Conservation & Science

Voyage to the White Shark Café

For nearly 20 years, researchers from Monterey Bay Aquarium and Stanford University have fitted electronic tracking tags on adult white sharks each fall and winter along the California coast around San Francisco Bay. Each year, the tags documented a consistent migration by the sharks to a region more than 1,200 miles offshore—halfway to Hawaii—that’s been considered an oceanic desert. They dubbed it the White Shark Café, guessing that opportunities to feed and to mate might be the draw.

Now a team of scientists will spend a month at the Café in a month-long expedition to learn why the sharks make an epic annual migration to such a distant and seemingly uninviting location. The multi-disciplinary team is bringing an impressive complement of sophisticated oceanographic equipment, from undersea robots and submersibles to windsurfing drones that will search signs of sharks and their possible prey.

Funded by the Schmidt Ocean institute (SOI), the team is led by Stanford University Professor Barbara Block and includes marine biologists and oceanographers from Stanford University, Monterey Bay Aquarium, Monterey Bay Aquarium Research Institute (MBARI), the University of Delaware, and NOAA’s Office of Ocean Exploration and Research.  They are traveling aboard the SOI research vessel Falkor and set sail from Honolulu on April 20. They will return to port in San Diego on May 19.

Unraveling a mystery

We’ve studied these sharks for nearly 20 years, and they’ve told us consistently that the White Shark Café is a really important place in the ocean—but we’ve never known why,” said Dr. Salvador Jorgensen, a senior research scientist and shark research lead at Monterey Bay Aquarium.

Sophisticated oceanographic monitoring tools like these Saildrones will collect data to document the presence of white sharks and their prey species in the cafe. Photo courtesy Schmidt Ocean Institute.

By documenting the biology, chemistry and physical conditions in the region—a swath of the Pacific Ocean the size of Colorado—the researchers hope to understand what makes the Café an annual offshore hot spot for one of the ocean’s most charismatic predators. Read more…

Taking a stand against shady seafood

The holidays came early for seafood lovers. Thanks to a new federal initiative, Americans will soon know more about where our imported seafood comes from.

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Customers use the Monterey Bay Aquarium Seafood Watch guide at a California fish market.

On Dec. 8, the National Oceanic and Atmospheric Administration (NOAA) announced a “traceability” program that will track certain seafood imports at risk of illegal, unreported and unregulated (IUU) fishing. More than 90 percent of the seafood available to consumers in the United States is imported.

Traceability allows regulators to electronically track seafood through the supply chain—from the moment it’s wild-caught or farm-harvested, to the U.S.border. This new information will help authorities keep illegal seafood products out of the U.S., and level the playing field for American fishermen who follow the rules. And, it also makes it easier for businesses and consumers to support seafood that was produced sustainably.

As we reported last February, traceability can also cut down on seafood fraud, which happens when seafood labels mislead consumers about the identity or source of their seafood.

Monterey Bay Aquarium works globally, through industry-led coalitions and other partnerships, to improve traceability in Southeast Asia, where much of the world’s seafood is produced.     Read more…

Honoring Congressman Sam Farr’s ocean legacy

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A surfbird hunts for prey in a Monterey Bay tide pool.

As a kid in the 1940s, Sam Farr used to frequent the tide pools on Carmel Beach, exploring and playing with the multitude of colorful creatures that lived there. But when he returned as an adult with his young daughter in tow, the tide pools weren’t quite how he remembered them.

“Not a single animal was there,” he recalls. “Not a sea urchin, not a sea anemone, not a hermit crab.”

The experience added to Farr’s already deep-seated belief that ocean health is crucial to the well-being of our planet and ourselves. First as a California State Assemblyman from 1980-1993, and then as a U.S. Congressman from 1993 to the present, he acted on that belief by creating state and federal legislation to protect our ocean and coast, and to support ocean research along Monterey Bay.

Now, after more than 40 years of public service, Farr is returning from Washington, D.C. to his home in Carmel, California to, in his words, “become a full-time grandfather” to his daughter Jessica’s children, Ella and Zachary.

On Dec. 1, 2016, Monterey Bay Aquarium honored Sam Farr’s lifelong contributions to ocean conservation at a reception for community leaders and philanthropists.

