To gear up for Discover Science Weekend, November 11–13, we’ve put together a guest blog series featuring some of the researchers who will be joining us for the event. Our second post comes to us from Trevor A. Branch, associate professor at the School of Aquatic and Fishery Sciences at the University of Washington, writing on the topic of “Antarctic blue whales: nearly whaled to extinction, now there is some hope.”
Antarctic blue whale. Photo via Isabel Beasley.
Blue whales are the largest animals ever to have lived on the Earth—larger than any dinosaur—and no blue whales are as big or used to be as numerous as those that feed in the krill-rich waters of the Antarctic. Some may have exceeded 100 feet (30.t m) in length, with the tongue alone weighing more than an adult elephant. Initially, Antarctic blue whales escaped the whaling plunder of the Yankee whalers’ Moby Dick era because they were too fast to catch, and sank upon death, but the industrial whaling era came upon them with a vengeance starting in 1904. These developments included fast boats, explosive-tipped harpoons, stern slipways that allowed on-board processing, air pumps to keep them afloat, and eventually floating fleets of catcher vessels, supply vessels and processing motherships that left no refuge for blue whales anywhere in the world.
In one year, these massive southern ocean whaling fleets caught more than 31,000 blue whales—twice today’s global population of blue whales. By the 1960s Antarctic blue whales had been reduced to less than a half percent of their original population size of 239,000. Worse was to come: despite a global ban on blue whales, Soviet whalers continued hunting them—illegally—using the biggest whaling fleets yet assembled, and the population collapsed further to just 360 individuals, a mere 0.15 percent of their pre-whaling levels.
Antarctic blue whale. Photo via Isabel Beasley.
Since 1973 though, whaling has ended, and the population has grown over time, reaching 2,280 in 1998, and likely increasing at seven percent per year since then. How do we know their trends in numbers over time? I used mathematics and computer models and applied these to data from expensive ship-based sighting surveys around the Antarctic. It’s surprisingly difficult and expensive to count blue whales since the ocean is vast and it’s hard to find a small number of gigantic yet elusive whales. Newer methods rely on taking photos of individuals and seeing how often you identify the same whales again from their splotch patterns. Such mark-recapture methods have suggested Antarctic blue whale numbers may have increased to 3,000–4,000: a remarkable tenfold increase from their lowest point.
The main threats to blue whales worldwide are deaths from being hit by ships and entanglement in fishing gear, with other concerns including loud noise from navy sonar and oil and gas exploration, pollution, and the harder-to-pin-down, long-term effects of global warming and ocean acidification on their main prey. All of these factors are minor, though, compared to the enormous toll that whaling took on blue whales during the 20th century.
Branch TA, Matsuoka K, Miyashita T (2004) Evidence for increases in Antarctic blue whales based on Bayesian modelling. Marine Mammal Science 20:726-754
Branch TA et al. (2007) Past and present distribution, densities and movements of blue whales Balaenoptera musculus in the Southern Hemisphere and northern Indian Ocean. Mammal Review 37:116-175
Trevor Branch is an associate professor in the School of Aquatic and Fishery Sciences at the University of Washington. He uses mathematical models and synthesis of available data to help conserve and manage large whale populations and fisheries. Among his scientific papers are 14 on blue whales including their status, distribution, subspecies separation, catches and trends over time.
Going to work can be such a drag, right? You get up early and choose an outfit for the day…then there’s the commute…and when you finally arrive, it feels like you’re surrounded by a bunch of wild animals!
Seattle Aquarium visitor engagement staff members Cari and Katie know just how that feels: they recently went out on the Aquarium boat with several Aquarium life sciences staff members to participate in our annual octopus census. On October 11, Katie went out with Chris, Rob and Jeff to dive sites at Day Island and Titlow Beach; while on October 12, Cari joined Andy, Joel and Kaela to check out Blake Island and Blakely Rock.
Both said it was a really fun experience to practice working on the boat and participating in Aquarium dive ops—as Kaela said of the Blake Island dive, “It’s like we’re diving with every animal in the whole Aquarium all at one time!”
