Collection

1. Feather River Hatchery Otolith Thermal Marking: A Closer Look at Hatchery Returns. Introduction The Feather River Fish Hatchery (FRFH) propagates two runs of Chinook salmon, fall run and spring run, currently spring run are listed as threatened by federal and California ESA. Dams, altered hydrologic regimes, and hatchery management practices have led to the introgression of these runs in the Feather River. Improvements to broodstock management practices have been implemented and future plans are aimed at reducing introgression and the proportion of hatchery origin fish within the broodstock. In order to evaluate the success of these efforts we need the ability to identify the origin and race of all returning fish. Marking and tagging with coded wire tags (CWT) is the most common method used to identify origin and race among Central Valley hatcheries. However, only a fraction of the fall run produced at the FRFH are marked and tagged. In 2005, we implemented an otolith thermal marking program (OTM) at the FRFH to “tag” all Chinook salmon released from the hatchery. OTM was used to identify the brood year, race, and origin of fish returning to the FRFH in 2009 and 2010. Michael Mercer¹, Ryon Kurth¹, Anna Kastner² and A.J. Dill² ¹California Department of Water Resources Division of Environmental Services, Feather River Studies ²California Department of Fish and Game, Feather River Fish Hatchery Contact: Michael Mercer- 460 Glen Dr. Oroville, CA 95966 (W) (530) 534-2314, (F) 530-534-2409, mmercer@water.ca.gov Temperature (oC) 1 :3:2 a) 11/14 11/18 11/21 11/23 11/11 11/16 b) c) Date N= 989 N= 1661 Methods Marking We thermally marked otoliths of Chinook salmon alevins by exposing them to a scheduled series of chilled water treatments while in their incubation trays at the FRFH. Each treatment lowered the temperature approximately 2oC for 7 hours (Figure 1). The otolith banding patterns followed the “interleaved two of five” bar code symbology, consisting of six bands and five spaces (Palmer 1989; Volk et al. 1994). A series of six unique codes were used to indicate the race and brood year for all Chinook produced at the FRFH (Figure 2). Every fourth brood year the series of codes will repeat. e) d) f) N= 9963 N= 19973 3 2 1 Figure 3. Proportion of hatchery origin spring and fall run Chinook at the FRFH. Proportions of race and origin from non-clipped fish were determined by otolith thermal mark (TM). Coded wire tag (CWT) was used to determine race and origin of clipped fish. The No TM (no thermal mark) group includes natural origin and out of basin strays.    Figure 2. Thermal marks from Feather River Chinook salmon ; a) 1-2-3 fall-run 2005, b) 3-2-1 fall-run 2006, c) 2-1-3 fall-run 2007, d) 1-3-2 spring-run 2005, e) 2-3-1 spring-run 2006, f) 3-1-2 spring-run 2007. • Discussion • The OTM program enabled us to identify the race and origin of salmon for the majority of individuals returning to the FRFH. If the other Central Valley hatcheries employed an OTM program we could assign race and origin to all fish returning to the valley. • Our results indicate mixing continues among FRFH fall and spring run returns and more work is needed to isolate the broodstocks.  • Our estimate of hatchery origin fish ranged from 89.30 to 99.53 %, other studies also indicate high proportions of hatchery origin fish among Central Valley salmon populations. •  90 ± 6% in a central California coastal fishery in 2002 (Barnett-Johnson et al. 2007). •  90.7 to 99.3 % in the Mokelumne River watershed in 2004 (Johnson et al. 2012). •  In 2010, CWT analysis estimates the FRFH fall-run hatchery origin at 95%, and spring-run hatchery origin at 82% (Kormos et al 2012). • OTM has potentially revealed a proportion of non-adipose fin clipped hatchery spring-run, 7.70% in 2009 and 11.15% in 2010 which may explain the discrepancy between CWT (Kormos et al 2012) and OTM estimates of hatchery origin fish in FRFH spring-run in 2010. • Otolith microchemistry analysis is being conducted on subsample of these otoliths to confirm their origin (hatchery or wild). • A valley wide OTM program would provide a viable means to assess management objectives aimed at increasing natural origin fish in hatchery broodstock, as well