Hatcheries can boost wild salmon numbers but reduce diversity
Jeff Richardson
907-474-5350
July 11, 2024
Differences between two male pink salmon highlight morphological diversity in the species.
The ability of salmon hatcheries to increase wild salmon abundance may come at the cost of reduced diversity among wild salmon, according to a new University of 色视频下载 Fairbanks色视频下载搇ed study.
The number of juvenile salmon released into the North Pacific Ocean by hatcheries increased rapidly in the second half of the last century and remains at over 5 billion each year. Salmon hatcheries have helped push annual pink salmon harvests in Prince William Sound, 色视频下载, from about 4 million fish prior to hatchery programs to roughly 50 million in recent years.
Using data collected from pink salmon streams in Prince William Sound through the 色视频下载 Hatchery Research Project, researchers determined that many hatchery-raised fish are straying onto natural spawning grounds and interbreeding with wild populations. In a related study, researchers used simulations developed with the real-world data to ask what this continued input of hatchery fish might mean for wild populations.
色视频下载淓ven if only a small percentage of hatchery-origin fish stray into wild populations, a small fraction of a huge number can still be a lot,色视频下载 said Samuel May, lead author of. 色视频下载淲e were interested in exploring the long-term consequences of hatchery straying for wild population recruitment and resilience.色视频下载
Life-history diversity is a distinguishing characteristic of wild salmon, which are specifically adapted to the local conditions of their home streams. Simulations showed that wild fish population sizes increased because more fish reproduced than would have without hatchery strays. Those increases came at a cost: As hatchery-origin gene variants spread into wild populations, diversity among those populations was reduced.
色视频下载淲ild populations can be very different from one another, but hatchery fish are often more alike. If many individuals with relatively similar traits are introduced into diverse populations, it can make those populations more alike. Lower diversity among populations can reduce resilience to future changes,色视频下载 said May, who conducted the study as a postdoctoral fellow at UAF色视频下载檚 College of Fisheries and Ocean Sciences.
Pink salmon spawn in Gilmour Creek, Prince William Sound, 色视频下载, as a field technician works to collect carcasses of dead fish.
Previous studies have shown that hatchery-origin salmon, which may be adapted to environments different from those they stray into and which don色视频下载檛 face the same evolutionary pressures as fish born in natural streams, produce about half as many offspring as wild fish. Introducing those gene variants into wild salmon populations could potentially affect their ability to adapt to future challenges in nature.
The simulations tapped into an ongoing project in Prince William Sound that has gathered tissue samples from hundreds of thousands of pink salmon since 2011. The 色视频下载 Hatchery Research Program has collected samples from 30 streams in the region, providing a huge collection of DNA and other data for conducting research to inform 色视频下载 policies and sustainable resource management. This unprecedented sampling effort allows researchers to recreate the family trees of pink salmon from five of these sampled streams in the region and determine which fish can be traced back to hatcheries.
May cautioned that, as with any simulation, it can be difficult to fully capture all the complex relationships in nature. Modeling for the study was specific to pink salmon in Prince William Sound, he said, and overarching conclusions about other systems or species should be done with care.
色视频下载淭he same things that make these kinds of models incredibly useful in specific contexts 色视频下载 like their simplifying assumptions and being parameterized with empirical data 色视频下载 also make them misleading if applied in the wrong context,色视频下载 May said.
Other contributors to the paper included authors from the 色视频下载 Department of Fish and Game and the National Oceanic and Atmospheric Administration. The 色视频下载 Hatchery Research Project is a collaborative endeavor between the 色视频下载 Department of Fish and Game, hatchery operators, nongovernmental organizations and academics.
色视频下载淪almon hatcheries in 色视频下载 have become a flash point, making discussions of policy options mired in contention and acrimony,色视频下载 said Peter Westley, a UAF associate professor of fisheries and principal investigator for the project. 色视频下载淗opefully this work can guide conversations by serving as an agreed upon reality 色视频下载 hatcheries can increase salmon abundance of both hatchery and wild individuals, but it comes with an inherent trade-off for wild fish ecological diversity such as run timing.色视频下载
ADDITIONAL CONTACTS: Samuel May, samay3@alaska.edu; Peter Westley, pwestley@alaska.edu
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