Chris Lowe - Department of Biological Sciences, Cal State University Long Beach

The Northwestern Hawaiian Islands (NWHI) host a variety of large vertebrate animals including sea birds, green sea turtles (Chelonia mydas), Hawaiian monk seals (Monanchus schauislandi) and large teleost fish such as trevally (Family Carangidae) and several species of sharks.  The air-breathing vertebrates have been the subject of relatively continuous and well-funded research programs over the past several decades, and many aspects of their biology in the NWHI has been fairly well documented.  However, studies directed at understanding the biology and ecology of large teleost fish and sharks in the NWHI have lagged substantially behind research conducted on birds, turtles and seals. During the summer of 2001 we began a study at Midway Atoll to monitor movements of Galapagos sharks (Carcharhinus galapagensis) near seal haulout beaches and to examine survivorship and behavior of giant trevally (Caranx ignobilis) captured and released in a commercial sport fishing operation conducted within the Midway National Wildlife Refuge.  Movements and residence of tiger sharks (Galeocerdo cuvier) were also investigated at Midway.  For each study experimental animals were captured and surgically fitted with long-life, individually coded acoustic transmitters and their movements monitored with an array of automated acoustic monitors deployed at various locations in the atoll. During two years of deployment at Midway, hundreds of detections of transmittered sharks and fish were recorded on the monitors.  These data enabled an assessment of long-term movement patterns of these large predators at Midway and within the NWHI.  Each species investigated demonstrated somewhat repeated and predictable behavioral patterns that provide a basis for improved understanding of determinants of behavior and for enhanced management of these animals and prey (birds, seals, turtles) with which they may interact.     

Detection history for three giant trevally (ulua) at Midway Atoll from September 2002-September 2003.