Estimating the harvest of Pacific walrus, Odobenus rosmarus divergens, in Alaska


ABSTRACT for J. L. Garlich-Miller): Manuscript accepted 13 January 1999 Fish. Bull. 97(4):1043–1046 (1999). For thousands of years, walrus hunting has been an important component of the economy and cul-ture of Native communities along the Bering and Chukchi Sea coasts (Ray, 1975). Today, the Pacific wal-rus (Odobenus rosmarus divergens) remains a valuable resource to coastal natives in Alaska (United States) and Chukotka (Russia) as a source of food and raw materials for traditional equipment and handicrafts. Accurate information regarding the number of animals removed annually from the population is fundamental for the conservation and management of any species. As the agency responsible for manag-ing Pacific walrus in U.S. waters, the U.S. Fish and Wildlife Service (FWS) gathers data on the size and composition of the subsistence wal-rus harvest in Alaska. The FWS presently administers two separate harvest monitoring programs: the Walrus Harvest Monitoring Project (WHMP) and the Marking Tagging and Reporting Program (MTRP). The WHMP is an observer pro-gram carried out at select walrus hunting villages in Alaska. Each spring, as the pack ice recedes northward, hunters from coastal communities in the Bering Strait region have access to herds of wal-rus as they migrate to their sum-mer range. Historical harvest infor-mation indicates that approxi-mately 80% of the annual reported walrus harvest in Alaska occurs in this region (Fay and Bowlby 1). WHMP monitors stationed at the primary walrus hunting villages in the Bering Strait region (Gambell, Savoonga, Little Diomede and Wales; Fig. 1) collect information on the size and composition of the wal-rus harvest. Harvest monitors meet boats as they return from walrus hunting trips in order to collect bio-logical samples and harvest infor-mation at the boat landing site (Garlich-Miller 2). The goal of the WHMP is to identify and record the gender and age class of every wal-rus retrieved by hunters from these villages during the monitoring pe-riod. Although there is no way of evaluating the degree to which this goal is achieved, WHMP monitors meet most of the returning boats, and the number of retrieved ani-mals not recorded during the har-vest monitoring period is believed to be small (Dickerson 3). The MTRP is a Federally man-dated year-round, statewide pro-gram (Fig. 1). The marking and tag-ging rule requires that all hunters certify (tag) walrus ivory (tusks) and report all walruses that are taken. The objectives of the MTRP are to collect harvest information and to certify specified marine mammal parts to help control ille-gal harvests and trade. Hunters are required to bring walrus tusks to a MTRP tagger within 30 days of the kill. The tagger attaches individu-ally numbered wire tags to the tusks and records the numbers on a tagging certificate. MTRP tags are not attached to calf walruses (or other walruses that may be miss-ing tusks); however, hunters are required to report all animals taken. The age class, gender, kill date, and kill location of each wal-rus are recorded on the certificate (Stephensen et al. 4). These two programs indepen-dently provide information on the size and composition of the harvest. Except in the case of the village of Wales, WHMP and MTRP staff are different people. Each of the two monitoring programs has its strengths and weaknesses. The WHMP benefits from the presence of on-site staff to collect accurate biological information from every walrus retrieved in a community during the monitoring period. Un-fortunately, the monitoring period is seasonal (restricted to the spring hunt) and operates only in four coastal villages. The MTRP is a statewide, year-round program; however hunter compliance with the MTRP rule is variable and ani-mals lacking tusks (e.g. calves, yearlings, and animals with broken tusks) often go unreported (Burn, 1998).

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    ABSTRACT: Decision rules are the agreed-upon points at which specific management interventions are initiated. For marine mammal management under the U.S. Marine Mammal Protection Act (MMPA), decision rules are usually based on either a numeric population or biological-removal approach. However, for walrus and other ice-associated pinnipeds, the inability to reliably assess population numbers or biological removals highlights a significant gap in the MMPA, particularly when the Arctic environment is rapidly changing. We describe the MMPA's ecosystem-based management goals, and why managers have bypassed these goals in favor of an approach that depends upon numerical population assessment. We then revisit the statute's primary goals in light of current knowledge about the Pacific walrus ecosystem and new developments in environmental governance. We argue that to monitor and respond to changes in the walrus ecosystem, decision rules should be based on scientific criteria that depend less on the currently-impractical goal of accurately enumerating population size and trends, or removals from that population. Rather, managers should base decisions on ecological needs and observed ecological changes. To implement this approach would require an amendment to the MMPA that supports filling the gap in management with achievable decision rules. Alternatively, walrus and other ice-associated pinnipeds will remain largely unmanaged during a period of profound environmental change.
    Journal of Environmental Management. 01/2009;
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    ABSTRACT: We conducted tests of airborne thermal imagery of Pacific walrus to determine if this technology can be used to detect walrus groups on sea ice and estimate the number of walruses present in each group. In April 2002 we collected thermal imagery of 37 walrus groups in the Bering Sea at spatial resolutions ranging from 1–4 m. We also collected high-resolution digital aerial photographs of the same groups. Walruses were considerably warmer than the background environment of ice, snow, and seawater and were easily detected in thermal imagery. We found a significant linear relation between walrus group size and the amount of heat measured by the thermal sensor at all 4 spatial resolutions tested. This relation can be used in a double-sampling framework to estimate total walrus numbers from a thermal survey of a sample of units within an area and photographs from a subsample of the thermally detected groups. Previous methods used in visual aerial surveys of Pacific walrus have sampled only a small percentage of available habitat, resulting in population estimates with low precision. Results of this study indicate that an aerial survey using a thermal sensor can cover as much as 4 times the area per hour of flight time with greater reliability than visual observation.
    Wildlife Society Bulletin 01/2009; · 0.95 Impact Factor
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    ABSTRACT: The hunting success of St. Lawrence Island walrus hunters from Savoonga (Sivungaq) and Gambell (Sivuqaq) is studied in relation to weather and sea ice conditions for the period 1979–2008. Satellite remote-sensing data, including ice concentration fields from passive-microwave radiometer data, have been examined over the entire time series in conjunction with walrus harvest data from two community-level monitoring programs. Important information to aid with interpretation of these data sets was provided by the hunters themselves, in particular through a log of ice conditions and ice use by L. Apangalook, Sr., of Gambell. From these data, we determined which ice conditions (concentrations >0 and <30%) and which wind speeds (1–5 m s–1 at Savoonga and 5–9 m s–1 at Gambell), temperatures (–5 to +5°C), and visibility (>6km) provide the most favorable conditions for the walrus hunt. The research demonstrated that at the local level, though not necessarily at the region-wide scale, the sea ice concentration anomaly is a very good predictor of the number of favorable hunting days. With the exception of 2007 (and to a lesser extent, 2008), negative anomalies (less ice or earlier onset of ice retreat) coincided with more favorable (Savoonga) or near-average (Gambell) hunting conditions, controlled mostly by access to ice-associated walrus. Ice access and temporal variability differ significantly between Savoonga and Gambell; in contrast with northern Alaska communities, St. Lawrence hunters were able to maintain typical levels of harvest success during the recent record – low ice years of 2007 and 2008. We discuss the potential value of data such as assembled here in assessing vulnerability and adaptation of Arctic communities depending on marine-mammal harvests to climate variability and change. KeywordsSea ice-Subsistence hunt-Ice conditions-Pacific walrus-Climate change
    12/2009: pages 115-144;

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