NOAA Scientists and Fishermen Work Together for Improved Understanding of Lobster Populations in the Northwestern Hawaiian Islands Ecosystem

June 8, 2006

As part of an ongoing cooperative research program, scientists of the NOAA Pacific Islands Fisheries Science Center (PIFSC) are now at work in the Northwestern Hawaiian Islands (NWHI) studying lobster populations with the technical assistance and expertise of Hawaii fishermen. The research will improve the ability of NOAA Fisheries Service to monitor fluctuations in the NWHI lobster populations and predict the response of the lobsters to natural and anthropogenic factors. These studies also enable marine scientists to better understand the role of lobsters in the NWHI ecosystem.

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Scientists taking measurement of carapace length of slipper lobster prior to PIT tagging

A primary objective of the study is to improve the mathematical models PIFSC uses to assess changes in the abundance of spiny lobster (Panulirus marginatus) and slipper lobster (Scyllarides squammosus). The models are based on the best available biological information about lobster including their growth, reproduction, survival, and movements.

Uncertainty about the lobster models and how the underlying biological factors are influenced by changes in oceanographic conditions, habitat, and fishing pressure led to a precautionary closure of Hawaii's NWHI lobster fishery in 2000. PIFSC then convened a panel of experts to review the models and recommend steps to improve them. The panel suggested that PIFSC could reduce model uncertainty by conducting a multi-year lobster tagging campaign in the NWHI. Tagging is a simple but powerful research method. Scientists catch lobsters using lobster traps, place identifying tags on them, and return the lobsters alive to their habitat on the sea floor. The recapture of tagged lobsters by researchers or fishing vessels in subsequent surveys provides a wealth of information about the biological factors central to the lobster population model. For example, biologists can analyze tag recapture data to determine how fast lobsters are growing and estimate their expected lifespan.

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Scientists inserting PIT tags into spiny lobster

In response to the expert's recommendation, PIFSC launched a tagging project in the summer of 2002 under the NOAA Fisheries Service National Cooperative Research Program. This program was established and funded by Congress to support collaboration between scientists and public sector stakeholders in marine fisheries research. In the NWHI, the cooperative tagging of lobsters is carried out each summer by PIFSC scientists using chartered commercial lobster fishing vessels and their experienced captains and crew to catch lobsters in several study areas. All lobster caught are used strictly for research and are then returned to their habitat.

This year, the research will be conducted on a pair of cooperating vessels, the Marie M and the Katy Mary. The Marie M will be deployed during June, and the Katy Mary will conduct similar work beginning in mid-July. Both vessels are well equipped for lobster trapping and their captains and crews have participated in previous NWHI cooperative lobster research.

On board each vessel, the tagging and biological studies will be carried out by a crew of three scientists including Chief Scientist Joseph O'Malley, a marine biologist employed by the NOAA-University of Hawaii Joint Institute of Marine and Atmospheric Research and a staff member of PIFSC. Research operations will be conducted at designated locations around Necker Island, Maro Reef, Gardner Pinnacles, and Laysan Island. At each location, the vessels' crew will set out baited traps to catch lobsters. After the traps are allowed to "soak" on the bottom overnight, they will be brought to the surface and lobsters caught in the traps will be removed, examined, tagged and released alive. During the inspection of each lobster, the scientists will measure the animal's size, determine its gender, and assess its reproductive status (maturity). Each lobster will also be scanned with a special instrument to see if it is carrying a tiny microchip called a Passive Integrated Transponder, or "PIT" tag. Each microchip emits a different radio-frequency code detected by the scanner. The harmless PIT tags have been implanted into over 40,000 lobsters by scientists on previous cooperative research expeditions. If a PIT tagged lobster is found in the catch, biologists will note its unique identification number. If no PIT tag is detected in the lobster, one will be carefully inserted. When the scientific work is completed, all lobsters caught will be returned alive to the seafloor, conveyed in a special release cage designed to protect them from potential predators during their descent.

After the trap catches are processed, the biological data and tag identification numbers will be recorded and archived into a PIFSC database for further analysis. This year the tagging project will be using new electronic technology that will enable data collected during the cruise to be automatically and directly entered into the database.

The tag recapture data and biological data collected during the cooperative research expeditions are a valuable supplement to information PIFSC gathers during the annual surveys of NWHI lobster by the NOAA Ship Oscar Elton Sette. The combined results of these studies enable marine scientists and resource managers to better understand the status of the lobster stocks and their role in the NWHI ecosystem.