Standard Talk (15 mins) Australian Society for Fish Biology Conference 2022

Assessing fisheries interactions population demographics and residency of the protected oceanic whitetip shark carcharhinus longimanus through citizen science and photo identification (#106)

Abigail Campbell 1 , Melanie Hutchinson 2 , Molly Scott 2 , Lacey Scheeler 3 , Deron Verbeck 4
  1. Northeastern University, Boston, MA
  2. NOAA, Cooperative Institute for Marine and Atmospheric Research, Honolulu, Hawaiʻi
  3. University of Hawaiʻi, Hilo
  4. I Am Aquatic, Kona, Hawaiʻi

Oceanic whitetip sharks (Carcharhinus longimanus) were listed as threatened under the Endangered Species Act in 2018, and stock assessments indicate that populations in the western and central Pacific are historically and currently overfished. Yet, large data gaps remain in relation to the basic biology, ecology and population structure of this species. Photographic identification is a common and non-invasive method used to evaluate metrics of elasmobranch population demographics, abundance, residency and movement, and social behaviors. The main Hawaiian Islands are a known ‘hotspot’ for C. longimanus where they typically exhibit seasonal residency, a finding that is also supported by local fisher knowledge. This study describes the results of the Hawaii Community Tagging Program, a citizen science initiative in which fishers, divers and snorkelers submitted images of C. longimanus interactions around the main Hawaiian Islands beginning in 2008. These interactions include the tagging of 114 individuals between 2015 and 2022. Over 2000 images of C. longimanus were analyzed, and dorsal fin patterns were used to determine the number of unique and resighted individuals. To date, this study has identified 337 unique individuals with 21 confirmed resights; the sex ratio of females to males is approximately 2:1 (169 females and 81 males identified). We identified 45 females (~26%) with scarring or injuries from potential mating interactions and 85 individuals (~34%) carried evidence of previous fishing interactions. The information obtained from this study can help provide necessary baseline information regarding the population demographics, residency and fishery interactions of C.longimanus around the main Hawaiian islands to help inform conservation and management measures for this protected species.