Tuesday, May 27, 2008
224

Short-term invertebrate response to experimentally increased salmon carcass retention in a Southeast Alaska stream

John Hudson1, Emily Y. Campbell2, Richard W. Merritt2, M. Eric Benbow2, Scott D. Tiegs3, and Gary A. Lamberti3. (1) Aquatics Alaska, 16445 Point Lena Loop Road, Juneau, AK 99801, (2) Entomology, Michigan State University, East Lansing, MI 48824, (3) Biological Sciences, University of Notre Dame, 292 Galvin, Notre Dame, IN 46556

Pacific salmon deliver marine-derived nutrients and energy to the streams in which they spawn and die. These resources enter aquatic food webs to help support benthic invertebrates and resident fishes. Benefits to stream organisms may depend on the ability of the channel to retain salmon carcasses. In Southeast Alaska intensive logging has reduced the frequency of pools and woody debris in streams, features that retain carcasses. We experimentally increased carcass retention in a reach of Maybeso Creek, Prince-of-Wales Island, Alaska, and monitored the abundance and community composition of benthic macroinvertebrates in comparison to an upstream control reach. Spawner abundance was similar between reaches, while carcass retention in the treated reach increased 5X. Six benthic samples were collected on 9 dates before, during, and after (BACI design) the spawning run (August-September 2007). After salmon arrived, invertebrate taxa abundance and richness decreased by >90% and >30%, respectively, presumably in response to disturbance from spawning activities. Four weeks after the salmon run, invertebrates had not recovered to pre-spawning levels in either reach. Collectively, results suggest that enhanced carcass retention did not significantly influence the invertebrate community in the short term due to the legacy of strong benthic disturbance imparted by spawning salmon.


Web Page: salmon, invertebrates, Alaska

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