Read more…

Fragile butterflies of the sea

From Nov. 30-Dec. 11, leaders from more than 190 nations will gather in Paris for the 2015 United Nations Conference on Climate Change, or COP21. The conference aims to achieve a binding international agreement to slow the pace of climate change. If we as a global community take bold and meaningful action in Paris, we can change course and leave our heirs a better world. In advance of COP21, Monterey Bay Aquarium is working to raise public awareness about the serious ways our carbon emissions affect ocean health, including ocean acidification, warming sea waters and other impacts on marine life. Today’s post focuses, in words and video, on the impact ocean acidification is having on some small but significant ocean animals.


 

Acidification illustrationOur colleagues at the independent Monterey Bay Aquarium Research Institute (MBARI) have been studying and documenting the lives of pteropods, swimming snails of the sea that play a critical role in ocean food webs. They’re delicate and beautiful animals, sometimes called “sea butterflies”, with interesting ways of finding food in the deep ocean. They’re also particularly vulnerable to ocean acidification, the change in chemistry that occurs as the ocean absorbs more of the rampant carbon dioxide produced when we burn fossil fuels.

Read more…

Feeding hotspots for Pacific bluefin tuna – discovered

After chowing down a big meal, you might feel your belly warm as your stomach muscles and digestive organs set to work breaking your food into smaller and smaller pieces rich in nutrients. A bluefin tuna’s stomach experiences a similar spike in temperature when it gulps down a mouthful of juicy sardines.

Chuck Farwell of the Monterey Bay Aquarium and Barbara Block of Stanford University tag a Pacific bluefin tuna for the study. Photo courtesy Tuna Research and Conservation Center
Chuck Farwell of the Monterey Bay Aquarium and Barbara Block of Stanford University tag a Pacific bluefin tuna for the study. Photo courtesy Tuna Research and Conservation Center

Now, scientists at Stanford University, Monterey Bay Aquarium and the National Oceanic and Atmospheric Administration (NOAA) have devised a way to measure that internal temperature increase in the fish – and connect it to how much the tuna ate and where it consumed its meal.

This is the first work to measure how much energy aquatic animals consume in the wild, and has allowed researchers to identify favorite dining spots for Pacific bluefin tuna along the North American coastline. The findings are published online in Science Advances, and could help develop conservation policies to protect a species that’s in steep decline.

Pacific bluefin tuna are superbly streamlined, bullet-shaped fish, with powerful swimming muscles capable of powering transoceanic travels. Unlike most other bony fishes, they are warm bodied, able to elevate their internal tissue temperatures above that of the surrounding water.

“Bluefin tuna are the pinnacle of bony fish evolution, endothermic or warm-bodied in a manner that rivals the metabolic performances of birds and mammals,” said senior author Barbara Block, a professor of marine sciences at Stanford’s Hopkins Marine Station and a senior fellow at the Stanford Woods Institute for the Environment.

Following the fish

Bluefin tuna remain warm by capturing the metabolic heat produced as their swimming muscles contract with every tailbeat. This happens via specialized net-like blood vessels, called counter-current heat exchangers, in their muscles and digestive organs that prevent heat loss through the gills. Maintaining warmer-than-water body temperatures allows the fish to swim more efficiently and spend less energy digesting food, and enables them to thrive in a wide range of ecological niches.

At the Tuna Research and Conservation Center, scientists learned to correlate digestion of precise quantities of food with changes in tunas' internal temperatures. Photo Monterey Bay Aquarium/Tyson Rininger
At the Tuna Research and Conservation Center, scientists learned to correlate digestion of precise quantities of food with changes in tunas’ internal temperatures. Photo Monterey Bay Aquarium/Tyson Rininger

The researchers focused on this thermal characteristic to measure energy intake, and from that to surmise the animals’ daily foraging habits. Researchers implanted small data-logging tags in more than 500 tunas off the coast of southern California and Mexico, and recorded the fishes’ body temperature, ambient water temperature, and their locations and diving patterns as they searched for prey. With the help of fishers, the researchers recovered more than one-third of the tags, containing data records as long as three years as the fish made seasonal migrations from the waters off Mexico to Oregon.

