Recently the journal Science, the world’s most prestigious scientific publication, published “Global seabird response to forage fish depletion – one-third for the birds.”  In addition to having an unusually catchy title, this paradigm-shifting study serves to underscore the importance of leaving plenty of fish in the sea for our seabirds and other marine wildlife.

Photo of Rhinoceros Auklet with sand lance by Geoff Shester

The researchers used data collected from 14 seabird species including murres, gannets, jaegers, terns, puffins, penguins and a species of gull from seven ecosystems worldwide. They measured the success of these species at producing offspring over long time periods and related this measurement to the abundance of their main fish food in the region around their breeding colonies. On the U.S./Canada west coast, they compared the breeding success of common murre, pigeon guillemot and rhinoceros auklet with the abundance of rockfish, a key seabird prey item, which has been hard hit by fisheries and climate change.

The results are stunning. When the abundance of rockfish fell below about one-third of the highest amount ever observed, the breeding success of these seabirds declined or failed altogether. What’s more, the authors found that very same relationship in 11 other seabirds assessed from other parts of the world, eating other types of prey. In every marine ecosystem, if the fish abundance fell below this one-third threshold then the success at producing chicks declined and in some cases resulted in breeding failure. Conversely, when the amount of fish in the sea was greater than one-third of the maximum ever recorded, the number of chicks produced was generally unaffected by changes in food availability.

These results have radical implications. Ecology is so messy that rarely does the behavior of populations of a single species show consistency, let alone different species with different life histories from different parts of the world. The leader of the team, Dr. Philippe Cury of the French Research Institute for Development, said “We were amazed by the consistency of the relationship around the globe. This suggests that we have found an important benchmark that could be used as a guide to limit the amount of fish taken from the sea in order to maintain seabird populations in the long term.”

In other words, there is now a practical reference point for fisheries managers and policy makers to use when setting harvest quotas for forage fish like sardines and anchovies- or whether to open a fishery at all. Another of the study’s co-authors, Dr. William Sydeman of the Petaluma-based Farallon Institute for Advanced Ecosystem Research, an Audubon California collaborator, said  “To conserve and manage fisheries to the benefit of both humans and wildlife, we need to better understand the needs of ecologically-dependent predators, including birds, mammals, and predatory fish. ‘Set asides’ for forage fish, squid, and zooplankton like krill are one way to ensure that the ecosystem will continue to be healthy enough to support wildlife as well as productive fisheries. This is not really a difficult concept – forage fish are valuable left in the sea to support fish and other wildlife.”

In an interesting twist of timing, this paper comes on the heels of another landmark study that appeared last year in the journal Nature, the other top scientific journal in the world, showing the elevated importance of the west coast to almost two dozen highly mobile marine predators including seabirds, whales, sharks, turtles and tunas tracked with satellite tags. The Pacific’s  mobile predators - such as the sooty shearwaters feeding in the nearshore zone in central California shown below -  will literally travel across the ocean to feed here. The urgency to protect their food base grows with the global demand for forage as we fish “down the food chain” for direct consumption and aquaculture.

Sooty shearwaters off of central California.

Sooty shearwater movement from breeding grounds in New Zealand to the California coast and a handful of other places. Image courtesy Dr. Scott Shaffer, Tagging of Pacific Pelagics.

So how are we doing in California to create forage set-asides, to keep “one-third for the birds” and other top predators? At the moment, not nearly well enough. This is exemplified by the state’s handling of two key forage species – squid and sardine – which have replaced our depleted big predatory fish as the state’s highest value commercial fisheries. Overall, forage species now make up 85% of California’s commercial landings by weight, versus 40% thirty years ago.

At the same time, the state does not recognize key forage species as unique nor call for management of these species differently from other fish. California is responsible for two key forage species for seabirds: market squid and herring. Market squid are foundationally important, the key winter prey item for local breeders such as common murre, and winter visitors like sooty shearwater, and one of the species tracked in the TOPP program featured in the Nature report discussed above. They are also the highest value commercial fishery in California. Through the state’s Market Squid Fishery Management Plan, there are some precautionary regulations in place such as weekend fishery closures and marine protected areas that protect significant spawning grounds. However, catch quotas are set based on the three highest consecutive catch years on record, and there is no biomass estimate. That is, squid are being removed at historic high levels of catch without knowing the population size – hardly precautionary and roundly criticized by an independent review contracted by the state.

Pacific herring are a critically important forage species on the west coast, consumed by marine mammals, seabirds, ducks, salmon, pinnipeds, and dozens of other predators. The fast-declining scoter group (surf, black, and white-winged scoters) are critically dependent on high-energy herring roe during winter migration. Herring used to comprise most of the diet of Chinook salmon in the spring on the west coast. Stocks have declined precipitously in Oregon and Washington. Herring have been commercially fished in California for at least 100 years, and stocks have declined greatly during that time. By 2006 the fishery was restricted to the population center in San Francisco Bay, and in 2007 crashed to a historic low.

While herring may have recovered somewhat from historic biomass lows, the figure below dramatically demonstrates that since the 1970's there has been a steady decrease in the frequency in the population of fish that are six years or older. Last year there were virtually no fish over four years old in the population. Could it be that seabirds, big fish and marine mammals in California were compensating for reduced numbers of anchovy available in the past year? If so, that would be a classic  example of  the strategy known as "prey-switching" and underscores the critical importance of accounting for the needs of predators when managing fisheries.

With our partners Oceana -  - which recently produced an important technical report on forage species in the California Current Ecosystem - we are engaged on a number of fronts to help conserve squid, herring and other forage species in California and beyond. Going forward, we will urge the use of “1/3 for the birds” as a powerful, practical benchmark for how we can share forage fish with our precious marine wildlife.

You can help. Tell the California Fish and Game Commission that it is important to you that we leave plenty of fish in the sea for seabirds, whales, sharks and other marine wildlife. Specifically, the state should adopt a strong policy that recognizes the importance of forage in the marine ecosystem and provides practical guidance for developing precautionary approaches to management. Send your comment to: fgc@fgc.ca.gov