Management Unit 7-45 Moose Inventory: December 2006

Transcription

1 Moose Inventory Summary Report Management Unit 7-45 Moose Inventory: December 2006 Report: January, 2007 Author: Mike Rowe 1 Wildlife Biologist British Columbia Ministry of Environment Environmental Stewardship Division Peace Region 1 Contact Address: th Avenue, Fort St John, BC V1J 6M7

2 Executive Summary A moose (Alces alces) inventory was proposed by Ministry of Environment staff for the Management Unit 7-45 (MU 7-45) and was completed in December of MU 7-45 is located northeast of Fort St John, BC and encompasses an area of approximately 6203km 2. It is roughly bounded by the Alaska Highway to the west, the Sikanni Chief River to the north, the Beatton River to the east, and the Blueberry River to the south. The inventory followed the methodology recommended by the BC Resource Inventory Committee (RIC, 2002) and described by Gasaway et al (1986). The main objective of the inventory was to estimate the size of the population within the MU and to compare it to values obtained during a February 1998 stratified random block count (the first stratified count conducted within this management unit). In 1998 the total moose population was estimated to be 2177 moose (0.351 moose/km 2 ), with bulls/100cows and calves/100cows (all to within known confidence limits). The December 2006 inventory used a similar methodology as the 1998 count. Blocks were delineated, stratified, and a random sample was counted to produce estimates for the moose population within the MU. The stratification used was based on weak criteria (there was no budget to stratify using fixed-wing reconnaissance), and the confidence limits around population estimates were tighter when considering the study area as unstratified. The unstratified 2006 moose population was estimated to be moose (0.653 moose/km 2 ). The ratio of bulls/100cows was estimated at and the ratio of calves/100cows was estimated at Total bull, calf, and cow populations were estimated to be , 916.7, and respectively (all to within known confidence limits). 1

3 TABLE OF CONTENTS Executive Summary Introduction Background Study Area Objectives Methods Block Delineation Methods Block Stratification Methods Census Flight Methods Results Stratification Results Count Results Discussion Acknowledgements References.. 16 LIST OF FIGURES Figure 1. Map of Management Unit 7-45 (MU 7-45) located northwest of Fort St. John, BC. 5 Figure 2. A comparison of estimates produced in 1998 and 2006 within Management Unit Figure 3. A comparison of calf to cow and bull to cow ratios for counts conducted in 1998 and 2006 within Management Unit Figure 4. Estimated number of hunter days, hunters and hunter kills within MU 7-45 between 1995 and 2005 for resident and non-resident hunters 15 Figure 5. Estimated ratios of days per kill and kills per hunters within MU 7-45 between 1995 and 2005 for resident and non-resident hunters 15 LIST OF TABLES Table 1. Stratification results used to determine the applicability of the strata used in the 1998 moose inventory within MU Table 2. Count results by block for the December 2006 MU 7-45 moose inventory.. 10 Table 3. 3 year average, 10 year average, and total average (1976 to 2005) for number of moose kills, hunter days, total hunters, and ratios of kills per hunters and days per kill for Management Unit

4 1.0 Introduction 1.1 Background Periodic inventories of moose (Alces alces) populations are a necessary part of the management of this highly utilized species. Inventories provide managers with not only an estimate of the total population, but also a breakdown of population demographics to within known confidence levels. During discussions with local First Nations in 2006, moose were often mentioned as a species of critical interest. Concerns have been expressed to Ministry of Environment staff that moose numbers are not sufficient to meet First Nation harvest needs within certain areas, and are perhaps over hunted locally. Concern was also communicated that the current harvesting system is too strictly focused on the mature bull sector of the population and that current harvest levels may be affecting overall pregnancy rates and/or population genetics. Stemming from these concerns and a general need for updated moose population numbers, a count was proposed for the Management Unit 7-45 (MU 7-45) area by Ministry of Environment staff. Funding was approved through the Environmental Policy funding envelope of the Ministry of Energy, Mines and Petroleum Resources. A separate project was proposed to review recent (previous ~20 years) moose research completed within the Peace Region and to discuss management and harvest options. The MU 7-45 inventory was completed in December 2006 while the Moose Management Review report is to be completed in An inventory had been completed in MU 7-45 in February of 1998 by Ministry of Environment staff. That count was the first stratified random block count conducted in the management unit. At that time, total density was estimated at moose per km 2 +/- 15.7% at 90% confidence (2177 total moose within the 6203 km 2 study area). During this 1998 survey, the estimated sex and age ratios were 37 bulls and 32 calves per 100 cows respectively. The 2006 MU 7-45 moose inventory was carried out with cooperation from four First Nation communities who share interest in the study area, including; Blueberry River First Nations, Doig River First Nation, Halfway River First Nation, and Prophet River First Nation. 3

