Cryptic paw (Nephroma occultum) COSEWIC assessment and status report: chapter 7
Population Sizes and Trends
Search effort
Most Canadian populations of Nephroma occultum occur on unprotected Crown Land which is subject to forest harvesting. Fieldwork in 2004 by P. Williston focused on determining the condition of unprotected populations of N. occultum in the Kispiox Valley, a region known to support several documented localities of this lichen, and which also is subject to active forest harvesting. Two days (September 23 and 24, 2004) were spent relocating previously documented localities and searching for new ones. The surveys took place along the Date Creek and Helen Lake Forest Service Roads in the Kispiox Valley, approximately 16 kilometers north of Hazelton, British Columbia. Representative collections and photographs were taken at most sites. Measurements of thallus lengths were recorded at four sites to better understand the population structure and GPS coordinates were recorded wherever cryptic paw lichen was found.
Lichenologists have collected macro-lichens in many parts of British Columbia. Sites visited by lichenologists as part of non-targeted surveys are shown in Figure 6 and are mapped against the CWH and ICH biogeoclimatic zones where potential habitat for the species may exist.
In Canada, where lichen surveys are not required in forest harvesting plans even in areas with habitat for rare species, there have been 24 newly discovered populations of Nephroma occultum since 1994. In Oregon, where lichen surveys have been integrated into forest harvesting practices, 182 populations of N. occultum have been documented in the past 10 years (see Appendix 1, Figure 7).
Populations
The populations listed in Table 1 combine those from the initial report (Goward 1995a) with those discovered after it was published. Included are populations documented during the field work carried out in 2004 by P. Williston, as well as data from additional discoveries by Trevor Goward and Toby Spribille since 1994. Twenty-four new locations have been documented in Canada since 1994 and two populations have been extirpated due to forest harvesting. As of December 2004, there are 45 extant populations of Nephroma occultum in Canada. These are listed in Table 1, arranged by date of the most recent observation at each location. There are also 6 populations known from Alaska, 8 from Washington and 182 from Oregon, for a global total of 241. Populations range in size from 1 to about 40 individuals. With a conservative approximation of 10 individuals (a single thallus represents one individual) per population, we can estimate there to be at least 450 individuals within Canada, and approximately 2,410 worldwide. Given the low search effort throughout most of the Canadian portion of the range, it is highly probable that the actual total number is considerably greater.
Extirpations
Two extirpations of Nephroma occultum populations have been documented and are listed below (dates refer to when the population was first recognized as extirpated). Both extirpations resulted from forest harvesting. It is highly likely that many additional populations have been extirpated in the past from the same cause. Localized extirpations almost certainly continue today throughout much of the Canadian portion of this species’s range wherever harvesting occurs in humid, old growth cedar-hemlock forests.
- Hazelton area. Lat./Long. 55°18’N 127°37’W. Elevation 400 m. 24 August 1992. T. Goward. Due to forest harvesting.
- Kispiox area, Helen Lake Forest Service Road. Lat./Long. 55°31’18”N 127°58’08”W. Elevation ca 500 m. 24 August 2004. P. Williston. Due to forest harvesting.
Description of Figure 6
Lichenologists have collected macro-lichens in many parts of British Columbia. Sites visited by lichenologists as part of non-targeted surveys are shown in Figure 6 and are mapped against the CWH and ICH biogeoclimatic zones where potential habitat for the species may exist.
