On Sunday August 18th 2013 scientists aboard the NOAA Ship Oscar Elton Sette departed Ford Island Hawaii (NOAA’s soon to be new home) en route to waters of Johnston Atoll. This research expedition will be engaged in a 19-day research project that will conduct scientific sampling operations in the waters around Johnston Atoll located some 700 nm southwest of Honolulu. These waters are part of the Pacific Remote Islands Marine National Monument established in 2009.
The primary focus of this research project will be to collect fin-clip tissue samples for DNA analyses from all species of the commercially important “Deep-7” bottomfish complex. These species include the Hawaiian grouper “hapu’upu’u” and the six species of deep-water snappers (“opakapaka”, “ehu”, “onaga”, “lehi”, “gindai”, and “kalekale”). After completion of the cruise, collaborating scientists at the Hawaii Institute of Marine Biology will conduct DNA analyses of the fin-clip tissues. The samples collected during this project at Johnston Atoll will provide the first opportunity to determine the possible extent that Johnston Atoll and the Hawaiian Archipelago populations of Deep-7 bottomfishes are genetically linked. Scientists have speculated that populations of both hapu’upu’u and opakapaka at Johnston Atoll and Hawaiian Archipelago may be genetically linked through the transport of pelagic larvae and juveniles stages. This pelagic (open water, away from land) stage in offshore waters is part of the normal early life cycle of these species. During this research project, midwater trawl sampling to capture specimens of these pelagic stage bottomfish will be conducted at night while the ship is at Johnston Atoll and also in distant waters during the ship’s transit back to Honolulu. The collection of young pelagic individuals and tissues from adult Deep-7 bottomfish will provide the necessary material to begin to investigate the extent that populations between Johnston Atoll and the Hawaiian Archipelago are interconnected.
The scientific team will conduct small boat bottomfish sampling operations within the 100-400 meter depth contours around Johnston Atoll. Fin-clip samples from 50 fish per species need to be collected at Johnston Atoll to obtain a large enough sample for later DNA analyses. Sampled bottomfish will be released after samples of fin tissue are removed except for the very largest individuals to be retained for otolith extraction and later age determination. Sampling of pelagic stage bottomfish around Johnston Atoll will be conducted at night some ~25 nm offshore using a Cobb midwater trawl net towed at depths of 170-175, 100-125 and 20-25 meters. Cobb trawls will also be conducted at night during the transit from Johnston Atoll back to Honolulu to evaluate the extent of the offshore distribution of pelagic stage individuals between these two island areas. Researchers will also collect oceanographic data such as current speed and direction with depth using an onboard instrument called an Acoustic Doppler Current Profiler (ADCP). Other oceanographic measurements of the water column will be collected by a device known as a conductivity-temperature-depth (CTD) instrument that is lowered and retrieved from the ship and provides a depth profile of temperature, salinity, and oxygen concentrations. Additionally, water-sampling bottles attached to the CTD will collect water at pre-determined depths that will be filtered and processed onboard the ship to determine water chemistry and chlorophyll content. These ocean measurements will help to characterize the physical environment that pelagic stage bottomfish may be associated with and may lead to a better understanding of their environmental habitat.
The results of this project will provide important information regarding the degree of isolation that Deep-7 bottomfish populations in Hawaii experience in relation to its closest geographic neighbor. See next bottomfish research expedition post: http://bit.ly/16BlZ3g