NOAA Expedition to the Northern Mariana Islands Focused on Insular Fisheries Research

Recently scientists from PIFSC joined colleagues from the Commonwealth of the Northern Mariana Islands (CNMI) to conduct joint studies of marine fish populations, ecosystems and habitat in waters of the CNMI. CNMI participants included researchers from the Division of Fish and Wildlife (DFW), Bureau of Environmental & Coastal Quality (BECQ), Northern Marianas Mayor's Office (NMMO), Northern Marianas College (NMC), and the CNMI Bio-Sampling team. The expedition was conducted using the NOAA Ship Oscar Elton Sette in waters of Uracas, Maug, and Asuncion within the Marianas Trench Marine National Monument (MTMNM) from June 19 to July 3 and in waters around Pagan, Alamagan, Guguan, Sarigan, and Anatahan in the Northern Mariana Islands (NMI) from July 7 to July 21. The primary objective of the mission was to support fisheries research proposals and interests of CNMI agency colleagues.

Figure 1.  Bathymetry maps of Maug. Pie diagrams show location of fishing operations by the NOAA Ship Oscar Elton Sette and 
        species composition of fish catch at each site.  Legend identifies each species by color and code name (combined first 2 letters of 
        genus and species names) and indicates the total number of fish caught at the island. Reef fish species are identified in the top 
        portion, and bottomfish species in the lower portion. Map courtesy of PIFSC Coral Reef Ecosystem Division.
Figure 1. Bathymetry maps of Maug. Pie diagrams show location of fishing operations by the NOAA Ship Oscar Elton Sette and species composition of fish catch at each site. Legend identifies each species by color and code name (combined first 2 letters of genus and species names) and indicates the total number of fish caught at the island. Reef fish species are identified in the top portion, and bottomfish species in the lower portion. Map courtesy of PIFSC Coral Reef Ecosystem Division.

Science activities aboard the Sette included "bio-sampling" of deep-slope bottomfish and shallow reef fish species, that is, collecting information and tissue samples of selected specimens of fish to support a variety of life history studies (to be conducted by PIFSC and DFW) and research on important ecosystem topics including latitudinal trophic shifts and genetic connectivity within the Mariana Archipelago (DFW). Using small boats launched from the Sette, BECQ scientists conducted a variety of field work including a survey of the benthos and investigation of water quality of the intertidal habitat around each island. Additional research included fishing for bottomfish and, when opportunities arose, photo-documenting any shark depredation interactions during the bottomfishing operations (NMC project). Other operations included conductivity-temperature-depth (CTD) casts to 1,000 meter depths to characterize oceanographic conditions in the water column and deployment of Isaacs-Kidd midwater trawls and drifting night-lights to sample early life stages of fish.

Figure 2.  Bathymetry maps of Pagan. Pie diagrams show location of fishing operations by the NOAA Ship Oscar Elton Sette 
        and species composition of fish catch at each site.  See caption of Figure 1 for further explanation.
Figure 2. Bathymetry maps of Pagan. Pie diagrams show location of fishing operations by the NOAA Ship Oscar Elton Sette and species composition of fish catch at each site. See caption of Figure 1 for further explanation.

Deep-slope bottomfish sampling targeted eteline snappers in the 200-350 meter depth range around each of the islands. Bottomfish sampling using hydraulic fishing reels onboard the Sette and electric reels onboard a NOAA small boat caught primarily six eteline snapper species (gindai Pristipomoides zonatus; opakapaka P. filamentosus; yelloweye opakapaka: P. flavipinnis; yellowtail kalekale P. auricilla; ehu Etelis carbunculus; and onaga E. coruscans) and one grouper species (eightbar grouper Hyporthodus octofasciatus). Gindai and yellowtail kalekale dominated the catch of deep-slope bottomfish at virtually all the islands surveyed. Other species such as opakapaka, onaga, and yelloweye opakapaka were abundant in the catch at particular islands while ehu was less abundant. Large specimens of the eightbar grouper were caught only at the three northernmost islands surveyed within the MTMNM. Highest catches of eteline snappers occurred at Maug within the MTMNM and at Pagan within the NMI (Figs 1 and 2). All eteline snapper and grouper specimens were sampled for otoliths, gonads, and muscle and fin tissues.

Using snorkel-spearfishing gear, staff from DFW, NMMO, and the CNMI Bio-Sampling team sampled fish populations, primarily targeting six shallow reef fish species (blue-lined surgeonfish Acanthurus lineatus; orange-spine unicornfish Naso literatus; blue-spine unicornfish N. unicornis; redlip parrotfish Scarus rubroviolaceus; bluefin trevally Caranx melampygus; and bigeye emperor Monotaxis grandoculis). These species constitute the most common components of the landed catch in CNMI and Guam. All collected specimens of these species were sampled for otoliths, gonads, and muscle and fin tissues.

Intertidal benthic surveys and water quality sampling were conducted by BECQ scientists at representative sites at all of the islands. Survey activities included fish counts, benthic photography, and observations of benthic species present. Water samples were also collected to test for physical properties and bacterial count.

Additional scientific operations completed were 16 CTD casts to depths of 1,000 meters, 14 Isaacs-Kidd tows that sampled both surface and midwater (~100 meters depth) habitats, and 6 drifting night-light stations. During leg 1, two archeologists where disembarked on the island of Alamagan to conduct 11 days of fieldwork prior to being retrieved by the Sette.

A diverse team of scientists, deck crew, and officers carried out the Sette expedition, representing NOAA, JIMAR, and 
        marine resource agencies of CNMI and Guam.
A diverse team of scientists, deck crew, and officers carried out the Sette expedition, representing NOAA, JIMAR, and marine resource agencies of CNMI and Guam.