The number and diversity of animals and habitats they saw on their dives was a fantastic reminder of how lucky we are to live near, and dive in, Puget Sound. Everyone had a great time, and got to do some important work collecting data for the octopus census at the same time.
Held each year, the Aquarium’s octopus census asks divers in the Puget Sound area to report sightings of giant Pacific octopuses to help us monitor our local octopus populations. This year’s census took place October 8–16. And how many octopuses were spotted by the Aquarium teams? Around 30—but that number is sure to increase as reports from other divers are compiled. We’ll share results when all report as tallied.
Not a bad day at work, all in all! Interested in learning more about our octopus census? Visit our website or read this blog post.
Even though this year’s Cedar River Salmon Journey is drawing to a close, the Seattle Aquarium is a great place to see and learn about salmon—no matter the season! Take a look at the chinook salmon eggs shown below; they were just added to our salmon hatchery trough. Their developing eyes tell us that they’re about a month old.
Think that looks like a lot of eggs? For chinook, it’s a drop in the bucket. Chinook, or king, salmon lay more eggs and bigger eggs than other Pacific salmon. Thomas Quinn reports in his book The Behavior and Ecology of Pacific Salmon & Trout that chinook lay an average of 5,400 eggs. Coming in a close second are steelhead with 4,900 eggs, and the other species ranging from 1,000+ to 3,000+ eggs.
In terms of size, chinook eggs weigh almost nothing: about .00066 of a pound! But they’re the heavyweights of Pacific salmon. Chum come in second at about .00063 of a pound—and other species’ eggs are significantly smaller than that.
As a general fish principle, we know that bigger females tend to lay more and bigger eggs, so it’s not a surprise that chinook salmon do both. However, why do steelhead (which are almost as large as a chinook) lay lots of smaller eggs, while chum (which are smaller than both steelhead and chinook) lay fewer, but bigger eggs? An interesting question that we can’t answer!
Want to learn more about salmon migration and salmon in general? Join us for the final weekend of the Cedar River Salmon Journey to talk to trained naturalists while watching salmon spawn! Click here for details.
To gear up for Discover Science Weekend, November 11–13, we’re putting together a guest blog series featuring some of the researchers who will be joining us for the event. Our first post comes to us from Amanda Phillips of The Puget Sound Marine Fish Science Unit at the Washington Department of Fish and Wildlife (WDFW).
Starry flounder caught by beach seine with Puget Sound Marine Fish Science Unit members Phil Campbell, Will Dezan, Amanda Phillips and Lisa Hilliard.
The Puget Sound Marine Fish Science Unit at the WDFW employs various techniques to preserve and protect our marine ecosystem. Conducting research on the 258 fish species in Puget Sound is complex and challenging; in a given month, the 16 members of the unit may have a dozen research projects in progress to address various management needs! Fish that inhabit Puget Sound are diverse in both habitat and ecosystem requirements, necessitating a range of methods to adequately study.
Remotely operated vehicle for exploring underwater habitat and fish species in Puget Sound.
This fall, members of the unit will engage in activities ranging from using a remotely operated vehicle (ROV ) to examine deep-water habitat used by rockfishes and lingcod; to assessing mid-water species like forage fish and jellyfish using trawling and hydroacoustics; to conducting scuba surveys in search of juvenile fish settling in nearshore habitats.
Yellow eye rockfish.
We begin surveys by determining the best method given the particular species, and questions, at hand. For example, our ROV can survey complex habitat that could easily snag a net while ensuring species found in rocky habitats are minimally impacted, making it ideal for studying endangered rockfishes. Conversely, our annual trawl survey is well-suited to enumerating flatfish—found on flat, muddy substrate throughout Puget Sound—that are difficult to identify with submarine cameras because they are very good at camouflage.
Puget Sound Marine Fish Science Unit members Erin Wright, Dayv Lowry, Courtney Adkins, Jen Blaine, Andrea Hennings, Pete Sergeeff and Bob Pacunski completing the bottom-trawl survey.