Location number | Locality | Elevation | Collection date | Collector |
---|---|---|---|---|
1. | Hazelton area | 730 m | 19 August 1981 | T. Goward 81-1876 |
2. | New Aiyansh area | 60 m | 24 August 1981 | T. Goward 81-2003 |
3. | Taku River | 150 m | 10 July 1982 | T. Goward |
4. | Sayward area | 100 m | 7 July 1991 | T. Goward 91-704 |
5. | Kispiox area, near Date Creek | 450 m | 23 August 1991 | T. Goward 91-932 |
6. | Terrace area | 375 m | 25 August 1991 | T. Goward 91-1064 |
7. | Terrace area | 200 m | 26 August 1991 | T. Goward |
8. | Kitimat Village | 0-10 m | 28 August 1991 | T. Goward 91-1240 |
9. | Shames Creek | 700 m | 31 August 1991 | T. Goward 91-1392 |
10. | Kispiox area | 510 m | 19 July 1992 | T. Goward |
11. | Azure Lake | 650 m | 5 August 1992 | T. Goward |
12. | Upper Fraser Rivernorth of McBride, Slim Creek | 750 m | 17 August 1992 | T. Goward 92-1224 |
13. | Upper Fraser Rivernorth of McBride | 800 m | 17 August 1992 | T. Goward 92-1246 |
14. | Upper Fraser Rivernorth of McBride | 750 m | 17 August 1992 | T. Goward 92-1210 |
15. | Upper Fraser Rivernorth of McBride | 800 m | 18 August 1992 | T. Goward 92-1305 |
16. | Chilliwack Lakearea | 650 m | 25 August 1992 | T. Goward |
17. | Murtle Lake | 1100 m | 9 September 1992 | T. Goward 92-1396 |
18. | Murtle Lake | 1170 m | 10 September 1992 | T. Goward |
19. | Upper Adams River | 900 m | 17 September 1992 | T. Goward 92-1432 |
20. | Upper Adams River | 700 m | 22 September 1992 | T. Goward 92-1474 |
21. | Upper Adams River | 750 m | 23 September 1992 | T. Goward 92-1516 |
22. | Robson Valley | 875 m | 4 June 1995 | T. Goward 95-99a |
23. | Kispiox area, near Carrigan Creek | 785 m | 2 July 1995 | T. Goward 95-228 |
24. | Kispiox area, near Skeena River | 745 m | 3 July 1995 | T. Goward 95-300 |
25. | Kispiox area, near Helen Lake | 550 m | 4 July 1995 | T. Goward 95-390 |
26. | Cranberry Junction, near Octopus Lake | 680 m | 4 July 1995 | T. Goward 95-399 |
27. | White Swan Lakearea | 515 m | 5 July 1995 | T. Goward 95-450 |
28. | Cranberry Junction, near Octopus Lake | 680 m | 4 July 1995 | T. Goward 95-399 |
29. | Meziadin Lakearea | 660 m | 6 July 1995 | T. Goward 95-457 |
30. | Meziadin Lakearea. | 650 m | 7 July 1995 | T. Goward 95-530 |
31. | Mt. Bell-Irving area | 445 m | 8 July 1995 | T. Goward 95-576 |
32. | Hazelton area | 645 m | 9 July 1995 | T. Goward 95-605 |
33. | Seymour Rivernear Blais Creek | 875 m | 7 August 1995 | T. Goward 95-831 |
34. | Seven Sisters area | 240 m | 21 June 1996 | T. Goward 96-47 |
35. | Cummins River Valley | 825 m | 23 July 1997 | T. Goward 17792 |
36. | Selkirk Mountains, along Incomappleux River, near confluence with Battle Brook | ca 600-50 m | 14 September 2002 | T. Spribille 12293 |
37. | Selkirk Mountains, near upper end of Duncan Lake, along Hall Creek just above confluence with Duncan River, just above main upper forestry Duncan Road | ca 690 m | 15 September 2002 | T. Spribille 12418 |
38. | Kispiox area, Date Creek Forest Service Road, 1200 Branch | 664 m | 23 September 2004 | P. Williston 4686 |
39. | Kispiox area, Date Creek Forest Service Road, near interpretive parking area | 487 m | 23 September 2004 | P. Williston |
40. | Kispiox area, Date Creek Forest Service Road, creek at Km 19 | 528 m | 23 September 2004 | P. Williston |
41. | Kispiox area, Botrychium Basin Sensitive Area, Date Creek Forest Service Road | 537 m | 23 September 2004 | P. Williston 4702, 4719 |
42. | Kispiox area, Helen Lake Forest Service Road | 496 m | 24 September 2004 | P. Williston 4722 |
43. | Kispiox area, Helen Lake Forest Service Road | 505 m | 24 September 2004 | P. Williston 4715 |
44. | Kispiox area, Helen Lake Forest Service Road | ca 500 m | 24 September 2004 | P. Williston |
45. | Kispiox area, Helen Lake Forest Service Road | ca 500 m | 24 September 2004 | P. Williston 4707 |
Rescue effect
In the event of extirpation, Canadian populations would not likely benefit from the rescue effect (immigration from an outside source) for three reasons: 1) Canadian populations (particularly inland localities) are spatially distant from neighbouring populations in the United States; 2) populations in neighbouring states are few in number (Alaska has 6 and Washington 8); and 3) Nephroma occultum is recognized as having poor dispersal capabilities.
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