HR: 1330h
AN: NB33B-04    [Abstracts]
TI: Effects of Aquatic Insect Life History Patterns on Bioassessments
AU: * Fend, S V
EM: svfend@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Rd. MS465, Menlo Park, CA 94025 United States
AU: Carter, J L
EM: jlcarter@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Rd. MS465, Menlo Park, CA 94025 United States
AU: Weissich, P
AF: California State University, East Bay, 25800 Carlos Bee Blvd., Hayward, CA 94542 United States
AB: Aquatic insect populations vary greatly over an annual cycle. Nevertheless, given practical constraints, biomonitoring programs focusing on these animals typically have broad sampling seasons (index periods). Stated or implicit assumptions are 1) replacement by different populations with similar environmental tolerance occurs, and/or 2) metrics can be generated that are sufficiently robust or can be seasonally adjusted. To support tests of seasonal variability in macroinvertebrate metrics, we analyzed life history patterns of dominant EPT species in 3 regulated and 3 non-regulated streams. Population peaks (recruitment periods) of taxa numerically dominant in both stream types (Baetis tricaudatus, Hydropsyche spp., and Malenka cf. californica) were asynchronous, even within streamflow category. Populations of some intolerant taxonomic groups occurring in non-regulated streams (e.g., Ephemerellidae) were restricted to the fall-spring period. Other groups (e.g., Rhyacophilidae, Heptageniidae) included species that maintained high summer populations. Therefore, defining an index period for all streams in a given area is difficult because life history patterns are often site-specific. Seasonal adjustments based on statistical properties of derived metrics may be useful for describing conditions over a large area but at the site level, behavior of individual populations may need to be considered for an accurate assessment.
DE: 4239 Limnology
DE: 4815 Ecosystems, structure and dynamics
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly