Another successful rescue and our first bit of science

by Lisa Munger
photos by Brian Hauk and Kara Osada-D'avella

Recovering the EAR

After a safe transport of personnel from Kure Atoll to Midway, we took advantage of our unexpected diversion to recover an Ecological Acoustic Recorder (EAR) deployed in May 2010 a few miles southeast of the atoll. The EAR is a passive listening device that records ambient underwater sounds on a programmable schedule, and stores the recordings on an internal hard drive. EARs are capable of recording for months or years, and provide long-term data on noise-producing marine animals such as snapping shrimp, fish, whales and dolphins, as well as human activities and natural events. The battery life of this EAR should have allowed it to record during the recent tsunami that arrived at Kure on March 11th, but we will not know until the EAR returns to Honolulu, where the data will be extracted.

The Kure EAR was anchored to the seafloor in a location over 100 meters deep, which prohibits retrieval by divers. Instead, the EAR was released from the bottom by sending an acoustic command (a specific series of pings at a set frequency) from a transducer aboard the ship. Within a few minutes, the EAR floated to the surface, where it was spotted by scientists watching from the bridge deck. The recovery took place from the ship, and it went incredibly smoothly thanks to the combination of excellent piloting by LTJG (sel) David Vejar, skillful gaffing by AB Carmen Greto, and the cooperation of many other crew members and scientists both on board and on land.

Sperm whales off our bow

One of the marine mammal species likely to be recorded on the Kure EAR is the sperm whale (Physeter macrocephalus). We enjoyed the opportunity to observe sperm whales first-hand in this area a couple of days ago, when we spotted a pod of approximately 14 females resting at the surface. Several more distant sperm whales were sighted today by L. Munger from the bridge. Sperm whales produce distinctive clicks when they are underwater; these clicks are used for communication with each other and for hunting squid, their primary prey. These air-breathing mammals can dive to depths greater than 3000 meters (almost 2 miles) and hold their breath for up to 90 minutes! Throughout the cruise we will be recording marine mammal sightings such as these and will taking ID photographs for the NOAA Pacific Islands Fisheries Science Center (PIFSC) cetacean research program.