Beaked whales (Cetacea: Ziphiidae) gillnet entanglements in the Northwestern Indian Ocean (Pakistan, Iran): are pelagic tuna fisheries a threat?

Beaked whales (Family Ziphiidae) are rarely reported in the Northwestern Indian Ocean. This study presents seven new records involving eight individuals from the deep offshore waters of the northern Arabian Sea (N=5) and the Gulf of Oman (N=2), encompassing areas under the jurisdiction of Pakistan and Iran. Observations primarily resulted from fishermen video-recording incidental entanglements in the pelagic tuna drift gillnet fishery between 2015 and 2018. Additional data from Iran were sourced through interviews with fishermen, video evidence, and media reports from 2013. Due to the non-specialist nature of the graphic evidence, most identifications were limited to higher taxonomic levels: three cases were attributed to Mesoplodon spp., three to unidentified Ziphiidae, and one was confirmed as Indopacetus pacificus from Pakistani waters. An additional ziphiid from Iran was identified as either I. pacificus or Ziphius cavirostris. Notably, one I. pacificus, one Mesoplodon sp., and one unidentified ziphiid displayed erupted apical tusks, indicating they were adult males. The successful release of all live-entangled beaked whales and the simultaneous entanglement of two Mesoplodon individuals are unprecedented observations. These findings suggest that ziphiids may be more prevalent in the Northwestern Indian Ocean than previously indicated in the literature. However, continued bycatch in the expansive tuna fishery poses potentially unsustainable threats to their conservation status.