What Is The Potential Impact Of Diel Vertical Migration Patterns Of Pacific Herring On The Prey-switching Behavior Of Resident Orcas In The Salish Sea During Periods Of Low Chinook Salmon Abundance?
The diel vertical migration (DVM) of Pacific herring in the Salish Sea likely plays a significant role in the prey-switching behavior of resident orcas, particularly during periods of low Chinook salmon abundance. Here's a structured summary of the potential impact:
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Prey Availability and Hunting Strategy:
- Pacific herring migrate to the surface at night and descend to deeper waters during the day. This pattern makes them more accessible to orcas at night, potentially prompting orcas to switch their prey when Chinook salmon is scarce.
- Orcas, known for their adaptability, might adjust their hunting times to target herring at night, leveraging the herring's surface presence for easier prey capture.
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Energy Considerations:
- Hunting deeper during the day may require more energy, which could deter orcas from pursuing herring then. However, nighttime surface availability reduces energy expenditure, making herring a more viable option.
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Ecosystem Implications:
- A shift to herring could impact herring populations, affecting other predators reliant on them and potentially altering the food web structure in the Salish Sea.
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Behavioral and Ecological Adaptations:
- Orcas may develop new hunting strategies, possibly leading to changes in social structures or hunting tactics. Long-term scarcity of Chinook salmon could drive specialization in herring predation.
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Research and Observations:
- Studies from other regions indicate orcas can switch to herring when salmon is scarce, supporting the feasibility of such a prey switch in the Salish Sea.
In conclusion, the DVM of herring facilitates orcas' prey-switching to herring, particularly at night, aiding their survival during low Chinook abundance. This switch may have broader ecological consequences and drive behavioral adaptations in orca populations.