On To Day 8Back To Day 6Day 7. New Survey Strategy

October 2, 1998. Excellent data come rolling in after determining a new survey strategy at the Puna Ridge. Because of the steep bumpy terrain we have found it is better to tow the fish downhill.

As you remember, whenever the flyer in the control van increases the vessel’s altitude (decreases its depth), the cable pulls the nose of the vessel up and forces the sonars into a bad angle. Furthermore, the change in angle causes the vessel to bob up and down. The result is streaky sonar images that are not especially useful. At the daily science briefing, Debbie suggested that we only map transects as we move down the ridge. When we reach the bottom, we would pull the DSL 120 back on board the ship, motor back to the top of the ridge, lower the vessel into the water, and start the next transect. The turnaround time would take eight hours, but the quality of the images would be much better.

A high quality side-scan sonar Low quality side scan data with vertical artifects
A comparison of a good sonar image (left) and a streaky image (right).

Fishing

Thirty-five days on a ship without a single stop at a supermarket. Although the produce on board may not be the freshest (actually, it is remarkably good), there are culinary advantages to living on the ocean. Fresh fish. Tonight, we dined on mahi mahi that had been caught this morning.

If you take a walk on the deck during the morning or evening, you will likely see the captain or a member of the crew casting a line over the railing. The fish they target include mahi mahi, tuna, wahoo, and if they are lucky, marlin.

Captain Glenn GomesTo the experienced fishers large flocks of birds such as shearwaters and petrels feeding off the water indicate good fishing. (There are no sea gulls in this area of the Pacific.) The large game fish are sloppy eaters, so the birds gather to feed on the scraps. But today, the birds were not necessary. The sonar swath we were mapping brought us quite close to a fish buoy. These buoys act as artificial reefs. Cages and other objects hanging from the buoy attract small fish seeking shelter. The small fish attract bigger fish. The bigger fish attract the really big fish. And, of course, the really big fish attract fishers. All day, we could see schools of bright blue mahi mahi swimming near the side of the ship.

Mahi MahiAfter dinner, I joined crew member Tim Hill on the deck as he methodically cast a big hook over the side of the ship, reeled it in, then cast it again. We could see mahi mahi below, but they weren’t biting.

At last he hooked a fish. He braced himself against the rail and pulled until his rod curved into a U. Finally, with the help of a net, he landed the flailing fish onto the deck. Mahi mahi for breakfast?

Go back to day 6. Go to day 8.