1. Development of a GIS-based Method to Refine Annual Herd-specific Caribou Harvest Estimates from Barrow, Alaska, using 2003-2007 Caribou Harvest and Satellite Telemetry Data Lincoln Parrett 1,Sverre Pedersen 1,Jim Dau 1, Geoff Carroll 1, Brian Person 2, Alex Prichard 3, Dave Yokel 4 1 Alaska Department of Fish and Game, 2 North Slope Borough Wildlife Management, 3 ABR Inc., 4 Bureau of Land Management Introduction Caribou are the most commonly harvested terrestrial subsistence resource in communities on the north slope of Alaska. Seasonal overlap between neighboring caribou herds can complicate attempts to estimate herd-specific harvest rates. This study was an attempt to refine methods to assign harvest from different communities to specific herds at realistic ratios. The Western Arctic (WAH) and Teshekpuk caribou (TCH) herds share seasonal ranges on the north slope. Prior to this study, caribou harvests in the community of Barrow were assumed to be 80% from the TCH and 20% from the WAH. Adjustments to this ratio have the potential to alter overall harvest rate estimates, particularly for the smaller TCH, which has historically been an order of magnitude smaller than the adjacent WAH. Methods A random sample of up to 12% of Barrow households were surveyed annually from 2003-2007. A second strata, consisting of up to 20 households known to be “high harvesters,” was also surveyed annually. Respondents were asked to recall harvests and location by month; harvest locations were assigned to one of 26 locally derived harvest area polygons. Mean harvests from each polygon were extrapolated using the reported harvest locations and mean harvest levels, by month. We limited the analyses to June-September, since80% of the total Barrow harvest occurred in those months during the study. We would anticipate that the pattern in harvest-by-herd seen in these 4 months would be consistent with the remaining months of the year; we plan to assess this in the future. Archived telemetry locations from 2002-2007 were screened for quality, and sub-sampled to reduce the dataset to 3 locations per-caribou, per- month, per-year (Table 1). Locations from the first 9 months of deployment were removed from the WAH dataset due to their bias toward the collaring location. Program Kernel HR was used to estimate fixed-kernel distributions for each herd, by month, 2003-2007. Results Although some herd overlap occurs, 99% of the attributable harvest was from the TCH (Table 2). Almost 20% of the reported harvest occurred in areas with estimated caribou densities of zero caribou, primarily in the vicinity of Barrow. Based on general patterns of distribution, these caribou were likely from the TCH (Figure 1). Harvest Documentation Caribou Distribution The estimated number of caribou at each grid intersection of the utilization distribution was calculated by multiplying the kernel densities, which sum to 1, by the estimated average population size of each herd during the study period. Population sizes were estimated as the average between recent photo- census estimates that overlapped the study period (53,000 for TCH, 440,000 for WAH). Harvest ratios were estimated by taking the average estimated number of caribou from each herd present within harvest polygons, and assuming that harvest came proportionally from the total number of caribou within the polygon. Table 2. Average monthly Barrow caribou harvest, 2003-2007, with new and (old) estimates of percentage harvest from each herd. Conclusions Areas with high hunter effort may produce substantial caribou harvests despite average caribou densities that are too low to be detected with current telemetry sample sizes. A harvest ratio of 400 bulls per 100 cows does not match the collar deployment ratio of 25 bulls per 100 cows. The method as implemented here assumes no sexual segregation, which is undoubtedly a poor assumption. The previous ratio (80 TCH:20 WAH) may have been more appropriate given caribou distributions in the 1990’s, but the current estimate should be revised as shown here (99 TCH:1 WAH). Adjusting the Barrow harvest ratio from the TCH from 80% to 99% means that the overall harvest rate would increase by 1-2% annually. The WAH harvest rate estimate would drop by 0.25%. Changes in caribou distribution and hunting effort over time require that similar estimates be made annually. Figure 1. Monthly estimates of average caribou distribution and harvest near Barrow, AK. Caribou distributions were estimated with fixed kernel utilization distributions, and harvests by polygon were estimated from household surveys. Key References/Acknowledgements JUN JUL AUGSEP TCH100% (80%) 97% (80%) WAH0% (20%) 3% (20%) HARVEST971843963524 JUN JUL AUG SEP TCH432 ( 78)450 (75)308 (67)406 (78) WAH279 ( 71) 353(73)301(65) Table 1. Total number of telemetry relocations and (collared caribou) per-month, by herd, 2002-2007. Carroll, GM. 2007. Unit 26A, Teshekpuk caribou herd. Pages 262–283 in P. Harper, editor. Caribou management report of survey and inventory activities 1 July 2004–30 June 2006. ADFG. Project 3.0 Juneau, Alaska, USA. Dau, J. 2007 Units 21D, 22, 23, 24, 26A caribou management report. Pages 174–231 in P. Harper, editor. Caribou management report of survey and inventory activities 1 July 2004–30 June 2006. ADFG. Project 3.0 Juneau, Alaska, USA Pedersen, Sverre. 2008. Annual Harvest Summary Report, No.4. Monitoring of Annual Caribou Harvests in Three Communities (Atqasuk, Barrow, and Nuiqsut) within the National Petroleum Reserve-Alaska: 2002-2007. ADFG, Division of Subsistence, Fairbanks, Alaska. Seaman, D. E., B. Griffith, and R. A. Powell. 1998. KERNELHR: a program for estimating animal home ranges. Wildlife Society Bulletin. 26:95-100. Funding sources include: ADFG, BLM, Conoco Phillips, NPS, NSB, USFWS August JuneJuly September