WORK ELEMENT B: Increase steelhead smoltification rate and decrease residuals at WNFH.
The USFWS is planning facility improvements that include installation of large circular rearing tanks to replace aging rectangular concrete raceways.  The installation of the large circular rearing tanks is expected to be complete in 2026.  The new tanks may provide an opportunity to increase smoltfication rates and reduce residual production in the steelhead conservation hatchery program at WNFH.  Several years of laboratory studies at the Manchester Research Station on age-2 steelhead from the Methow River stock have consistently demonstrated that rearing in circular vessels results in lower rates of precocious male maturation than rearing in raceways at the WNFH.  During the FY 2023 period the USFWS conducted a feasibility analysis to determine whether circular rearing tanks could be installed at the WNFH for use in pilot studies.  A suitable covered location and sufficient water were identified and the USFWS decided to proceed with installation of four 10-ft diameter fiberglass tanks.  

FY 2024 TASKS
In the FY 2024 performance period, NOAA will provide the circular tanks for their excess inventory and the USFWS will transport and install the tanks at the WNFH.  NOAA will provide technical assistance during the installation.  After installation, the tanks will be stocked with juvenile steelhead produced from broodyear 2024 (2,000 fish per tank), and reared to produce age-2 smolts.  NOAA will provide technical assistance in developing feeding protocols and fish culture procedures.  Steelhead produced in the circular tanks will be compared to the age-2 production groups currently reared in raceways in the FY 2025 performance period.  USFWS will culture the juvenile steelhead in the pilot circular tank installation.


WORK ELEMENT C: Identify physiological traits affecting growth and their genetic basis to minimize domestication selection.
The project develops rearing strategies for steelhead to reduce fitness loss by minimizing hatchery-induced selection (domestication). The primary objective is to allow expression of natural growth rates within hatchery environments to promote smoltification and reduce size-selective mortality occurring after release. The project conducts mechanistic experiments at the laboratory scale to elucidate the physiological traits affecting growth rate variation and the genetic basis of those traits.  The approaches developed in the laboratory are applied to the conservation hatchery program for steelhead at the Winthrop National Fish Hatchery (WNFH) to determine effectiveness and transferability at the hatchery scale. All experiments feature juveniles produced from natural-origin broodstock (Methow River) and spawned at the WNFH, but experiments are designed to be applicable and transferable to harvest hatcheries.

Laboratory experiments:
Energy available for growth is determined by metabolic processes. In fishes, metabolic rate can vary threefold among individuals after controlling for other factors and show temporal stability for individuals in consistent environments, such as hatcheries. Metabolism in fish is measured indirectly as oxygen uptake rates using respirometry.  The standard metabolic rate (SMR) is the minimum energy required to sustain homeostasis.  Maximum metabolic rate (MMR) represents the maximum rate of aerobic metabolism of an animal and is therefore associated with the maximal rate at which oxygen can be transported from the environment to the tissue mitochondria.  The difference between MMR and SMR is the aerobic scope (AS) and can be interpreted as the amount of energy available for growth and activity.

FY 2024 TASKS
Task 1: In FY23 we acquired swimming respirometers and tested the equipment to develop methods for future studies to measure aspects of metabolic phenotypes beyond the standard metabolic rate (i.e., maximum metabolic rate, and aerobic scope), and to assess how different hatchery and natural rearing environments affect growth, smoltification, and swimming performance.  In FY24, we will raise steelhead produced from natural-origin broodstock spawned at WNFH in hatchery tanks and in a semi-natural stream channel.  We will measure and assess SMR, MMR, and AS in select individuals from both environments to determine which aspects of metabolic phenotype drives growth in hatchery and natural environments.  We will conduct a genetic parentage analysis of individuals measured from both environments to account for family effects and to determine heritability of metabolic and growth traits.  This analysis will test whether different metabolic phenotypes are favored in hatchery and natural environments, and their consequences for growth and performance.  Heritability estimates for metabolic traits (the proportion of phenotypic variance associated with additive genetic effects) can be used to determine the adaptive potential for growth and smoltification traits in steelhead.

Task 2: A pilot study conducted in FY23 revealed significant variability in oxygen consumption rate for individual embryos when using static respirometry techniques. This result indicated that embryos are more metabolically diverse than previously thought, and that static respirometry techniques are insufficient to determine metabolic rates in embryos. Consequently, we acquired intermittent flow respirometry equipment to improve estimates SMR for embyros and alevins and developed methods for collecting data on these fragile organisms.  In FY24 we will use these methods to investigate the developmental timeline of metabolic phenotypes which will determine when to implement new hatchery rearing practices to increase their effectiveness.

Task 3: In FY24 we will complete the analysis standard metabolic rate data collected in FY23.  We will estimate individual SMR from the oxygen uptake data, determine variability among individuals, and temporal stability within individuals to determine if metabolic phenotypes exist in hatchery steelhead. Strength and direction of correlations between SMR, growth and smoltification will indicate how metabolic phenotypes influence growth and smoltification traits and their role in domestication.

Task 4: Investigate the genetic basis of growth and seawater survival traits using 1,200 individuals from broodyear 2021.  Genetic data (RADseq and and whole genome) will be analyzed to determine the role of family effects on growth and smoltification, identify regions of the genome under selection in hatcheries, and estimate breeding values for growth and seawater challenge mortality using genomic prediction.