Surf Scoters are known for eating a lot of mussels, but a recently published SeaDoc-supported paper by Eric Anderson and James Lovvorn shows that scoters also depend heavily on eelgrass habitats.
Thousands of Scoters can be found eating mussels in Penn Cove, Washington during the fall and early winter. But then they leave. Why?
Well, as it turns out, they prefer to eat small mussels (2-30mm) and once those are gone, the larger mussels and worms left are not as as appealing. It's more productive for them to move to eelgrass habitats where they can feed on creatures like small crabs and shrimp that live on the eelgrass.
The authors even hypothesize that declines in eelgrass beds may be part of the reason that scoter populations have declined so significantly.
This study is another reminder that food webs are complex (something we've been saying for years) and that the ecosystem and its varied habitats are highly interconnected. Science helps us understand these relationships and helps us identify and protect important habitats and species. To read the abstract, visit http://www.seadocsociety.org/node/726 or email us for a copy of the full paper.
ABSTRACT: Foraging profitability can be strongly affected by the size structure of different prey, so that predator distributions are not a simple function of total prey biomass. For a bottom-feeding avian predator, the surf scoter Melanitta perspicillata, we assessed effects of prey size and other prey attributes on seasonal shifts in scoter use of 2 major foraging habitats in Puget Sound, Wash- ington, USA. During early winter, many thousands of scoters fed at an unvegetated site where profitable prey appeared limited to mussels Mytilus trossulus of smaller sizes (2 to 30 mm) despite their much lower biomass relative to larger mussels and several other prey types. Accordingly, scoter numbers decreased at that site as small mussels declined over winter. During pre-migratory fattening in spring and feather molt in summer, >8000 surf scoters aggregated at a seagrass site where they fed mainly on epifaunal crustaceans (50 to 73%) and gastropods (12 to 27%). Body sizes of most crustacean prey had increased substantially since winter. Thus, prey size had oppo- site effects on the profitability of unvegetated habitats that provide mainly mussels (smaller items likely reduce shell processing costs) versus seagrass crustaceans (larger items are likely more vis- ible and yield greater energy per prey item, although relative mobility of prey can alter their value). Total prey biomass, and prey distributions relative to water and sediment depths, appeared less important than prey size to shifts in scoter diets and numbers. Our synthesis of past studies indicates that biomass and production of mussel beds are typically an order of magnitude greater than for entire assemblages of seagrass macroinvertebrates. However, because of sea- sonal shifts in prey size structure, seagrass sites can be an important complement to mussel beds when the narrow size fraction of mussels that are profitable to scoters declines.
Scoter photo by Blind Grasshopper via Flickr Creative Commons
Seasonal dynamics of prey size mediate complementary functions of mussel beds and seagrass habitats for an avian predator
Ecological implications of invasive tunicates associated with artificial structures in Puget Sound, Washington, USA
We recently learned of the Invertebrates of the Salish Sea website put together by Dr. David Cowles of the biology department at Walla Walla University.
The site has information about many different invertebrates as well as an identification key that will help you identify pretty much any invertebrate you might happen across.
What can you learn from digging into someone’s 1,000-year-old lunchbox?
By examining mussel shells from ancient middens of the Makah Nation, and then comparing them to shell samples taken in the 1970s and the 2000s, SeaDoc funded scientist Dr. Cathy Pfister and her colleagues found that there’s been an unprecedented change in the chemistry of shells from our local marine waters.
With ocean acidification a major concern, and our Northwest coast and Salish Sea among the most rapidly acidifying areas in the world, researchers have been closely monitoring the water’s pH.
What Dr. Pfister and colleagues determined by looking at isotope ratios in mussel shells is that the changes occurring are even greater than can be explained simply by the ocean’s absorption of increased atmospheric CO2, or by local upwelling, or by changes in nitrate and phosphate.
Everything from the oysters we eat to the plankton that feed the juvenile salmon that in turn feed orcas and us depend on surviving a changing ocean. So it’s critical we figure out precisely what’s going on. That’s why SeaDoc continues to fund important foundational work like this.
