caught in 2022 CDFW fall midwater trawl survey as Delta Tunnel moves forward
I t ’ s final — for the sixth year in
a row , the California Department of Fish and Wildlife ’ s Fall
Midwater Trawl Survey ( FMWT ) has found zero Delta Smelt in the Sacramento-San Joaquin River Delta . The slender 2 to 3 inch fish that smells like cucumber was once the most abundant fish in the Delta . The smelt , found only in the Delta , is considered an indicator species that shows the relative health of the imperiled estuary . The results of the survey were summed up and analyzed in a memorandum from James White , environmental scientist for the CDFW ’ s Bay Delta Region , to Erin Chappell , Regional Manager Bay Delta Region , on Dec . 29 , 2022 : Memorandum : 2022 FMWT Annual Fish Abundance and Distribution , California Department of Fish and Wildlife ( 759 KB ). According to White , the 2022 abundance index was zero and “ continues the trend of no catch in the FMWT since 2017 .” No Delta Smelt were collected from any stations during the four month survey from Sept . -Dec. 2022 . “ An absence of Delta Smelt catch in the FMWT is consistent among other surveys in the estuary ,” White wrote . “ The Enhanced Delta Smelt Monitoring ( EDSM ) survey of the U . S . Fish and Wildlife Service ( USFWS ) caught 3 Delta Smelt among 61 sampling days ( between 9 / 6 and 12 / 15 ) comprised of 1,997 tows .” Despite the release of many thousands of hatchery-raised Delta Smelt in Dec . 2021 and Jan ., Feb . and Nov . 2022 , no Delta smelt were found in any of the surveys . “ On Nov . 29- 30 , 2022 , the Experimental Release Technical Team released 12,942 marked adult Delta Smelt from culture into the Sacramento River near Rio Vista ,” said White . “ Neither FMWT nor EDSM caught these released Delta Smelt during December sampling .” However , White noted , “ While FMWT did not catch any Delta Smelt , it does not mean there were no smelt present , but the numbers are very low and below the effective detection threshold by most sampling methods .” The Delta smelt is now near-extinction in the wild , although U . C . Davis continues to raise the fish in a captive breeding program . On Dec . 14 and 15 , 2021 , the U . S . Fish and Wildlife Service and
CDFW , along with the California Department of Water Resources and U . S . Bureau of Reclamation , experimentally released 12,800 hatchery-raised Delta smelt into the Delta for the first time . The significance of the Delta smelt ’ s role in the Bay-Delta Estuary is huge . ” Delta Smelt are the thread that ties the Delta together with the river system ,” said Caleen Sisk , Chief of the Winnemem Wintu Tribe . “ We all should understand how that affects all the water systems in the state . They are the irreplaceable thread that holds the Delta system together with Chinook salmon .” The 2022 abundance index ( a relative measure of abundance ) for Longfin Smelt , a cousin of the Delta Smelt , was 403 , representing a 20 % increase from last year ’ s index , but still just a fraction of historical numbers . The index for Striped Bass , a popular introduced gamefish pursued by anglers that has declined dramatically in recent years , was 66 , representing a 15 % increase from last year ’ s index . The index for Threadfin Shad , an introduced forage fish species , was 257 , representing a 14 % increase from last year ’ s index , but still well below historical numbers . For American Shad , another introduced gamefish , the abundance index was 698 , representing a 43 % increase from last year ’ s index . “ Indices have fluctuated substantially during the period 2018-2022 , ranging from a low of 398 to a high of 1,955 ,” White stated . Finally , zero Sacramento Splittail , a member of the minnow family found only in Central Valley rivers and the Delta , were collected at index or non-index stations in September through December . White said the 2022 sampling season began Sept . 6 and was completed on Dec . 