5 1.2 Study Area Management Unit 7-45 encompasses an area of approximately 6203km 2 northwest of Fort St. John, BC. It is bounded roughly by the Blueberry River in the south, the Beatton River along portions of the east, the Alaska Highway (Highway 97) in the west, and the Sikanni Chief River in the north (Figure 1). The MU falls mainly within 2 biogeoclimatic ecosections; the Halfway Plateau (of the Boreal Plains Ecoprovince) to the south, and the Muskwa Plateau (of the Taiga Plains Ecoprovince) in the north (Demarchi, 1996). The boreal black and white spruce zone (BWBS) is the only biogeoclimatic zone present within MU Subzones present include BWBS mw (moist warm) from m elevation and BWBS wk (wet cool) from m (rare in MU 7-45). The MU exists primarily as a mosaic of standing forests, burned areas, agricultural developments, oil and gas developments, and forestry cut blocks of varying age. Predominant forest types include mixed aspen-white spruce in better-drained sites, and mixed pine-black spruce within more poorly drained areas (Harrison, 1998). 1.3 Objectives The 3 primary objectives of the population inventory were; 1. To produce estimates for moose density, sex-ratio, and calf recruitment for the population within MU 7-45 (with a 90% confidence interval width of less than +/- 25%) 2. To compare estimates obtained to previous values produced within the study area 3. Propose recommendations 4

6 Figure 1. Map of Management Unit 7-45 (MU 7-45) located northwest of Fort St. John, BC. Also shown is the grid of survey blocks used to sample the management unit for moose. 5

7 2.0 Methods Population parameters were estimated within MU 7-45 using a stratified random block technique modelled after the Gasaway method for determining estimates of moose populations (Gasaway et al, 1986). Gasaway s technique was modified during this population survey from using an exclusively fixed-wing searching platform, to one that incorporated the use of helicopters for the count flights. It was thought that the use of helicopters would allow observers to increase the sightability of moose and also allow for more reliable classification of animals by sex and age due to the greater manoeuvrability and better visibility provided by helicopters (Harper, 1985). The stratified random sampling technique consists of 3 distinct steps: (1) delineating blocks; (2) stratifying all blocks based on suspected moose density, and; (3) thoroughly examining a random sample from each of the strata. A fourth step is often applied to correct for sightability error which is a measure of the bias associated with moose that are present but not observed during count flights. In producing the estimates contained within this report, sightability was not corrected. A correction factor for sightability bias was not feasible because sightability was perceived to vary greatly across many of the blocks making it difficult and costly to determine a correction factor that could be applied to the entire study area. Since the estimates contained herein do not correct for sightability error, they are considered to be conservative when compared to the actual values for the population. The 1998 survey also did not correct for sightability bias. 2.1 Block Delineation Methods Blocks were delineated using GIS software. A grid of 208 blocks of equal size was overlaid on the study area. Each block covered an area of 30 km 2 (6km north-south by 5km east-west). Although these blocks did not perfectly align with the non-linear boundaries of the management unit, they closely approximated the total area covered by the MU. Blocks that occurred along the boundaries of the MU were considered part of the study area only if greater than 50% of the total area was situated within the MU boundary. Digital delineation of block boundaries allowed the grid to be visualized both on a hand-held GPS and on a laptop using the moving map function of the computer application Oziexplorer. 6

