Genetic testing is suggesting that
hatchery-reared spring chinook salmon at segregated hatcheries may differ in
traits with fish from integrated hatcheries in return and spawn timing,
according to a recent study.
The study looked at six traits in adult
chinook salmon from the same stream, but from captive brood programs that used
two alternative management approaches, and evaluated how the two types of
hatcheries affected variations in those traits – return timing, length and
weight at return, age at maturity, spawn timing and a daily growth coefficient.
The two lines of fish had the same wild origin
from the same era, but one line was from an integrated hatchery line and the
other from a segregated hatchery line, both at the Cle Elum Supplementation and
Research Facility in Cle Elum, Washington.
The integrated line uses only wild-born broodstock,
and all hatchery-born fish from this line are allowed to spawn in the wild. In
contrast, the segregated line uses only hatchery-born broodstock, and all
hatchery-born fish from this line are removed from the river before
By comparing these lines, the study is one of
the first to utilize genomic approaches to determine the effectiveness of a
conservation strategy -- managed gene flow – on trait-associated – and
potentially adaptive – loci (chromosomal position of a gene), said Charles D.
Waters, a PhD candidate in the School of Aquatic and Fishery Sciences at the
University of Washington.
“These results suggest that some traits,
particularly return and spawn timing, may be affected by hatchery rearing,”
Waters said. “However, the results also suggest that integrated management
reduces these effects. The ultimate, long-term goal of this and future research
would be to inform management practices that minimize genetic change caused by
hatchery rearing and, in turn, maximize the success of hatcheries to supplement
Previous studies have found that
hatchery-reared salmon differ from their wild counterparts, including reduced
reproductive success, differences in growth rate and morphology, and increased
vulnerability to predation, the study says. Integrating wild or natural-origin
fish into hatchery broodstock can counter those differences.
The study, “Genome-wide association analyses
of fitness traits in captive-reared Chinook salmon: Applications in evaluating
conservation strategies,” was published online Jan. 21, 2018, in the journal
Evolutionary Applications (http://onlinelibrary.wiley.com/doi/10.1111/eva.12599/abstract).
Waters co-authors are Jeffrey D. Hard,
supervisory research fishery biologist, Conservation Biology Division, Genetics
& Evolution Program, NOAA Fisheries - Northwest Fisheries Science Center;
Marine S.O. Brieuc, postdoctoral fellow, Centre for Ecological and Evolutionary
Synthesis, Department of Biosciences, University of Oslo, Norway; David E.
Fast, senior research scientist, Yakama Nation Fisheries; Kenneth I. Warheit,
supervisor, Molecular Genetics and Fish Health Laboratories, Washington
Department of Fish and Wildlife; Curtis M. Knudsen, research scientist, Oncorh
Consulting; William J. Bosch, data manager, Yakama Nation Fisheries; Kerry A.
Naish, professor, School of Aquatic and Fishery Sciences, University of
Waters said that the first goal of the study
was to identify genetic markers that are associated with key traits in chinook
salmon, such as return and spawn timing.
“Identifying these genetic markers is
important because it would improve our understanding of how key traits in
salmon are affected by genetic variation as opposed to environmental factors,”
he said. “This information is also important because these markers would
improve our ability to monitor hatchery and wild salmon populations to
determine if genetic variation is changing over time and in response to
Continuing, he said that there has been a lot
of research that indicate that hatchery-origin fish from some systems are less
fit after release into the wild compared to wild salmon, but what’s not known
is if this fitness decline is pervasive or limited geographically by species.
“Furthermore, if fitness declines do occur, we
do not know the exact mechanisms, and if certain management actions may
mitigate potential negative effects of hatchery-rearing,” he said. Integrated
hatcheries appear to be able to mitigate this risk.
In another recent study, collaborating with
the Yakama Nation, WDFW, and NOAA Fisheries, Waters and his co-authors provided
the first empirical evidence that integrated salmon hatchery management, when
compared to segregated management, successfully reduces genetic divergence of
hatchery from wild fish “This, in turn, is likely to reduce the genetic risks
of hatchery production to the wild population,” Waters said.
In this study, as a second goal, they aimed to
extend their previous work and “determine if integrated management, again
relative to segregated management, successfully limited genetic change at
markers associated with key fitness traits.”
“The ultimate, long-term goal of this and future
research would be to inform management practices that minimize genetic change
caused by hatchery rearing and, in turn, maximize the success of hatcheries to
supplement wild populations,” Waters said.
He warned that there are caveats that could
limit the applicability of the study’s findings:
--these are short-term findings (four
generations in the case of this study), but the long-term is unknown.
--the Cle Elum integrated hatchery uses 100
percent wild-born salmon as broodstock. Other hatcheries may include both wild
and hatchery broodstock.
--the study doesn’t investigate fitness
directly, meaning the contribution that a wild-born or hatchery-born fish makes
to the next generation.
--the study focused on chinook salmon and the
results may not be applicable to other species of salmonids.
--hatchery objectives vary and what’s good
management at one hatchery may not be so at another.
However, the results lay the foundation for
the development of tools to better monitor hatchery and wild populations over
time, he said.
“Furthermore, the genetic markers that we
identified are starting points for more in-depth investigations that aim to
identify both the specific traits and specific genes that are affected by
hatchery rearing,” Waters said. “If we understand how the hatchery environment
affects the fitness of salmon, then we can potentially adjust management
practices to minimize these effects and improve supplementation efforts. The
field is in its infancy, and geneticists are currently researching ways in
which trait-linked markers might contribute to conservation efforts.”
The Yakama Nation, WDFW, NOAA Fisheries,
Washington Sea Grant and U of W’s Hall Conservation Genetics Research Award,
all contributed to this study, Waters said.