Pacific herring spawn events influence nearshore subtidal and intertidal species

Athough we know that herring play a pivotal ecological role in nearshore ecosystems, from a scientific perspective little is known about the amount of energy and nutrients (spatial subsidies) they transfer from the ocean to the land.

A Pacific herring stops moving for a moment; figures from the research about herring are on the right hand side.

Photo by Daiju Azuma.

Although we know that herring play a pivotal ecological role in nearshore ecosystems, from a scientific perspective little is known about the amount of energy and nutrients they transfer from the ocean to the land. Therefore, researchers at Raincoast Conservation Foundation, University of Victoria, and Dalhousie University, aimed to determine if the nutrients that herring contribute to intertidal and subtidal ecosystems during spawning events are cycling through coastal food webs.

The resulting research paper by Caroline Fox, Paul Paquet and T.E. Reimchen has been published in the Marine Ecology Progress Series by Inter-Research Science Center.

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“Waves of spawning activity still occur, at least in some locations (e.g. eastern Vancouver Island; C.H. Fox pers. obs.). Although some populations in BC are considered relatively healthy in terms of benchmarks set during the mid-20th century (e.g. ‘aggregate Strait of Georgia stock’), longstanding low biomass and closed commercial fisheries characterize large regions of BC (Fisheries and Oceans Canada 2016). Unfortunately, these population declines and recovery failures are not limited to BC (e.g. Hay et al. 2001, Landis et al. 2004). Further, just as the reasons for these declines and recovery failures remain very poorly understood from scientific perspectives (e.g. Schweigert et al. 2010), the ecological consequences of reduced herring abundances, and in turn, the diminished delivery of spawning resources to coastal ecosystems, are poorly known.”

Fox CH, Paquet PC, Reimchen TE (2018) Pacific herring spawn events influence nearshore subtidal and intertidal species. Mar Ecol Prog Ser 595:157-169. https://doi.org/10.3354/meps12539

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Supplementary material (PDF)

Abstract

ABSTRACT: As intermediaries between the bottom and top of food webs, forage fish fuel a diversity of coastal consumers and are of socioecological importance throughout the world’s oceans. Many forage fish are migratory, but despite their recognized importance, relatively little is known about their role in providing spatial subsidies, which are the movements of energy, material, and organisms across ecosystems. Until recently, spatial subsidies associated with Pacific herring Clupea pallasii, a dominant migratory forage fish that spawns in subtidal and intertidal zones, received little scrutiny. Building on research that traced links between herring spawns and coastal ecosystems, we used stable isotopes of carbon (δ13C) and nitrogen (δ15N) to assess whether herring spawning events influenced isotopic signatures of 10 macrophyte and invertebrate species across beaches where spawning did or did not occur. Overall, species collected from spawning beaches had significantly greater δ15N levels (general linear mixed model parameter estimate = 1.58 ± 0.17 SE, F1,370 = 83.77, p < 0.001); no significant effects were detected for δ13C (parameter estimate = 0.03 ± 0.23 SE, F1,343 = 0.01, p = 0.914). In terms of total nitrogen, macrophytes from spawning beaches had significantly elevated concentrations (parameter estimate = 5.03 ± 0.94 SE, F1,180 = 28.71, p < 0.001). Using directional statistics, mean angles of isotopic change differed significantly between species collected from spawning and non-spawning beaches (Watson-Williams F-test; F1,48 = 10.44, p = 0.002). Our study identifies multiple species as recipients of herring-derived nutrients at spawning events, providing additional evidence of the broad ecological influence of Pacific herring.

Select figures

Fig. 1. Locations of beaches on which Pacific herring
Fig. 1. Locations of beaches on which Pacific herring Clupea pallasii spawn, and spawn-free control beaches in Quatsino Sound, British Columbia, Canada, that were used in this study in 2011 and 2012
Four small diagrams showing the mean directional isotopic change (length and angle) of macrophytes at (A) control and (B) spawning sites, and invertebrates at (C) control and (D) spawning sites relative to mean pre-spawn isotopic values
Fig. 4. Mean directional isotopic change (length and angle) of macrophytes at (A) control and (B) spawning sites, and invertebrates at (C) control and (D) spawning sites relative to mean pre-spawn isotopic values using δ13C (‰) and δ15N (‰). Arrows represent individual species or genera, averaged across multiple sites. Arrow length represents the magnitude of isotopic change (‰). The grey line represents the mean vector of change (μ), indicating the mean angle of the data displayed in individual plots

Authors & affiliations

C. H. Fox1,2,4,*
P. C. Paquet2,3
T. E. Reimchen1

1. Department of Biology, University of Victoria, Victoria
2. Raincoast Conservation Foundation
3. Department of Geography, University of Victoria, Victoria, BC V8W 2Y2, Canada
* Department of Oceanography, Dalhousie University, Halifax, NS B3H 4R2, Canada

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