Pacific Herring: Underpinning the coastal foodweb
Program Coordinator and PhD Student: Caroline Fox
University of Victoria Adviser: Dr. T. Reimchen,
Raincoast Adviser: Dr. P. Paquet
A cornerstone in marine ecosystems
Other than salmon, few species in BC hold the ecological, cultural and economic importance of Pacific herring, Clupea pallasi. As one of the most abundant fishes in BC’s coastal waters, Pacific herring are a cornerstone of the marine foodweb and support a diversity of marine predators. In addition to wildlife, they have sustained coastal First Nation communities for many thousands of years and, in more recent decades, have been the foc.s of largest commercial fishery in BC, eclipsing all salmon species combined.
After the collapse of the Pacific sardine (above) commercial fishery in the late 1940s, Pacific herring became the largest fishery off Canada’s Pacific coast. Catches increased to over 200,000 ton/yr in the early 1960s but then dramatically declined over a few short years until the fishery was closed in 1967.
From their beginnings as tiny, translucent eggs scattered along the shore to dense schools consisting of hundreds of tonnes of energy-rich adults, Pacific herring are fed upon by a diversity of marine predators that include marine birds, mammals, fishes and invertebrates. For example, off the coast of Vancouver Island, adult herring comprise major proportions of predator diets (e.g. Chinook Salmon – 62%, Coho Salmon – 58%, Lingcod – 71% and Harbour Seals – 32%, source: DFO).
As one of the great fishes of the North Pacific Ocean, Pacific herring still underpin much of the coastal foodweb. Unfortunately, like many fishes throughout the world’s oceans, Pacific herring have been heavily exploited. BC’s herring populations collapsed in the 1960’s due to overfishing. Following several decades of rebuilding, herring are again in trouble and many areas of the coast remain closed to fishing due low herring biomass.
Our Work: Understanding ecosystem linkages
The miky spawn of Pacific herring can cover kilometers of coastal beaches and kelp beds.
Herring are a cornerstone species in marine ecosystems. These small, silvery fish fuel marine foodwebs and directly support predators such as salmon, pinnipeds, whales and a large diversity of marine birds. They also stage one of the natural world’s most spectacular events with their annual spawn. Each year, tens of thousands of tonnes of herring migrate from offshore waters to more sheltered nearshore bays and estuaries where they spawn en masse. Male herring release milt (containing sperm), which colors nearshore waters a chalky white, sometimes for many kilometers of coastline. In this opaque water, female herring lay eggs upon the intertidal and nearshore vegetation, which often includes eelgrass and kelp. These dense aggregations of spawning herring – and their deposited eggs – often attract tremendous numbers of predators and scavengers. In some areas, several hundred thousand marine birds, hundreds of sea lions, seals and dozens of humpback and grey whales actively forage for several weeks.
As part of our at-sea marine bird surveys, we had the opportunity to witness multiple herring spawn events at locations along the BC coast. The spawns we observed were small in comparison to previous years, yet still attracted Bald Eagles, Black Brant, cormorants, loons, ducks and gulls.
Pacific herring eggs are negatively buoyant. By depositing many layers of eggs on fronds of kelp, the spawn of herring has been known to sink entire kelp forests. Upon hatching and the release of tiny, swimming herring larvae, the forests rise again.
Our observations led to questions regarding the ecological role of herring in marine, intertidal and potentially, terrestrial ecosystems. With more recent herring declines, we are also concerned about the ecological consequences of such reductions.
Already a diminished legacy, we seek to trace the myriad of ecological relationships between Pacific herring and the broader food web. Similar to our research on the ‘salmon forest’, our work will broaden our understanding of herring and the coastal ecosystems they influence. This knowledge will also support conservation measures that better integrate ecosystem values.
