Identifying important foraging sites for highly mobile marine predators has relied mainly on relating their distributions to broadly defined habitat data. However, understanding functional dependencies on foraging sites also requires knowledge of the relative contributions of foods to predator condition. We coupled predator distributions with measures of their diet and condition to assess the importance of Pacific herring Clupea pallasii spawning events to 2 closely related and declining sea duck species. In Puget Sound, Washington, the numerical response of scoters to spawn increased with increasing biomass of spawning herring; this response was 4-fold greater for surf scoters Melanitta perspicillata than for white-winged scoters M. fusca after accounting for local differences in their abundances. In the Strait of Georgia, British Columbia, diets estimated from fatty acids and stable isotopes indicated that both scoter species gained mass by consuming spawn during late March to early April. At a site without spawn during this period, only male white-winged scoters gained mass. In contrast, body mass of male surf scoters declined appreciably before spawn became available in one study year, suggesting greater dependence on spawn for restoring depleted reserves. From winter to spring, surf scoters attained greatest body mass during late April to mid-May while migrating through southeast Alaska; during this period, plasma triglycerides suggested that fattening was not related solely to spawn consumption, yet surf scoters aggregated to consume spawn whenever it was available. Although it is not clear whether herring are essential to their population processes, surf scoters and a range of other predators for which spawning areas are clearly preferred foraging sites would likely benefit from efforts that preserve declining herring stocks.
Many productive ocean ecosystems are also highly variable, resulting in complex trophic interactions. We analyzed interannual patterns in the diet of a seabird, the common murre Uria aalge, in a region of high oceanographic productivity, the northern California Current, to investigate how these top predators adjust their chick provisioning to cope with environmental variability. Murres relied chiefly on Pacific herring Clupea harengus pallasi and surf smelt Hypomesus pretiosus to provision chicks, although they regularly returned 8 other fish taxa. Provisioning success was measured by the energy return rate to chicks, which in turn was disarticulated into energy per meal (quality) and meal delivery rate (quantity). Parents exhibited ‘compensation’ during 2 years in which smaller, low quality prey were returned more quickly than in years with normal (i.e. ‘good’) provisioning. Despite the increased delivery rate, energy return rates were still lower in ‘compensation’ vs. ‘good’ years. The lowest energy return rates occurred in 3 ‘poor’ years, during which ocean productivity was also depressed. Our results suggest that murres in this system have the ability to shift provisioning strategies to deal with some variability in prey resources, but not when limited by exceptionally poor environmental conditions.
Vilchis, L. I. C. K. Johnson, J. R. Evenson, S. F. Pearson, K. L. Barry, P. Davidson, M. G. Raphael, and J. K. Gaydos. 2014. Assessing Ecological Correlates of Marine Bird Declines to Inform Marine Conservation. Conservation Biology. doi: 10.1111/cobi.12378. (Open access publication)
Where have all the birds gone?
The last 30 years have seen precipitous declines in many of the bird species that visit the Salish Sea during the winter.
Using various tools, private money and strategic collaborations, SeaDoc made a substantial investment to understand the problem of declining marine birds. We recently completed research demonstrating that diving birds that eat schooling forage fish are the species most likely to be in decline.
Tackling such a big issue is not easy. Understanding how we worked through this issue gives you a good idea of how SeaDoc can address what might seem to be insurmountable obstacles to healing the Salish Sea. It also shows you how private support makes our work possible.
Step 1: Identify the information gap
In 2005, SeaDoc brought researchers and managers from the US and Canada together to talk about the state of marine bird populations in the Salish Sea. It became clear that we were facing a big problem. Birds were declining in different jurisdictions, but it wasn’t clear how steep the declines were, which species were involved or what factors were behind these declines.
Because no one took a big-picture approach, bird restoration efforts were focused on one species at a time. But was there something going on at the ecosystem level causing multiple species to be declining?
We realized we needed an ecosystem-level look at which species were in decline and why.
Step 2. Get around transboundary roadblocks
Decades worth of data had been collected in Washington and British Columbia by the Washington Department of Fish and Wildlife (WDFW), Audubon, and Bird Studies Canada. But the organizations used different survey techniques and geographic scales so people had not been able to look at the data to get a perspective for the entire ecosystem.
SeaDoc was the ideal group to take on the challenge of merging these differing data sets from two different countries. State, provincial, and federal governments rarely have the time for this kind of effort. Also they have political constraints and pressures that make it hard to see past their borders.
Step 3. Hire a scientist to do the work
Collaborating with multiple groups, merging complex data sets and analyzing decades of data is a full time job for several years. Stephanie Wagner, a woman who loved the Salish Sea and its creatures, made a legacy gift to SeaDoc before she died. This gift provided the funding that allowed us to hire Dr. Nacho Vilchis to lead this important work.
Step 4. Use an epidemiological approach
Dr. Vilchis’ first task was to get the data sets to “talk to each other.” WDFW conducts aerial transects from a plane. Bird Studies Canada and Audubon use point counts. Both are good techniques, but they produce surveys that are difficult to compare.
Nacho, who has a background in the statistical manipulations of large data sets, found a way to combine and use the three surveys in one overall analysis. Then he trimmed the set down to just 39 core species, removing the occasional visitors and the birds for which he didn’t have enough data to draw robust conclusions.
