Science Bullet

Connectivity Studies

The genetic survey of fish and invertebrate species is designed to assess the level of connectivity between the Papahānaumokuākea Marine National Monument and the Main Hawaiian Islands (MHI). Scientists have long debated whether the Northwestern Hawaiian Islands (NWHI) serves as a source of larvae that produce the next generation of fish and invertebrates for the MHI. Scientists also want to know whether the NWHI are a series of isolated ecosystems that must be managed atoll-by-atoll, or whether the Archipelago is a single ecosystem that can withstand human influences such as debris accumulation and climate change. Population connectivity can be determined using genetics across a broad range of coral reef invertebrates and fishes. Results thus far argue that no single species appears to be a good predictor of population structure for others and that there can be large differences among species in their degree of connectivity throughout the Archipelago. Nonetheless, results indicate that there are a number of shared genetic breaks between segments of the Papahānaumokuākea Marine National Monument and the Main Hawaiian Islands. For example, the first study of connectivity for corals across the Hawaiian Archipelago has just been completed which show distinct populations, limiting exchange between Papahānaumokuākea and the Main Hawaiian Islands. This project is lead by Dr. Robert Toonen and Dr. Brian Bowen.

Top Predator Movements
Top predators like sharks, play an important role in ecosystems by shaping communities in the Papahānaumokuākea Marine National Monument. Science-based management of the fish resources in the Hawaiian Archipelago requires that we know whether key species are site attached to specific areas and, if not, how frequently and extensively they move. To understand top predators in the Monument, acoustic and satellite telemetry is used to look at movements between open-ocean and atolls, and to determine habitat use. There are now a total of 90 receivers that have recorded over 300 tagged top predators in Monument waters. Results indicate that tiger sharks (Galecerdo cuvier) are the most wide-ranging top predator in the Monument, and there have been no inter-island movements by ulua or uku (C. ignobilis & Aprion virescens). Empirical data quantifying long-term movements and habitat use of sharks has also been used to help understand monk seal predation at French Frigate Shoals. This project is lead by Dr. Kim Holland and Dr. Carl Meyer.