sak does not work in earn-a-buck units
DESCRIPTION
SAK Does Not Work in Earn-A-Buck Units. Key Assumption of SAK: Buck Harvest can Index Population Trends Buck Harvest Rates are Relatively Stable Buck Harvest Rates Affected by: Earn-a-buck Permit Structure. 1996 Earn-A-Buck Units. 16 farmland management units - PowerPoint PPT PresentationTRANSCRIPT
SAK Does Not Work in Earn-A-Buck Units
• Key Assumption of SAK: – Buck Harvest can Index Population Trends– Buck Harvest Rates are Relatively Stable
• Buck Harvest Rates Affected by:– Earn-a-buck Permit Structure
1996 Earn-A-Buck Units
• 16 farmland management units
• Developed a accounting-style model
• Patterned after POP-II – commercially available big game population
model
• Similar to bear and furbearer population model we have used for many years
Accounting Population Models
• Deterministic: checkbook accounting style models• Simulates changes over time in number of deer in each
sex- and age-class.• Model does not directly estimate population size:
– Requires input of population size in initial year– Simulate seasonal changes in population size over several years– Simulated trends sensitive to initial population size– Can estimate likely population size if independent population
trend data exists
• Assess effects of future harvest strategies
Population Model Inputs
• Initial population size, sex & age composition
• Harvest mortality by sex and age
• Age- & year-specific pregnancy rates, litter size
• Age-specific rates of summer and winter non-harvest mortality
• Registration compliance
Population Model Logic
1. Create pre-birth population for initial year
A. Initial number of deer
B. Sex ratio of adults in initial year
C. Age composition in initial year
2. Determine fawn production
A. Age-specific pregnancy rates
B. Mean litter size
C. Age composition of females in pre-birth population
D. Sex ratio of fawns
3. Add fawn production to pre-birth population for post-birth population and increase ages by 1 (eg. fawns become yearlings, etc.)
Population Model Logic 2
4. Subtract summer non-harvest mortality from post-birth population to determine pre-hunt population
5. Determine harvest by age and sex using:
A. Total registered harvest by antlered/antlerless (mandatory registration)
B. Age structure of harvest (aging data)
C. Estimate of registration compliance
6. Subtract harvest from pre-hunt population to determine post-hunt population
7. Subtract overwinter non-harvest mortality from post-hunt population to determine pre-birth population in year 2
8. Repeat steps 2-7 for year 2, year 3, etc.
Initial Pre-birth Population Size 3,000Initial Sex Ratio (% Males) 50%
Initial Population Age Structure% Juv. % Yrlg % Adults
Females 34% 19% 47%Males 34% 19% 47%
Initial Pre-birth PopulationJuv. Yrlg Adults Total
Females 510 285 705 1,500Males 510 285 705 1,500Total 1,020 570 1,410 3,000
Example of calculations used to create pre-birth population in year 1
Example of calculations used to determine kit production
Age % Pregnant Litter SizeYearling 80% 2.3Adult 85% 2.6
KitsFemales in Pre-Birth Population Produced
Yearlings 285 x 0.8 x 2.3 = 524Adults 705 x 0.85 x 2.6 = 1,558Total 2,082
Sex Ratio of Kits Assumed to be Equal 1,041 Female Kits1,041 Male Kits
Kit production is added to pre-birth population for post-birth population
Pre-Birth Juv. ==> Yearlings and Pre-Birth Yearlings ==> Adults
Pre-birth Population
Juv. Yrlg Adults Total
Females 510 285 705 1,500
Males 510 285 705 1,500
Total 1,020 570 1,410 3,000
Kits Females 1,041 Males 1,041
Post-birth Population
Juv. Yrlg Adults Total
Females 1,041 510 990 2,541
Males 1,041 510 990 2,541
Total 2,082 1,020 1,980 5,082
Summer losses =post-birth population * summer non-harvest mortality rates
Post-birth Population Juv. Yrlg Adults Total
Females 1,041 510 990 2,541
Males 1,041 510 990 2,541
Total 2,082 1,020 1,980 5,082
Summer Non-Harvest Mortality Rates
Juv. Yrlg Adults
25% 12% 10%
Summer Losses Juv. Yrlg Adults Total
Females 260 61 99 421
Males 260 61 99 421
Total 521 122 198 841
Subtract summer losses from post-birth population to determine pre-hunt population
Post-birth Population Juv. Yrlg Adults Total
Females 1,041 510 990 2,541
Males 1,041 510 990 2,541
Minus
Summer Losses Juv. Yrlg Adults Total
Females 260 61 99 421
Males 260 61 99 421
Pre-Hunt Population Juv. Yrlg Adults Total
Females 781 449 891 2,121
Males 781 449 891 2,121
1,562 898 1,782 4,241
Harvest by sex and age
Reported Harvest Females 50 Males 50
Harvest Age Structure % Juv. % Yrlg % AdultsFemales 43% 28% 29%Males 53% 18% 29%
Poaching/Wounding (% of Registered Harvest) 75%
Harvest Related Mortality Juv. Yrlg Adults TotalFemales 38 25 25 88Males 46 16 25 88
84 40 51 175
Subtract harvest related mortality from pre-hunt population to determine post-hunt population
Pre-Hunt Population Juv. Yrlg Adults TotalFemales 781 449 891 2,121Males 781 449 891 2,121
1,562 898 1,782 4,241MinusHarvest Related Mortality Juv. Yrlg Adults Total
Females 38 25 25 88Males 46 16 25 88
84 40 51 175
Post-Hunt Population Juv. Yrlg Adults TotalFemales 743 424 866 2,033Males 735 433 866 2,033
1,478 857 1,731 4,066
Winter Losses =Post-Hunt Population * Winter Non-Harvest Mortality Rates
Post-Hunt Population Juv. Yrlg Adults TotalFemales 743 424 866 2,033Males 735 433 866 2,033Total 1,478 857 1,731 4,066
Winter Non-Harvest Mortality RatesJuv. Yrlg Adults
25% 12% 10%
Winter Losses Juv. Yrlg Adults TotalFemales 186 51 87 323Males 184 52 87 322Total 369 103 173 645
Subtract Winter Losses From Post-Hunt Population to Determine Pre-Birth Population in Year 2
Post-Hunt Population Juv. Yrlg Adults TotalFemales 743 424 866 2,033Males 735 433 866 2,033
MinusWinter Losses Juv. Yrlg Adults Total
Females 186 51 87 323Males 184 52 87 322
Pre-Birth Population Yr. 2 Juv. Yrlg Adults TotalFemales 557 373 779 1,710Males 551 381 779 1,711
1,108 754 1,558 3,421
Repeat for Year 2, Year 3, etc.
