Cordova, Alaska—The number of fish in the sea, long a metaphor for limitless possibility, is finally coming to a head count. An ongoing, decadelong effort by scientists from more than 80 countries to fathom the contents of the global ocean will culminate next year in a definitive Census of Marine Life.
Inspired by the depth of human ignorance about the underwater realm, census researchers have already found what they believe are more than 5,000 previously unknown marine species. The teams have also tagged and tracked many familiar creatures, uncovering surprises to science and commercial fisheries alike. For example, California green sturgeon, once considered homebodies, actually gather each year at Vancouver Island in British Columbia before swimming another 1,500 miles to winter in Alaska.
The census encompasses an alphabet soup of projects, including ChEss (Biogeography of Deep-Water Chemosynthetic Ecosystems) and TOPP (Tagging of Pacific Predators). But, just as a journey of a thousand miles begins with a single step, the grand scope of the Census of Marine Life can be appreciated through the study of a single species of fish—in this case, the lingcod, Ophiodon elongatus, tracked through the Pacific Ocean Shelf Tracking Project (POST). Prized by diners for its tasty white flesh, the yard-long lingcod is a voracious predator that ambushes other fish among the submerged rock pinnacles and kelp thickets of Prince William Sound. Over the past couple of decades, authorities fear, lingcod stocks in some areas along the Pacific coast have been dangerously depleted by overfishing.
I had never seen or (knowingly) eaten a lingcod before visiting its habitat near this coastal fishing town in south central Alaska, where I joined ecologist Mary Anne Bishop and researcher Brad Reynolds, both of the Prince William Sound Science Center in Cordova, on a field trip to monitor lingcod movements by tracking acoustic transmitters implanted in the fish.
Bishop and Reynolds start out by fishing for lingcod much the way any vacationer might, with a hook and line. But when they land their subjects, they anesthetize and prep them for surgery. Cradled upside down in the V-shaped surgery board with a steady stream of piped seawater aerating its gills, each lingcod gets an acoustic transmitter, about the size of a double-A battery, implanted in its abdomen. The transmitter emits an electronic ping every minute or two at a specific sonic frequency (69 kilohertz, far above human hearing) that allows observers to follow the fish’s trail.
“It’s tricky work,” Reynolds says of the implantation process. On a large fish, he has to cut through nearly an inch of muscle. When he nears the abdominal wall, he has to proceed “maybe a millimeter at a time,” to avoid injuring internal organs.
“The lingcod mouth is just cavernous,” he points out in a photo he took while diving among them. “And their bellies are often so distended, as though they can’t tell when to stop eating. They’re the one fish that makes me glad I’m not a fish.”
After inserting the transmitter, Reynolds closes each incision with two sutures, spreads an antibiotic compound on the wound, and puts the fish in a “recovery tub” for a few minutes until its normal, upright swimming proves that it has fully awakened from anesthesia. Before throwing the lingcod back into its element, he punches a tiny, external plastic tag through the muscle beneath its dorsal fin as a signal to fishermen. Sport fishermen and members of the local fishing fleet are alert to the possibility of netting an “experimental fish” and are aware that they should call the phone number on the tag if they find one. Receiving such a call would be gratifying, Bishop allows, but it would mean that a fish had migrated out of the study and onto someone’s dinner plate. To date, all the tagged lingcod have eluded this fate.
Fortunately for fish and scientist alike, neither the pinging of the transmitter nor the red color of the little plastic tag seems to mark the lingcod as easy prey. “Red pretty much disappears at a depth of 30 feet,” Reynolds explains, while lingcod spend most of their lives down at 100 to 200 feet. And, he adds, tests have shown that hungry predators are not attracted by the acoustic pings.
By the time of my visit, the team had tagged 14 lingcod. (They plan to tag another 16, for a total of 30, soon.) If that seems like a small number of subjects for a major study, consider the fact that each acoustic transmitter costs approximately $300 to $550, not counting the investment of researchers’ time and the expense of chartering a boat for the implantation phase. Nonetheless, since transmitter batteries last about two and a half years, the amount of information gathered from the small sample will eclipse the sum of all prior knowledge. What’s more, half the fish chosen for implants are “subadults” whose changing behavior patterns can be followed over several seasons as the fish mature, mate, and reproduce.
Since receiving their implants last October, the 14 locally broadcasting lingcod have continually reported their whereabouts to an array of receivers moored at the bottom of a bay northwest of Cordova called Port Gravina. The system functions automatically. Tagged fish constantly emit their periodic pings, and every time one of them swims past an underwater receiver, the device hears the ping and takes note: It records the identification number of the passerby along with the date and exact time. The more expensive transmitters also provide a measure of the fish’s depth.