Download a copy of the manuscript, recently published in the acclaimed journal PLoS ONE, here.
To do this important work, Dr. Pfister and her team sectioned mussels, shown above, which enabled them to analyze differences in mussel growth and chemistry by year. This enabled them to evaluate changes over a decade looking at the sections of a ten year old mussel. Pretty cool. Check out the annular rings on the mussel photo above.
Pfister works closely with the Makah Nation, and her research was carried out with their permission and assistance.
Cathy Pfister is an associate professor in the department of Ecology and Evolution at the University of Chicago. Her work concentrates on rocky intertidal areas of Washington State. Her homepage has information on her research, and you can watch a short video featuring Cathy Pfister discussing her research interests (it's on the SeaDoc website, but the page may take a while to load if you're on a slow connection).
Shellfish harvesting has been closed in numerous Washington counties due to the presence of the marine biotoxin Alexandrium, which causes Paralytic Shellfish Poisoning (PSP). Harvesting is closed whenever naturally occurring harmful biotoxins are detected. Once called "red tides," blooms of naturally occurring biotoxins are now more commonly referred to as Harmful Algal Blooms as there are some red algal blooms that are not harmful. Naturally occurring biotoxins like PSP are not destroyed by cooking or freezing. Please check the Washington State Department of Health for more information and each time before you harvest shellfish: http://ww4.doh.wa.gov/gis/mogifs/biotoxin.htm
Courtesy of SeaDoc intern Sara Heidelberger.
Restoring a vast, complex ecosystem like the Salish Sea costs money — that long green stuff with the short future. With politicians and public opinion involved, tough fights often break out over spending on improvements that, to some, appear subjective: Is it worth $100,000 to remove a certain bulkhead or replant a certain eel grass bed? Maybe… And that’s where good science can inform great policy.
One of the best examples of science coming to the rescue of a dollar-and-cents conservation issue occurred when the SeaDoc Society recently got caught up in the question of abandoned fishing nets. In partnership with the Northwest Straits Initiative, SeaDoc developed a predictive model that clearly shows the cost of these ghost nets that continue to trap and kill marine life for decades.
Northwest Straits Initiative-funded researchers made multiple dives on derelict nets, counting trapped critters, studying decomposition rates, and determining how much of the dead marine life fell out of the nets as they were recovered (Over 17% of the catch never made it to the surface, showing how critical it is to have underwater scientists on the job). SeaDoc then dove into the data, actually inventing a statistical model to predict each cast-off net’s killing capacity.
The results? Abandoned nets catch and kill more than 1,000 invertebrates (mainly crabs), 150 fish, and nearly 80 birds every year, year after year after year – and most of these silent killers have been doing their dirty work since the 1970s. Run that data through the seafood value calculator and it quickly adds up, with each net wasting $19,656 in Dungeness crab alone, every 10 years. The one-time cost to retrieve a derelict net? $1,358. It doesn’t take an accountant to do that cost-benefit analysis.
Only through funding from private donors like you was SeaDoc able to do this ground-breaking (and net-cutting) science, which has led to clear policy and, more importantly, vital and measurable improvement in the Salish Sea ecosystem. Thank you.
To view the manuscript just published in Marine Pollution Bulletin, click here (pdf).
For more about SeaDoc's derelict fishing gear project, see our lost fishing gear page.
How to report derelict fishing gear.
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Marine species mortality in derelict fishing nets in Puget Sound, WA and the cost/benefits of derelict net removal
Tim Carpenter's talk on octopuses and cephalopods was the final Marine Science Lecture for the 2009/2010 year. This year also marks the seventh year of the lecture series.
Tim shared several videos featuring the interesting adaptive behaviors of octopuses.
Here are a few videos that may or may not be the exact same ones he showed:
An octopus using a coconut shell to hide in:
Shark vs Octopus (this video is a little hyped: Tim shared the real story behind the film)
Octopus "walking" on two arms