Model Calculations
------ Pre-Birth Population ------ ------ ------ Post-birth Population ------ ------ Summer Non-Harvest Mortality ------ Pre-Hunt Population
=======Females==============Males ==== =======Females==============Males ==== =======Females==============Males ==== =======Females
Year Juv. Yrlgs Adults Juv. Yrlgs Adults Juv. Yrlgs Adults Juv. Yrlgs Adults Juv. Yrlgs Adults Juv. Yrlgs Adults Juv. Yrlgs
1984 527 295 729 527 295 729 1076 527 1023 1076 527 1023 269 63 102 269 63 102 807 464
1985 577 387 806 570 394 806 1246 577 1192 1246 570 1200 312 69 119 312 68 120 935 508
1986 673 425 943 666 428 949 1433 673 1368 1433 666 1377 358 81 137 358 80 138 1075 592
1987 777 499 1085 773 503 1094 1658 777 1584 1658 773 1597 414 93 158 414 93 160 1243 684
1988 841 532 1209 831 559 1227 1825 841 1741 1825 831 1785 456 101 174 456 100 179 1369 740
1989 952 594 1350 938 608 1388 2038 952 1944 2038 938 1996 509 114 194 509 113 200 1528 838
1990 1059 670 1504 1022 677 1535 2278 1059 2174 2278 1022 2212 569 127 217 569 123 221 1708 932
1991 1184 740 1722 1152 717 1726 2583 1184 2462 2583 1152 2444 646 142 246 646 138 244 1937 1042
1992 1377 867 1950 1403 860 1937 2952 1377 2817 2952 1403 2797 738 165 282 738 168 280 2214 1212
------ Harvest+Poaching Mortality ------ ------ Post-Hunt Population ------ ------ Winter Non-Harvest Mortality
=======Females==============Males ==== =======Females =======Males ==== =======Females=== =======Males ====
Year Juv. Yrlgs Adults Juv. Yrlgs Adults Juv. Yrlgs Adults Juv. Yrlgs Adults Juv. Yrlgs Adults Juv. Yrlgs Adults
1984 38 25 25 46 16 25 769 439 895 761 448 895 192 53 90 190 54 90
1985 38 25 25 46 16 25 897 483 1048 888 486 1055 224 58 105 222 58 105
1986 38 25 26 44 15 24 1037 567 1206 1031 571 1216 259 68 121 258 69 122
1987 122 79 82 135 46 74 1122 605 1343 1108 635 1363 280 73 134 277 76 136
1988 100 65 67 118 40 64 1269 675 1500 1251 691 1542 317 81 150 313 83 154
1989 117 76 79 166 56 91 1412 762 1671 1362 769 1706 353 91 167 341 92 171
1990 130 91 43 172 84 73 1578 841 1913 1536 815 1918 395 101 191 384 98 192
1991 101 56 49 67 37 47 1836 986 2166 1870 977 2153 459 118 217 468 117 215
1992 518 250 226 539 270 255 1696 962 2309 1676 964 2262 424 115 231 419 116 226
Simulated Population Trend for Wisconsin Fishers
0
2,000
4,000
6,000
8,000
10,000
12,000
1982 1986 1990 1994 1998 2002Year
Nu
mb
er
of F
ish
ers
Pre-hunt
Post-hunt
Simulated trend sensitive to initial population size
0
2,000
4,000
6,000
8,000
10,000
12,000
14,000
1982 1986 1990 1994 1998 2002Year
Nu
mb
er
of
Fis
he
rs
Initial population = 2,900
Initial population = 3,000
Initial population = 3,100
Fisher Tracks/Transect, Statewide, 1980-2003
0
1
2
3
4
5
6
7
1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002
Year
Tra
cks
/Tra
ns
ect
Annual Tracks/Transect
3-yr average
Calibrate simulated population to independent information on population trend
3,000
4,000
5,000
6,000
7,000
8,000
9,000
10,000
11,000
1982 1986 1990 1994 1998 2002Year
Nu
mb
er
of
Fis
he
rs
0
1
2
3
4
5
6
7
Tra
cks/T
ran
se
ct
Posthunt PopulationTracks/Transect
Population Model Assumptions
• Does Not Assume:
– Harvest age structure reflect population age structure
– Buck harvest rates are stable
• Does Assume:
– Initial population size and composition can be accurately
estimated
– Nonharvest mortality rates and reproduction can be accurately
estimated
Accounting Models Most Useful
• When long histories (10+ years) of independent estimates of population size or trend are available