The quality of the food sockeye salmon eat along their migratory routes is more important than quantity to their growth and fitness, a new study has found, highlighting concerns about the effects of climate change on ocean conditions and salmon. The work has been published in FACETS.
Researchers from the Institute for the Oceans and Fisheries (IOF) at the University of British Columbia, the Department of Fisheries and Oceans (DFO), University of Toronto, Dalhousie University and the Hakai Institute examined young sockeye salmon at three locations along their migration route. in coast of British Columbia. In 2015 and 2016, the body condition and nutritional health of juvenile sockeye were sampled in the northern Strait of Georgia, the highly tidal mixed Johnstone Strait and Queen Charlotte Strait.
“We measured the fatty acids in the sockeye salmon tissues, particularly by looking at stored fatty acids that are important for mobilizing energy during periods of famine, such as what these salmons in Johnstone Strait face,” said lead author Dr. Jessica Garzke, an IOF postdoctoral fellow. “We found that short-term health changes differed from year to year, but were not related to zooplankton biomass, abundance, average size or species composition. Rather, it was the quality of the zooplankton that played an important role.”
Leaving the generally productive and good foraging area of the Strait of Georgia to the typically nutrient-poor conditions of the Johnstone Strait has a major impact on the young salmon. When juvenile sockeye salmon entered Johnstone Strait in 2015, they were generally in good physical and nutritional condition and were able to use stored energy resources to traverse this section, where prey availability was low, to get to Queen Charlotte Strait. However, in 2016, juvenile sockeye salmon entered Johnstone Strait with poor body and nutritional condition, and they struggled to regain fitness once they reached Queen Charlotte Strait.
“It was clear from our study that the differences in the condition of the smolts between the two years were due to changes in the food quality available to the fish, more than any other factor. Incorporating food quality measurements in addition to the analysis of the amount of prey is essential for understanding changes in fish condition and survival between years,” said Dr. Garzke.
By understanding how diet affects salmon growth and health early in life, researchers can understand the species’ long-term population trends, including their decline, Dr. Garzke says. Sockeye salmon is an iconic species in British Columbia, important both commercially and culturally, and is in decline.
The research highlighted how variable the ocean conditions are faced by young salmon in British Columbia, said senior author and IOF associate professor Dr. Brian Hunt, where migrating salmon experience “boom and bust” feeding conditions. “Importantly, feeding conditions are not consistent from year to year. They are affected by the changing climate, and areas that had good feeding conditions one year may be poor the next. The more areas switch to poor feeding conditions, the more difficult it’s for youngsters to survive the coastal migration and their first winter at sea.”
You are what you eat is just as important to fish as it is to humans
Jessica Garzke et al, Dynamic coastal pelagic habitat drives rapid changes in growth and condition of juvenile sockeye salmon (Oncorhynchus nerka) during early marine migration, FACETS (2022). DOI: 10.1139/facets-2022-0068
Quote: Food quality may be key to growth and survival of young sockeye salmon (2022, October 20) retrieved October 21, 2022 from https://phys.org/news/2022-10-food-quality-key-juvenile- sockeye.html
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