ESR prepress abstract   -  DOI: https://doi.org/10.3354/esr01267

ABSTRACT: Scalloped hammerhead sharks (Sphyrna lewini) are a circumglobal species found in tropical and subtropical waters. Globally, populations of S.lewini have undergone dramatic declines in recent decades and four of six distinct population segments are at risk of extinction and listed under the United States Endangered Species Act. Despite this, limited data exist on movement behavior or habitat use requirements of S.lewini, especially in the Central Pacific region. In this long-term (2009 - 2020) telemetry study, 27 S. lewini (24 male [n=22 adult, n= 2 juvenile], and n=3 juvenile female) ranging in size from 106 – 310 cm (TL) were tagged with a combination of acoustic and / or satellite tags in a known nursery area, Kāneʻohe Bay, Hawai’i. Acoustic data revealed repeated movements of adult male S.lewini to Kāneʻohe Bay between May - September across multiple years. Horizontal movements away from the Bay indicate these individuals are highly associated with the Hawaiian Archipelago (i.e. Northwestern and main Hawaiian Islands), while vertical movements were dynamic with repeated, nocturnal deep dives to depths beyond 800 m and temperatures as low as 5.0 °C. We conclude that adult male and juvenile S.lewini tagged in Kāneʻohe Bay exhibit fairly restricted movements throughout the Hawaiian Archipelago, and mature males specifically exhibit strong seasonal site fidelity to Kāneʻohe Bay. These data add crucial baseline information on habitat preferences of S.lewini around the Hawaiian Islands, and can be used to help structure conservation strategies for a portion of the Central Pacific population.