as, strategies for reducing introgression between spring and fall at the FRFH. Figure 1. Temperature fluctuations create banding patterns on otoliths. Table 1. Validation matrix of known otolith reads. Collection Otolith collection occurred at the FRFH during the spawning period from approximately September 15th to November 1st. Otoliths were primarily collected from non-CWT tagged fish; however, some CWT tagged fish were collected as known samples for use in training and validation. Some validation samples were also collected from in-river carcass surveys. Preparation Otolith processing begins by attaching otoliths to glass microscope slides using thermal plastic (Crystal Bond). Otoliths are ground on both sides using 1200 grit polishing paper until the primordial is just visible. Polishing continues manually using 9 micron and 3 micron polishing paper until thermal marks become distinct under 200X magnification. Samples are imaged and downloaded before being enhanced slightly for reading. Table 2. Otolith reads before and after application of maximum likelihood estimator. Analysis Our analysis uses a modified maximum likelihood estimator originally developed to estimate age distributions of fish populations (Kimura and Chikuni, 1987). This method uses a validation matrix (Table 1) based on the accuracy of otolith reads from known race and brood year samples (CWT; n= 153) to adjust the proportions of read thermal marks from the unknown samples (n=746) using an iterative application which corrects for reader bias (Table 2). Origin and race determinations from OTM reads were expanded to include all non-clipped returns. To calculate the proportion of origin and race of fall and spring run Chinook returning to the FRFH we divided the sum of race and origin determined by OTM and CWT by the total escapement for each race. • Results • A total of 862 otoliths were successfully prepared and analyzed from spring and fall run hatchery returns in 2009 and 2010. • We successfully determined the origin of hatchery returns 97.4% of the time and the race of hatchery individuals 73.33% and 92.31% of the time for spring and fall run, respectively. Table 1 shows the accuracies of specific mark groups for each year. • Results indicate mixing in both fall and spring run escapement. Spring-run hatchery returns in 2010 include 14.84% fall-run fish. Alternatively, fall-run hatchery returns in 2010 include 21.97% spring-run fish (Figure 3). • Results suggest natural spawner (“wild”) contribution to hatchery broodstock is low, returns of non-FRFH produced fish ranged from 0.47% (Spring-run 2010) to 10.70% (Fall-run 2010) (Figure 3). (Contribution rates are based on “No Thermal Mark” reads which may include out of basin strays.) References Barnett-Johnson R, Grimes C, Royer C, Donohoe C (2007) Identifying the contribution of wild and hatchery Chinook salmon (Oncorhynchustshawytscha) to the ocean fishery using otolith microstructure as natural tags. Can J Fish AquatSci 64:1683–1692 Kormos B, Palmer-Zwahlen M and Low A (2012) Recovery of Coded-Wire Tags from Chinook Salmon in California’s Central Valley Escapement and Ocean Harvest in 2010. California Department of Fish and Game. Fisheries Branch Administrative Report 2012-02. March 2012 Johnson RC, Weber PK, Wikert JD, Workman ML, MacFarlane RB, et al. (2012) Managed Metapopulations: Do Salmon Hatchery ‘Sources’ Lead to In-River ‘Sinks’ in Conservation? PLoS ONE 7(2): e28880. doi:10.1371/journal.pone.0028880 Palmer R (1989) The bar code book. Helmers, Peterborough, New Hampshire. Volk EC, Schroder SL, Grimm JJ & Ackley HS (1994). Use of a Bar Code Symbology to Produce Multiple Thermally Induced OtolithMarks,Transactions of the American Fisheries Society, 123:5, 811-816 Acknowledgements Thanks to the DFG’s Feather River Hatchery staff for their efforts implementing and carrying out marking operations. Thanks to the DWR staff for their help in the collections and processing of otoliths. A special thanks to Brett Kormos of DFG ‘s Ocean Salmon Project for his assistance with the MLE. Incubator stacks at the Feather River Hatchery (FRFH). Juveniles during the marking period still carry their yolk sack. Otolith preparation in the laboratory involves grinding and polishing.