8 2.2 Block Stratification Methods The usual method of block stratification involves the use of fixed-wing aircraft to determine to which stratum each block should be assigned (Gasaway et al, 1986). Due to rising fuel prices and aviation charter costs, it was not feasible to fly the entire study area in order to complete a proper stratification. A number of stratification methods were undertaken prior to the inventory including; scoring blocks based on Broad Ecosystem Inventory habitat suitability, scoring blocks based on vegetative characteristics gleaned from the Vegetation Resource Inventory (VRI) database, and applying the stratification used in the 1998 inventory. In the end, we used a stratification based on the 1998 inventory since the effort used to produce that stratification was high (6 days of fixed-wing flights). The 1998 stratification was matched to the 2006 block boundaries based on percent of each type occurring within the 2006 survey units. In order to verify that the stratification would still be applicable, a 4 hour reconnaissance flight was flown in a Cessna 180J Skywagon just prior to count flight commencement. 2.3 Census Flight Methods Census flights were completed using a Bell 206 Jet Ranger helicopter and a crew of 4 individuals (2 observers, a navigator, and the pilot). A random sample of blocks was selected from each stratum to be searched intensively to determine the number, sex, and age of moose present. Blocks were surveyed following a randomized distribution. A linear transect search pattern was used in each of the selected blocks with the goal of achieving a visual coverage of the area that approximated 100%. The distance between transects varied depending on vegetative cover, habitat type, and landscape features. Each visual occurrence of a moose or group of moose prompted the pilot to drop in elevation and approach to a distance where the sex of each adult and the number of calves could be determined. Geographic position and physical location within the block was measured and visualized using a combination of a hand-held Garmin GPS V receiver connected to a Panasonic CF-28 laptop with Oziexplorer. Real-time location was displayed on the laptop screen using the moving-map function of Oziexplorer, allowing the navigator to view position within the block and the navigator to place waypoint markers where moose were encountered. The waypoint recorded both time and position of all moose groups and provided a quick reference to eliminate double counting. 7

9 The absence of antlers on some adult bulls during this survey made it necessary to examine secondary sexual characteristics in order to confirm classification of antlerless adult moose encountered. The primary trait used in the classification of antlerless adult moose was the presence/absence of a vulval patch (a patch of white hair observed near the vulva of cows). The presence of pedicel scars, where the antlers had been shed from adult bulls, was another means to identify the sex of the animal. Other sexual characteristics such as snout coloration, and bell size were used to corroborate the sex classification of the animals, but were not used independently as indicators of sex. Bulls that had not shed their antlers were classified according to their antler architecture. Three categories were recognized: yearling bulls (smaller body size, spike or forked antlers), medium bulls (palmated main palm extending beyond ear tip, antler spread estimated to be < 100cm), and large bulls (palmated brow tine with 2 or more points, antler spread estimated to be > 100cm). 3.0 Results 3.1 Stratification Results Approximately 26% of the blocks were flown to verify stratification. Of the 54 blocks verified during the fixed-wing stratification flight, 27 (50%) were stratified identically to the strata used in 1998 and 26 (48%) were assigned to strata directly adjacent to the 1998 strata (i.e. low to moderate, moderate to high and vice versa) as seen in Table 1. One block was stratified opposite to the 1998 stratification (high in 1998 to low in 2006). Table 1. Stratification results used to determine the applicability of the strata used in the 1998 moose inventory within MU Total % of Total Identical Stratification (1998 to 2006) % Adjacent Stratification (1998 to 2006) % Opposite Stratification (1998 to 2006) % Not Stratified in % Total 2006 Blocks % 8

