High food quality can help juvenile salmon to survive and recover from low food quantity periods.
The first months after juvenile salmon enter the ocean are one of the critical periods in their life history.
Environmental conditions experienced during this time, particularly the availability of zooplankton prey, determine fitness and growth of these young fish, and therefore their ability to avoid predators, resist infection, and survive their first winter at sea.
This may be an important factor contributing to fluctuations in salmon returns.
Read this open access paper on the FACETS website.
Knowledge of the coastal ocean in British Columbia indicates that feeding conditions for juvenile salmon may vary spatially across the marine habitats that they migrate through on their way to the open ocean.
Feeding conditions might also vary across habitats because of changes in environmental conditions from year to year.
To investigate this, we measured juvenile sockeye salmon health parameters in relation to available prey in two years (2015 and 2016) and during outmigration from south to north through the northern Strait of Georgia, Johnstone Strait, and Queen Charlotte Strait.
We found that feeding conditions in Johnstone Strait were particularly poor, with low zooplankton quantity negatively affecting fitness and growth.
Importantly, the nutritional quality of consumed prey, especially the amount of essential fatty acids, was an important factor in juvenile salmon’s ability to endure and recover from periods of poor food supply.
In 2016, when food quality was poor in the Strait of Gerogia, juvenile salmon were not able to rapidly recover when they emerged from Johnstone Strait into the better feeding area of Queen Charlotte Strait.
Our study showed the importance of taking into account food quality when making projections about salmon survival rates.
Read the paper — Dynamic coastal pelagic habitat drives rapid changes in growth and condition of juvenile sockeye salmon (Oncorhynchus nerka) during early marine migration by Jessica Garzke, Ian Forster, Sean C. Godwin, Brett T. Johnson, Martin Krkošek, Natalie Mahara, Evgeny A. Pakhomov, Luke A. Rogers, and Brian P.V. Hunt.