Beyond the Aquarium
PIPA: Dead Fish Swimming
This is a cross post from the Semester at Sea (SEA) Robert C. Seamans blog written by Jan Witting, Chief Scientist with SEA. The expedition sailed into harbor in American Samoa today, ending the six-week journey.
Friday, August 12
On board the Robert C. Seamans
At anchor, Pago Pago Harbor
The sleek grey shape gliding into a patch of calm water next to our ship confirms the bow lookout’s call just a moment before. A shark! And there it is, off our science deck, dorsal fin sticking out of the water, languidly, gracefully moving past us. You can count four remoras clinging to its back, the hangers-on to this top dog of the pelagic, open-ocean ecosystem. For that is where we are, two days out of PIPA, nearest land a tiny island in the Tokelau group and American Samoa five hundred miles away. Our carousel water sampler is still in the water, we are on science station with the ship hove to and motionless, other than the gentle roll from the passing swells. The shark makes some passes, then loses interest and moves on.
If you’re a regular to our blog, you’ve heard many mentions of sharks by now and might wonder what the big deal is about another one. For one, this is an open-ocean species and is not associated with any island like the reef sharks we encountered in PIPA. The bigger deal yet is that we are seeing one at all. The 19th century sailors who plied the same waters we have in whalers and trading ships, wrote about sharks and their abundance. Yet for us, in six weeks at sea, this was the only such sighting. One of the reasons for this catastrophic decline in shark numbers pulls into view moments later, as a small raft clad in black seine netting, towing a basketball-sized shiny float, is sighted off the quarter deck. We quickly identify it as a fish aggregating device, or a FAD.
Now, FADs are a key component of the modern method of purse seine fishing. For whatever reason, fish of all kind are attracted to floating objects in the open ocean. These floats quickly build a large community of various fish species, ranging in size from small baitfish to tuna and sharks. Purse seiner vessels, up to 200′ and longer and equipped with a small auxiliary open workboat and often a helicopter, use them to help gather and find schools of tuna, circle the school in a huge net more than a mile long, and finally gather the net into a purse, hoist it out of the ocean with giant gantries, and dump the whole mass of writhing fish into one of its frozen holds.
The shiny float attached to it is a sophisticated satellite GPS tracking and Sonar device, and this very FAD is being tracked, moment-by-moment, by the fishing company that launched it. It sends out GPS coordinates of its location, together with information on how much fish has aggregated below it in the ocean. When the catch density promises to be right, a purse seiner will arrive and scoop up everything under the raft, tuna or not. Our shark is a dead fish swimming.
After retrieving our science gear, we fire up the engine and motor windward to take a closer look at the FAD. In fifteen minutes it is floating under our lee, and we are able to observe schools of fish turning in large circles under the small raft. Together with them, we sight three more small sharks right at the surface. The scene of us all, lined up at the rail and taking in this incredible sight of the vibrant life of the ocean, is so much like another scene a few days earlier, while we were at anchor at Nikumaroro. The sight, our wonder, the similarity of the scene, is as striking as is the difference in the prospects of the life at which we are marveling. The fish, dolphins, sharks and turtles of Nikumaroro will be there for the next fortunate visitor to see. The creatures by our ship, under the FAD, will end.
Sometimes simple answers are the best. We visited the Phoenix Islands Protected Area for more than three weeks on this fantastic journey of exploration, our goal to gather data to help answer the question of how well do very large marine protected areas work for conserving the open ocean ecosystems. To that end, we sailed some 3500 nautical miles, conducted 42 CTD casts, towed 107 plankton tows, and analyzed hundreds of nutrient and pH samples. We’ve spent hundreds of hours counting and identifying fish larvae, appendicularians, plankton of all shapes and sizes, and all this information will help to monitor, manage, and discover new things about PIPA. But here is evidence of the very starkest kind. In PIPA, the creatures we saw have a future. The ones here, by our ship, do not.
To have value, though, a simple answer can’t be simplistic. The ocean has no boundaries. Sharks, tuna, dolphins, whales, myctophids, appendicularians, they all move – either by ocean currents or their own tail. What once gets a respite in PIPA will not forever remain there, unless they are a resident of one of its islands, reefs, or seamounts. Yet for even these visitors, PIPA offers a moment free of fishing pressure, a moment to feed, to grow and to reproduce. How big is this effect, how much does it help in the conservation of blue water species? Some of that detail will emerge from our samples of plankton, larval fish, and other data we collected.
All of us onboard the Robert C. Seamans, though, are convinced that PIPA provides an invaluable service. All of us leave inspired by what we saw, changed by this voyage, and determined in our own different ways to work to make sure these sights can be seen by generations to come. And we all, I suspect, leave the ship with a lifelong urge to return.
SEA Cruise S268, Protecting the Phoenix Islands