Growth Rate Modulation in Chinook salmon supplementation

A major focus of current actions under Northwest Power and Conservation Council (NWPCC) and Bonneville Power Administration (BPA) programs is the support of multiple supplementation programs to assist in recovery of Chinook salmon listed as threatened or endangered under the ESA. Hatchery supplementation programs are one of the primary tools used by tribal, state, and regional organizations (e.g., BPA, CRITFC, PUDs) in the Columbia River Basin to directly address salmon recovery goals, and more than 50 such programs now exist in the region. Importantly, progeny of ESA-listed supplementation hatchery adult salmon directly contribute to recovery goals as they return to natural spawning areas.  A significant concern for these programs is that they release fish that are ecologically, genetically, and phenotypically similar to their wild cohorts.

The primary goals of this project are to assesses smolt associated physiological development and life-history (i.e precocious male maturation rates, etc.) in Chinook salmon produced in supplementation and conservation hatcheries in the Columbia and Snake River Basins and to conduct both basic and applied research to help develop and revise rearing protocols to produce fish with similar physiological, morphological and life-history attributes as wild fish to maximize survival and recovery. Previously, we have identified the prevalence and magnitude of age-2 male maturation (minijack) in conservation and supplementation programs for Spring and Summer Chinook salmon in the Columbia River Basin. In some programs, in some years, 60% of the males produced are destined to mature at age 2. For example, in the Yakima Supplementation program the average minijack rate over 10 years was 41% of males, which is 9-fold the rate we have estimated in wild Yakima River Spring Chinook salmon (Harstad et al. 2014; Larsen et al. 2019). This represents an obvious loss of production. More insidiously, the minijack phenotype also results in unnatural selection profiles on the smolts released from the hatchery and profound demographic effects on the spawning grounds, ultimately and undeniably altering the genetic structure of the natural populations that the conservation programs were designed to protect. Minijacks represent an ecological presence that may prey on and compete for food and habitat with native stocks. Finally, high minijack rates represent a significant source of error in calculations of smolt-to-adult return rates (SAR's); the central currency for survival estimates throughout the Columbia Basin.

Through this project we have documented that hundreds of thousands of minijacks are released from hatchery programs each year. These are actually not smolts when released and they rarely return as adults to the spawning grounds. It is essential to quantify their presence prior to release in programs of interest and devise methods to control production of unnaturally high minijack rates. Reduction in the rate of minijack production can lead to direct increases in smolt production and reduction in domestication selection. However, there are significant challenges associated with these efforts as growth profiles that reduce early male maturation often produce small smolts. Numerous studies have shown that smolt size is highly correlated with adult survival. This project is specifically designed to reconcile the paradox presented by these conflicting principles. We have conducted experiments that suggest reducing growth rates and lipid deposition in the autumn/winter of the fish’s 1st year will reduce early male maturation rates.  Furthermore changes to early rearing designed to  minimize early male maturation and optimize smolt survival have been found to have profound long term effects on SAR's and age at maturation of returning adults.  So, in hatchery rearing regimes have a significant impact to long-term success of recovery efforts.

Rearing regimes designed, in part, through this project were developed primarily in conventional flow-through raceway rearing facilities.  However, in light of current and anticipated impacts of global climate change and infrastructure upgrades throughout the CRB, several supplementation hatchery programs have initiated major transformations to their fish rearing regimes by replacing conventional, rectangular flow-through raceways with circular tanks and in some cases utilizing partial water re-use aquaculture systems (pRAS). These seemingly simple changes to rearing conditions may have major implications for the phenotype of juvenile salmonids, as fish in circular tanks must continuously swim, and thus have a fundamentally different “exercise” regimen than fish reared in slack-water within raceways. Phenotypic changes induced by enhanced exercise training may affect post-release survival, and size and age at maturity, thereby altering domestication selection. Moreover, these phenotypic changes may have significant positive or negative effects on the resiliency of smolts released from hatcheries. The change in phenotype of released smolts may therefore directly alter how hatchery fish contribute to recovery goals. In the near future, many more hatchery programs are slated to switch from raceways to circular tanks and pRAS, as pRAS is an effective tool to mitigate decreases in water availability to hatcheries, higher water temperatures and hatchery effluent quality. A goal of this project is to identify and describe emerging issue with pRAS systems and guide hatcheries on optimizing rearing regimes in them to maximize post-release survival (robustness) and contributions to recovery of Upper Columbia and Snake River Chinook salmon stocks.

