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  3. Salmon-Herring Interactions
Pacific herring are the dominant forage fish in the Salish Sea and are of critical importance to Pacific salmon populations.

Herring constitute the majority of adult Strait of Georgia Chinook and Coho salmon diets. They are also important prey for seals and other marine predators, buffering the impacts of these predators on juvenile Pacific salmon of all species.  Consumption of juvenile herring supports accelerated growth of juvenile Chinook and coho salmon, a critical role given growing evidence for linkages between early marine growth, marine survival, and population productivity. The Salish Sea Marine Survival Project provided substantial evidence for these links between herring availability and salmon growth and survival. This proposal seeks to build on these results to address several outstanding knowledge gaps including what factors impact the availability of juvenile and adult herring to Pacific salmon; the quality and usage of spawn habitat; and the health and structure of Strait of Georgia herring populations. The project will be led by PSF along with academic and First Nation partners.

Key components of the project are program co-development and capacity building within Strait of Georgia First Nations, particularly with respect to utilization of novel technologies such as small vessel-based hydroacoustic units. Our study area will include the Strait of Georgia including the Gulf Islands, and mainland coast and inlets. Our work will contribute to a more complete understanding of the food web that supports Pacific salmon, benefiting salmon survival while building capacity among First Nations communities.

The primary activities within the project include:

Interactions between age-0 herring and juvenile Chinook and Coho Salmon

Through analysis of existing data collected in DFO surveys in the 1990s and a new summer sampling program of juvenile salmon diet surveys, this activity intends to address the following questions:

  • Does availability of age-0 herring to juvenile salmon differ by region of the Strait of Georgia and is it related to occurrence of abundant local spawning and/or environmental conditions?
  • Does herring size and growth differ by region of the Strait of Georgia?
  • Do the age-0 herring consumed by juvenile and adult salmon represent only the smallest, slowest growing individuals in the population, does this vary by region?
  • Does consumption of juvenile herring provide a growth advantage to juvenile salmon?
Biomass assessment and otolith-based detection of adult non-migratory herring in the Strait of Georgia

This activity will develop an hydroacoustic survey to monitor non-migratory herring biomass, distinguish non-migratory from migratory herring using an otolith microchemistry tag, and improve our understanding of these two components of the population through application of the microchemistry tag to fishery catches and fishery independent samples from spawning events.

Herring Spawn Habitat: Gap Analysis, Characterization and Assessment of Anthropogenic Stressors

This activity will investigate the habitats where herring spawn and no longer spawn. To supplement existing DFO overflight spawn surveys, satellite imagery will be used to attempt to detecting small/transient spawn events that occur outside core spawning areas and peak spawn times. Assessing historical satellite imagery will provide a picture of spatial and temporal prevalence of these spawns, and a gap analysis with the current overflights will be conducted. We will also investigate potential drivers of spawn habitat loss by characterizing habitat quality in areas where spawns have disappeared or are intermittent and regions where DFO data show they are relatively persistent.

Compilation of Herring Traditional Ecological Knowledge from First Nations in the Strait of Georgia

The significance of the loss of First Nations relationships and interaction with the marine environment as a result of the historic loss of herring will be investigated. This activity is intended to be a community outreach and educational initiative and will provide valuable context to other projects in this proposal. Convening groups will host discussions with First Nations and communities to be carried out by convening groups to discuss the importance of herring, discuss how this information can best be distributed to others, and display any results from established projects in this proposal. These sessions will allow for broad discussions with First Nation communities on the ecological changes seen, changes to their local spawn, spatial and temporal presence of juvenile and adult herring, and key anthropogenic changes.

Eggs of the Pacific herring, Clupea pallasii, laid on a frond of Eel grass in the intertidal zone. The developing embryos are ten days old at this point and are quite visible. Photo credits: Eiko Jones

Funding for this project is provided by the BC Salmon Restoration and Innovation Fund, a contribution program funded jointly between Fisheries and Oceans Canada and the Province of BC.

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