Once a survey method is selected, a field crew is gathered, boats are staged, and gear is loaded onto one of our vessels. On some surveys, scientists spend a week sleeping in bunks aboard ship, while other surveys involve spending the morning exploring sunken ships occupied by giant Pacific octopuses, massive lingcod and hundreds of black rockfish—and still getting home in time for dinner.
Giant Pacific octopus seen on scientific dive surveys.
The unit collects a treasure trove of data throughout the year, and after field operations are complete these data must be compiled and analyzed. This season, we are analyzing 15 years of scuba and trawl survey data to publish several reports, defining population structure and abundance using genetic analyses, and engaging heavily in permit writing to ensure research continues into the foreseeable future. And that is all before Halloween!
Contributing to research used for conservation of Puget Sound resources is richly rewarding and the Puget Sound Marine Fish Science Unit at WDFW is excited to share more about what we do during Discover Science Weekend at the Seattle Aquarium. Come by and see us!
Amanda has worked as a scientific technician with the Puget Sound Marine Fish Science Unit at the Washington Department of Fish and Wildlife (WDFW) for the past three years. She is currently focused on piloting and reviewing videos collected by WDFW’s remotely operated vehicle and examining the spatial and temporal distribution of plankton in Puget Sound. Prior to WDFW, she worked with the Center for Conservation Biology at the University of Washington, utilizing scat-detection canines to collect and analyze southern resident killer whale scat; she also spent a year at sea as an on-board fisheries observer for the West Coast Groundfish Bottom Trawl Fishery.
Off the water, she can be found outdoors, backpacking, rock climbing or snowshoeing in Washington’s wilderness areas.
This is the season we celebrate salmon returning to their natal streams and rivers right here in Seattle, but how do salmon find their way home? Before we tackle that, though, a larger question: why do they do it?
The ultimate purpose for salmon to return to their home streams and rivers is to reproduce and ensure the survival of their offspring. Simple enough. But why is returning to the natal site part of the process? Consider the alternative: swimming upstream to just any old river could have some pitfalls. A random river might not have suitable sites for spawning, but a salmon’s birthplace is already a proven success for spawning. It may not have mates of the same species. Or conditions might not favor that type of salmon. For all these reasons, we can see why salmon navigate their way home.
In recent years, studies have shown that in the open ocean environment, salmon use the magnetic field of the Earth to guide their migration. This helps them move from the coastal areas near their spawning grounds to rich feeding areas, and then back again toward the end of their lives. For example, most of the salmon returning to Seattle-area rivers right now are coming from feeding grounds in Alaska, but some may be traveling from as far as Japan.
Salmon use both the intensity and the inclination of Earth’s magnetic field to orient themselves. Unlike their navigation by sense of smell (discussed below), this ability appears to be genetically inherited by a salmon, not learned along its migration.
Young salmon learn the smell of their home stream, possibly even memorizing it at various points along the way, as they migrate toward the ocean. As adults returning to freshwater, when they encounter that familiar smell, it stimulates them to swim upstream. So there may be some “testing of the waters” as salmon migrate home. If they swim up the wrong river, that memorized scent of their birth stream will fade, decreasing their drive to swim upstream. Then they may travel downstream for a bit, until they encounter that home stream smell again. The more they sense the smell of their birthplace, the more they swim upstream. It’s a bit like playing that child’s game of “hot and cold.”
There are still many unknowns in the famous story of the salmon swimming upstream. Evidence exists that salmon from different reaches of the same river will tend to migrate to the same stretch where they originated. But do they return to the very same nest site where they were hatched? How close do they get? At some point, that urge to return home will be up against other factors: selecting a nest site, selecting a mate, using remaining energy stores.
Interested in learning more about salmon migration and salmon in general? Join us for the Cedar River Salmon Journey to talk to trained naturalists while watching salmon spawn! Click here for remaining dates, times, locations and directions.