This project has 5 central objectives in various states of progression (initiation, continuation, completion) in contract year 2024 as noted in parentheses next to each Objective:  

Objective 1) Improve survival and reduce fitness loss in Columbia River URB Fall Chinook salmon. (Completion)

Background:   This study explored the effects of High and Low Ration and High and Low lipid diet on life-history development over four consecutive brood years (BY's 2010-2013 released 2012-2015) at the Umatilla Hatchery in partnership with co-managers from the Confederated Tribes of the Umatilla Indian Reservation (CTUIR) and Oregon Department of Fish and Wildlife (ODFW - Lance Clarke-now retired). During previous contract periods we determined rates of minijack production (through measurement of plasma 11-ketotestosterone levels) and associated physiological development including growth, whole body lipid, plasma IGF-1 (endocrine index of growth physiology) and Na+/K+-ATPase activity (enzyme indicator of smolt development) in Umatilla stock URB Fall Chinook Salmon (serving as a proxy for listed Snake River stocks) reared at Bonneville Hatchery for a production scale 2x2 factorial experiment.  Our in hatchery monitoring effort for this work started in FY 2011 and continued until spring 2015. The effectiveness of this work was monitored through compilation of physiological profiles for each brood year and treatment group, minijack surveys conducted for each treatment at the time of release, juvenile survival and minijack migration via pit-tag interrogation in the Columbia River hydro by-pass systems and adult ladders and ultimately via adult return rates from 2014-2019. Final results and conclusions have been reported in annual and final contract reports, at scientific conferences and in peer reviewed publication(s).  

During the two previous (2022-2023) contract periods we published the first of two manuscripts in peer review describing this investigation in Transactions of the American Fisheries Society entitled:  "The effect of variation in ration and dietary lipid on precocious male maturation in Chinook Salmon:  a production scale hatchery experiment.

FY 2023 -Adult returns from this production scale hatchery experiment were complete.  During that contract period we analyzed all outmigration PIT tag interrogation records and adult coded wire tag (CWT) and PIT-tag return data from this experiment.  We analyzed all demographic data available describing treatment effects on age structure and sex ratios of returning adults.  

FY 2024 - During the current contract period we will complete and publish a second manuscript describing this adult return data in the peer reviewed journal Transactions of the American Fisheries Society.

Objective 2) The interaction of genetic and environmental effects on minjack and jack production in hatchery spring/summer Chinook salmon. (Continuation)

Test the hypothesis:  Spring Chinook salmon stocks that possess an increased propensity for minijack maturation will also possess an increased propensity for jack maturation.

Background:  This work involves a 2x2 factorial investigation involving captive culture of McCall, ID (high propensity for minijack maturation) and Carson, WA (low propensity for minijack maturation) hatchery spring Chinook salmon at the Northwest Fisheries Science Center hatchery under a high and low growth regime to evaluate minijack and jack maturation rates.  We evaluated growth profiles that increase and decrease the propensity for early male maturation (minijack and jack) in stocks with variable genetic thresholds for expressing these life histories in order to develop hatchery rearing regimes for BPA and other sponsored hatchery programs throughout the Columbia and Snake River basins.

