Pacific herring (Clupea pallasii), a major forage fish species in the eastern Pacific Ocean, are key prey for many marine species throughout their range, including for threatened salmonid species in Puget Sound. Puget Sound herring spawning stock biomass has been declining locally over the past 40 years, including the San Juan Island spawning populations. Salmon in the area of the San Juan Islands have been found to be particularly reliant upon herring for prey. At present, while there are many hypothesized causes of herring declines, there is little agreement on the primary cause or, therefore, the best management or policy actions for recovery. Lead Ecologist Tessa Francis is leading a 3-year effort to address this gap in understanding through 3 primary activities: (1) convene an expert elicitation workshop to evaluate key threats to San Juan Island herring; (2) quantify changes in the abundance and distribution of eelgrass used as spawning habitat for San Juan Island-spawning herring using historical data; and (3) monitor herring spawning sites to measure early-life-stage (i.e. embryonic) mortality rate.
In November 2017, Francis, with colleagues from the Washington Department of Fish and Wildlife, convened an expert workshop to evaluate hypotheses about declines in herring in the Salish Sea, including the San Juan Islands. At present, Francis is developing a Qualitative Network Model to evaluate the relative support for different hypotheses about what is causing herring declines.
Habitat modeling, based upon a spatial model developed by NOAA scientist and PSI collaborator Ole Shelton, will be conducted in 2018. Field work is planned for the herring spawning season in 2019.
Fig. 1. Site-scale changes in eelgrass area at herring spawning sites in Puget Sound. This project supports the analysis of these patterns in the San Juan Islands. From Shelton et al. 2017.
Pacific herring (Clupea pallasii) are an abundant and foundational species in the Salish Sea. Presently, monitoring, assessment, and management efforts treat Salish Sea herring as two separate groups: a Puget Sound herring stock, and a Strait of George herring stock. Building on my previous work to evaluate limits to Puget Sound herring recovery, I have teamed up with Washington Department of Fish and Wildlife staff to evaluate the state of knowledge and provide recommendations on the conservation and management of Salish Sea herring.
We first formed a trans-boundary technical team comprised of tribes and First Nations scientists, agency scientists, and university scientists. Our team started by collecting leading hypotheses about the factors influencing changes in herring abundance and distribution in the Salish Sea. Those hypotheses, including shoreline development, contaminants and pollutants, and food web changes, were used to develop a conceptual model of Salish Sea herring, including key ecological connections and influencing factors. A public workshop was held at the Canada House of Western Washington University to review the conceptual model with additional experts from both sides of the border.
At present, I am developing a Qualitative Network Model, based on the conceptual model and the workshop results, which can be used to test the relative support for different hypotheses about key influences on herring abundance and distribution in the Salish Sea.
This work is funded by the SeaDoc Society and WA DFW collaborators are Dayv Lowry, Todd Sandell, and Phil Dionne.
Starting this spring, I will be collaborating with researchers at NOAA’s Northwest Fisheries Science Center to assess the effectiveness of shoreline restoration projects for species and habitat beyond the beach and intertidal zones, including key species such as salmonids and Pacific herring.
The removal of hard armor from Puget Sound shorelines has become a high priority for the Puget Sound restoration program, with expected benefits for beach and intertidal communities, following reconnection of the terrestrial and marine habitats. However, connections between shoreline restoration and habitats and species deeper than intertidal habitats are presently largely ignored in monitoring efforts, even though beach-intertidal-subtidal processes are tightly linked. Restoring shorelines likely has impacts on multiple ecosystem endpoints found in deeper waters, including eelgrass, salmon, and herring.
In 2018 and 2019, we’ll be conducting monthly SCUBA, snorkel (even in March… brrr!), and seine surveys at existing armor removal sites, along with paired reference and armored sites, to monitor the effects of armor removal for subtidal habitats and species. This work is funded by a National Estuary Program-funded grant from the Washington Department of Fish and Wildlife, and conducted with in collaboration with Dr. Jameal Samhouri at NOAA.