He also used GIS maps of the Salish Sea to connect each data point not only to a geographical area but also to major habitat characteristics, such as water depth.
Drawing heavily on the “Doc” part of SeaDoc, we used an epidemiological approach to find a likely diagnosis. Just as the family doc quizzes you for risk factors for diabetes or heart disease, SeaDoc found that two lifestyle factors among seabirds correlated to a very high risk of population decline.
Step 5. Translate results into recovery
The work, published in the internationally-acclaimed peer-reviewed journal Conservation Biology, showed that birds that dive to find food are much more likely (11 times as likely) to be in decline compared to non-divers.
But it’s worse if you’re a diver on a restricted fish diet. Diving birds that focus their efforts on small schooling fishes called forage fish were 16 times as likely to be in decline. Forage fish are small schooling fish that convert plankton into fat and are eaten by other fish, birds and mammals. These include herring, smelt, anchovies, eulachon, sardines, and sand lance.
But publishing a paper is not the end. It actually is just the beginning. This paper is now being used by scientists, managers and policy makers as evidence for the need to recover marine birds. Recovering forage fish will not just benefit birds, however. Because forage fish turn plankton into fat that’s available for other animals, they are a key part of the ecosystem and their recovery will benefit salmon, lingcod, rockfish, harbor porpoise and many other species within the Salish Sea.
Four key factors made this project successful.
1. Good data
Dr. Vilchis could not have conducted this analysis without scientists and citizens having already spent decades collecting rigorous data. The collection of these data took money, persistence, and forethought.
From the beginning, this project has been a story of collaboration. From the individuals collecting data over two decades to the senior scientists who worked out a way to share their data, it’s taken the work of many people working in different jurisdictions to make this happen. Our collaborators shared three huge datasets collected on two sides of an international border. They only did so because they were confident that SeaDoc would be able to use the data to produce robust scientific results.
3. Working on the level of the ecosystem, not the politics
This was the first study to look at bird declines across the entire Salish Sea marine ecosystem.
Most Canadian or US maps stop at the border, but the Salish Sea does not. Too often, the mandates and responsibilities of the people who work at the various state, provincial, and federal agencies tasked with keeping wildlife populations healthy also stop at the border.
SeaDoc, being privately supported by people like you who understand how important it is to treat the ecosystem as a whole, works across the entire ecosystem.
4. An extraordinary legacy gift
In the end, one person’s financial gift made this project possible.
Without Stephanie Wagner’s legacy gift, this project would have been just a good idea that never got done. Instead, we made it someone’s job to find the truth that was hidden in the data.
Stephanie Wagner’s thoughtful gift enabled us to point clearly to a hidden problem affecting the productivity of the entire Salish Sea ecosystem. With her gift we were able to do good science that will make a difference in how scientists and managers work on healing the Salish Sea.
Put plainly, money can change the world for the better.
Please contact SeaDoc or your financial advisor if you’re interested in including SeaDoc in your will so you can leave a legacy for the health of the Salish Sea.
NOAA recently published the proceedings of the Rockfish Recovery Workshop we helped host in 2011. It’s 124 pages of state of the art science on the status, history and future of rockfish populations, many of which are way down from historic levels and several of which are listed on the Endangered Species List.
Download the PDF here: Rockfish Recovery Workshop Proceedings
Rockfish are pretty amazing. Some live up to 200 years. Others will find their way back to their rock-pile homes if you transport them to another spot miles away.
SeaDoc’s role in sponsoring the workshop is a good example of how we’re able to bring our whole-ecosystem perspective to the table. Obviously rockfish recovery has to take place on both sides of the international border. But things quickly become complicated when you’re talking about scientists traveling over the border to attend a workshop. Canadian scientists couldn’t get travel money from their agencies. NOAA and the Washington Department of Fish & Wildlife, being US government organizations, couldn’t pay for the travel of foreign nationals. But SeaDoc could. Because we’re funded mostly by private donations, we can spend money in ways government organizations can’t. So we sponsored a couple of high-ranking scientists from British Columbia to come down and share their experiences and perspectives.
SeaDoc has done numerous projects on rockfish over the years.
- SeaDoc’s mapping lab partner, Tombolo, led by Gary Green, Ph.D, has been instrumental in mapping rockfish habitat in the Salish Sea over the past decade. You can see rockfish habitat in our recent Maps of the Month in our November 2012 and January 2013 newsletters.
- We’ve sampled harbor seal scat to find out whether they are eating depressed rockfish stocks: http://www.seadocsociety.org/node/377
- Genetic identification of brown rockfish stocks: http://www.seadocsociety.org/node/216
- Analyzed otoliths (ear bones) to understand population structures of quillback rockfish: http://www.seadocsociety.org/node/498
- Studied whether river otter predation is affecting rockfish: http://www.seadocsociety.org/river-otter-diet-project
- Investigated whether Marine Protected Areas are effective for rockfish recovery: http://www.seadocsociety.org/rockfish-mpa-research
- Trained recreational divers to collect data on fish populations: http://www.seadocsociety.org/node/84
Watch our 2011 marine science lecture on rockfish here: http://www.seadocsociety.org/node/653