10 3.2 Count Results Twenty-seven (13%) of 208 blocks were surveyed during 5 days of count flights. Effort was distributed evenly throughout the 3 strata (9 blocks counted in each of the low, moderate, and high strata). A total of 529 moose were observed during these flights (Table 2). Estimates produced below result from analyzing the count data in an unstratified manner. The total number of moose was estimated to be / % at 90%CI (density of moose/1000km 2 ). Sex and age ratios were estimated to be bulls/100cows +/ % at 90% CI and calves/100cows +/ % at 90% CI. Of 112 cow/calf groups encountered, 7 of these groups were twin calves with a cow (6.25% of total cow/calf groups) % of bulls encountered had cast their antlers prior to census, prohibiting classification beyond adult bull. Of the 69 bulls that could be classified according to antler architecture, 24 (34.78%) were classified as yearling bulls, 37 (53.62%) were classified as medium bulls, and 8 (11.59%) as large bulls. An example of how these population estimates were calculated is available in Estimating moose population parameters from aerial surveys, Gasaway,

11 Table 2. Count results by block for the December 2006 MU 7-45 moose inventory. stratum block block visit date total bulls total cows total calves total unclassified total moose Moderate Low Low Moderate Moderate Low Moderate High High High High High Moderate Moderate Moderate High Moderate High Low Low High Low Moderate Low Low High Low Total

12 4.0 Discussion The stratification used failed to produce population estimates to within adequate confidence intervals (i.e. < +/- 25% at 90% C.I.). Confidence limits were tighter when considering the count as an unstratified random block count. It was recognized that dropping the stratification in the analysis introduced bias toward the high and moderate blocks despite the fact that sampling effort was even across the three strata used. Bias was introduced because the strata were sampled disproportionately to their abundance within the study area (i.e. high and moderate blocks were overrepresented). The rationale for dropping the stratification was that there was little difference observed between the high and low strata (23 moose per block on average for high blocks and 22 moose per block on average for low blocks). If the overrepresentation of high and moderate blocks in the sample had the effect of skewing the estimates upward, this would be moderated by the fact that no sightability estimate was applied; meaning moose that were overlooked were not counted. Using an unstratified anlaysis, estimates fall within +/- 25% at the 90% CI (apart from the total bull estimate with an error of +/-25.53% at 90% CI). With errors around estimates considered, there was an observed increase in the estimates for total moose, bulls, cows and calves as compared to values estimated in 1998 (Figures 2 and 3). The ratio of calves to 100 cows was higher in December 2006 than in February 1998 (although some loss of calves would be expected between December and February). The error around the bull estimate makes it unclear whether the proportion of bulls in the population has changed. Licensed hunting pressure since 1995 has trended down overall (see Figure 4). The 3 year average harvest (2003 to 2005) was approximately moose per year (8.8% of the bulls estimated in the December 2006 survey, and approximately 2.5% of the total population). This licensed harvest has been a bull only harvest with a 15 day any bull season from August 15 to August 31 followed by a spike-fork, Tripalm, or 10-point only season from September 1 to October 31 (implemented in 1996). The regional licensed bag limit for moose is currently set at 1 moose per year. A ratio of 30 bulls per 100 cows has been suggested as a minimum to assure adequate breeding takes place (Hatter, 1998). The population in MU 7-45 currently appears to be exceeding this minimum target with a population of bulls estimated at 56.7/100 cows +/ % at 90% CI (between 44 and 70 bulls per 100 cows, 9 times out of 10). The number of mature bulls in the population was difficult to measure owing to the fact that 53.38% of bulls encountered had cast their antlers prior to census. Previous studies suggested that older bulls 11

