Counting Fish: Bubbles or Not? Expedition underway to assess reef fish populations in the Main Hawaiian Islands

From June 14 to July 3, 2015, the NOAA Ship Hi‘ialakai will be the platform for a research cruise to gather data and improve assessments of the status of coral reef fish populations in the main Hawaiian Islands. Led by project leader, Kevin Lino, and lead scientist, Ivor Williams, of the NOAA PIFSC Coral Reef Ecosystem Division (CRED), the cruise is a multi-agency effort, involving participants from the Papahānaumokuākea Marine National Monument, State of Hawai‘i Division of Aquatic Resources, and the University of Hawai‘i.

A school of unicornfish (Naso unicornis) swarm in the coral reefs off the coast of Maui. NOAA photo by Kevin Lino.

A school of unicornfish (Naso unicornis) swarm in the coral reefs off the coast of Maui. NOAA photo by Kevin Lino.

During the 20-day expedition, scientists plan to conduct approximately 300 underwater visual surveys of reef fishes and habitat, with sites spread widely across coral reef areas in all of the populated Hawaiian Islands, from the Big Island of Hawai‘i to Ni‘ihau. The survey methods and sampling design used for the cruise are consistent with those implemented for NOAA’s existing long-term coral reef monitoring program in the U.S. Pacific, which allows multiple data sets to be readily combined and easily compared.

Scientists survey fish populations using the "Stationary Point Count" method, in which pairs of divers record the number, size, and species of all fishes observed within adjacent visually estimated cylinders 15 meters in diameter. NOAA photo by Paula Ayotte.

Scientists survey fish populations using the “Stationary Point Count” method, in which pairs of divers record the number, size, and species of all fishes observed within adjacent visually estimated cylinders 15 meters in diameter. NOAA photo by Paula Ayotte.

These survey efforts are primarily designed to improve the ability of PIFSC and partners to generate an accurate picture of the status and trends of coral reef fishes around the Hawaiian Islands, but because the overall dataset is highly consistent and widely representative of reef areas across the region, it is suitable for multiple purposes and is being increasingly used for large-scale scientific research by NOAA and external researchers.

Divers conduct surveys from small boats launched from the NOAA Ship Hiʻialakai.

Divers conduct surveys from small boats launched from the NOAA Ship Hiʻialakai.

One project that will be investigated during the cruise will be to compare fish counts gathered by divers on closed-circuit rebreather (CCR) with fish counts by divers using SCUBA. Because divers on CCR do not produce bubbles, they are much quieter and a less intrusive presence in the marine environment. Therefore, it is possible that use of CCR may enable divers to get better information on marine species that are wary of divers.

As with all data collected by NOAA, any information gathered during the cruise will be available on request. All coral reef survey data sets, compiled and analyzed by CRED staff and project partners, are routinely reported in post-cruise monitoring briefs and annual data reports.

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