Oral Presentation Australian Society for Fish Biology Conference 2024

Combining telemetry and fisher knowledge to investigate movement and habitat preferences of oceanic whitetip and silky sharks around the Central Pacific  (111442)

Molly E Scott 1 , Melanie R Hutchinson 2
  1. Hawaii Institute of Marine Biology, Maroubra, NSW, Australia
  2. Inter-America Tropical Tuna Commission, IATTC, La Jolla, San Diego, USA

Fish aggregating devices (FADs) are a critical fisheries enhancement tool for tropical commercial (i.e., purse seine fisheries) and small-scale fisheries throughout the world. Oceanic whitetip (Carcharhinus longimanus) and silky (Carcharhinus falciformis) sharks as well as many other species of pelagic shark are temporally resident at anchored FADs around the main Hawaiian Islands. Both species are often captured incidentally by recreational and commercial fishers targeting tuna and billfish around the Hawai`i FAD array. As such, these species have been implicated as major contributors to shark depredation rates and are considered a nuisance by local fishermen. A result of these interactions is that fishermen may harm sharks captured in their gear or if they appear to be ‘scaring tuna away’. This study describes the results from the Hawaii Community Tagging Program (HCTP), a citizen-science initiative established in 2016 that works directly with local fishers and in-water users to tag incidentally captured sharks and establish methods of reducing shark interactions. To date, the HCTP has tagged a total of 303 pelagic and coastal sharks (n=125 C.lonigmanus ; n=67 C.falciformis) with acoustic, satellite and conventional identification tags. To complement the tagging study, the HCTP collects imagery of oceanic whitetip sharks to determine baseline population demographics for the species. Data generated from this collaborative project has increased understanding of species-specific FAD associative behavior and elucidated potential spatial and temporal hotspots including areas of biological significance for shark populations, including the threatened oceanic whitetip shark, around Hawaii and the broader Central Pacific.