Journal
MARINE ECOLOGY PROGRESS SERIES
Volume 617, Issue -, Pages 53-66Publisher
INTER-RESEARCH
DOI: 10.3354/meps12485
Keywords
Age-0 herring; Abundance; Condition; Bottom-up; Top-down; Forage fish; Strait of Georgia; Density dependence
Categories
Funding
- Pacific Salmon Foundation
- Herring Conservation and Research Society
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Small pelagic fish are key planktivores and prey in marine ecosystems, and their population abundances undergo strong temporal and spatial variability. Top-down (predator controlled) and bottom-up (prey-driven) processes during early life history are important for determining forage fish survival and recruitment. We examined biological and environmental factors hypothesized to influence age-0 Pacific herring Clupea pallasi in the Strait of Georgia (SOG), British Columbia, Canada. Primarily bottom-up processes affected interannual variability in age-0 herring abundance and condition, with some evidence of top-down effects on condition. Age-0 herring abundance increased with increasing adult spawning biomass and peaked when most adults spawned about 20 d prior to the peak spring primary production bloom. This timeline would temporally align first-feeding herring larvae with their prey, such as small copepods. Age-0 herring abundance also increased with increasing juvenile salmon abundance, indicating that conditions favourable for herring were also favourable for their predators and competitors. Age-0 herring condition decreased with increasing spawning biomass, increased when most adults spawned closer to the peak spring bloom, increased with increasing temperatures above 8.2 degrees C, and increased then stabilized with increasing prey zooplankton density. Age-0 herring condition had a dome-shaped relationship with predator abundance, indicating that high predator abundances negatively affected fish condition. Study results suggest that density-dependent processes, such as intraspecific competition, may be important in the SOG. A positive correlation between age-0 herring abundance and subsequent age-3 recruit abundance may provide a leading indicator of low recruitment years.
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