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Studying the potential impacts of bottomfishing in the Northwest Hawaiian Islands Coral Reef Ecosystem Reserve

by Christopher D. Kelley and Rachel Shackelford

Map of the Northwestern Hawaiian Islands (NWHI) relative to the Main Hawaiian Islands.

Figure 1. Map of the Northwestern Hawaiian Islands (NWHI) relative to the Main Hawaiian Islands.

The Northwest Hawaiian Islands Coral Reef Ecosystem Reserve was created by an executive order from President Clinton in 1998. This reserve was designed to protect the unique natural resources of a chain of islets, atolls, submerged banks, and seamounts in the Hawaiian Archipelago extending over 1,000 miles northwest of the island of Niihau (Fig. 1). While it has the distinction of being the largest marine reserve in the United States, it is also the most poorly known, particularly below the depths accessible by SCUBA. That, however, is changing as various agencies are joining forces to use deep submergence vehicles for exploring and studying its strange and magnificent realms below 200 ft.

HURL's deep-diving submersible Pisces V being lowered into the water

Figure 2. HURL's deep-diving submersible Pisces V being lowered into the water.

HURL's remotely operated vehicle RCV-150 under the water.

Figure 3. HURL's remotely operated vehicle RCV-150 under the water.

Until last year, only nine submersible dives had ever been conducted in this region. In September 2001 that number was more than doubled during a two and a half week cruise aboard the R/V Kaimikai-o-Kanaloa (KOK). A team of researchers led by NOAA's Hawaii Undersea Research Laboratory (HURL) and the National Marine Fisheries Service Honolulu Laboratory (NMFS-HL) made ten 8-hr daylight dives in the Pisces V submersible (Fig.2) on East French Frigate Shoals, Brookes Bank, West St. Rogatien Bank, Raita Bank, and a deep pinnacle north of French Frigate Shoals. The project involved 24-hour operations, so each evening, after the sub was recovered, the RCV-150 ROV (Fig. 3) was deployed for another 8 hours to obtain noctural observations. Finally, from 3 to 7 a.m., the KOK's Sea Beam multibeam sonar system was used to map tracks across and around the banks in an effort to determine their true geographic positions.

Over half of this work was conducted around West St. Rogatien and Raita Banks. In Clinton's executive order, special conditions were attached to these banks regarding their use by commercial bottomfishers. Specifically, fishing will be allowed to continue until 2003 while a study is conducted to assess its impacts on the ecosystem. HURL biologists, along with a team of researchers from NMFS-HL and the State of Hawaii's Department of Land and Natural Resources (DLNR), initiated the study with funding from the National Ocean Service (NOS). Submersible and ROV dives were used to survey known fishing sites on the banks. Identification and counts were made of all fish and invertebrates species, lost anchors and anchor lines, fishing gear, and trash that may have been left by the fishers. At specific locations, bait was put out near the sub to attract and document bottomfish species (Fig. 4). Fish around the bait stations were videotaped without any artificial light using a new CCD camera installed on the Pisces V (Fig. 5).

Commercially valuable snapper was photographed when attracted to bait used for documentation.

Figure 4. Pristipomoides sieboldii, one of the commercially valuable snappers observed in the NWHI.

Figure 5. Images of fish obtained with the new CCD video camera. This camera allows us to view fish without the interference of artificial light, giving us a more accurate representation of how they behave in their natural environment.

Fish habitat photographed in natural light A school of fish photographed in natural light A school of fish photographed in natural light

So what did they find? The multibeam mapping tracks indicated that Raita Bank was relatively close to where it is supposed to be according to nautical charts, but West St. Rogatien Bank was found to be almost 2 miles to the northeast of its shown location! From the sub and ROV observations, the tops of the banks were covered with rhodoliths formed by calcareous algae, while the slopes were characterized by low relief carbonate rock interspersed with sand channels. Researchers found large numbers of fish, including huge schools of beautiful little anthiid groupers (Fig. 6), but were very surprised at the lack of deepwater coral species that could be damaged by anchors and lead fishing weights. Very little fishing debris was observed, likely due to the low number of boats that fish these banks. These initial findings will surely be well received by the bottomfishers; however, conclusions and recommendations will only be made after additional dives are completed next fall.

A school of groupers seen in the deep waters of NWHI

A close-up view of a lone grouper in the Reserve

Figure 6. Anthiid groupers observed around the NWHI.

These dives into the deep waters of the Northwest Hawaiian Islands Reserve produced valuable information on the impacts of bottomfishing on two banks in the reserve. The fish and invertebrate counts are still being analyzed, but will lead to the development of a baseline from which the impacts of bottomfishing can be assessed. Information on the ecology of an endangered seal and a number of potential new species in this area were gained as well (see http://www.soest.hawaii.edu/HURL/Q2_2002.html). These dives furthermore underscored just how little we know about this huge area of the marine environment now under federal protection

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Updated: April 1, 2005