During FY 2019-2020 all fish were PIT-tagged and identified to sex using a genetic marker.  All female fish were then removed from the study to decrease tank densities in order to maintain experimental growth regimes.  During the FY2020-2021 period treatment groups were reared according to the experimental design and surveyed for minijack maturation rates in Autumn 2020.  At the time of minijack enumeration (FY 2020) and early spring (2021), physiological indicators of jack maturation were collected from a subset of immature male fish.  Factors collected included length, weight, condition factor, GSI (gonadasomatic index), plasma 11-ketotestosterone (maturation hormone), pituitary FSH and LH mRNA (molecular indicator of maturation), tests IGF3, and AMH mRNA (molecular testicular indicator of maturation status).  These factors were evaluated for their utility as early indicators of jack maturation status 1 year prior to spermiation.  

Final enumeration of jack maturation status in this experiment was conducted during the termination of the study in summer 2021 at a time when maturation status could  be indicated via simple testicular morphology (GSI).  Final enumeration of maturation rates was compared with rates determined via physiological indicators measured in autumn (~10 months before spermiation) and spring (~6 months prior to spermiation).  Since all fish were PIT-tagged individual growth profiles could be analyzed for their effect on ultimate maturation status (minijack, jack, age 4+) and used to optimize rearing regimes associated with variation in genotype (McCall vs. Carson) in Columbia basin hatcheries.  

FY 2024 - During this contract period all results will be compiled in a draft manuscript to be published in a peer reviewed publication (journal TBD).

Objective 3 - Leavenworth National Fish Hatchery partial water re-use (Partial Reuse Aquaculture System or PRAS) vs. conventional raceway spring Chinook salmon comparative evaluation (Continuation)

Background:  The U.S Fish and Wildlife Service's Leavenworth National Fish Hatchery (LNFH) rears spring Chinook Salmon using intensive fish culture methods. Current compliance permits have directed LNFH to reduce water withdraws and improve effluent discharge. LNFH is facing the choice of either reducing production of spring Chinook Salmon or adopting methods, such as water reuse. LNFH seeks to use PRAS as an alternative rearing strategy, such that it will uphold tribal trust responsibilities by maintaining current production targets with less flow. This evaluation is to test the effectiveness of a “pilot” PRAS to rear spring Chinook Salmon at LNFH. The pilot system selected uses a total of four circular rearing tanks (two tanks per system) and associated reuse infrastructure housed in a stand-alone building. Additionally, the pilot will evaluate the effectiveness of effluent treatment and determine if aggressive effluent treatment is capable of significantly reducing phosphorus discharge to Icicle Creek. The circular tank system was selected because of suggested benefits of ease in operation, improved fitness to the fish reared in a higher velocity environment, lower flow requirements, and the ability to concentrate fish waste while conserving water.

FY 2022 and 2023 we conducted comparative evaluations of conventionally reared (raceway) and PRAS reared spring Chinook salmon at LNFH.  Fish were evaluated for growth, condition, smolt and maturation physiology throughout the year.

FY 2024 - During the current contract period we will continue monitoring fish from year 3 of 4-5 (Brood year 2021-2025 released in 2023-2027) evaluation trial at LNFH in cooperation with USFWS staff comparing conventionally reared (raceway) vs. PRAS reared fish for growth, smolt development, early male maturation, stress, and juvenile and adult survival.

Objective 4 - Walla Walla Hatchery Spring Chinook monitoring and evaluation. (Continuation)

Background:  Indigenous spring Chinook salmon were extirpated from the Walla Walla River in the mid to early 1900s and efforts to reestablish a Chinook population are being led by the Walla Walla Spring Chinook Hatchery Program (WWHP) and are outlined in the Walla Walla Spring Chinook Hatchery Master Plan (2008). The main objectives of this Plan are to: 1) establish self-sustaining natural populations in the South Fork Walla Walla River, Mill Creek, and Touchet River,  2) provide non-tribal and tribal fisheries in the subbasin, and  3) develop a localized brood stock.

