Ecosystem Observations

During HICEAS, we do more than just look and listen for cetaceans; we study the ecosystem, including the oceanographic properties of the waters we traverse and the occurrence of seabirds and sea turtles. Seabirds are important indicators of overall ecosystem health and many species of seabirds, along with all species of sea turtles in Hawaii are protected by Federal laws. It is important to understand as many components of the ecosystem as we can, in order to get a well-rounded picture of the ecosystem as a whole and to make the most of the opportunity of our time on the research vessels.

Why do we study the ecosystem?

Knowing the distribution and abundance of cetacean populations only gives us part of the picture in understanding their overall health. For a fuller picture, we must assess the habitat of cetaceans and the greater health of their ecosystem. Oftentimes changes in the ecosystem are tightly linked with the dynamics of cetacean populations. A better understanding of the habitat helps us determine why some species are thriving and others might be declining

How do we study the ecosystem?

The large research vessel has a variety of oceanographic sensors onboard that continuously record sea temperature, salinity, and fluorescence (a measure of the level of primary productivity). Each NOAA ship also carries a Conductivity-Temperature-Depth (CTD) instrument that can be cast to depths of 1000 meters or more. The CTD measures temperature, salinity, oxygen, and other nutrients from the surface to depth. It collects water samples at specific depths for more detailed information on water properties. During HICEAS, we conduct a CTD each morning before sunrise and each evening after sunset to help characterize the ecosystem of the cetaceans we are studying.

The occurrence and abundance of seabirds are excellent indicators of ocean conditions and health. During HICEAS, we collect seabird data from the ship’s flying bridge, sun-up to sundown, using visual observers following strip-transect methods. Strip-transect methods mean that the observers record all seabirds flying or sitting on the water that are within a specified distance from the ship, usually a few hundred meters. Seabirds beyond that distance may be noted if they are unique, but are not used for evaluating density or abundance. The seabird observers will work simultaneously and alongside the visual observers searching for cetaceans.

Five species of sea turtles are known to occur in Hawaiian waters. To take advantage of our research platform and vast coverage within our study area, we make note of opportunistic sightings of sea turtles at sea. When a sea turtle is encountered, we will record the location of the turtle and collect photographs for species identification. If we find sea turtles entangled in debris, we will launch a small boat to capture the turtle, remove the debris, and release the turtle back to the ocean. We keep the debris onboard with us and dispose of it when we return to port so that other animals don’t become entangled.

Deploying the CTD for data collection.
Visual observers follow ship-transect methods when collecting seabird data from the ship's flying-bridge.
Opportunistic sightings of sea turtles are recorded during the expedition.