16 . While there are several factors that scientists pinpoint for the ecosystem collapse , including toxic chemicals , decreasing water quality and invasive species , no factors figure greater in the collapse than water diversions from Central Valley rivers and the export of massive quantities of state and federal project water from the Delta to San Joaquin Valley agribusiness interests and Southern California water agencies . The decline of the Delta ’ s pelagic species , including three once-abun- dant fish species pursued by anglers , has been catastrophic since the State Water Project went into operation in 1967 . Between 1967 and 2020 , the state ’ s Fall Midwater Trawl abundance indices , a measure of relative abundance for striped bass , Delta smelt , longfin smelt , American shad , splittail and threadfin shad . have declined by 99.7 , 100 , 99.96 , 67.9 , 100 , and 95 percent , respectively , according to the California Sportfishing Protection Alliance . Thomas Cannon , retired fisheries biologist with the California Sportfishing Protection Alliance ( CSPA ), said there are many issues the smelt and other species are suffering from at this time . “ These include Temporary Urgency Change Petitions , low Delta inflow / outflows , the upstream position of the Low Salinity Zone ( LSZ ) that makes its critical habitat vulnerable to export , and Bay and Delta water temperatures from low flows and water exports drawing lower Sacramento warm water into the north , west and central Delta ,” he stated . “ The Cache Slough Complex is too warm in summer now - partly a consequence of too much shallow tidal area restoration . The Suisun Marsh Salinity Control Gates are bad for the marsh , Montezuma Slough and West Delta / Suisun Bay ,” he added . To restore the Delta smelt and other species , he recommended stocking more hatchery smelt in low salinity prime habitat in early spring and protecting this key habitat with flows to keep it in Suisun Bay from Chipps Island to Collinsville . He also recommended not letting the Low Salinity Zone anywhere near Three Mile Slough and Rio Vista and keeping it west of Sherman and Antioch . In addition , he suggested getting rid of predator habitat in and adjacent to main channels and bay . “ Non-native invasive aquatic plants are taking all the primary production out of the pelagic system and making water clearer and providing non-native predator and prey fish habitat ,” Cannon stated . The December and January 2023 atmospheric rivers that have hammered are a mixture of good and bad for Delta pelagic species and Central Valley salmon , according to Cannon .
By Dan Bacher
“ Wet years are all good except for flood damage in rivers can be bad - restoration and maintenance are important ,” Cannon said . “ But they are great for the Bay and Delta - it gets rid of clams and aquatic plants , washes out pollutants and bad algae and sediments . They are usually good for smelt and splittail spawn and very good for San Joaquin River salmon . The rains should also be good for sturgeon recovery after the bay fish kill .” “ There are some concerns about damages ( remember the 1982-83 , 2006 floods ; it may not be best for smelt if floods go into spring ). The storms could also damage fall run , spring run and late fall-run salmon production - since there is lots of bypass stranding . The high water should help get hatchery smolts to the ocean , which is usually very good .” “ It should also be great for the ocean - if you get NOAA to talk about that in layman ’ s terms . It should be good for Napa River Smelt Sanctuary — if they don ’ t stock 20 million hatchery salmon smolts there ,” he quipped . Meanwhile , the California Water Department of Water Resources continues to forge ahead with its gigantic Delta Conveyance Project , AKA Delta Tunnel , under the Sacramento San Joaquin River Delta . The project would divert Sacramento River from the North Delta before it flows through the Bay-Delta Estuary , making the dire situation of Delta Smelt and Longfin Smelt , Sacramento River winter-run Chinook salmon , Central Valley steelhead , green sturgeon and other species even worse than it is now . On Wednesday January 18 , 2023 the US Army Corps of Engineers ( USACE ) held a virtual hearing to receive public comments on the Draft Environmental Impact Statement ( DEIS ) for the Delta Conveyance Project . Even though the hearing is over , you can still comment on the proposal . The Draft EIS for the Delta Tunnel is available for public review and comment from December 16 , 2022 through March 16 , 2023 . The comment period was recently extended from the original February 14 , 2023 end date . For more information on the Draft EIS and USACE public review period , visit the USACE website .