Work Element C: 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 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 same 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.  Similar reductions in precocious maturation have been observed in other stocks of summer and winter steelhead when these fish are raised in circular tanks instead of rectangular raceways. 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.  In the FY 2024 performance period, NOAA provided the starter and grow-out circular tanks from their excess inventory and the USFWS transported and installed the tanks at the WNFH with NOAA providing physical, and technical assistance.  The banks of starter tanks were stocked with 8,000 steelhead fry and completed their first year of rearing during the FY24 performance cycle.
  
FY2025 TASKS
The 8,000 BY24 fish will complete their second year of rearing in the larger grow-out tanks, be implanted with PIT-tags in October 2024, and released as age-2 smolts in April 2026.  In March 2026, up to 3,000 of the BY24 age-2 steelhead from both treatments (raceways, circular rearing tanks) will be assessed for smoltification and maturation, weighed, and measured.  After release survival and migration speed will be determined using the PIT tag detections collected at established interrogation arrays in the Methow and Columbia Rivers available in PTAGIS.  Steelhead produced in the circular tanks will be compared to the age-2 production groups currently reared in raceways to assess any improvements in smoltification, reductions in precocious maturation, and improvements in survival during migration.
The study will be restocked with BY25 steelhead in the starter tanks during the FY25 performance period to provide a replicate broodyear in the data set.  NOAA will continue to provide technical assistance in developing feeding protocols and fish culture procedures.    USFWS will culture the juvenile steelhead in the pilot circular tank installation.

Work Element D: Identify mechanisms of fitness loss in hatchery steelhead:

Inadvertent Selection:
Almost all steelhead hatcheries produce age-1 smolts (S1), and there is strong evidence that growth rate is under inadvertent selection in S1 hatchery programs, that selection occurs after release, and that it leads to transgenerational effects on growth rates.  Selection favoring larger body size in steelhead smolts occurs after release from hatcheries. Variation in size at release largely reflects growth differences established once steelhead start feeding on their own after absorbing their yolk.  The consequence of size-selective mortality after release combined with moderate heritability for growth traits during a year of hatchery rearing likely explains why offspring of hatchery produced steelhead grow faster under hatchery conditions than offspring of their founding wild populations (Blouin et al. 2021).
One way to reduce unintentional directional selection on growth rate is to ensure that more or all of the released fish exceed the range of sizes that are selected against.  Extending the rearing period from one to two years can greatly reduce the number of small fish that are released and therefore the opportunity for selection on growth rate (Tatara et al. 2017, 2019, Middleton et al. 2024).  The inadvertent selection for rapid growth rate in the hatchery evident in S1 rearing programs (Blouin et al. 2021) is not expected to occur in S2 rearing programs.  If this turns out to be true, it would indicate that S2 rearing is a mechanism to reduce inadvertent selection on growth rate.

Fitness consequences of inadvertent selection:
Offspring of S1 hatchery fish exhibit reduced fitness, and in two Columbia River tributaries, evidence suggests that the fitness loss has a genetic basis (Hood River, Wenatchee River). Potential mechanisms of fitness loss include reproductive traits, embryonic development, or offspring survival. However, selection favoring rapid growth rate is likely associated with other traits that may be advantageous in a hatchery setting but disadvantageous in the wild, thus offspring survival is a very likely mechanism.  For example, offspring of farmed Atlantic salmon grow faster but have reduced survival in natural environments (McGinnity et al. 2003).  In steelhead, offspring of S1 hatchery-origin adults exhibit higher levels of aggression when food is limited during the first few months of life (Berejikian et al. 1996) and increased vulnerability to predators (Berejikian 1995).  If S2 hatchery populations do not undergo size-selective mortality at release, selection for disadvantageous traits associated with rapid growth may be reduced, and survival under natural conditions of S2 hatchery fish may be more similar to natural populations.

Proposed work:
There are three summer steelhead conservation hatchery programs in the Methow River Basin that utilize natural origin broodstock, but raise them to smolt at different ages.  The different growth rates and rearing procedures between the programs can produce different potential for inadvertent domestication on growth traits. The Winthrop National Fish Hatchery (WNFH) conservation program uses natural-origin (wild) broodstock raised as S2 smolts. The Twisp and Douglas PUD conservation programs use natural-origin broodstock and raise S1 smolts.  Experiments comparing offspring from wild broodstock, the adult returns from S1 rearing programs (Twisp, Douglas PUD), and adult returns from S2 rearing programs (WNFH) provide a unique opportunity to determine how broodstock selection and rearing methods may alleviate potential for inadvertent selection on growth traits and to further identify physiological mechanisms driving selection for rapid growth.
In the 2025 performance period NOAA will design and implement common garden experiments using progeny from these three distinct hatchery populations raised in two environments (hatchery tanks under age-1 rearing and an experimental stream channel.  Parentage assignment will be used to monitor the performance of the three populations during rearing and to determine family effects on survival and the heritability of growth and metabolic traits.  The analyses will help determine if age-2 rearing protocols used at WNFH alleviate inadvertent selection for growth.  Knowing mechanisms of inadvertent selection in hatcheries and how to avoid it should increase the conservation and recovery potential of conservation hatcheries, and improve the efficiency of mitigation efforts of the Fish and Wildlife Program to sustain the fisheries resources of the Columbia Basin.

Experiments will be designed to test the following hypotheses:
Ha1:  Offspring of S1 steelhead should grow more quickly during hatchery rearing compared with offspring of S2 and natural origin fish.  
Ha2: Offspring of S1 steelhead should grow more quickly under natural conditions compared with offspring of S2 and natural origin fish.
Ha3: Offspring of S1 steelhead should exhibit lower survival under more natural conditions (including limited food and predation pressure) than offspring of S2 and natural origin fish.

Physiological mechanisms underlying selection.
Measures of metabolism are correlated with growth rates, but can also be affected by the quantity of food consumed by an organism, plastic and genetic digestive organ system response to handling food, and genetic variation in growth rate among individuals.  We will raise juvenile steelhead produced from natural origin broodstock on a high ration treatment (S1) and a low ration treatment (S2) and measure metabolic rates using respirometry, growth rates, and the weight of digestive organs systems.  We will determine correlations between metabolic rates, growth, and food processing organ mass (GI tract).  This experiment will primarily test for plastic responses associated with ration size.

Ha4: Measures of GI tract upregulation should be positively correlated with both growth rate and metabolic rate in both rearing treatments.
Ha5: More individual steelhead in the S1 ration treatment will display upregulation of the digestive system than individuals in the S2 ration treatment.