“THIS IS HARDER than it should be,” Barbara Block muttered as she leaned over the gasping fish. Blood dripped from her left hand where the tuna’s teeth had slashed her. Though covered from neck to toe in a neoprene wet suit, she shivered.
Block, a 44-year-old marine biologist, was in a skiff in Monterey Bay, California, offshore the facility she codirects, the Tuna Research and Conservation Center. Apearly light shone through a lifting layer of fog. In a sling in the center of the boat, a pair of four-foot-long bluefin tuna lay side by side. “Keep the hose on that one,” she told an associate, and he trained a stream of aerated water into its mouth and thus through its gills.
She picked up a tool that resembles a spear. Attached to one end was an electronic device containing a sensor and a transmitter. It looks like a wireless microphone and can beam a signal to an orbiting satellite, conveying the transmitter’s whereabouts on the globe. Block bent over the animal and stuck the “satellite tag” into the fish just below the dorsal fin. The researchers lifted a sling holding the fish and then lowered it over the side of the boat and into the water. “One, two, three!” they chanted, and pushed the tuna free. For a minute the tuna appeared to swim woozily near the surface, the tag bobbing above its back like a mechanical pilot fish, before disappearing into the depths.
In the coming months, the device would make a daily record of the tuna’s travels, then, after roughly six months, detach itself from the animal, float to the surface and upload the data to a satellite. One of the fish that Block and her coworkers tagged that November day swam some 1,300 miles over the next several months, at depths of up to 1,000 feet, and was last detected in March near Magdalena Bay, Mexico, about 200 miles north of Cabo San Lucas.
The animal played a bit part in an unprecedented global biological research project known as the Census of Marine Life, an estimated $1 billion, ten-year effort by scientists in at least 40 nations to identify, characterize and track the movements of scores of life-forms. Those include a wide range of animals other than bluefin tuna, from whales and turtles to sea-bottom bloodworms and albatrosses. Some researchers will scuba dive. Others will send robots to the ocean floor. And still others will soar above the sea’s surface in aircraft equipped with laser-based radar devices that can penetrate the ocean and monitor, among other variables, the locations of schools of fish. Researchers also plan to study historical records to gain a view of ocean life in the past.
Assessing the status of marine life around the world has gained urgency in this era of coastal pollution and alarming overfishing. Policymakers who set ocean-fishing quotas and pollution limits are working with outmoded or incomplete data, the census researchers say. They argue that the project is needed because the oceans, which make up 90 percent of the Earth’s biosphere, “are largely unexplored, and the life in them largely undescribed.”
Block’s study of Pacific bluefin is only part of the larger census project, but it highlights how the researchers hope to gain a detailed picture of not only where the creatures go but also the watery world they inhabit. “Let’s take the animals we know that can carry the electronics and get them to sample the oceans for us,” Block says. “Let’s use the organism as a way to get a window into the world it lives in—to get the organism’s-eye view.”
After releasing the tagged fish, Block and her associates motored back to the tuna research center, where a group of graduate students was matching wits with two dozen bluefin swimming around a 40-foot-diameter tank. The center is world famous for its studies of captive bluefin tuna, most of which are caught off the Southern California coast and trucked to the facility. Tuna can survive in the tanks for several years.The water in the tanks turns over every 70 minutes, and its temperature, acidity and oxygen content are carefully regulated.
The water in the tank had been drawn down to hip level, and the graduate students, wearing wet suits, maneuvered a vinyl mesh corral to capture the circling fish. Once the students caught a fish, they guided it into a sling, which was hoisted out of the water, transferred to a forklift and rushed to the dock. Block trotted alongside the animal like an emergency room physician tending to a patient on a gurney. She jumped into the skiff, and the crew raced out to the bay to release the fish.
Block is among the world’s leading experts on warm-blooded ocean fish— tuna, mackerel sharks and billfishes such as marlin. She has authored or coauthored 60 studies on their physiology, behavior, genetics and ecology and has pioneered methods for keeping tuna in captivity. In 1996, she received a MacArthur Foundation grant, and she poured most of the $250,000 socalled genius award into the research center at Monterey Bay.