Résumé
Over the past five decades, marine mammal interactions with fisheries have becomea major human-wildlife conflict globally. The emergence of longline fishing is concomitantwith the development of depredation-type interactions i.e., marine mammalsfeeding on fish caught on hooks. The killer whale (Orcinus orca) is one of the speciesmost involved in depredation on longline fisheries. The issue was first reported inhigh latitudes but, with increasing expansion of this fishing method, other fisherieshave begun to experience interactions. The present study investigated killer whaleinteractions with two geographically isolated blue-eye trevalla (Hyperoglyphe antarctica)fisheries operating in temperate waters off Amsterdam/St. Paul Islands (Indian Ocean)and south-eastern Australia. These two fisheries differ in the fishing technique used(vertical vs. demersal longlines), effort, catch, fleet size and fishing area size. Using7-year (201016) long fishing and observation datasets, this study estimated thelevels of killer whale interactions and examined the influence of spatio-temporal andoperational variables on the probability of vessels to experience interactions. Killerwhales interactions occurred during 58.4% and 21.2% of all fishing days, and over 94%and 47.4% of the fishing area for both fisheries, respectively. In south-eastern Australia,the probability of occurrence of killer whale interactions during fishing days variedseasonally with a decrease in spring, increased with the daily fishing effort and decreasedwith the distance travelled by the vessel between fishing days. In Amsterdam/St. Paul,this probability was only influenced by latitude, with an increase in the southern partof the area. Together, these findings document two previously unreported cases of highkiller whale depredation, and provide insights on ways to avoid the issue. The studyalso emphasizes the need to further examine the local characteristics of fisheries andthe ecology of local depredating killer whale populations in as important drivers ofdepredation.