Marianas Islands Sea Turtle and Cetacean Survey (MISTCS)

Background

The United States NAVY wishes to conduct naval exercises around the Marianas Operating Area and surrounding waters.  In order to carry out these military activities, the NAVY must be compliant with a suit of federal environmental and natural resources laws and regulations that have been set forth to protect our natural resources.

The primary environmental laws that govern NAVY activities in the marine environment include: the National Environmental Policy Act (NEPA), the Marine Mammal Protection Act (MMPA), the Endangered Species Act (ESA), and the Magnuson-Stevens Fishery Conservation and Management Act/Sustainable Fisheries Act (MSFCMA/SFA).

To comply with these regulations, prior to commencing naval activities, the NAVY is conducting a marine resources assessment (MRA).  By being informed about the spatial and temporal occurrence of protected species within the Marianas study area, Navy operations can be scheduled in such a way as to avoid or minimize potential impacts.

One of the recommendations to help understand the marine resources in and around the  Marianas operating area, especially resources potentially affected by Navy operations, was to conduct a shipboard (including acoustic) marine mammal and sea turtle survey.

Objective

The primary objective was to conduct a systematic line-transect survey to collect data necessary to generate a Technical Report that provides marine mammal and sea turtle density estimates for the U.S. NAVY Marianas Operating Area and surrounding waters.  The project was broken down into three components:

1) Visual marine mammal and sea turtle observations

2) Acoustic data collected from marine mammals

3) Oceanographic data

Method

The period of the survey was between Jan 13, 2007 until April 13, 2007.  The scientific crew consisted of ten people: cruise leader, six marine mammal observers, one oceanographer, and two bioacousticians.  An additional seven crewmembers were required to take care of the logistics of vessel operation.

Marine Observers

At a speed of 10 knots along the designated trackline, marine observers used 25 X 150 MTM “bigeye” binoculars, hand-held binoculars, and unaided eyes to spot marine mammals and turtles.  Photographs were taken when possible to confirm species, group size, and behavior.

Acoustics

A towed hydrophone array was used to find and record marine mammal vocalizations, and localize their positions.

Oceanography

Subsurface oceanographic data was collected using expendable bathythermograph (XBT) launches.  These data measured the surface homogenous layer and mixed layer depths and temperatures of the ocean.  Water samples were taken regularly to determine chlorophyll concentrations in order to estimate primary productivity.  A thermosalinograph (TSG) was used to continuously measure sea surface temperatures, salinity, conductivity, and sound velocity.  HAMER played a role in the collection of oceanographic data.

Boat

All operations were conducted from the MV Kahana, a 140 ft vessel transited from Honolulu to Guam.  All port calls took place in Apra Harbor, Guam.  The survey followed pre-determined tracklines providing a uniform survey of the entire study area.

Study Area

The islands of the Mariana archipelago are located in the western North Pacific Ocean between latitude 13 degrees (°) N and 20°N and are approximately 5,800 km west of Hawai’i, 2,250 km south of Japan, and 7,600 km north of Sydney, Australia.  The archipelago is a chain of 16 islands extending roughly 800 km from Guam in the south to the uninhabited island of Farallon de Pajaros in the north.  Guam is the westernmost U.S. territory and is the largest, most populated island in Micronesia.  The study area includes several dominant physiographic features including seamounts, active submarine volcanoes, and the 11,000 m deep Marianas Trench.

There are eight marine mammal species that are listed as endangered under the ESA with confirmed or possible occurrence in the study area: North Pacific right whale, humpback whale, sei whale, fin whale, blue whale, sperm whale, Hawaiian monk seal, and the dugong.  Four of the world’s seven living species of sea turtles have been reported in the waters surrounding the study area. These include the green, hawksbill, leatherback, and olive ridley turtles.