Cooperative Study Investigates Behavior of False Killer Whales in Relation to Longline Fishing Gear

Deployed on longline gear, several High-frequency Acoustic Recording Packages (HARPs) will collect data enabling the study of 
               cetacean behavior in relation to the gear.
Deployed on longline gear, several High-frequency Acoustic Recording Packages (HARPs) will collect data enabling the study of cetacean behavior in relation to the gear.

In March 2013, scientists in the PIFSC Cetacean Research Program will initiate a project in cooperation with the Hawaii longline fleet to better understand the behavior of false killer whales around longline fishing gear. Using funds provided by the NOAA Bycatch Reduction Engineering Program, longline vessels were chartered to help gather data aimed at answering high-priority research questions outlined in the False Killer Whale Take Reduction Plan for the Hawaii deep-set longline fishery. Of particular importance is learning more about the behavior of these cetaceans during their encounters with longline gear. Accordingly, during the study, the chartered vessels will be directed to fishing areas where there is a high likelihood of false killer whale depredation of longline catch. The aim of the research is to discover ways of reducing risks to the animals posed by longline fishing, particularly ways that also minimize impacts on welfare of fishers.

Research observations will be collected aboard the chartered vessels by a scientific observer provided by the Hawaii longline observer program administered by the NOAA Fisheries Pacific Islands Regional Office. Collection of data will continue until at least 8 longline sets with depredation have been documented , so the study could potentially involve several fishing trips. During each longline set, 6 High-frequency Acoustic Recording Packages (HARPs) will be attached at various points along the length of the 40-mile long mainline to record acoustic signals produced by the whales that can be used to determine where and when they detect the gear and to document their subsequent behavior in relation to the gear. Each recorder should be capable of detecting whale sounds at a distance of 3-5 nmi and will be positioned to minimize overlap in spatial coverage between sensors, thereby enabling the sensors to monitor as much of the mainline as possible. The recorders power on and off via a saltwater switch and are capable of continuous acoustic recording at a 200 kHz sample rate for 2 weeks, or approximately fifteen 18-hour sets. Whistles produced by whales close to the longline gear should be audible on 1 or 2 time-synchronized recorders, allowing for analysis of the animal's movement along the gear. The HARPs to be deployed have been specifically designed for use on longlines, with a compact size for easy handling and minimal disruption to the fishing process.