The WWHP and BPA recently constructed a new hatchery facility on the South Fork of the Walla Walla River (SFWWH) to aid in these efforts. This program is co-managed by the Confederated Tribes of the Umatilla Indian Reservation (CTUIR), the Oregon Department of Fish and Wildlife (ODFW), and Washington Department of Fish and Wildlife (WDFW) and will produce up to 500,000 yearling spring Chinook salmon annually. In order to evaluate the effectiveness of the SFWWH rearing strategy and its overall contributions to the larger Walla Walla Basin goals, the Walla Walla Hatchery Monitoring and Evaluation Plan (2018) outlines four hatchery monitoring priorities: 1) Smolt-to-adult survival (Total Recruitment),  2) In-hatchery survival,  3) Ecological and genetic effects, and 4) Minijack rates and smolt growth and development.  As pointed out in the ISRP Review (2015), post release quantification of minijack rates could “shed light on the apparently high rate of loss of hatchery smolts (nearly 60% loss) enumerated at the downstream trap” as well as “help the proponents evaluate the impact of the project on natural origin fishes”.

In FY 2022-2023 in cooperation with the CTUIR we initiated a multi-brood year Walla Walla Chinook salmon smolt quality evaluation.

In FY2024 we will complete a second and initiate a third year (of 3-4) of smolt quality and physiological evaluation of brood year 2021-2024 (release year 2023-2026) of Walla Walla spring Chinook salmon. Fish are reared in circular flow through tanks at the Walla Walla Fish Hatchery under on a “naturalized” feeding regime with a size target at release of 10 fish/lb (45g). Fish are allowed to volitionally release directly into the Walla Walla River for three or four weeks before being flushed out at the end of April. Fish are sampled from 2 circular tanks at five different time points that span from summer to spring (August, October, January, February, and April) to allow calculation of growth rates as well as obtain a seasonal profile of smolt development. Data collected at these time points include size, condition factor, whole body lipid, and smolt development (via Na+/K+-ATPase enzyme activity). At the final sampling we collect plasma from several hundred male fish to assess rates of early male maturation (11-ketotestosterone ).

Objective 5 - Exercise Physiology Experiment in pRAS systems. (Initiate)

Background:  We propose to determine if and how current (and forthcoming) changes to rearing regimens in regional hatchery supplementation programs affect Chinook salmon smolt phenotypes by applying existing physiological tools (associated with growth, smoltification and maturation) and developing new physiological tools to determine the effects of exercise training on hatchery salmonids. Research will focus on assessing muscle development, growth, metabolism (via respirometry), lipid and carbohydrate utilization, and stress/health. Laboratory-scale evaluations will be conducted at the NOAA, Manchester Research Station, WA to examine the effects of varying degrees of exercise on salmonid physiology. We will use this information to conduct an assessment of relationships between physiological indices and smolt migration and juvenile survival (via PIT-tagged hatchery fish) as part of our ongoing studies at new circular pRAS facilities currently being tested in the Columbia River Basin (Leavenworth, Walla Walla, Winthrop hatcheries). Ultimately, the ability of these optimized regimes to contribute to salmon recovery can be quantified through monitoring smolt-to-adult return (SAR) and adult size and age at maturity. Results from these controlled studies will help inform  hatchery protocols used by regional supplementation hatcheries to aid recovery efforts throughout the CRB.

Reference

Harstad, D.L., Larsen, D.L., and Beckman, B.R., 2014.  Variation in minijack rate in Columbia Basin hatchery Chinook salmon.  Transactions of the American Fisheries Society. 143: 768-778.

Larsen, D. A., D. L. Harstad, A. E. Fuhrman, C. M. Knudsen, S. L. Schroder, W. J. Bosch, P. F. Galbreath, D. E. Fast, and B. R. Beckman. 2019. Maintaining a wild phenotype in a conservation hatchery program for Chinook Salmon: The effect of managed breeding on early male maturation. Plos One https://doi.org/10.1371/journal.pone.0216168.