13 undergo antler casting earlier than younger bulls (Oswald, 1984; VanBallenberghe, 1982). Of the bulls that could be classified according to antler architecture, 8 (11.59%) were classified as large bulls. With differential antler casting for various age groups of bulls, this proportion is assumed to be higher. The overall number of bulls would appear to be adequate to ensure maximum first oestrous breeding within this management unit and the December 2006 calf ratios were considered good (suggesting high pregnancy rates). The number of large bulls estimated in this survey seems to be meeting targets established for the hunting season. A population composition survey conducted shortly after the end of hunting season (and prior to antler drop) would help answer the remaining questions about potential over-harvest of large bulls. The spike-fork/tripalm or 10 point moose season in September and October is meant to promote recruitment to the mature bull class (by affording protection to medium bulls). Hunter effort of 25 to 35 days per harvested moose has been set as a benchmark target for hunter success within BC (Hatter, 1998). The 3 year average, 10 year average, and total average over the life of the dataset (1976 to 2005) are all estimated to be well below this level (Table 3). The total success rate (kills/hunters) for hunters has remained relatively consistent since over the last 30 years according to Ministry of Environment estimates (approximately 36% success rate). A clear trend in hunter effort (days/harvest moose) and success (kills/hunters) does not emerge looking at data from 1995 to 2005 (Figure 5). Table 3. 3 year average, 10 year average, and dataset average (1976 to 2005) for number of moose kills, hunter days, total hunters, and ratios of kills per hunters and days per kill for Management Unit YEAR AVERAGE (2003 to 2005) 10 YEAR AVERAGE (1995 to 2005) DATASET AVERAGE (1976 to 2005) # kills # days # hunters kills/hunters days/kill

14 RATIO PER 100 COWS total moose density (moose/1000km2) number bulls number cows number calves Figure 2. A comparison of estimates of moose in MU 7-45 for 1998 and The blue lines represent error bars at the 90% confidence interval. 13

15 DENSITY or NUMBER calves per 100 cows bulls per 100 cows Figure 3. A comparison of calf to cow and bull to cow ratios for counts conducted in 1998 and 2006 within Management Unit The blue lines represent error bars at the 90% confidence interval. 14

16 number of hunters or number of kills # kills # hunters # days number of hunter days year 0 Figure 4. Estimated number of hunter days, hunters and hunter kills within MU 7-45 between 1995 and 2005 for resident and non-resident hunters days/kill kills/hunters days/kill kils/hunters year 0 Figure 5. Estimated ratios of days per kill and kills per hunters within MU 7-45 between 1995 and 2005 for resident and non-resident hunters. 15

17 5.0 Acknowledgements The following people were instrumental in the successful completion of this project, and I wish to thank each of them: Brian Acko of Doig River First Nation Darcy Chipesia of Prophet River First Nation Darlene Davis of Blueberry River First Nations David Verbisky of Trek Aerial Surveys Jason Lee of Treaty 8 Tribal Association John Elliott of Ministry of Environment Kelly Croswell of Qwest Helicopters Lorne Hunter of Halfway River First Nation Stan Pile of Blueberry River First Nations Theresa Morris of Ministry of Energy, Mines and Petroleum Resources Thank you to the Ministry of Energy, Mines and Petroleum Resources for funding this project through their Environmental Policy Program. 6.0 References British Columbia Ministry of Sustainable Resource Management: Terrestrial Information Branch Aerial-based Inventory Methods for Selected Ungulates: Bison, Mountain Goat, Mountain Sheep, Moose, Elk, Deer, and Caribou. Version pp. Demarchi, D.A An introduction to the ecoregions of BC. Ministry of Environment, Lands, and Parks. Gasaway, W.C., S.D. Dubois, D.J. Reed, and S.J. Harbo Estimating moose population parameters from aerial surveys. Biological Papers of the University of Alaska; no pp. Harper, F.E Peace River Moose Inventory. Unpub. Rep. 32pp. Hatter, I.W Moose Conservation and Harvest Management in Central and Northern British Columbia. Unpub. Rep. 47pp. Oswald, K Antler casting in an unhunted moose population in north-eastern Ontario. Alces 20: Reed, D.J Draft. Moosepop: program documentation and instructions. Alaska Department of Fish and Game. Fairbanks, AK. 15pp. VanBallenberghe, V Growth and development of moose antlers in Alaska. Caesar Kleberg Wildlife Research Institute, Kingsville, Texas. Pages