Experimental determination of key factors affecting herring egg survival
Presentation Abstract
Pacific herring play pivotal roles in coastal social-ecological systems, yet our understanding of the factors controlling spawning events, and the survivorship of deposited herring eggs is lacking. Traditional ecological knowledge (TEK) from British Columbia First Nations puts forward two factors as key contributors to herring egg survivorship: predation and freshwater outflow. In addition, diver-based observations suggest that herring adhere differentially amongst macrophyte substrates. We hypothesized that predation and freshwater outflow would have negative effects on herring egg density and maturation, with differential effects amongst substrates. We tested this experimentally using herring eggs naturally deposited on 4 substrate types: Zostera marina, Macrocystis pyrifera, Saccharina latissima, and Egresia menziesii. These were suspended ~1m above the benthos at stream outflow and non-outflow locations, using predator exclusion treatments (cage vs. un-caged). We quantified change in percent cover and wet weight of herring eggs to evaluate effects of these factors on egg survivorship. Counter to our hypotheses, freshwater outflow had very little effect on egg survivorship. Predation effects were site-specific, and we observed potential herring egg predators including sea stars and urchins contributing to egg loss. Substrate type accounted for the greatest difference in egg loss rates we observed. Parameterization of egg loss rates is important to Pacific herring stock assessments, and our study re-emphasizes that this substrate-level variability can be large, suggesting that herring egg survivorship may benefit from substrate choice. However, preliminary experimental work on substrate selectively and preference is inconclusive and demands further research.
Session Title
Ecological and cultural context of Pacific herring in the Salish Sea
Conference Track
Species and Food Webs
Conference Name
Salish Sea Ecosystem Conference (2016 : Vancouver, B.C.)
Document Type
Event
Start Date
2016 12:00 AM
End Date
2016 12:00 AM
Location
2016SSEC
Type of Presentation
Oral
Genre/Form
conference proceedings; presentations (communicative events)
Contributing Repository
Digital content made available by University Archives, Heritage Resources, Western Libraries, Western Washington University.
Subjects – Topical (LCSH)
Pacific herring--Spawning--Salish Sea (B.C. and Wash.); Pacific herring--Monitoring--Salish Sea (B.C. and Wash.); Pacific herring--Predators of--Salish Sea (B.C. and Wash.)
Geographic Coverage
Salish Sea (B.C. and Wash.); British Columbia
Rights
This resource is displayed for educational purposes only and may be subject to U.S. and international copyright laws. For more information about rights or obtaining copies of this resource, please contact University Archives, Heritage Resources, Western Libraries, Western Washington University, Bellingham, WA 98225-9103, USA (360-650-7534; heritage.resources@wwu.edu) and refer to the collection name and identifier. Any materials cited must be attributed to the Salish Sea Ecosystem Conference Records, University Archives, Heritage Resources, Western Libraries, Western Washington University.
Type
Text
Language
English
Format
application/pdf
Experimental determination of key factors affecting herring egg survival
2016SSEC
Pacific herring play pivotal roles in coastal social-ecological systems, yet our understanding of the factors controlling spawning events, and the survivorship of deposited herring eggs is lacking. Traditional ecological knowledge (TEK) from British Columbia First Nations puts forward two factors as key contributors to herring egg survivorship: predation and freshwater outflow. In addition, diver-based observations suggest that herring adhere differentially amongst macrophyte substrates. We hypothesized that predation and freshwater outflow would have negative effects on herring egg density and maturation, with differential effects amongst substrates. We tested this experimentally using herring eggs naturally deposited on 4 substrate types: Zostera marina, Macrocystis pyrifera, Saccharina latissima, and Egresia menziesii. These were suspended ~1m above the benthos at stream outflow and non-outflow locations, using predator exclusion treatments (cage vs. un-caged). We quantified change in percent cover and wet weight of herring eggs to evaluate effects of these factors on egg survivorship. Counter to our hypotheses, freshwater outflow had very little effect on egg survivorship. Predation effects were site-specific, and we observed potential herring egg predators including sea stars and urchins contributing to egg loss. Substrate type accounted for the greatest difference in egg loss rates we observed. Parameterization of egg loss rates is important to Pacific herring stock assessments, and our study re-emphasizes that this substrate-level variability can be large, suggesting that herring egg survivorship may benefit from substrate choice. However, preliminary experimental work on substrate selectively and preference is inconclusive and demands further research.
