Estimates of cetacean mortality and injury in two U.S. Pacific longline fisheries, 1994-2002
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Estimates of cetacean mortality and injury in two U.S. Pacific longline fisheries, 1994-2002

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    This report presents estimates of annual mortality and serious injury of cetaceans for the Hawaii-based longline fishery during 1994-2002, and for the California-based fishery between August 2001 and December 2002. Hawaii-based vessels primarily targeted tunas and swordfish, until a 2001 ban on swordfish fishing north of the equator was implemented. Subsequently, a portion of the swordfish fleet relocated to California, where the restrictions on swordfish fishing did not apply, and continued to target swordfish in some of the same areas as the previous Hawaii-based swordfish fleet. Observer coverage in the California-based fleet during 2001-2002 was limited (9 trips including 198 sets, representing about 5.5% of the estimated 3,612 sets made), and no marine mammals were reported injured or killed. Observer coverage in the Hawaii-based fleet ranged from 3.5% to 24.9% during 1994-2002, and fishing effort totaled an estimated 10,323 trips encompassing 110,336 sets. Annual effort was roughly constant at about 1,100 trips encompassing 12,000 sets. During the 905 observed Hawaii-based trips, 44 cetaceans were observed hooked or entangled. Four of the cetaceans (two short-finned pilot whales, Globicephala macrorhynchus, one pan-tropical spotted dolphin, Stenella attenuata, and one Blainville's beaked whale, Mesoplodon densirostris) were observed killed. The 40 other interactions involved injuries of 10 false killer whales, Pseudorca crassidens, seven Risso's dolphin, Grampus griseus, three short-finned pilot whales, two bottlenose dolphins, Tursiops truncatus, two spinner dolphins, Stenella longirostris, two humpback whales, Megaptera novaeangliae, one sperm whale, Physeter macrocephalus, one short-beaked common dolphin, Delphinus delphis, and 12 unidentified cetaceans. One sperm whale was additionally injured in an experimental longline set, but this set was not included in the estimation of fleet-wide mortality and serious injury. The severity of injuries sustained by cetaceans was evaluated based on observer descriptions of the nature of the interaction, using previously established guidelines. Interactions with insufficient information to make a determination of the severity of injury were prorated based on the severity of known interactions for each species. Ten cetaceans were categorized as not seriously injured and 30 as seriously injured. Total (cumulative) mortality and serious injury during the 9-year period was estimated as: 130 (CV=0.40) Risso's dolphins, 50 (CV=0.71) bottlenose dolphins, 4 (CV=1.0) pantropical spotted dolphins, 81 (CV=0.38) false killer whales, 44 (CV=0.47) short-finned pilot whales, 4 (CV=1.0) Blainville's beaked whales, 4 (CV=1.0) humpback whales, and 118 (CV=0.40) unidentified cetaceans. Estimates for sperm whales and spinner dolphins are zero because injuries for these species were categorized as not serious. Cetacean mortality and injury were also calculated separately for waters within and outside of U.S. Exclusive Economic Zones to facilitate management of cetaceans in U.S. waters.
  • Content Notes:
    Karin A. Forney

    "October 2004."

    System requirements: Adobe Acrobat Reader.

    Includes bibliographical references (pages 9-10).

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    Public Domain
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