Previously, observation work led by Rebecca Whitlock, a postdoctoral scholar at Stanford, made with fish held at the Tuna Research and Conservation Center, had created a model to translate changes in tuna heat signatures into caloric intake. At the center – a partnership between Stanford and the Monterey Bay Aquarium – researchers could count single sardines or squid consumed by individual tunas and match the warming signal in the stomach to the energy value of the prey item digested.

Documenting their dining

The thermal data showed exactly when the tunas ate a meal, and the researchers estimated how much energy a free-swimming bluefin receives per unit of time, as well as how temperature changes impact that energy intake.

Researchers fit a data tag in a Pacific bluefin tuna, one of 500 implanted as part of the study. Photo Monterey Bay Aquarium/Andre Boustany

“We’ve been able to follow what Pacific bluefin tuna do in the open sea and record their feeding and meal size, every day for up to three years,” said Whitlock, the lead author of the new paper. “Combining laboratory observations with electronic tagging can provide amazingly rich data and insights into the life of a wild marine predator.”

Tag data showed that wild tunas consumed prey on 90 percent of the days observed during the study. The empirical data analyses and energetic model output allowed scientists to chart precisely how much the fish ate – typically sardines and squid – and the total energy they consumed as they journeyed through the ocean.

A roadmap in the ocean

From this, the scientists mapped the position data from the tags to satellite observations of sea temperature, chlorophyll levels and ocean currents – all factors that can combine to create nutrient-rich feeding grounds. The location of these feeding grounds coincided well with successful tuna feedings, though interestingly the fish didn’t always camp out at places with the best conditions to take advantage of the buffet.

“Foraging success was correlated to environmental features,” said co-author Elliott Hazen, a research ecologist with NOAA’s Southwest Fisheries Science Center. “Tuna may use the oceanography as a roadmap to move from hotspot to hotspot, and temperature appears to be the most important environmental cue.”

Interestingly, the study demonstrated a potential tradeoff between feeding in the richest areas and avoiding the physiological constraints associated with feeding in waters that are either very cold (which slows the heart) or very warm (which are energetically taxing). This answered a long-standing question about the species’ traditional range limits, from north of Oregon to south of the Baja Peninsula, despite the fact that close relatives of bluefin (yellowfin and albacore tuna) thrive outside of those latitudes.

Good places to digest

Tag data showed that tuna tend to stay in waters where they can remain at an optimum temperature to promote rapid digestion. Too high or too low an ocean temperature, and the increased demands of digestion can strain the cardiovascular system.

Preferred feeding habitats varied by season and by size of the fish.
Preferred feeding habitats varied by season and by size of the fish.

“Digestion is metabolically costly, and the bluefin are doing it most efficiently,” Block said. “Our results suggest that physiological constraints on the tunas’ whole organismal performance constrain their thermal distribution, and thus the latitudinal distribution of the fish.”

Block calls this portion of the Pacific Ocean the “Blue Serengeti,” an open ocean ecospace where currents concentrate nutrients and plankton, attracting forage fish such as sardines or anchovies, which in turn lure larger predatory fish such as bluefin tuna.

Understanding the locations of Blue Serengeti “watering holes” for these large migratory fish remains a mystery, but is a key part in planning better conservation efforts that protect essential habitat. Linking the regions both physiologically and to environmental correlates has been an objective of the research team.

The new work helps close that gap by identifying feeding hotspots (areas of highly successful feeding) for Pacific bluefin tuna: along the Baja Peninsula in June and July, off Northern California from October to November, and near Central California in January and February.

“Our results add to our understanding of predator-prey dynamics in the California Current,” Block said. “By understanding where bluefin forage most, we can help protect these places and improve efforts to rebuild Pacific bluefin tuna stocks.”

– Bjorn Carey is a life sciences public information officer for Stanford News Service

Learn more about the aquarium’s efforts to recover Pacific bluefin tuna.

Reference: Rebecca E. Whitlock, Elliott L. HazenAndreas WalliCharles FarwellSteven J. BogradDavid G. FoleyMichael Castleton and Barbara A. Block. “Direct quantification of energy intake in an apex marine predator suggests physiology is a key driver of migration.” Science Advances  25 Sep 2015: Vol. 1, no. 8, e1400270 DOI: 10.1126/sciadv.1400270
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