Changes in density,age structure and age‐specific mortality in two western pearlshell (Margaritifera falcata) populations in Washington (1995–2006) |
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| Authors: | Lee C Hastie Kelly A Toy |
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| Institution: | 1. Department of Zoology, University of Aberdeen, Tillydrone Avenue, Aberdeen AB24 2TZ, Scotland, UK;2. Jamestown S'Klallam Tribe, Natural Resources Department, 1033 Old Blyn Highway, Sequim, WA 98370, USA |
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| Abstract: | - 1. Two western pearlshell (Margaritifera falcata) populations in western Washington were surveyed in 1995 and re‐surveyed in 2006. Significant declines in mussel numbers had occurred in both streams during the past decade.
- 2. In Bear Creek, overall density dropped from 56.0–6.9 mussels m?2, and in Battle Creek, overall density dropped from 80.7–13.4 mussels m?2 in 2006.
- 3. Large numbers of empty shells were found in Bear Creek in 2006, indicating high levels of mortality. A disproportionate loss of large, old mussels resulted in a forward shift in modal age class, from 51–60 years to 31–40 years.
- 4. In Battle Creek, survival appeared to be higher, although significant numbers of shells were found in places. A lack of juvenile mussels indicated recruitment problems, possibly due to habitat degradation following colonization of the stream corridor by beavers and/or a lack of migratory host fish.
- 5. Effective remedial actions for the Bear Creek and Battle Creek M. falcata populations are required within the next 5–10 years and 50 years, respectively, in order to ensure their long‐term survival.
Copyright © 2007 John Wiley & Sons, Ltd. |
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| Keywords: | freshwater mussels beavers conservation decline |
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